RNA compositions and related methods

Abstract

RNA molecules comprising selenoribonucleosides are disclosed. In some embodiments, the RNA molecule is an mRNA molecule that encodes a polypeptide. In some embodiments, the nucleoside is situated in a coding region, polyA tail, 5' UTR, or 3' UTR. Also provided are methods of making and using the RNA molecules described herein.

Description

[0001]Attorney Docket No.: F2001-7001WO(VL99001-W1) RNA COMPOSITIONS AND RELATED METHODS RELATED APPLICATIONS This application claims priority to U.S. Serial No.: 63 / 695,613 filed September 17, 2024, the entire contents of which are incorporated herein by reference. SEQUENCE LISTING The instant application contains a Sequence Listing which has been submitted electronically in XML format and is hereby incorporated by reference in its entirety. Said XML copy, created on September 15, 2025, is named F2001-7001WO_SL.xml and is 6,914 bytes in size. BACKGROUND There is a need for novel therapeutic modalities to address unmet medical need. SUMMARY OF THE INVENTION Described herein are pharmaceutical RNA compositions, constructs, preparations, methods of using such compositions, constructs and preparations, and methods of making the same. Enumerated Embodiments 1. An RNA molecule that has a length of at least 20 nucleotides and comprises one or more selenoribonucleosides. 2. An RNA molecule that encodes an effector (e.g., a therapeutic effector) and comprises one or more selenoribonucleotides. 3. An RNA molecule comprising a plurality of nucleosides, wherein: at least one nucleoside of the RNA molecule comprises a structure according to Formula (I): 1602179968.1 1 Attorney Docket No.: F2001-7001WO(VL99001-W1) , OMe or F; B is a nucleobase; and the RNA molecule has a length of at least 20 nucleosides. 4. The RNA molecule of embodiment 1 or 3, which comprises an effector sequence that encodes an effector (e.g., a therapeutic effector). 5. The RNA molecule of any of the preceding embodiments, which is an mRNA. 6. The RNA molecule of any of embodiments 1-4, which is a tRNA, gRNA, saRNA, siRNA, ribozyme, or aptazyme. 7. An RNA molecule comprising a plurality of nucleosides, wherein: at least one nucleoside of the RNA molecule comprises a structure according to Formula (I): , OMe or F; B is a nucleobase; and the RNA molecule comprises an effector sequence that encodes an effector (e.g., a therapeutic effector). 8. The RNA molecule of any of embodiments 3-7, wherein the nucleoside of Formula (I) is comprised in a nucleotide of Formula (Ia): phosphorus-containing group. 1602179968.1 2 Attorney Docket No.: F2001-7001WO(VL99001-W1) 9. The RNA molecule of embodiment 8, wherein the phosphorus-containing group is phosphate, phosphorothioate, phosphorodithioate, or methyl phosphonate. 10. The RNA molecule of any of embodiments 3-9, wherein the 2’ carbon of Formula (I) has the stereochemistry of: . 11. is single stranded. 12. The RNA molecule of any of embodiments 1-10, which is double stranded. 13. The RNA molecule of any of embodiments 1-10, which comprises a single stranded region and a double stranded region. 14. The RNA molecule of any of the preceding embodiments, which is linear or circular. 15. The RNA molecule of any of the preceding embodiments, which comprises a 5’ cap, e.g., 7-methylguanylate. 16. The RNA molecule of any of the preceding embodiments, which comprises a 5’ cap analog, e.g., a 5’ cap analog that is more resistant than 7- methylguanylate to a decapping enzyme, e.g., a 5’ cap analog that is more resistant than 7- methylguanylate to Dcp2. 17. The RNA molecule of any of the preceding embodiments, which comprises a 3’ polyA tail. 18. The RNA molecule of embodiment 17, wherein the 3’ polyA tail has a length of 50-100, 100-200, or 200-300 ribonucleotides. 19. The RNA molecule of embodiment 17 or 18, wherein the nucleobases in the 3’ polyA tail are exclusively adenine. 20. The RNA molecule of any of the preceding embodiments, which has a length of at least 30, at least 40, at least 50, at least 100, at least 150, at least 200, at least 500, at least 1000, or at least 1500 nucleotides. 21. The RNA molecule of any of embodiments 1-19, which has a length of 20-50, 50-100, 100-150, 150-200, 200-500, 500-1000, or 1000-1500 nucleotides. 1602179968.1 3 Attorney Docket No.: F2001-7001WO(VL99001-W1) 22. The RNA molecule of any of the preceding embodiments, which comprises a second nucleoside having a chemically modified nucleobase. 23. The RNA molecule of any of the preceding embodiments, which comprises a second nucleoside having a chemically modified sugar. 24. The RNA molecule of any of the preceding embodiments, which comprises a second nucleotide having a backbone modification (e.g., phosphorothioate). 25. The RNA molecule of any of embodiments 3-24, wherein B comprises a canonical nucleobase, wherein optionally the canonical nucleobase is A, C, G, or U. 26. The RNA molecule of any of embodiments 3-24, wherein B comprises thymine. 27. The RNA molecule of any of embodiments 3-24, wherein B comprises a chemically modified nucleobase. 28. The RNA molecule of any of embodiments 3-27, wherein at least 2, at least 5, at least 10, at least 20, at least 50, or at least 100 nucleosides of the RNA molecule each independently comprises a structure according to Formula (I). 29. The RNA molecule of any of embodiments 3-28, wherein at least 0.01%, at least 0.1%, at least 1%, at least 2%, at least 5%, at least 10%, at least 20%, at least 25%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 90%, or at least 99% of the nucleosides of the RNA molecule each independently comprises a structure according to Formula (I). 30. The RNA molecule of any of embodiments 3-29, wherein the RNA molecule contains all four of an adenosine nucleoside, cytosine nucleoside, uridine nucleoside, and guanosine nucleoside. 31. The RNA molecule of any of embodiments 3-30, wherein at least 25%, at least 50%, at least 75%, or at least 99% of the adenosine nucleosides of the RNA molecule each independently comprises a structure according to Formula (I). 32. The RNA molecule of any of embodiments 3-31, wherein at least 25%, at least 50%, at least 75%, or at least 99% of the cytosine nucleosides of the RNA molecule each independently comprises a structure according to Formula (I). 33. The RNA molecule of any of embodiments 3-32, wherein at least 25%, at least 50%, at least 75%, or at least 99% of the uridine nucleosides of the RNA molecule each independently comprises a structure according to Formula (I). 1602179968.1 4 Attorney Docket No.: F2001-7001WO(VL99001-W1) 34. The RNA molecule of any of embodiments 3-33, wherein at least 25%, at least 50%, at least 75%, or at least 99% of the guanosine nucleosides of the RNA molecule each independently comprises a structure according to Formula (I). 35. The RNA molecule of any of embodiments 3-34, wherein 0.01-1%, 1-2%, 2-5%, 5-10%, 10-20%, 20-30%, 30-40%, 40-50%, 50-60%, 60-70%, 70-80%, 80-90%, or 90-100% of the nucleosides of the RNA molecule each independently comprises a structure according to Formula (I). 36. The RNA molecule of any of embodiments 3-35, wherein 1-25%, 25-50%, 50-75%, or 75-100% of the adenosine nucleosides of the RNA molecule each independently comprises a structure according to Formula (I). 37. The RNA molecule of any of embodiments 3-36, wherein 1-25%, 25-50%, 50-75%, or 75-100% of the cytosine nucleosides of the RNA molecule each independently comprises a structure according to Formula (I). 38. The RNA molecule of any of embodiments 3-37, wherein 1-25%, 25-50%, 50-75%, or 75-100% of the uridine nucleosides of the RNA molecule each independently comprises a structure according to Formula (I). 39. The RNA molecule of any of the preceding embodiments, wherein one or more nucleotides of the RNA molecule comprise a canonical phosphate group. 40. The RNA molecule of any of the preceding embodiments, wherein one or more nucleosides of the RNA molecule comprise Formula (II): , OMe or F; and B is a nucleobase. 41. The RNA molecule of any of the preceding embodiments, wherein one or more nucleosides of the RNA molecule comprise a canonical ribose group. 42. The RNA molecule of any of embodiments 3-41, wherein the nucleoside comprising the structure of Formula (I) is situated in a coding region. 1602179968.1 5 Attorney Docket No.: F2001-7001WO(VL99001-W1) 43. The RNA molecule of any of embodiments 3-41, wherein the nucleoside comprising the structure of Formula (I) is situated in a polyA tail. 44. The RNA molecule of any of embodiments 3-42, which comprises a polyA tail, wherein the polyA tail does not comprise any nucleoside having the structure of Formula (I). 45. The RNA molecule of any of embodiments 3-44, wherein the nucleoside comprising the structure of Formula (I) is situated in a 5’ UTR or 3’ UTR. 46. The RNA molecule of any of embodiments 3-44, wherein the nucleoside comprising the structure of Formula (I) is situated in an intron or an exon. 47. The RNA molecule of any of 3-43, 45, or 46, wherein every adenosine nucleoside in the RNA molecule comprises a structure according to Formula (I). 48. The RNA molecule of any of embodiments 3-47, wherein every cytosine nucleoside in the RNA molecule comprises a structure according to Formula (I). 49. The RNA molecule of any of embodiments 3-48, wherein every guanosine nucleoside in the RNA molecule comprises a structure according to Formula (I). 50. The RNA molecule of any of embodiments 3-49, wherein every uridine nucleoside in the RNA molecule comprises a structure according to Formula (I). 51. The RNA molecule of any of embodiments 2 or 4-50, wherein the effector comprises a polypeptide (e.g., a DNA binding protein; an epigenetic modifying factor; an antigen; a hormone; an enzyme; a CRISPR-linked enzyme; a mobile genetic element protein; a gene writer; an antibody; a signaling peptide; a receptor ligand; a receptor; or a clotting factor). 52. The RNA molecule of any of embodiments 2 or 4-51, which further encodes a second effector. 53. The RNA molecule of embodiment 52, wherein the effector and the second effector have the same sequence or different sequences. 54. The RNA molecule of any of embodiments 2 or 4-53, wherein the effector has a length of at least 5, at least 10, at least 20, or at least 50, at least 100, at least 200, or at least 500 amino acids. 55. The RNA molecule of any of embodiments 2 or 4-54, wherein the effector has a length of 5-10, 10-20, or 20-5050-100, 100-200, or 200-500 amino acids. 56. The RNA molecule of any of embodiments 2 or 4-55, wherein the effector sequence does not encode a viral protein. 1602179968.1 6 Attorney Docket No.: F2001-7001WO(VL99001-W1) 57. The RNA molecule of any of the preceding embodiments, which is unencapsidated. 58. The RNA molecule of any of the preceding embodiments, which does not comprise a viral packaging signal. 59. The RNA molecule of any of the preceding embodiments, which does not comprise a viral ITR. 60. The RNA molecule of any of the preceding embodiments, which is essentially free of (e.g., free of) viral proteins. 61. The RNA molecule of any of the preceding embodiments, which is essentially free of (e.g., free of) 4’-thio-modified nucleotides. 62. The RNA molecule of any of the preceding embodiments, which is essentially free of (e.g., free of) 4’-thio-substituted furanose rings. 63. The RNA molecule of any of the preceding embodiments, which further comprises a conjugated non-nucleic acid moiety. 64. The RNA molecule of embodiment 63, wherein the conjugated non-nucleic acid moiety comprises a peptide, lipid, or carbohydrate. 65. The RNA molecule of any of embodiments 2 or 4-64, which expresses the effector when present in a cell. 66. The RNA molecule of any of the preceding embodiments, which is translated when present in a cell. 67. The RNA molecule of any of embodiments 2 or 4-66, wherein when the RNA molecule is introduced to a cell, the cell expresses the effector at a level no less than 10%, no less than 20%, no less than 30%, no less than 40%, or no less than 50% of that of a control cell of the same cell type that was contacted with an otherwise similar RNA molecule having the same sequence as the RNA molecule at the same molar amount as the RNA molecule, but comprising all canonical ribose sugars. 68. The RNA molecule of any of embodiments 2 or 4-66, wherein when the RNA molecule is introduced to a cell, the cell expresses the effector at a level no less than 10%, no less than 20%, 30%, no less than 40%, or no less than 50% of that of a control cell of the same cell type that was contacted with an otherwise similar RNA molecule having the same sequence as the RNA molecule at the same molar amount as the RNA molecule, but comprising only canonical nucleotides. 1602179968.1 7 Attorney Docket No.: F2001-7001WO(VL99001-W1) 69. The RNA molecule of embodiment 67 or 68, wherein expression is measured at 48 hours post transfection, e.g., in an assay according to Example 11. 70. The RNA molecule of any of the preceding embodiments, which has a half-life of greater than 10, greater than 20, greater than 30, or greater than 40 minutes in the presence of XRN-1 at 0.05 units / µL and RppH at 0.25 units / µL at 37 ˚C, e.g., in an assay of Example 7. 71. The RNA molecule of any of the preceding embodiments, which has a half-life of greater than 30, greater than 45, or greater than 60 minutes in the presence of ExoT at 0.25 units / µL at 37 ˚C, e.g., in an assay of Example 7. 72. The RNA molecule of any of the preceding embodiments, which has a half-life of greater than 30, greater than 45, or greater than 60 minutes in the presence of RNase A at 25 pg / µL at 37 ˚C, e.g., in an assay of Example 8. 73. The RNA molecule of any of the preceding embodiments, which has a half-life of greater than 20, greater than 40, or greater than 60 minutes in the presence of 0.064% fetal bovine serum (FBS) at 37 ˚C, e.g., in an assay of Example 9. 74. The RNA molecule of any of the preceding embodiments, which has a half-life of greater than 30 or greater than 45 minutes in the presence of 5 mM MgCl2and 5 mM NaOH at 37 ˚C, e.g., in an assay of Example 10. 75. A composition comprising a plurality of copies of the RNA molecule of any of the preceding embodiments, wherein all RNA molecules in the composition have substantially the same length in nucleotides (e.g., all RNA molecules have the same length in nucleotides). 76. A composition comprising a plurality of copies of the RNA molecule of any of embodiments 1-74, wherein the effector region of all RNA molecules in the composition have substantially the same length in nucleotides (e.g., the effector region of all RNA molecules in the composition have the same length in nucleotides). 77. A composition comprising a plurality of copies of the RNA molecule of any of embodiments 1-74, wherein all RNA molecules in the composition have a length of between 1, 2, 5, 10, or 20 nucleotides of each other. 78. A composition comprising a plurality of copies of the RNA molecule of any of embodiments 1-74, wherein all RNA molecules in the composition have a length of between 20- 50, 25-75, 50-100, 100-500, 500-1000, or 1000-1500 nucleotides. 1602179968.1 8 Attorney Docket No.: F2001-7001WO(VL99001-W1) 79. A composition comprising a plurality of copies of the RNA molecule of any of embodiments 1-74, wherein all RNA molecules in the composition encode substantially the same effector (e.g., all RNA molecules in the composition encode the same effector). 80. A composition comprising a plurality of copies of the RNA molecule of any of embodiments 1-74, wherein all RNA molecules in the composition have substantially the same sequence (e.g., all RNA molecules in the composition have the same sequence). 81. A nucleic acid molecule comprising a plurality of nucleosides, wherein: at least one nucleoside of the nucleic acid molecule comprises a structure according to Formula (I): , OMe or F; and B is a nucleobase; and the nucleic acid molecule has a length of at least 20 nucleosides. 82. A pharmaceutical composition comprising the RNA molecule of any of embodiments 1- 74 and a pharmaceutically acceptable carrier or excipient. 83. The pharmaceutical composition of embodiment 82, wherein the RNA molecule is comprised in a lipid nanoparticle (LNP). 84. The pharmaceutical composition of embodiment 82, which is substantially free of (e.g., is free of) LNPs. 85. The pharmaceutical composition of embodiment 82, which is substantially free of (e.g., is free) of lipids. 86. A method of modulating (e.g., increasing or decreasing) a biological activity in a target cell, the method comprising: contacting a target cell with the RNA molecule of any of embodiments 2 or 4-74 or the pharmaceutical composition of any of embodiments 82-85, wherein the effector modulates a biological activity in the target cell; thereby modulating the biological activity in the target cell. 1602179968.1 9 Attorney Docket No.: F2001-7001WO(VL99001-W1) 87. The method of embodiment 86, which comprises maintaining (e.g., incubating) the cell under conditions suitable for translation of the RNA molecule. 88. The method of embodiment 86 or 87, wherein the biological activity comprises cell growth, cell metabolism, cell signaling, cell movement, specialization, interactions, division, transport, homeostasis, osmosis, or diffusion. 89. The method of any of embodiments 86-88, wherein the cell is an animal cell, e.g., a mammalian cell, e.g., a human cell. 90. A method of treating a cell, tissue, or subject in need thereof, the method comprising: administering to the cell, tissue, or subject the RNA molecule of any of embodiments 1- 74 or the pharmaceutical composition of any of embodiments 82-85; thereby treating the cell, tissue, or subject. 91. The method of any of embodiments 86-90, which is performed ex vivo or in vivo. 92. A method of making an RNA molecule, the method comprising: providing a mixture comprising: a DNA template having a promoter, an RNA polymerase compatible with the promoter, and a plurality of nucleotide triphosphates, wherein one or more of the nucleotide triphosphates comprises a structure according to Formula (I): , OMe or F; and B is a nucleobase, and incubating the mixture under conditions that allow for transcription, thereby making the RNA molecule. 93. The method of embodiment 92, wherein the RNA molecule has a length of at least 20 nucleotides. 94. The method of embodiment 92 or 93, wherein the RNA molecule comprises an effector sequence that encodes an effector (e.g., a therapeutic effector). 95. The method of any of embodiments 92-94, wherein the RNA polymerase is T7 RNAP. 1602179968.1 10 Attorney Docket No.: F2001-7001WO(VL99001-W1) 96. The method of any of embodiments 92-95, wherein the RNA molecule is an RNA molecule of any of embodiments 1-74. 97. A method of making an RNA molecule of any of embodiments 1-74, the method comprising performing solid phase synthesis. 98. The method of embodiment 97, wherein solid phase synthesis comprises: iteratively, adding a nucleotide having a protecting group, allowing the nucleotide to react with a growing RNA molecule, and removing the protecting group. 99. An RNA molecule made by the method of any of embodiments 92-98. 100. A method of making a compound, the method comprising performing one or more of (e.g., 2, 3, 4, 5, 6, or all of) the following steps: 1) converting Compound 1001 into Compound 1002; 2) converting the Compound 1002 into Compound 1003; 3) protecting the free -OH group in the Compound 1003 to form Compound 1004; 4) opening the tetrahydrofuran ring of the Compound 1004 to form Compound 1005; 5) protecting the free -OH groups in the Compound 1005 to form Compound 1006; 6) converting the Compound 1006 into Compound 1007 having a tetrahydroselenophene ring; and 7) oxidizing the Se atom in the tetrahydroselenophene ring of the Compound 1007 into selenoxide to thus form Compound 1008. 101. The method of embodiment 100, wherein the step 1) comprises reacting the Compound 1001 with methanesulfonyl halide such as methanesulfonyl chloride (MsCl) to form the Compound 1002. 102. The method of embodiment 100 or 101, wherein the step 2) comprises a first reaction under a base condition and a second reaction under an acid condition. 103. The method of any of embodiments 100-102, wherein the step 3) uses a protecting agent. 104. The method of any of embodiments 100-103, wherein the protecting agent comprises a tert-butyldiphenylsilyl (TBDPS) halide such as TBDPS chloride (TBDPSCl). 105. The method of any of embodiments 100-104, wherein the step 4) comprises using a reducing agent to open the tetrahydrofuran ring of the Compound 1004. 106. The method of any of embodiments 100-105, wherein the reducing agent comprises NaBH4. 1602179968.1 11 Attorney Docket No.: F2001-7001WO(VL99001-W1) 107. The method of any of embodiments 100-106, wherein the step 5) comprises reacting the Compound 1005 with a protecting agent. 108. The method of any of embodiments 100-107, wherein the protecting agent comprises methanesulfonyl halide such as methanesulfonyl chloride (MsCl). 109. The method of any of embodiments 100-108, wherein the step 6) comprises reacting the Compound 1006 with Selenium (Se) to form the Compound 1007. 110. The method of any of embodiments 100-109, wherein the step 7) comprises reacting the Compound 1007 with an oxidizing agent such as meta-chloroperoxybenzoic acid (m- CPBA) to form Compound 1008. 111. A method of making a compound, the method comprising performing one or more of (e.g., 2, 3, 4, 5, 6, 7, 8, or all of) the following steps: i) oxidizing the Se atom in the tetrahydroselenophene ring of the Compound 1007 into selenoxide to form Compound 1008; ii) converting the Compound 1008 into Compound 2009; iii) converting the Compound 2009 into Compound 2010 by adding a base molecule into the tetrahydroselenophene ring of the Compound 2009; iv) selectively removing one of the protecting groups to release the free -OH group to form Compound 2011; v) reacting the free -OH group of the Compound 2011 with a phosphite agent to form Compound 2012; vi) oxidizing the phosphorus atom in the Compound 2012 to form Compound 2013; vii) converting the base molecule of the Compound 2013 into a nucleotide base to thus form Compound 2014; viii) removing the protecting groups in the Compound 2014 to form Compound 2015; and ix) reacting the Compound 2015 with a phosphate agent to form Se modified adenosine triphosphate (ATP). 112. The method of embodiment 111, wherein the step i) comprises reacting the Compound 1007 with an oxidizing agent such as meta-chloroperoxybenzoic acid (m-CPBA). 113. The method of embodiment 111 or 112, wherein the step ii) comprises reacting the Compound 1008 with an anhydride to form the Compound 2009. 1602179968.1 12 Attorney Docket No.: F2001-7001WO(VL99001-W1) 114. The method of any of embodiments 111-113, wherein the anhydride is an acetic anhydride. 115. The method of any of embodiments 111-114, wherein the base molecule in the step iii) is an adenine derivative. 116. The method of any of embodiments 111-115, wherein the adenine derivative has the following chemical structure: . any of embodiments 111-116, wherein the step iv) comprises reacting the Compound 2010 with a deprotecting agent such as tetra-n-butylammonium fluoride (TBAF) to form the Compound 2011. 118. The method of any of embodiments 111-117, wherein the phosphite agent in the step v) has the following chemical structure: . embodiments 111-118, wherein the step vi) comprises reacting the Compound 2012 with an oxidizing agent such as meta-chloroperoxybenzoic acid (m- CPBA). 120. The method of any of embodiments 111-119, wherein the nucleotide base in the step vii) is adenine. 121. The method of any of embodiments 111-120, wherein the step viii) comprises reacting the Compound 2014 with an acid such as HCl to form the Compound 2015. 122. The method of any of embodiments 111-121, wherein the phosphate agent in the step ix) comprises H4P2O7.2NBu3. 1602179968.1 13 Attorney Docket No.: F2001-7001WO(VL99001-W1) 123. A method of making a compound, the method comprising performing one or more of (e.g., 2, 3, 4, 5, or all of) the following steps: a) converting the Compound 1008 into Compound 3009 comprising adding a nucleotide base into the tetrahydroselenophene ring of the Compound 1008; b) selectively removing one of the protecting groups of the Compound 3009 to release the free -OH group to form Compound 3010; c) reacting the free -OH group of the Compound 3010 with a phosphite agent to form Compound 3010E; d) oxidizing the phosphorus atom in the Compound 3010E to form Compound 3010F; e) removing the protecting groups in the Compound 3010F to form Compound 3010G; and f) reacting the Compound 3010G with a phosphate agent to form the Se modified Uridine triphosphate (ATP). 124. The method of embodiment 123, wherein the nucleotide base in the step a) is uracil. 125. The method of embodiment 123 or 124, wherein the step b) comprises reacting the Compound 3009 with a deprotecting agent such as tetra-n-butylammonium fluoride (TBAF) to form the Compound 3010. 126. The method of any of embodiments 123-125, wherein the phosphite agent in the step c) has the following chemical structure: . any of embodiments 123-126, wherein the step d) comprises reacting the Compound 3010E with an oxidizing agent such as meta-chloroperoxybenzoic acid (m- CPBA) to form the Compound 3010F. 128. The method of any of embodiments 123-127, wherein the step e) comprises reacting the Compound 3010F with an acid such as HCl to form the Compound 3010G. 129. The method of any of embodiments 123-128, wherein the phosphate agent in the step f) comprises H4P2O7.2NBu3. 1602179968.1 14 Attorney Docket No.: F2001-7001WO(VL99001-W1) 130. A method of making a compound, the method comprising performing one or more of (e.g., 2, 3, 4, 5, 6, or all of) the following steps: A) converting the Compound 1008 into Compound 4009 comprising adding a base molecule into the tetrahydroselenophene ring of the Compound 1008; B) selectively removing one of the protecting groups of the Compound 4009 to release one free -OH group to form Compound 4010; C) reacting the free -OH group of the Compound 4010 with a phosphite agent to form Compound 4011; D) oxidizing the phosphorus atom in the Compound 4011 to form Compound 4012; E) removing the protecting groups for the remaining two -OH groups in the Compound 4012 to form Compound 4013; F) reacting the Compound 4013 with a phosphate agent to form Compound 4014; and G) removing the protecting group from the base molecule of Compound 4014 to form the Se-modified Cytosine Triphosphate. 131. The method of embodiment 130, wherein the base molecule in the step A) is a Cytosine derivative. 132. The method of embodiment 130 or 131, wherein the Cytosine derivative has the following chemical structure: . of any of embodiments 130-132, wherein the step B) comprises reacting the Compound 4009 with a deprotecting agent such as tetra-n-butylammonium fluoride (TBAF) to form the Compound 4010. 134. The method of any of embodiments 130-133, wherein the phosphite agent in the step C) has the following chemical structure: 1602179968.1 15 Attorney Docket No.: F2001-7001WO(VL99001-W1) . 130-134, wherein the step D) comprises reacting the Compound 4011 with an oxidizing agent such as meta-chloroperoxybenzoic acid (m- CPBA). 136. The method of any of embodiments 130-135, wherein the step E) comprises reacting the Compound 4012 with an acid such as H3PO4to form the Compound 4013. 137. The method of any of embodiments 130-136, wherein the phosphate agent in the step F) comprises H4P2O7.2NBu3. 138. The method of any of embodiments 130-137, wherein the step G) comprises reacting the Compound 4014 with NH3.H2O. 139. A method of making a compound, the method comprising performing one or more of (e.g., 2, 3, 4, or all of) the following steps: I) selectively removing the protecting group in the Compound 1008 to form Compound 5010c; II) converting the Compound 5010c into Compound 5011d comprising adding a base molecule into the tetrahydroselenophene ring of the Compound 5010c; III) converting the Compound 5011d into Compound 5012; IV) protecting the free amine of nucleotide base in the Compound 5012 to thus form Compound 5013; and V) selectively removing the protecting group from the Compound 5013 to form Compound 5014. 140. The method of embodiment 139, wherein the step I) comprises reacting the Compound 1008 with an anhydride such as acetic anhydride to form the Compound 5010c. 141. The method of embodiment 139 or 140, wherein the base molecule in the step II) is a guanosine derivative. 1602179968.1 16 Attorney Docket No.: F2001-7001WO(VL99001-W1) 142. The method of embodiment 141, wherein the guanosine derivative has the following chemical structure: . any of embodiments 139-142, wherein the step III) comprises reacting the Compound 5011d with a mercaptoalcohol such as 2-mercaptoethanol to form the Compound 5012. 144. The method of any of embodiments 139-143, wherein the nucleotide base in the step IV) is guanosine. 145. The method of any of embodiments 139-144, wherein the step V) comprises reacting the Compound 5013 with an acid such as acetic acid (HOAc) to form the Compound 5014. 146. A method of making a compound, the method comprising performing one or more of (e.g., 2, 3, 4, or all of) the following steps: (1) removing the protecting group from the amine of the nucleotide base in the Compound 5014 to thus form Compound 5015; (2) protecting both free -OH and free amine groups in the Compound 5015 to form Compound 5016; (3) selectively removing the protecting group from one of the OH groups in the Compound 5016 to form Compound 5017; (4) reacting a single free -OH group of the Compound 5017 with a phosphite agent to form Compound 5018; and (5) removing all the protecting groups in the Compound 5018 to form a Se modified guanosine triphosphate (GTP). 147. The method of embodiment 146, wherein the step (1) comprises reacting the Compound 5014 with ammonia (NH3). 148. The method of embodiment 146 or 147, wherein the step (2) comprises reacting the Compound 5015 with acetyl halide such as acetyl chloride (CH3COCl) to form the Compound 5016. 1602179968.1 17 Attorney Docket No.: F2001-7001WO(VL99001-W1) 149. The method of any of embodiments 146-148, wherein the step (3) comprises reacting the Compound 5016 with a deprotecting agent such as tetra-n-butylammonium fluoride (TBAF) to form the Compound 5017. 150. The method of any of embodiments 146-149, wherein the phosphite agent in the step (4) comprises at least one of 2-chloro-4H-1,2,3-dioxaphosphorin-4-one and bis(tri-n- butylammonium)pyrophosphate. 151. The method of any of embodiments 146-150, wherein the step (5) comprises reacting the Compound 5018 with ammonia in water (NH3.H2O). Definitions As used herein, the term "antibody" refers to a molecule that specifically binds to, or is immunologically reactive with, a particular antigen and includes at least the variable domain of a heavy chain, and normally includes at least the variable domains of a heavy chain and of a light chain of an immunoglobulin. Antibodies and antigen-binding fragments, variants, or derivatives thereof include, but are not limited to, polyclonal, monoclonal, multispecific, human, humanized, primatized, or chimeric antibodies, heteroconjugate antibodies (e.g., bi- tri- and quad-specific antibodies, diabodies, triabodies, and tetrabodies), single-domain antibodies (sdAb), epitope- binding fragments, e.g., Fab, Fab' and F(ab')2, Fd, Fvs, single-chain Fvs (scFv), rlgG, single- chain antibodies, disulfide-linked Fvs (sdFv), nanobody, fragments including either a VL or VH domain, fragments produced by an Fab expression library, and anti-idiotypic (anti-Id) antibodies. Antibodies described herein can be of any type (e.g., IgG, IgE, IgM, IgD, IgA, and IgY), class (e.g., IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2) or subclass of immunoglobulin molecule. Moreover, unless otherwise indicated, the term "monoclonal antibody" (mAb) is meant to include both intact molecules as well as antibody fragments (such as, for example, Fab and F(ab')2 fragments) that are capable of specifically binding to a target protein. Fab and F(ab')2 fragments lack the Fc fragment of an intact antibody. As used herein, the term “carrier” means a compound, composition, reagent, or molecule that facilitates or promotes the transport or delivery of a composition (e.g., an RNA molecule described herein) into a cell. For example, a carrier may be a partially or completely encapsulating agent. 1602179968.1 18 Attorney Docket No.: F2001-7001WO(VL99001-W1) As used herein, the term “chemically modified ribonucleotide,” as used herein with respect to RNAs, refers to a ribonucleotide comprising one or more structural differences relative to the canonical ribonucleotides (i.e., G, C, A, and U). A chemically modified ribonucleotide may have (relative to a canonical ribonucleotide) a chemically modified nucleobase, a chemically modified sugar, a chemically modified phosphodiester linkage, or a combination thereof. No particular process of making is implied; for instance, a chemically modified ribonucleotide can be produced directly by chemical synthesis, or by covalently modifying a canonical ribonucleotide. As used herein, the term “nucleotide triphosphate” refers to a molecule comprising a nucleoside and three phosphate-containing groups. In some embodiments, one, two, or three of the phosphate-containing groups are phosphate groups (PO4). As used herein, the term “nucleoside” refers to a moiety comprising a sugar and a nucleobase. The nucleobase may be a canonical nucleobase or a chemically modified nucleobase. The sugar may be a canonical sugar or a chemically modified sugar. In some embodiments, the sugar is a pentose sugar, e.g., a ribose sugar. In some embodiments, the nucleoside is part of a nucleotide (e.g., a ribonucleotide). In some embodiments, the nucleoside is part of an RNA molecule. As used herein, the term “ribonucleoside” refers to a moiety comprising a sugar and a nucleobase, wherein the sugar comprises a moiety other than H at the 2’ position. In some embodiments, the ribonucleoside has -OH at the 2’ position. The nucleobase may be a canonical nucleobase or a chemically modified nucleobase. The sugar may be a canonical sugar or a chemically modified sugar. In some embodiments, the sugar is a pentose sugar, e.g., a ribose sugar. In some embodiments, the ribonucleoside is part of a ribonucleotide. In some embodiments, the ribonucleoside is part of an RNA molecule. As used herein, the term “phosphate containing group” refers to a moiety comprising a phosphate atom, wherein the moiety can bridge two nucleosides in an RNA molecule. In some embodiments, the phosphate containing group is a phosphate. In some embodiments, the phosphate group comprises a phosphorothioate bond. As used herein, the term “RNA molecule” refers to any compound and / or substance that comprises at least two (e.g., at least 10, at least 20, at least 50, at least 100) covalently linked ribonucleotides. In some embodiments, the RNA molecule is a single oligonucleotide chain, 1602179968.1 19 Attorney Docket No.: F2001-7001WO(VL99001-W1) while in other embodiments, the RNA molecule comprises a plurality of oligonucleotide chains, while in yet other embodiments the RNA molecule is a portion of an oligonucleotide chain. In some embodiments, the RNA molecule is a compound and / or substance that is or can be incorporated into an oligonucleotide chain via a phosphodiester linkage. In some embodiments, the RNA molecule comprises solely canonical ribonucleotides. In some embodiments, the RNA molecule comprises one or more chemically modified ribonucleotides. In some embodiments, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or 100% of the sugars of the RNA molecule are ribose sugars. In some embodiments, the RNA was prepared by one or more of: isolation from a natural source, enzymatic synthesis by polymerization based on a complementary template (in vivo or in vitro), reproduction in a recombinant cell or system, and chemical synthesis. As used herein, the term “heterologous”, when used to describe a first element in reference to a second element means that the first element and second element do not exist in nature disposed as described. For example, a heterologous polypeptide, nucleic acid molecule, construct or sequence refers to (a) a polypeptide, nucleic acid molecule or portion of a polypeptide or nucleic acid molecule sequence that is not native to a cell in which it is expressed, (b) a polypeptide or nucleic acid molecule or portion of a polypeptide or nucleic acid molecule that has been altered or mutated relative to its native state, or (c) a polypeptide or nucleic acid molecule with an altered expression as compared to the native expression levels under similar conditions. For example, a heterologous regulatory sequence may be used to regulate expression of a gene or a nucleic acid molecule in a way that is different than the gene or a nucleic acid molecule is normally expressed in nature. In another example, a heterologous domain of a polypeptide or nucleic acid sequence (e.g., a DNA binding domain of a polypeptide or nucleic acid encoding a DNA binding domain of a polypeptide) may be disposed relative to other domains or may be a different sequence or from a different source, relative to other domains or portions of a polypeptide or its encoding nucleic acid. In certain embodiments, a heterologous nucleic acid molecule may exist in a native host cell genome, but may have an altered expression level or have a different sequence or both. In other embodiments, heterologous nucleic acid molecules may not be endogenous to a host cell or host genome but instead may have been introduced into a host cell by transformation (e.g., transfection, electroporation), wherein the added molecule may integrate into the host genome or can exist as extra-chromosomal genetic 1602179968.1 20 Attorney Docket No.: F2001-7001WO(VL99001-W1) material either transiently (e.g., mRNA) or semi-stably for more than one generation (e.g., episomal viral vector, plasmid or other self-replicating vector). As used herein, the term “heterologous functional sequence” refers to a nucleic acid sequence that is heterologous to an adjacent (e.g., directly adjacent) nucleic acid sequence and has one or more biological function. As used herein, the terms "increasing" and "decreasing" refer to modulating resulting in, respectively, greater or lesser amounts, of function, expression, or activity of a metric relative to a reference. For example, subsequent to administration of a RNA molecule in a method described herein, the amount of the metric described herein (e.g., the level of gene expression) may be increased or decreased in a subject by at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95% or at least 98% or more relative to the amount of the marker prior to administration, or relative to administration of a control RNA molecule. Generally, the metric is measured subsequent to administration at a time that the administration has had the recited effect, e.g., at least one day, at least one week, at least one month, at least 3 months, or at least 6 months, after a treatment regimen has begun. As used herein, a "pharmaceutical composition" or "pharmaceutical preparation" is a composition or preparation which is indicated for animal, e.g., human or veterinary pharmaceutical use, for example, non-human animal or human prophylactic or therapeutic use. A pharmaceutical preparation comprises an active agent having a biological effect on a cell or tissue of a subject, e.g., having pharmacological activity or an effect in the mitigation, treatment, or prevention of disease, in combination with a pharmaceutically acceptable excipient or diluent. A pharmaceutical composition also means a finished dosage form or formulation of a prophylactic or therapeutic composition. As used herein, the terms “peptide,” “polypeptide,” and “protein” are used interchangeably and refer to a compound comprising amino acid residues covalently linked by peptide bonds, or by means other than peptide bonds. A protein or peptide must contain at least two amino acids, and no limitation is placed on the maximum number of amino acids that can comprise a protein’s or peptide’s sequence. Polypeptides include any peptide or protein comprising two or more amino acids joined to each other by peptide bonds or by means other 1602179968.1 21 Attorney Docket No.: F2001-7001WO(VL99001-W1) than peptide bonds. As used herein, the term refers to both short chains, which also commonly are referred to in the art as peptides, oligopeptides and oligomers, for example, and to longer chains, which generally are referred to in the art as proteins, of which there are many types. In some embodiments, a polypeptide comprises a non-canonical amino acid residue. As used herein, "treatment" and "treating" refer to the medical management of a subject with the intent to improve, ameliorate, stabilize (i.e., not worsen), prevent or cure a disease, pathological condition, or disorder. This term includes active treatment (treatment directed to improve the disease, pathological condition, or disorder), causal treatment (treatment directed to the cause of the associated disease, pathological condition, or disorder), palliative treatment (treatment designed for the relief of symptoms), preventative treatment (treatment directed to minimizing or partially or completely inhibiting the development of the associated disease, pathological condition, or disorder); and supportive treatment (treatment employed to supplement another therapy). Treatment also includes diminishment of the extent of the disease or condition; preventing spread of the disease or condition; delay or slowing the progress of the disease or condition; amelioration or palliation of the disease or condition; and remission (whether partial or total), whether detectable or undetectable. "Ameliorating" or "palliating" a disease or condition means that the extent and / or undesirable clinical manifestations of the disease, disorder, or condition are lessened and / or time course of the progression is slowed or lengthened, as compared to the extent or time course in the absence of treatment. "Treatment" can also mean prolonging survival as compared to expected survival if not receiving treatment. Those in need of treatment include those already with the condition or disorder, as well as those prone to have the condition or disorder or those in which the condition or disorder is to be prevented. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a schematic of the synthetic scheme used to generate the precursor for the selenoribonucleotides. For all selenoribonucleotides tested, the synthetic scheme used to generate Compounds 1007 and 1008 is identical. The Se=O in compound 1008 may be shown as a double bond, as in FIG.1, or as a dipole arrow between the Se and O, as in FIGs 2, 3, 4, and 12A. FIG.2 is a schematic of the synthetic scheme to generate SeATP. The starting material for this synthesis can be generated by the synthetic scheme shown in FIG.1. 1602179968.1 22 Attorney Docket No.: F2001-7001WO(VL99001-W1) FIG.3 is a schematic of the synthetic scheme to generate SeUTP. The starting material for this synthesis can be generated by the synthetic scheme shown in FIG.1. FIG.4 is a schematic of the synthetic scheme to generate SeCTP. The starting material for this synthesis can be generated by the synthetic scheme shown in FIG.1. FIG.5A is the 1H NMR spectrum of the Se-modified uridine phosphoramidite, which was synthesized according to Example 6 and as shown in FIG.5B. FIG.5B is a schematic of the synthetic scheme used to generate Se-modified uridine phosphoramidite, for use in automated oligonucleotide synthesis of poly-SeU oligonucleotides. FIG.6A is a graph showing the time-course of the proportion of full-length 75% Se- modified RNA and, as a control, the proportion of full-length unmodified RNA, when exposed to the 5’-3’ exonuclease XRN-1. The RNA used here is HiBiT mRNA as described in Example 5. The 75% Se-modified RNA sustains a higher proportion of full-length RNA compared to the unmodified control over the course of the reaction. FIG.6B is a graph showing the time-course of the proportion of full-length 100% Se- modified RNA and, as a control, the proportion of full-length unmodified RNA when exposed to the 3’-5’ exonuclease ExoT. The RNA used here is Se-modified uridine homopolymer as described in Example 6, or unmodified uridine homopolymer as a control. The 100% Se- modified RNA sustains a higher proportion of full-length RNA compared to the unmodified control over the course of the reaction. FIG.7A is a graph showing the time-course of the proportion of full-length 75% Se- modified RNA and, as a control, the proportion of full-length unmodified RNA, when exposed to bovine RNase A, which is an endonuclease. The RNA used here is HiBiT mRNA as described in Example 5. The 75% Se-modified RNA sustains a higher proportion of full-length RNA compared to the unmodified control over the course of the reaction. FIG.7B is a graph showing the time-course of the proportion of full-length 100% Se- modified RNA and, as a control, the proportion of full-length unmodified RNA, when exposed to bovine RNase A. The RNA used here is Se-modified uridine homopolymer as described in Example 6, or unmodified uridine homopolymer. The 100% Se-modified RNA sustains a higher proportion of full-length RNA compared to the unmodified control over the course of the reaction. 1602179968.1 23 Attorney Docket No.: F2001-7001WO(VL99001-W1) FIG.8 is a graph showing the time-course of the proportion of full-length 75% Se- modified RNA and, as a control, the proportion of full-length unmodified RNA when incubated in 0.08% fetal bovine serum (FBS). The RNA used here is HiBiT mRNA as described in Example 5. The 75% Se-modified RNA sustains a higher proportion of full-length RNA compared to the unmodified control over the course of the reaction. FIG.9 is a graph showing the time-course of the proportion of full-length 75% Se- modified RNA and, as a control, the proportion of full-length unmodified RNA when incubated in a solution containing 5 mM magnesium chloride and 5 mM sodium hydroxide. The RNA used here is HiBiT mRNA as described in Example 5. The 75% Se-modified RNA sustains a higher proportion of full-length RNA compared to the unmodified control over the course of the reaction. FIG.10 is a graph showing the luminescence detected 48 hours post-transfection of Huh- 7 cells with HiBiT reporter mRNA. Both unmodified and 75% Se-modified RNA show luminescence, indicating that the 4’Se modification still allows for functional protein translation. FIG.11 is a graph showing the luminescence detected 48 hours post-transfection of Huh- 7 cells with secreted NLuc reporter mRNA. Both unmodified and 25% Se-modified RNA (incorporating either Se-ATP or Se-UTP) show luminescence, indicating that the 4’Se modification still allows for functional protein translation. FIGs.12A and 12B are schematics of the synthetic scheme used to generate SeGTP. The starting material for this synthesis can be generated by the synthetic scheme shown in FIG.1. DETAILED DESCRIPTION This disclosure relates to compositions and methods for providing an effector, e.g., a therapeutic effector, to a cell, tissue or subject, e.g., in vivo or in vitro. The effector may be a polypeptide, e.g., a therapeutic protein, or an RNA. Chemically modified RNA molecules This disclosure provides, for example, RNAs comprising selenoribonucleotides and selenoribonucleosides. In some aspects, the present disclosure provides: an RNA molecule comprising a plurality of nucleosides, wherein at least one nucleoside of the RNA molecule comprises a sugar having a 5-member ring comprising four carbons and one selenium, wherein 1602179968.1 24 Attorney Docket No.: F2001-7001WO(VL99001-W1) the selenium is bound to the 4’ carbon and the 1’ carbon of the sugar. In some embodiments, the nucleoside has OH, OMe, or F at the 2’ carbon of the sugar. In some aspects, the present disclosure provides: an RNA molecule comprising a plurality of nucleosides, wherein: at least one nucleoside of the RNA molecule comprises a structure according to Formula (I): , than hydrogen, and B is a nucleobase. A selenoribose may also be used with an abasic site. Consequently, in some aspects, the present disclosure provides an RNA molecule comprising a plurality of nucleosides, wherein: at least one nucleoside of the RNA molecule comprises a structure according to Formula (I): , or F; and B is a nucleobase or hydrogen. In some embodiments, the RNA molecule has a length of at least 20 nucleosides. In some embodiments, the RNA molecule comprises an effector sequence that encodes an effector (e.g., a therapeutic effector). In some embodiments, in the portion of the mRNA molecule excluding the polyA tail, at least 10%, at least 20%, at least 25%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 90%, or at least 99% of the nucleosides each independently comprises a structure according to Formula (I). In some embodiments, the RNA molecule comprises at least 1, at least 2, at least 5, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 50, at least 1602179968.1 25 Attorney Docket No.: F2001-7001WO(VL99001-W1) 60, at least 70, or at least 80 nucleosides each independently comprising a structure according to Formula (I). In some embodiments, the RNA molecule comprises at least 1, at least 2, at least 5, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, or at least 40 adenosine nucleosides each independently comprising a structure according to Formula (I). In some embodiments, the RNA molecule comprises at least 1, at least 2, at least 5, at least 10, at least 15, or at least 20 cytosine nucleosides each independently comprising a structure according to Formula (I). In some embodiments, the RNA molecule comprises at least 1, at least 2, at least 5, at least 10, at least 15, or at least 20 uridine nucleosides each independently comprising a structure according to Formula (I). The RNA molecules comprising selenoribonucleosides may further comprise other chemical modifications. For instance, the RNA molecules may have chemical modifications of the nucleobases, sugars, and / or the phosphate backbone. While not wishing to be bound by theory, such modifications can be useful for protecting an RNA molecule from degradation (e.g., from exonucleases, endonucleases, or non-enzymatic degradation). Typically, a chemically modified nucleobase maintains the same base pairing activity as its canonical counterpart; for example, a codon comprising a chemically modified version of an adenine nucleobase would pair with the same tRNA as an otherwise similar codon that contained a canonical adenine in place of the chemically modified version of the adenine. In some embodiments, the RNA molecule comprises one or more (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or more) modified nucleobases. In some embodiments, all nucleobases of the RNA molecule are modified. In some embodiments, the RNA molecule is modified at one or more (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or more) positions in the backbone. In some embodiments, all backbone positions of the RNA molecule are modified. In some embodiments, the RNA molecule comprises one or more modified nucleobases (or nucleotides or nucleosides comprising modified nucleobases) such as dihydrouracil, inosine, 5-methylcytidine (5mC), 3-methylcytosine (m3C); 5-methyl uridine, 5-methyl m-cytidine, 5- methyl m-uridine, C-5 propynyl-cytidine (pC), C-5 propynyl-uridine (pU), C-5 propynyl-f- cytidine (pfC), C-5 propynyl-f-uridine (pfU), 5-methyl f-cytidine, 5-methyl f-uridine, C-5 propynyl-m-cytidine (pmC), C-5 propynyl-f-uridine (pmU), 2,6-diaminopurine, pseudouridine (Ψ), 1-N-methylpseudouridine (1-Me-Ψ), 5-methoxyuridine (5-MO-U), N6-Methyladenosine 1602179968.1 26 Attorney Docket No.: F2001-7001WO(VL99001-W1) (m6A, 6mA); 5-formylcytosine, 5-carboxylcytosine, 5-hydroxymethylcytosine, 5- glucosylmethylcytosine; 5-methyl pyrimidine; 8-oxoguanine (8-oxoG), or 7-methylguanine. One or more atoms of a pyrimidine nucleobase may be replaced or substituted with optionally substituted amino, optionally substituted thiol, optionally substituted alkyl (e.g., methyl or ethyl), or halo (e.g., chloro or fluoro). In some embodiments, an RNA molecule as described herein may comprise a phosphorothioate-modified nucleotide. In some embodiments, the RNA molecule described herein may include S and R phosphorothioate modified nucleotide linkages. In some embodiments, an RNA molecule described herein may include a boranophosphate modified nucleotide. Boranophosphate modified nucleotides are commercially available. An RNA described herein (e.g., an mRNA) may comprise a cap, such as a canonical cap or a chemically modified cap. In some embodiments, the RNA molecule comprises one or more type of modified nucleobase and one or more type of backbone modification; one or more type of modified nucleobase and one or more modified cap; one or more type of modified cap and one or more type of backbone modification; or one or more type of modified nucleobase, one or more type of backbone modification, and one or more type of modified cap. In embodiments, an RNA molecule described herein comprises between 1-100% chemically modified nucleotides, between 1%-90% chemically modified nucleotides, between 1%-80% chemically modified nucleotides, between 1%-70% chemically modified nucleotides, between 1%-60% chemically modified nucleotides, between 1%-50% chemically modified nucleotides, between 1%-40% chemically modified nucleotides, between 1%-30% chemically modified nucleotides, between 1%-20% chemically modified nucleotides, between 1%-15% chemically modified nucleotides, between 1%-10% chemically modified nucleotides, between 20%-90% chemically modified nucleotides, between 20%-80% chemically modified nucleotides. In embodiments, an RNA molecule described herein, or one strand comprises at least 1% chemically modified nucleotides, at least 5% chemically modified nucleotides; at least 10% chemically modified nucleotides; at least 15% chemically modified nucleotides; at least 20% chemically modified nucleotides; at least 25% chemically modified nucleotides; at least 30% chemically modified nucleotides; at least 40% chemically modified nucleotides; at least 50% chemically modified nucleotides; at least 60% chemically modified nucleotides; at least 70% chemically modified nucleotides; at least 80% chemically modified nucleotides; at least 85% 1602179968.1 27 Attorney Docket No.: F2001-7001WO(VL99001-W1) chemically modified nucleotides; at least 90% chemically modified nucleotides; at least 92% chemically modified nucleotides; at least 95% chemically modified nucleotides; at least 97% chemically modified nucleotides. In embodiments, an RNA molecule described herein, or one strand comprises chemically modified nucleotides at between 0%-100% of each distinct nucleotide, e.g., 0%-100% chemically modified U nucleotides, 0%-100% chemically modified A nucleotides, 0%-100% chemically modified C nucleotides, and 0%-100% chemically modified G nucleotides for each construct. In embodiments, an RNA molecule described herein comprises chemically modified nucleotides at between 0-100%, 10%-100%, 20%-100%, 30%-100%, 40%- 100%, 50%-100%, 60%-100%, 10%-50% of each distinct nucleotide, e.g., between 0-100%, 10%-100%, 20%-100%, 30%-100%, 40%-100%, 50%-100%, 60%-100%, 10%-50% of chemically modified U nucleotides; between 0-100%, 10%-100%, 20%-100%, 30%-100%, 40%- 100%, 50%-100%, 60%-100%, 10%-50% of chemically modified A nucleotides; between 0- 100%, 10%-100%, 20%-100%, 30%-100%, 40%-100%, 50%-100%, 60%-100%, 10%-50% of chemically modified C nucleotides; or between 0-100%, 10%-100%, 20%-100%, 30%-100%, 40%-100%, 50%-100%, 60%-100%, 10%-50% of chemically modified G nucleotides. For example, an RNA molecule could contain 100% chemically modified U nucleotides, 50% chemically modified A nucleotides, 0% chemically modified C nucleotides, and 25% chemically modified G nucleotides. In embodiments, chemically modified nucleotides, e.g., modifications described herein, can be introduced in the RNA molecules described herein throughout the entire sequence; within an element of a sequence, e.g., an element described herein; at a 5'- or 3'- end; and / or at the last 10, 8, 6, 5, 4, 3, or 2 nucleotides at the 5’- or 3’- end. Structural elements of RNA molecules In some embodiments, the RNA molecule is linear and single stranded. In some embodiments, the RNA molecule comprises two free ends. In some embodiments, the RNA molecule is a circular single-stranded RNA, in which the RNA lacks a free end. A circular RNA may be covalently closed or may form a closed structure without free RNA ends through non-covalent interactions, e.g., the RNA may be closed through a splint, e.g., a nucleic acid (e.g., DNA or RNA) splint, through a moiety such as a protein that binds and brings together both ends of a linear RNA, or through binding of a plurality of 1602179968.1 28 Attorney Docket No.: F2001-7001WO(VL99001-W1) proteins, each of two of the plurality binding to a different RNA end, and then binding to each other or a third moiety to close the RNA structure. In the case of circular RNA, the term circular does not imply that the RNA structure lacks all intramolecular structure; rather, a circular RNA may have short regions of intramolecular double stranded regions or other structures. An RNA molecule being single stranded does not imply that it is entirely devoid of any intramolecular base pairing. In some embodiments, a single-stranded RNA molecule described herein may have less than a threshold level of intramolecular complementarity or double stranded structures. In some embodiments, the single stranded RNA molecule does not comprise more than 10, more than 8, more than 7, more than 5, more than 4, more than 3, more than 2, or more than 1 double stranded region longer than 20, longer than 15, longer than 10, or longer than 5 base pairs. In some embodiments, the single stranded RNA molecule does not comprise more than 10, more than 8, more than 7, more than 5, more than 4, more than 3, more than 2, or more than 1 double stranded region longer than 20 base pairs. In some embodiments, the single stranded RNA molecule does not comprise any regions of intramolecular complementarity longer than 20, longer than 15, longer than 10, or longer than 5 base pairs. In some embodiments, the single stranded RNA molecule does not comprise any regions of intramolecular complementarity longer than 20 base pairs. In some embodiments, the single stranded RNA molecule comprises 1, 2, 3, 4, 5, 7, 8, or 10 double stranded regions, e.g., wherein the double stranded regions are no more than 20, no more than 15, no more than 10, or no more than 5 base pairs. In some embodiments, the single-stranded RNA molecule does not form a double stranded structure longer than 20 base pairs. In some embodiments, the single-stranded RNA molecule does not comprise a first sequence that hybridizes with a second sequence, wherein the first sequence and the second sequence are at least 5, at least 10, at least 15, at least 20, or at least 25 nt long, and wherein the first sequence and the second sequence are positioned less than 6, less than 5, less than 4, less than 3, less than 2, or less than 1 nucleotides apart from each other. In some embodiments, the RNA is double stranded. The RNA may be double stranded and circular. The RNA may be double stranded and linear. In some embodiments, the RNA molecule has a GC content of 30-40%, 40-50%, 50- 60%, or 60-70%. In some embodiments, the RNA molecule lacks a viral packaging site, or wherein the RNA molecule does not encode a viral capsid gene. 1602179968.1 29 Attorney Docket No.: F2001-7001WO(VL99001-W1) In some embodiments, an RNA molecule disclosed herein is at least about 15 nucleotides, at least about 20 nucleotides, at least about 30 nucleotides, at least about 40 nucleotides, at least about 50 nucleotides, at least about 75 nucleotides, or at least about 100 nucleotides in length. In some embodiments, the RNA disclosed herein is between 20-30, 30-40, 40-50, 50-75, or 75-100 nucleotides in length. In some embodiments, the size of an RNA molecule disclosed herein is a length sufficient to encode useful polypeptides. In some embodiments, 80%, 85%, 90%, 95%, 98%, 99%, or 100% of the sugars of an RNA molecule described herein comprise -OH at their 2’ position. In some embodiments, an RNA molecule described herein is recognized by a ribosome. In some embodiments, an RNA molecule described herein is translated, e.g., in a cell or a lysate. In an embodiment, the single stranded RNA molecule is a sense strand. In an embodiment, the single stranded RNA molecule is an antisense strand. mRNAs In some embodiments, an RNA molecule that comprises a selenoribonucleoside is a messenger RNA (mRNA). Typically, an mRNA has sufficient elements to be recognized by a ribosome and direct translation of a polypeptide. In some embodiments, the mRNA comprises a cap. In some embodiments, the mRNA comprises a polyA tail situated 3’ of the effector sequence. A 5’ cap may be canonical or chemically modified. In some embodiments, the mRNA comprises one or more of ARCA: anti-reverse cap analog (m27.3´-OGP3G), GP3G (Unmethylated Cap Analog), m7GP3G (Monomethylated Cap Analog), m32.2.7GP3G (Trimethylated Cap Analog), m5CTP (5´-methyl-cytidine triphosphate), m6ATP (N6-methyl- adenosine-5´-triphosphate), s2UTP (2-thio-uridine triphosphate), Ѱ (pseudouridine triphosphate), a hypermethylated cap analog; an NAD+-derived cap analog (e.g., as described in Kiledjian, Trends in Cell Biology 28, 454-464 (2018)); or a modified, e.g., biotinylated, cap analog (e.g., as described in Bednarek et al., Phil Trans R Soc B 373, 20180167 (2018)). In some embodiments, the mRNA comprises a 7-methylguanosine cap (e.g., a O-Me- m7G cap). 1602179968.1 30 Attorney Docket No.: F2001-7001WO(VL99001-W1) In some embodiments, the mRNA comprises a 3’ polyA tail. In some embodiments, the 3’ polyA tail has a length of 50-100, 100-200, or 200-300 ribonucleotides. In some embodiments, the nucleobases in the 3’ polyA tail are exclusively adenine. Sequence elements of RNA molecules In some embodiments, an RNA molecule described herein comprises an effector sequence. The effector sequence may either encode an effector (e.g., a polypeptide) or may itself be a functional RNA sequence. In some embodiments, an RNA molecule described herein comprises a heterologous functional sequence. In some embodiments, the RNA molecule comprises both of an effector sequence and a heterologous functional sequence. In some embodiments, the effector sequence encodes a polypeptide (e.g., a protein). In some embodiments, the effector sequence comprises a functional RNA (e.g., a miRNA, siRNA, or tRNA). In some embodiments, the effector sequence comprises a self amplifying RNA (saRNA). In some embodiments, the effector sequence is heterologous to a target cell. The RNA molecule described herein may also include other native or heterologous expression control elements, such as a polyA tail or Kozak consensus sequences. Effector sequence The effector sequence of an RNA molecule described herein may be, e.g., a functional RNA sequence, e.g., a therapeutically functional RNA sequence; or a RNA sequence encoding a therapeutic peptide, polypeptide or protein. In embodiments, the RNA molecule can include a plurality of effector sequences. The plurality may be the same or different types, e.g., an RNA molecule can include an effector sequence that is a structural RNA and a second effector sequence that is an RNA sequence encoding a functional RNA or polypeptide. In some embodiments, the RNA comprises a second effector sequence which is the same as or different than the first effector sequence. An RNA molecule can include an effector sequence that is a functional RNA and a second effector sequence that is an RNA sequence encoding a functional polypeptide. The plurality of effector sequences may be the same or different sequences of the same type. 1602179968.1 31 Attorney Docket No.: F2001-7001WO(VL99001-W1) Polypeptide effectors An RNA sequence encoding a therapeutic polypeptide may be an RNA sequence encoding one or more effectors which is a peptide, protein, or combinations thereof. For example, the RNA sequence is an mRNA. The peptide or protein may be: a DNA binding protein; an RNA binding protein; a transporter; a transcription factor; a translation factor; a ribosomal protein; a chromatin remodeling factor; an epigenetic modifying factor; an antigen; a hormone; an enzyme (such as a nuclease, e.g., an endonuclease, e.g., a nuclease element of a CRISPR system, e.g., a Cas9, dCas9, aCas9-nickase, Cpf / Cas12a); a CRISPR-linked enzyme, e.g. a base editor or prime editor; a mobile genetic element protein (e.g., a transposase, a retrotransposase, a recombinase, an integrase); a gene writer; a polymerase; a methylase; a demethylase; an acetylase; a deacetylase; a kinase; a phosphatase; a ligase; a deubiquitinase; a protease; an integrase; a recombinase; a topoisomerase; a gyrase; a helicase; a lysosomal acid hydrolase); an antibody (e.g., an intact antibody, a fragment thereof, or a nanobody); a signaling peptide; a receptor ligand; a receptor; a clotting factor; a coagulation factor; a structural protein; a caspase; a membrane protein; a mitochondrial protein; a nuclear protein; or an engineered binder such as a centyrin, darpin, or adnectin. In some embodiments, the peptide or protein may be an interleukin, a cytokine, or a chemokine. See, e.g., Gebauer & Skerra.2020. Annual Review of Pharmacology and Toxicology 60:1, 391-415. In embodiments, an RNA molecule described herein may include one or a plurality of sequences encoding a polypeptide. Each of the plurality may encode the same or different protein. For example, a sequence described herein may include multiple sequences encoding multiple proteins, e.g., a plurality of proteins in a biological pathway. In some embodiments, an RNA molecule or sequence described herein may include a plurality of sequences encoding a polypeptide, separated by a self-cleaving peptide, e.g., P2A, T2A, E2A or F2A. Self-cleaving peptides are 18-22 amino acids long, and can induce ribosomal skipping during protein translation so that two polypeptides can be encoded in the same transcript. Each of the polypeptides may encode the same or different protein. In one embodiment, an RNA molecule or sequence described herein may include a sequence encoding a first polypeptide of interest, followed by a sequence encoding a 2A self-cleaving peptide, a sequence encoding a second polypeptide of interest, and a polyA tail. 1602179968.1 32 Attorney Docket No.: F2001-7001WO(VL99001-W1) In some embodiments, the effector comprises a cell penetrating polypeptide. In some embodiments, the effector is a fusion protein that comprises a cell penetrating polypeptide and a second amino acid sequence. In some embodiments, the RNA molecule does not comprise a cell penetrating polypeptide. For example, in some embodiments, the RNA molecule does not comprise a fusion protein that comprises a cell penetrating polypeptide. In some embodiments, an effector described herein comprises an immunogen. In some embodiments, an effector described herein comprises a viral antigen, a bacterial antigen, a fungal antigen, or a tumor antigen. In some embodiments, an effector described herein comprises a peptide antigen. In some embodiments, a composition described herein is administered to a subject as a vaccine. In some aspects, the present disclosure provides a method of vaccinating a subject, comprising administering to the subject a composition described herein. In some embodiments, the effector sequence that encodes a polypeptide or protein is codon optimized, e.g., codon optimized for expression in a mammal, e.g., a human. In general, codon optimization means modifying a nucleic acid sequence for enhanced expression in the host cells of interest by replacing at least one codon (e.g., at least 1%, at least 5%, at least 10%, at least 20%, at least 25%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90% or 100%) of the native sequence with codons that are more frequently or most frequently used in the genes of that host cell while maintaining the native amino acid sequence. Codon usage tables are available, for example, at the "Codon Usage Database" available at kazusa.or.jp / codon / . These tables can be adapted in a number of ways, see, e.g., Nakamura et al., 2000, Nucl. Acids Res.28:292. Computer algorithms for codon optimizing a particular sequence for expression in a particular host cell are also available, such as Gene Forge. RNA effector sequences In some embodiments, the effector sequence forms a functional RNA. For example, as described in more detail below, the effector sequence may comprise a tRNA, gRNA, ribozyme, or aptamer. In some embodiments, the effector comprises an allele-specific oligonucleotide (an RNA ASO). In some embodiments, the effector sequence comprises a saRNA. An effector sequence may be an RNA sequence comprising a non-coding RNA, e.g., one or more of a short interfering RNA (siRNA), a microRNA (miRNA), a piwi-interacting RNA (piRNA), a small nucleolar RNA (snoRNA), a small Cajal body-specific RNA (scaRNA), a 1602179968.1 33 Attorney Docket No.: F2001-7001WO(VL99001-W1) transfer RNA (tRNA), a ribosomal RNA (rRNA), an RNA aptamer, and a small nuclear RNA (snRNA). In some embodiments, the RNA molecule disclosed herein comprises a regulatory RNA, e.g., an RNA that modifies expression of an endogenous gene and / or an exogenous gene. In some embodiments, the RNA molecule disclosed herein can comprise a sequence that is antisense to a regulatory nucleic acid like a non-coding RNA, such as, but not limited to, tRNA, lncRNA, miRNA, rRNA, snRNA, microRNA, siRNA, piRNA, snoRNA, snRNA, exRNA, scaRNA, Y RNA, and hnRNA. In one embodiment, the regulatory nucleic acid targets a host gene. A regulatory nucleic acid may include, but is not limited to, a nucleic acid that hybridizes to an endogenous gene, e.g., an antisense RNA, a guide RNA, a nucleic acid that hybridizes to an exogenous nucleic acid such as a viral DNA or RNA, nucleic acid that hybridizes to an RNA, nucleic acid that interferes with gene transcription, nucleic acid that interferes with RNA translation, nucleic acid that stabilizes RNA or destabilizes RNA such as through targeting for degradation, and nucleic acid that modulates a DNA or RNA binding factor. In one embodiment, the sequence is an miRNA. In some embodiments, the regulatory nucleic acid targets a sense strand of a host gene. In some embodiments, the regulatory nucleic acid targets an antisense strand of a host gene. An RNA molecule disclosed may comprise certain regulatory nucleic acids that can inhibit gene expression through the biological process of RNA interference (RNAi). RNAi molecules comprise RNA or RNA-like structures typically containing 15-50 base pairs (such as about 18-25 base pairs) and having a nucleobase sequence identical (complementary) or nearly identical (substantially complementary) to a coding sequence in an expressed target gene within the cell. Such RNAi molecules include, but are not limited to: short interfering RNAs (siRNAs), double-strand RNAs (dsRNA), micro RNAs (miRNAs), short hairpin RNAs (shRNA), meroduplexes, dicer substrates (U.S. Pat. Nos.8,084,5998,349,809 and 8,513,207), and RNA antisense oligonucleotides (RNA ASOs). The RNA molecule disclosed herein may comprise a regulatory nucleic acid substantially complementary, or fully complementary, to a fragment of an endogenous gene or gene product (e.g., mRNA). The regulatory nucleic acids may complement sequences at the boundary between introns and exons, in between exons, or adjacent to exon, to prevent the maturation of newly- generated nuclear RNA transcripts of specific genes into mRNA for transcription. The regulatory 1602179968.1 34 Attorney Docket No.: F2001-7001WO(VL99001-W1) nucleic acids that are complementary to specific genes can hybridize with the mRNA for that gene and prevent its translation. In some embodiments, the regulatory nucleic acid comprises a protein-binding site that can bind to a protein that participates in regulation of expression of an endogenous gene or an exogenous gene. The length of an RNA molecule disclosed herein that may comprise a regulatory nucleic acid that hybridizes to a transcript of interest and may be, for instance, between about 5 to 30 nucleotides, between about 10 to about 30 nucleotides, or about 11, about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, about 25, about 26, about 27, about 28, about 29, about 30 or more nucleotides. The degree of identity of the regulatory nucleic acid to the targeted transcript should be at least 75%, at least 80%, at least 85%, at least 90%, or at least 95%. An RNA molecule disclosed herein may comprise a micro-RNA (miRNA) molecule identical to about 5 to about 30 contiguous nucleotides of a target gene. In some embodiments, the miRNA sequence targets a mRNA and commences with the dinucleotide AA, comprises a GC-content of about 30-70% (about 30-60%, about 40-60%, or about 45%-55%), and does not have a high percentage identity to any nucleotide sequence other than the target in the genome of the mammal in which it is to be introduced, for example as determined by standard BLAST search. In some embodiments, the RNA molecule disclosed herein encodes at least one miRNA, e.g., 2, 3, 4, 5, 6, or more. In some embodiments, the RNA molecule disclosed herein comprises a sequence that encodes an miRNA having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or 100% nucleotide sequence identity to any one of the nucleotide sequences or a sequence that is complementary to a target sequence. Lists of known miRNA sequences can be found in databases maintained by research organizations, such as Wellcome Trust Sanger Institute, Penn Center for Bioinformatics, Memorial Sloan Kettering Cancer Center, and European Molecule Biology Laboratory, among others. Known effective siRNA sequences and cognate binding sites are also well represented in the relevant literature. RNAi molecules are readily designed by technologies known in the art. In addition, there are computational tools that increase the chance of finding effective and specific sequence motifs (see, e.g., Lagana et al., Methods Mol. Bio., 2015, 1269:393-412). 1602179968.1 35 Attorney Docket No.: F2001-7001WO(VL99001-W1) The RNA molecule disclosed herein may modulate expression of RNA encoded by a gene. Because multiple genes can share some degree of sequence homology with each other, in some embodiments, the RNA molecule disclosed herein can be designed to target a class of genes with sufficient sequence homology. In some embodiments, the RNA molecule disclosed herein can contain a sequence that has complementarity to sequences that are shared amongst different gene targets or are unique for a specific gene target. In some embodiments, the RNA molecule disclosed herein can be designed to target conserved regions of an RNA sequence having homology between several genes thereby targeting several genes in a gene family (e.g., different gene isoforms, splice variants, mutant genes, etc.). In some embodiments, the RNA molecule disclosed herein can be designed to target a sequence that is unique to a specific RNA sequence of a single gene. In embodiments, the effector sequence comprising a regulatory RNA has a length less than 200 nucleotides, less than 100 nucleotides, less than 50 nucleotides, less than 40 nucleotides, less than 30 nucleotides, less than 20 nucleotides, less than 10 nucleotides, or less). In some embodiments, the effector sequence has, independently or in addition to, a length greater than 10 nucleotides (e.g., at least about 10 nucleotides, at least about 20 nucleotides, at least about 30 nucleotides, at least about 40 nucleotides, at least about 50 nucleotides, at least about 60 nucleotides, at least about 70 nucleotides, at least about 80 nucleotides, at least about 90 nucleotides, at least about 100 nucleotides, or greater). In embodiments, an RNA molecule described herein may include one or a plurality of functional RNA sequences, e.g., 2, 3, 4, 5, 6, or more sequences, which may be the same or different. In some embodiments, an RNA molecule disclosed herein comprises one or more of the features described herein, e.g., one or more structural RNA sequences, a sequence encoding one or more peptides or proteins, a sequence encoding one or more regulatory element, a sequence comprising one or more regulatory nucleic acids, e.g., one or more non-coding RNAs, other expression sequences, and any combination of the aforementioned. A construct described herein may have one or a plurality of effector sequences. In the case of a plurality of effector sequences in a single construct, the effector sequences may be the same or different. 1602179968.1 36 Attorney Docket No.: F2001-7001WO(VL99001-W1) tRNAs In some embodiments, the effector sequence comprises a transfer RNA (tRNA). Typically, a tRNA comprises an anticodon that can base pair with a codon in mRNA. In some embodiments, the codon is a start codon, a stop codon, or a codon that encodes an amino acid. The tRNA may comprise an amino acid (e.g., a canonical amino acid or a chemically modified amino acid). In some embodiments, the amino acid is covalently linked to the 3’ end of the tRNA. A tRNA is typically 76 to 90 nucleotides in length. The tRNA may comprise an acceptor stem, TΨC loop, variable loop, anticodon loop, and D loop. Th tRNA may comprise a CCA tail at its 3’ end. In some embodiments, the tRNA has a wild-type nucleotide sequence of a human tRNA, and in other embodiments, the tRNA may have one or more sequence differences relative to the closest wild-type human tRNA nucleotide sequence. gRNAs In some embodiments, the effector sequence comprises a guide RNA (gRNA). Guide RNA sequences are generally designed to have a sequence having a length of between 15-30 nucleotides (e.g., 17, 19, 20, 21, 24 nucleotides) that is complementary to the targeted nucleic acid sequence, and a region that facilitates complex formation (e.g., with a tracrRNA or a nuclease). Custom gRNA generators and algorithms are available commercially for use in the design of effective guide RNAs. Gene editing has also been achieved using a chimeric "single guide RNA" ("sgRNA"), an engineered (synthetic) single RNA molecule that mimics a naturally occurring crRNA-tracrRNA complex and contains both a tracrRNA (for binding the nuclease) and at least one crRNA (to guide the nuclease to the sequence targeted for editing). Chemically modified sgRNAs have also been demonstrated to be effective in genome editing; see, for example, Hendel et al. (2015) Nature Biotechnol., 985-991. The gRNA may recognize specific DNA sequences (e.g., sequences adjacent to or within a promoter, enhancer, silencer, or repressor of a gene). In one embodiment, the gRNA is used as part of a CRISPR system for gene editing. For the purposes of gene editing, the RNA molecule disclosed herein may be designed to include one or multiple sequences encoding guide RNA sequences corresponding to a desired 1602179968.1 37 Attorney Docket No.: F2001-7001WO(VL99001-W1) target DNA sequence; see, for example, Cong et al. (2013) Science, 339:819-823; Ran et al. (2013) Nature Protocols, 8:2281-2308. Ribozymes In some embodiments, the effector sequence comprises a ribozyme. In some embodiments the ribozyme has cleavage activity, e.g., the ability to cleave itself or a substrate other than itself. In some embodiments, the ribozyme has ligation activity. In some embodiments, the ribozyme has aminoacylation activity. In some embodiments, the ribozyme catalyzes the formation of a peptide bond. In some embodiments, the ribozyme binds a metal ion. Aptamers In some embodiments, the effector sequence comprises an aptamer. The aptamer may bind a target molecule. In some embodiments, the aptamer changes conformation upon binding to the target molecule. The target molecule may be, for example, a nucleotide (e.g., ATP). In some embodiments, the aptamer binds a protein (e.g., a growth factor or a coagulation factor). Aptazymes In some embodiments, the effector sequence comprises an aptazyme. The aptazyme typically comprises an aptamer domain that binds a target molecule and a ribozyme domain with catalytic activity. Other elements An RNA molecule disclosed herein may also include other control elements operably linked to the effector sequence, e.g., the sequence encoding an effector, in a manner which permits its transport, localization, translation and / or expression in a target cell, or which promotes its degradation or repression of expression in a non-target cell. As used herein, "operably linked" sequences include both expression control sequences that are contiguous with the sequence encoding the effector and expression control sequences that act in trans or at a distance to control the sequence encoding the effector. The precise nature of regulatory sequences needed for gene expression in host cells may vary between species, tissues or cell 1602179968.1 38 Attorney Docket No.: F2001-7001WO(VL99001-W1) types, but in general may include, as necessary, 5' non-translated sequences involved with the initiation of translation, such as a Kozak sequence. The constructs described herein may optionally include 5' leader or signal sequences. In some embodiments, the RNA molecule may comprise a sequence encoding a 5’ untranslated region and / or a sequence encoding a 3’ untranslated region. The RNA molecule may comprise a non-coding region. In some embodiments, the non- coding region is completely free of predicted ORFs. In some embodiments, the non-coding region does not encode a protein sequence. In some embodiments, the non-coding region is not translated or is not translated at a substantial level. Production In some embodiments, the method comprises making or manufacturing an RNA molecule, the method comprising (a) providing an RNA molecule described herein, and (b) determining whether the structure of the RNA molecule matches a reference structure, thereby making or manufacturing the RNA molecule. In some embodiments, the determining of (b) comprises sequencing the RNA molecule. In some embodiments, the structure of the RNA molecule that matches the reference structure is identical to the reference structure. In some embodiments, the structure of the RNA molecule that matches the reference structure has the same sequence as the reference structure. In some embodiments, the structure of the RNA molecule that matches the reference structure has the same length as the reference structure. The RNA molecule may be enriched from impurities or byproducts selected from the group consisting of: endotoxin, mononucleotides, chemically modified mononucleotides, single stranded DNA, circular DNA, proteins (e.g., enzymes, e.g., ligases, restriction enzymes), DNA fragments or truncations. In some embodiments, the RNA molecule is substantially free of process byproducts and impurities, e.g., process byproducts or impurities described herein. In some embodiments, an RNA molecule is formulated with a lipid based carrier, e.g., a lipid nanoparticle (LNP). The RNA molecule may be sequenced to confirm the desired, designed sequence. In embodiments, other structural analysis of the RNA molecule may be performed to confirm or verify its sequence. 1602179968.1 39 Attorney Docket No.: F2001-7001WO(VL99001-W1) Enrichment A composition described herein is typically enriched to remove process impurities and / or contaminants. In some embodiments, a composition comprising an RNA molecule described herein is enriched. For instance, in some embodiments, at least 60%, at least 65%, at least 70%, at least 75%, or at least 80% by mass of total RNA in the composition may be the RNA molecule. As an example, the composition may also comprise other forms of RNA, e.g., as a process impurity, for instance host cell DNA or RNA. As an example, the composition may comprise a contaminant, such as bacterial or viral or fungal agents. In some embodiments, a composition described herein (e.g., a composition comprising a RNA molecule, e.g., a pharmaceutical composition comprising an RNA molecule, or a manufacturing intermediate) is free of or is substantially free of one or more process impurity or contaminant, e.g., as described in this section. In some embodiments, a method described herein results in a composition that is free of or is substantially free of one or more process impurity or contaminant, e.g., as described in this section. In some embodiments, a method described herein comprises a step of assaying for one or more process impurity or contaminant, e.g., as described in this section. In some embodiments, the method comprises approving or releasing a batch if the batch is free of or substantially free of the process impurity or contaminant or meets a release criterion for that process impurity or contaminant. In some embodiments, the process impurity comprises a nonhuman animal serum (e.g., fetal bovine serum); an enzyme, e.g., a ligase, a polymerase, or a digestive enzyme (e.g., a trypsin, a collagenase, a DNase, a RNase, an exonuclease, or an endonuclease, e.g., a restriction endonuclease); a growth factor; a cytokine; an antibody (e.g., a monoclonal antibody); a bead (e.g., an antibody-coated bead); an antibiotic; a cell culture medium; a component of a cell culture medium; a detergent; a protein, e.g., a host cell protein; an extraneous nucleic acid sequence (e.g., a mononucleotide (e.g., a modified mononucleotide), or a DNA fragment or truncation); helper virus contaminant (e.g., infectious virus, viral DNA, or viral proteins); a solvent; a cellular debris; a cell; a pyrogen; a fungus; or any combination thereof, or a portion of any of the foregoing. In some embodiments, the contaminant was a component introduced during a manufacturing process. In some embodiments, the contaminant comprises a viral protein. 1602179968.1 40 Attorney Docket No.: F2001-7001WO(VL99001-W1) In some embodiments, the contaminant comprises an agent for transmissible spongiform encephalopathy (TSE). In some embodiments, a test for this contaminant is performed on a composition for which a bovine material was used in manufacturing. In some embodiments, the contaminant comprises a zoonotic virus, a porcine circovirus 1, a porcine circovirus 2, or a porcine parvovirus; or any combination thereof, or a portion of any of the foregoing. In some embodiments, a test for this contaminant is performed on a composition for which non-human animal material, e.g., a porcine material, was used in manufacturing. In some embodiments, the contaminant comprises a virus or portion thereof, e.g., a human virus; human immunodeficiency virus (HIV); HIV-1; HIV-2; hepatitis B virus (HBV); hepatitis C virus (HCV); human TSE, including Creutzfeldt-Jakob disease (CJD); variant CJD (vCJD); Treponema pallidum (syphilis); human T-lymphotropic virus (HTLV), HTLV-1, HTLV-2; or cytomegalovirus, human herpesvirus (e.g., human herpesvirus -6, -7 or -8 (HHV-6, - 7, or -8)), JC virus, BK virus, Epstein-Barr virus (EBV), human parvovirus B19, human papillomavirus (HPV); an adenovirus, e.g., adenovirus E1; SV40 Large T antigen sequence; HPV E6 or E7 DNA; or any combination thereof, or a portion of any of the foregoing. In some embodiments, a test for this contaminant is performed on a composition for which human donor cells (e.g., leukocyte-rich cells) were used in manufacturing. In some embodiments, a test for this contaminant is performed on a cell bank. In some embodiments, the contaminant comprises a microbe or a portion thereof; a bacterium (e.g., a Gram-negative bacterium); mycoplasma; spiroplasma (e.g., when insect cells are used); bacterial toxin (e.g., endotoxin); or an adventitious agent, e.g., an adventitious viral agent or a non-viral adventitious agent, or any combination thereof, or a portion of any of the foregoing. In some embodiments, the contaminant comprises a simian virus, e.g., simian polyomavirus SV40 or simian retrovirus, or any combination thereof, or a portion of any of the foregoing. In some embodiments, the contaminant comprises an arbovirus. In some embodiments, the contaminant comprises a bacteriophage. In some embodiments, a test for this contaminant is performed on a cell bank, e.g., a cell bank of bacterial cells. In some embodiments, the contaminant or process impurity comprises DNA from a host cell, e.g., wherein the host cell is a non-tumorigenic cell. In some embodiments, the DNA is 1602179968.1 41 Attorney Docket No.: F2001-7001WO(VL99001-W1) present at a level of less than 10 ng / dose. In some embodiments, the DNA size is below about 200 nucleotides in length. In some embodiments, the contaminant is an endotoxin. In some embodiments, a level of the endotoxin is less than 5 Endotoxin Unit (EU) / kg body weight / hour, e.g., wherein the composition is formulated for parenteral administration. In some embodiments, a level of the endotoxin is less than 0.2 EU / kg body weight / hour, e.g., wherein the composition is formulated for intrathecal administration. In some embodiments, a level of the endotoxin is not more than 2.0 EU / dose / eye, e.g., wherein the composition is formulated for injection or implantation into the eye, or not more than 0.5 EU / mL, e.g., wherein the composition is formulated for intraocular administration. In some embodiments, a process impurity comprises an organic solvent, e.g., an aromatic organic solvent, e.g., phenol or chloroform. In some embodiments, the contaminant or process impurity is described in Chemistry, Manufacturing, and Control (CMC) Information for Human Gene Therapy Investigational New Drug Applications (INDs) - Guidance for Industry (U.S. Department of Health and Human Services, Food and Drug Administration, Center for Biologics Evaluation and Research, January 2020), which is herein incorporated by reference in its entirety. In some embodiments, the composition is substantially free of (e.g., is free of) a polymerase. In some embodiments, the composition is substantially free (e.g., is free of) lipids, e.g., LNPs. In some embodiments, the composition is substantially free (e.g., is free of) nanoparticles. In some embodiments, the composition is substantially free of (e.g., is free of) agarose. In some embodiments, the composition is substantially free of (e.g., is free of) acrylamide. In some embodiments, the composition is substantially free of (e.g., is free of) polypeptides. Pharmaceutical compositions The present disclosure includes an RNA molecule and related compositions in combination with one or more pharmaceutically acceptable excipients and / or carriers. 1602179968.1 42 Attorney Docket No.: F2001-7001WO(VL99001-W1) Pharmaceutical compositions may optionally comprise one or more additional active substances, e.g., therapeutically and / or prophylactically active substances. Pharmaceutical compositions of the present invention are generally sterile and / or pyrogen-free. An RNA molecule described herein may be formulated without a carrier, e.g., the RNA molecule described herein may be administered to a host cell, tissue or subject “naked”. A naked formulation may include pharmaceutical excipients or diluents but lacks a carrier. Pharmaceutically acceptable excipients or diluents may comprise an inactive substance that serves as a vehicle or medium for the compositions described herein, such as any one of the inactive ingredients approved by the United States Food and Drug Administration (FDA) and listed in the Inactive Ingredient Database, which is incorporated by reference herein. Non- limiting examples of pharmaceutically acceptable excipients or diluents include solvents, aqueous solvents, non-aqueous solvents, tonicity agents, dispersion media, cryoprotectants, diluents, suspension aids, surface active agents, isotonic agents, thickening agents, emulsifying agents, preservatives, hyaluronidases, dispersing agents, preservatives, lubricants, granulating agents, disintegrating agents, binding agents, antioxidants, buffering agents (e.g., phosphate buffered saline (PBS)), lubricating agents, oils, and mixtures thereof. General considerations in the formulation and / or manufacture of pharmaceutical agents may be found, for example, in Remington: The Science and Practice of Pharmacy 21st ed., Lippincott Williams & Wilkins, 2005 (incorporated herein by reference). Carriers An RNA molecule described herein may also be formulated, or included, with a carrier. General considerations of carriers and delivery of pharmaceutical agents may be found, for example, in “Delivery Technologies for Biopharmaceuticals: Peptides, Proteins, Nucleic Acids and Vaccines” (Lene Jorgensen and Hanne Morck Nielson, Eds.) Wiley; 1st edition (December 21, 2009); and Vargason et al.2021. Nat Biomed Eng 5, 951–967. Non-limiting examples of carriers include carbohydrate carriers (e.g., an anhydride- modified phytoglycogen or glycogen-type material, GalNAc), nanoparticles (e.g., a nanoparticle that encapsulates or is covalently linked to the RNA molecule, gold nanoparticles, silica nanoparticles), lipid particles (e.g., liposomes, lipid nanoparticles), cationic carriers (e.g., a cationic lipopolymer or transfection reagent), fusosomes, non-nucleated cells (e.g., ex vivo 1602179968.1 43 Attorney Docket No.: F2001-7001WO(VL99001-W1) differentiated reticulocytes), nucleated cells, exosomes, protein carriers (e.g., a protein covalently linked to the RNA molecule), peptides (e.g., cell-penetrating peptides), materials (e.g., graphene oxide), single pure lipids (e.g., cholesterol), DNA origami (e.g., DNA tetrahedron). In one embodiment, the RNA molecules, compositions, constructs and systems described herein can be formulated in liposomes or other similar vesicles. Liposomes are spherical vesicle structures composed of a uni- or multilamellar lipid bilayer surrounding internal aqueous compartments and a relatively impermeable outer lipophilic phospholipid bilayer. Liposomes may be anionic, neutral or cationic. Liposomes are biocompatible, nontoxic, can deliver both hydrophilic and lipophilic drug molecules, protect their cargo from degradation by plasma enzymes, and transport their load across biological membranes and the blood brain barrier (BBB) (see, e.g., Spuch and Navarro, Journal of Drug Delivery, vol.2011, Article ID 469679, 12 pages, 2011. doi:10.1155 / 2011 / 469679 for review). Vesicles can be made from several different types of lipids; however, phospholipids are most commonly used to generate liposomes as drug carriers. Methods for preparation of multilamellar vesicle lipids are known in the art (see for example U.S. Pat. No.6,693,086, the teachings of which relating to multilamellar vesicle lipid preparation are incorporated herein by reference). Although vesicle formation can be spontaneous when a lipid film is mixed with an aqueous solution, it can also be expedited by applying force in the form of shaking by using a homogenizer, sonicator, or an extrusion apparatus (see, e.g., Spuch and Navarro, Journal of Drug Delivery, vol.2011, Article ID 469679, 12 pages, 2011. doi:10.1155 / 2011 / 469679 for review). Extruded lipids can be prepared by extruding through filters of decreasing size, as described in Templeton et al., Nature Biotech, 15:647-652, 1997, the teachings of which relating to extruded lipid preparation are incorporated herein by reference. Exosomes can also be used as drug delivery vehicles for the compositions and systems described herein. For a review, see Ha et al. July 2016. Acta Pharmaceutica Sinica B. Volume 6, Issue 4, Pages 287-296; https: / / doi.org / 10.1016 / j.apsb.2016.02.001. Ex vivo differentiated red blood cells can also be used as a carrier for an agent (e.g., a RNA molecule) described herein. See, e.g., WO2015073587; WO2017123646; WO2017123644; WO2018102740; WO2016183482; WO2015153102; WO2018151829; WO2018009838; Shi et al.2014. Proc Natl Acad Sci USA.111(28): 10131–10136; US Patent 1602179968.1 44 Attorney Docket No.: F2001-7001WO(VL99001-W1) 9,644,180; Huang et al.2017. Nature Communications 8: 423; Shi et al.2014. Proc Natl Acad Sci USA.111(28): 10131–10136. Fusosome compositions, e.g., as described in WO2018208728, can also be used as carriers to deliver the RNA molecules described herein. Lipid Nanoformulations / Lipid-based carriers In some embodiments, compounds, e.g., RNA molecules, described herein are formulated into a lipid-based carrier (or lipid nanoformulation). In some embodiments, the lipid-based carrier (or lipid nanoformulation) is a liposome or a lipid nanoparticle (LNP). In one embodiment, the lipid-based carrier is an LNP. In some embodiments, the lipid-based carrier (or lipid nanoformulation) comprises a cationic lipid (e.g., an ionizable lipid), a non-cationic lipid (e.g., phospholipid), a structural lipid (e.g., cholesterol), and a PEG-modified lipid. In some embodiments, the lipid-based carrier (or lipid nanoformulation) contains one or more compounds described herein, or a pharmaceutically acceptable salt thereof. As described herein, suitable compounds to be used in the lipid-based carrier (or lipid nanoformulation) include all the isomers and isotopes of the compounds described above, as well as all the pharmaceutically acceptable salts, solvates, or hydrates thereof, and all crystal forms, crystal form mixtures, and anhydrides or hydrates. In addition to one or more compounds described herein, the lipid-based carrier (or lipid nanoformulation) may further include a second lipid. In some embodiments, the second lipid is a cationic lipid, a non-cationic (e.g., neutral, anionic, or zwitterionic) lipid, or an ionizable lipid. One or more naturally occurring and / or synthetic lipid compounds may be used in the preparation of the lipid-based carrier (or lipid nanoformulation). The lipid-based carrier (or lipid nanoformulation) may contain positively charged (cationic) lipids, neutral lipids, negatively charged (anionic) lipids, or a combination thereof. Cationic Lipids (Positively Charged) and Ionizable Lipids In some embodiments, the lipid-based carrier (or lipid nanoformulation) comprises one or more cationic lipids, e.g., a cationic lipid that can exist in a positively charged or neutral form depending on pH, or an amine-containing lipid that can be readily protonated. In some 1602179968.1 45 Attorney Docket No.: F2001-7001WO(VL99001-W1) embodiments, the cationic lipid is a lipid capable of being positively charged, e.g., under physiological conditions. Exemplary cationic lipids include one or more amine group(s) which bear the positive charge. Examples of positively charged (cationic) lipids include, but are not limited to, N,N'- dimethyl-N,N'-dioctacyl ammonium bromide (DDAB) and chloride DDAC), N-(l-(2,3- dioleyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTMA), 3β-[N-(N',N'- dimethylaminoethyl)carbamoyl) cholesterol (DC-chol), 1,2-dioleoyloxy-3-[trimethylammonio]- propane (DOTAP), 1,2-dioctadecyloxy-3-[trimethylammonio]-propane (DSTAP), and 1,2- dioleoyloxypropyl-3-dimethyl-hydroxy ethyl ammonium chloride (DORI), N,N-dioleyl-N,N- dimethylammonium chloride (DODAC), N,N-dimethyl-2,3-dioleyloxy)propylamine (DODMA), 1,2-Dioleoyl-3-Dimethylammonium-propane (DODAP), 1,2-Dioleoylcarbamyl-3- Dimethylammonium-propane (DOCDAP), 1,2-Dilineoyl-3-Dimethylammonium-propane (DLINDAP), 3-Dimethylamino-2-(Cholest-5-en-3-beta-oxybutan-4-oxy)-1-(cis,cis-9,12- octadecadienoxy)propane (CLinDMA), 2-[5′-(cholest-5-en-3-beta-oxy)-3′-oxapentoxy)-3- dimethyl-1-(cis, cis-9′,12′-octadecadienoxy)propane (CpLin DMA), N,N-Dimethyl-3,4- dioleyloxybenzylamine (DMOBA), and the cationic lipids described in e.g. Martin et al., Current Pharmaceutical Design, pages 1-394, which is herein incorporated by reference in its entirety. In some embodiments, the lipid-based carrier (or lipid nanoformulation) comprises more than one cationic lipid. In some embodiments, the lipid-based carrier (or lipid nanoformulation) comprises a cationic lipid having an effective pKa over 6.0. In some embodiments, the lipid-based carrier (or lipid nanoformulation) further comprises a second cationic lipid having a different effective pKa (e.g., greater than the first effective pKa) than the first cationic lipid. In some embodiments, cationic lipids that can be used in the lipid-based carrier (or lipid nanoformulation) include, for example those described in Table 4 of WO 2019 / 217941, which is incorporated by reference. In some embodiments, the cationic lipid is an ionizable lipid (e.g., a lipid that is protonated at low pH, but that remains neutral at physiological pH). In some embodiments, the lipid-based carrier (or lipid nanoformulation) may comprise one or more additional ionizable lipids, different than the ionizable lipids described herein. Exemplary ionizable lipids include, but are not limited to, 1602179968.1 46 Attorney Docket No.: F2001-7001WO(VL99001-W1) , 1602179968.1 47 Attorney Docket No.: F2001-7001WO(VL99001-W1) , some comprises one or more compounds described by WO 2021 / 113777 (e.g., a lipid of Formula (3) such as a lipid of Table 3 of WO 2021 / 113777), which is incorporated herein by reference in its entirety. In one embodiment, the ionizable lipid is a lipid disclosed in Hou, X., et al. Nat Rev Mater 6, 1078–1094 (2021). https: / / doi.org / 10.1038 / s41578-021-00358-0 (e.g., L319, C12-200, and DLin-MC3-DMA), (which is incorporated by reference herein in its entirety). Examples of other ionizable lipids that can be used in lipid-based carrier (or lipid nanoformulation) include, without limitation, one or more of the following formulas: X of US 2016 / 0311759; I of US 20150376115 or in US 2016 / 0376224; Compound 5 or Compound 6 in US 2016 / 0376224; I, IA, or II of US 9,867,888; I, II or III of US 2016 / 0151284; I, IA, II, or IIA of US 2017 / 0210967; I-c of US 2015 / 0140070; A of US 2013 / 0178541; I of US 2013 / 0303587 or US 2013 / 0123338; I of US 2015 / 0141678; II, III, IV, or V of US 2015 / 0239926; I of US 2017 / 0119904; I or II of WO 2017 / 117528; A of US 2012 / 0149894; A of US 2015 / 0057373; A of WO 2013 / 116126; A of US 2013 / 0090372; A of US 2013 / 0274523; A of US 2013 / 0274504; A of US 2013 / 0053572; A of WO 2013 / 016058; A of WO 2012 / 162210; I of US 2008 / 042973; I, II, III, or IV of US 2012 / 01287670; I or II of US 2014 / 0200257; I, II, or III of US 2015 / 0203446; I or III of US 2015 / 0005363; I, IA, IB, IC, ID, II, IIA, IIB, IIC, IID, or III-XXIV of US 2014 / 0308304; of US 2013 / 0338210; I, II, III, or IV of WO 2009 / 132131; A of US 2012 / 01011478; I or XXXV of US 2012 / 0027796; XIV or XVII of US 2012 / 0058144; of US 1602179968.1 48 Attorney Docket No.: F2001-7001WO(VL99001-W1) 2013 / 0323269; I of US 2011 / 0117125; I, II, or III of US 2011 / 0256175; I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII of US 2012 / 0202871; I, II, III, IV, V, VI, VII, VIII, X, XII, XIII, XIV, XV, or XVI of US 2011 / 0076335; I or II of US 2006 / 008378; I of WO2015 / 074085 (e.g., ATX-002); I of US 2013 / 0123338; I or X-A-Y-Z of US 2015 / 0064242; XVI, XVII, or XVIII of US 2013 / 0022649; I, II, or III of US 2013 / 0116307; I, II, or III of US 2013 / 0116307; I or II of US 2010 / 0062967; I-X of US 2013 / 0189351; I of US 2014 / 0039032; V of US 2018 / 0028664; I of US 2016 / 0317458; I of US 2013 / 0195920; 5, 6, or 10 of US 10,221,127; III-3 of WO 2018 / 081480; I-5 or I-8 of WO 2020 / 081938; I of WO 2015 / 199952 (e.g., compound 6 or 22) and Table 1 therein; 18 or 25 of US 9,867,888; A of US 2019 / 0136231; II of WO 2020 / 219876; 1 of US 2012 / 0027803; OF-02 of US 2019 / 0240349; 23 of US 10,086,013; cKK-E12 / A6 of Miao et al (2020); C12-200 of WO 2010 / 053572; 7C1 of Dahlman et al (2017); 304-O13 or 503- O13 of Whitehead et al; TS-P4C2 of U S9,708,628; I of WO 2020 / 106946; I of WO 2020 / 106946; (1), (2), (3), or (4) of WO 2021 / 113777; and any one of Tables 1-16 of WO 2021 / 113777, all of which are incorporated herein by reference in their entirety. In some embodiments, the lipid-based carrier (or lipid nanoformulation) further includes biodegradable ionizable lipids, for instance, (9Z,l2Z)-3-((4,4-bis(octyloxy)butanoyl)oxy)-2-((((3- (diethylamino)propoxy)carbonyl)oxy)methyl)propyl octadeca-9,l2-dienoate, also called 3- ((4,4- bis(octyloxy)butanoyl)oxy)-2-((((3-(diethylamino)propoxy)carbonyl)oxy)methyl)propyl (9Z,l2Z)-octadeca-9,l2-dienoate). See, e.g., lipids of WO 2019 / 067992, WO 2017 / 173054, WO 2015 / 095340, and WO 2014 / 136086, which are incorporated herein by reference in their entirety. Non-Cationic Lipids (e.g., Phospholipids) In some embodiments, the lipid-based carrier (or lipid nanoformulation) further comprises one or more non-cationic lipids. In some embodiments, the non-cationic lipid is a phospholipid. In some embodiments, the non-cationic lipid is a phospholipid substitute or replacement. In some embodiments, the non-cationic lipid is a negatively charged (anionic) lipid. Exemplary non-cationic lipids include, but are not limited to, distearoyl-sn-glycero- phosphoethanolamine, distearoylphosphatidylcholine (DSPC), dioleoylphosphatidylcholine (DOPC), dipalmitoylphosphatidylcholine (DPPC), dioleoylphosphatidylglycerol (DOPG), 1602179968.1 49 Attorney Docket No.: F2001-7001WO(VL99001-W1) dipalmitoylphosphatidylglycerol (DPPG), dioleoyl-phosphatidylethanolamine (DOPE), palmitoyloleoylphosphatidylcholine (POPC), palmitoyloleoylphosphatidylethanolamine (POPE), dioleoyl-phosphatidylethanolamine 4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (DOPE- mal), dipalmitoyl phosphatidyl ethanolamine (DPPE), dimyristoylphosphoethanolamine (DMPE), distearoyl-phosphatidyl-ethanolamine (DSPE), monomethyl-phosphatidylethanolamine (such as 16-O-monomethyl PE), dimethyl- phosphatidylethanolamine (such as 16-O-dimethyl PE), 18-l-trans PE, 1-stearoyl-2-oleoyl-phosphatidyethanolamine (SOPE), hydrogenated soy phosphatidylcholine (HSPC), egg phosphatidylcholine (EPC), dioleoylphosphatidylserine (DOPS), sphingomyelin (SM), dimyristoyl phosphatidylcholine (DMPC), dimyristoyl phosphatidylglycerol (DMPG), distearoylphosphatidylglycerol (DSPG), dierucoylphosphatidylcholine (DEPC), palmitoyloleyolphosphatidylglycerol (POPG), dielaidoyl- phosphatidylethanolamine (DEPE), 1,2-dilauroyl- sn-glycero-3-phosphocholine (DLPC), Sodium 1,2- ditetradecanoyl-sn-glycero-3-phosphate (DMPA), phosphatidylcholine (lecithin), phosphatidylethanolamine, lysolecithin, lysophosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, egg sphingomyelin (ESM), phosphatidylethanolamine (cephalin), cardiolipin, phosphatidic acid, cerebrosides, dicetylphosphate, lysophosphatidylcholine, dilinoleoylphosphatidylcholine, or mixtures thereof. It is understood that other diacylphosphatidylcholine and diacylphosphatidylethanolamine phospholipids can also be used. The acyl groups in these lipids are preferably acyl groups derived from fatty acids having C10-C24carbon chains, e.g., lauroyl, myristoyl, paimitoyl, stearoyl, or oleoyl. Additional exemplary lipids, in certain embodiments, include, without limitation, those described in Kim et al. (2020) dx.doi.org / 10.1021 / acs.nanolett.0c01386, which is incorporated herein by reference. Such lipids include, in some embodiments, plant lipids found to improve liver transfection with mRNA (e.g., DGTS). In some embodiments, the lipid-based carrier (or lipid nanoformulation) may comprise a combination of distearoylphosphatidylcholine / cholesterol, dipalmitoylphosphatidylcholine / cholesterol, dimyrystoylphosphatidylcholine / cholesterol, 1,2- Dioleoyl-sn-glycero-3-phosphocholine (DOPC) / cholesterol, or egg sphingomyelin / cholesterol. Other examples of suitable non-cationic lipids include, without limitation, nonphosphorous lipids such as, e.g., stearylamine, dodecylamine, hexadecylamine, acetyl palmitate, glycerol ricinoleate, hexadecyl stearate, isopropyl myristate, amphoteric acrylic 1602179968.1 50 Attorney Docket No.: F2001-7001WO(VL99001-W1) polymers, triethanolamine-lauryl sulfate, alkyl-aryl sulfate polyethyloxylated fatty acid amides, dioctadecyl dimethyl ammonium bromide, ceramide, sphingomyelin, and the like. Other non- cationic lipids are described in WO 2017 / 099823 or US 2018 / 0028664, which are incorporated herein by reference in their entirety. In one embodiment, the lipid-based carrier (or lipid nanoformulation) further comprises one or more non-cationic lipid that is oleic acid or a compound of Formula I, II, or IV of US 2018 / 0028664, which is incorporated herein by reference in its entirety. The non-cationic lipid content can be, for example, 0-30% (mol) of the total lipid components present. In some embodiments, the non-cationic lipid content is 5-20% (mol) or 10- 15% (mol) of the total lipid components present. In some embodiments, the lipid-based carrier (or lipid nanoformulation) further comprises a neutral lipid, and the molar ratio of an ionizable lipid to a neutral lipid ranges from about 2:1 to about 8:1 (e.g., about 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, or 8:1). In some embodiments, the lipid-based carrier (or lipid nanoformulation) does not include any phospholipids. In some embodiments, the lipid-based carrier (or lipid nanoformulation) can further include one or more phospholipids, and optionally one or more additional molecules of similar molecular shape and dimensions having both a hydrophobic moiety and a hydrophilic moiety (e.g., cholesterol). Structural Lipids The lipid-based carrier (or lipid nanoformulation) described herein may further comprise one or more structural lipids. As used herein, the term “structural lipid” refers to sterols (e.g., cholesterol) and also to lipids containing sterol moieties. Incorporation of structural lipids in the lipid nanoparticle may help mitigate aggregation of other lipids in the particle. Structural lipids can be selected from the group including but not limited to, cholesterol or cholesterol derivative, fecosterol, sitosterol, ergosterol, campesterol, stigmasterol, brassicasterol, tomatidine, tomatine, ursolic acid, alpha-tocopherol, hopanoids, phytosterols, steroids, and mixtures thereof. In some embodiments, the structural lipid is a sterol. In certain embodiments, the structural lipid is a steroid. In certain embodiments, the structural lipid is cholesterol. In certain embodiments, the structural lipid is an analog of cholesterol. In 1602179968.1 51 Attorney Docket No.: F2001-7001WO(VL99001-W1) certain embodiments, the structural lipid is alpha-tocopherol. In some embodiments, structural lipids may be incorporated into the lipid-based carrier at molar ratios ranging from about 0.1 to 1.0 (cholesterol phospholipid). In some embodiments, sterols, when present, can include one or more of cholesterol or cholesterol derivatives, such as those described in WO 2009 / 127060 or US 2010 / 0130588, which are incorporated herein by reference in their entirety. Additional exemplary sterols include phytosterols, including those described in Eygeris et al. (2020), Nano Lett.2020;20(6):4543- 4549, incorporated herein by reference. In some embodiments, the structural lipid is a cholesterol derivative. Non-limiting examples of cholesterol derivatives include polar analogues such as 5a-cholestanol, 53- coprostanol, cholesteryl-(2’-hydroxy)-ethyl ether, cholesteryl-(4'- hydroxy)-butyl ether, and 6- ketocholestanol; non-polar analogues such as 5a-cholestane, cholestenone, 5a-cholestanone, 5p- cholestanone, and cholesteryl decanoate; and mixtures thereof. In some embodiments, the cholesterol derivative is a polar analogue, e.g., cholesteryl-(4'-hydroxy)-buty1 ether. Exemplary cholesterol derivatives are described in WO 2009 / 127060 and US 2010 / 0130588, each of which is incorporated herein by reference in its entirety. In some embodiments, the lipid-based carrier (or lipid nanoformulation) further comprises sterol in an amount of 0-50 mol% (e.g., 0-10 mol %, 10-20 mol %, 20-50 mol%, 20- 30 mol %, 30-40 mol %, or 40-50 mol %) of the total lipid components. Polymers and Polyethylene Glycol (PEG) - Lipids In some embodiments, the lipid-based carrier (or lipid nanoformulation) may include one or more polymers or co-polymers, e.g., poly(lactic-co-glycolic acid) (PFAG) nanoparticles. In some embodiments, the lipid-based carrier (or lipid nanoformulation) may include one or more polyethylene glycol (PEG) lipid. Examples of useful PEG-lipids include, but are not limited to, 1,2-Diacyl-sn-Glycero-3- Phosphoethanolamine-N-[Methoxy(Polyethylene glycol)- 350] (mPEG 350 PE); 1,2-Diacyl-sn- Glycero-3-Phosphoethanolamine-N- [Methoxy(Polyethylene glycol)-550] (mPEG 550 PE); 1,2- Diacyl-sn-Glycero-3- Phosphoethanolamine-N-[Methoxy(Polyethylene glycol)-750] (mPEG 750 PE); 1,2-Diacyl-sn- Glycero-3-Phosphoethanolamine-N-[Methoxy(Polyethylene glycol)-1000] (mPEG 1000 PE); 1,2-Diacyl-sn-Glycero-3-Phosphoethanolamine-N-[Methoxy(Polyethylene glycol)-2000] (mPEG 1602179968.1 52 Attorney Docket No.: F2001-7001WO(VL99001-W1) 2000 PE); 1,2-Diacyl-sn-Glycero-3-Phosphoethanolamine-N- [Methoxy(Polyethylene glycol)- 3000] (mPEG 3000 PE); 1,2-Diacyl-sn-Glycero-3- Phosphoethanolamine-N- [Methoxy(Polyethylene glycol)-5000] (mPEG 5000 PE); N-Acyl- Sphingosine-1- [Succinyl(Methoxy Polyethylene Glycol) 750] (mPEG 750 Ceramide); N-Acyl- Sphingosine-1- [Succinyl(Methoxy Polyethylene Glycol) 2000] (mPEG 2000 Ceramide); and N- Acyl- Sphingosine-1-[Succinyl(Methoxy Polyethylene Glycol) 5000] (mPEG 5000 Ceramide). In some embodiments, the PEG lipid is a polyethyleneglycol-diacylglycerol (i.e., polyethyleneglycol diacylglycerol (PEG-DAG), PEG-cholesterol, or PEG-DMB) conjugate. In some embodiments, the lipid-based carrier (or nanoformulation) includes one or more conjugated lipids (such as PEG-conjugated lipids or lipids conjugated to polymers described in Table 5 of WO 2019 / 217941, which is incorporated herein by reference in its entirety). In some embodiments, the one or more conjugated lipids is formulated with one or more ionic lipids (e.g., non-cationic lipid such as a neutral or anionic, or zwitterionic lipid); and one or more sterols (e.g., cholesterol). The PEG conjugate can comprise a PEG-dilaurylglycerol (C12), a PEG- dimyristylglycerol (C14), a PEG-dipalmitoylglycerol (C16), a PEG-disterylglycerol (C18), PEG- dilaurylglycamide (C12), PEG-dimyristylglycamide (C14), PEG-dipalmitoylglycamide (C16), and PEG-disterylglycamide (C18). In some embodiments, conjugated lipids, when present, can include one or more of PEG- diacylglycerol (DAG) (such as l-(monomethoxy-polyethyleneglycol)-2,3- dimyristoylglycerol (PEG-DMG)), PEG-dialkyloxypropyl (DAA), PEG-phospholipid, PEG- ceramide (Cer), a pegylated phosphatidylethanoloamine (PEG-PE), PEG succinate diacylglycerol (PEGS-DAG) (such as 4-0-(2',3'-di(tetradecanoyloxy)propyl-l-0-(w- methoxy(polyethoxy)ethyl) butanedioate (PEG-S-DMG)), PEG dialkoxypropylcarbam, N- (carbonyl-methoxypolyethylene glycol 2000)- 1 ,2-distearoyl-sn-glycero-3-phosphoethanolamine sodium salt, and those described in Table 2 of WO 2019 / 051289 (which is herein incorporated by reference in its entirety), and combinations of the foregoing. Additional exemplary PEG-lipid conjugates are described, for example, in US 5,885,613, US 6,287,591, US 2003 / 0077829, US 2003 / 0077829, US 2005 / 0175682, US 2008 / 0020058, US 2011 / 0117125, US 2010 / 0130588, US 2016 / 0376224, US 2017 / 0119904, US 2018 / 0028664, and WO 2017 / 099823, all of which are incorporated herein by reference in their entirety. 1602179968.1 53 Attorney Docket No.: F2001-7001WO(VL99001-W1) In some embodiments, the PEG-lipid is a compound of Formula III, III-a-I, III-a-2, III-b- 1, III-b-2, or V of US 2018 / 0028664, which is incorporated herein by reference in its entirety. In some embodiments, the PEG-lipid is of Formula II of US 2015 / 0376115 or US 2016 / 0376224, both of which are incorporated herein by reference in their entirety. In some embodiments, the PEG-DAA conjugate can be, for example, PEG-dilauryloxypropyl, PEG- dimyristyloxypropyl, PEG-dipalmityloxypropyl, or PEG-distearyloxypropyl. In some embodiments, the PEG-lipid includes one of the following: In some embodiments, lipids conjugated with a molecule other than a PEG can also be used in place of PEG-lipid. For example, polyoxazoline (POZ)-lipid conjugates, polyamide-lipid conjugates (such as ATTA-lipid conjugates), and cationic-polymer lipid (GPL) conjugates can be used in place of or in addition to the PEG-lipid. Exemplary conjugated lipids, e.g., PEG-lipids, (POZ)-lipid conjugates, ATTA-lipid conjugates and cationic polymer-lipids, include those described in Table 2 of WO 2019 / 051289A9, which is incorporated herein by reference in its entirety. In some embodiments, the conjugated lipid (e.g., the PEGylated lipid) can be present in 1602179968.1 54 Attorney Docket No.: F2001-7001WO(VL99001-W1) an amount of 0-20 mol% of the total lipid components present in the lipid-based carrier (or lipid nanoformulation). In some embodiments, the conjugated lipid (e.g., the PEGylated lipid) content is 0.5-10 mol% or 2-5 mol% of the total lipid components. When needed, the lipid-based carrier (or lipid nanoformulation) described herein may be coated with a polymer layer to enhance stability in vivo (e.g., sterically stabilized LNPs). Examples of suitable polymers include, but are not limited to, poly(ethylene glycol), which may form a hydrophilic surface layer that improves the circulation half-life of liposomes and enhances the amount of lipid nanoformulations (e.g., liposomes or LNPs) that reach therapeutic targets. See, e.g., Working et al. J Pharmacol Exp Ther, 289: 1128-1133 (1999); Gabizon et al., J Controlled Release 53: 275-279 (1998); Adlakha Hutcheon et al., Nat Biotechnol 17: 775-779 (1999); and Koning et al., Biochim Biophys Acta 1420: 153-167 (1999), which are incorporated herein by reference in their entirety. Percentages of Lipid Nanoformulation Components In some embodiments, the lipid-based carrier (or lipid nanoformulation) comprises one of more of the compounds described herein, optionally a non-cationic lipid (e.g., a phospholipid), a sterol, a neutral lipid, and optionally conjugated lipid (e.g., a PEGylated lipid) that inhibits aggregation of particles. In some embodiments, the lipid-based carrier (or lipid nanoformulation) further comprises a payload (e.g., an RNA molecule described herein). The amounts of these components can be varied independently and to achieve desired properties. For example, in some embodiments, the ionizable lipid including the lipid compounds described herein is present in an amount from about 20 mol% to about 100 mol% (e.g., 20-90 mol%, 20-80 mol%, 20-70 mol%, 25-100 mol%, 30-70 mol%, 30-60 mol%, 30-40 mol%, 40-50 mol%, or 50- 90 mol%) of the total lipid components; a non-cationic lipid (e.g., phospholipid) is present in an amount from about 0 mol% to about 50 mol% (e.g., 0-40 mol%, 0-30 mol%, 5-50 mol%, 5-40 mol%, 5-30 mol%, or 5-10 mol%) of the total lipid components, a conjugated lipid (e.g., a PEGylated lipid) in an amount from about 0.5 mol% to about 20 mol% (e.g., 1-10 mol% or 5- 10%) of the total lipid components, and a sterol in an amount from about 0 mol % to about 60 mol% (e.g., 0-50 mol%, 10-60 mol%, 10-50 mol%, 15-60 mol%, 15-50 mol%, 20-50 mol%, 20- 40 mol%) of the total lipid components, provided that the total mol% of the lipid component does not exceed 100%. 1602179968.1 55 Attorney Docket No.: F2001-7001WO(VL99001-W1) In some embodiments, the lipid-based carrier (or lipid nanoformulation) comprises about 25-100 mol% of the ionizable lipid including the lipid compounds described herein, about 0-50 mol% phospholipid, about 0-50 mol% sterol, and about 0-10 mol% PEGylated lipid. In some embodiments, the lipid-based carrier comprises a payload (e.g., an RNA molecule described herein, etc.) that is formulated in a lipid nanoparticle, wherein the lipid nanoparticle comprises about 25-100 mol% of the ionizable lipid including the lipid compounds described herein, about 0-50 mol% phospholipid, about 0-50 mol% sterol, and about 0-10 mol% PEGylated lipid. In some embodiments, the encapsulation efficiency of the payload may be at least 70%. In one embodiment, the lipid-based carrier (or lipid nanoformulation) comprises about 25-100 mol% of the ionizable lipid including the lipid compounds described herein; about 0-40 mol% phospholipid (e.g., DSPC), about 0-50 mol% sterol (e.g., cholesterol), and about 0-10 mol% PEGylated lipid. In some embodiments, the lipid-based carrier comprises a payload (e.g., an RNA molecule described herein) that is formulated in a lipid nanoparticle, wherein the lipid nanoparticle comprises about 25-100 mol% of the ionizable lipid including the lipid compounds described herein; about 0-40 mol% phospholipid (e.g., DSPC), about 0-50 mol% sterol (e.g., cholesterol), and about 0-10 mol% PEGylated lipid. In some embodiments, the encapsulation efficiency of the payload may be at least 70%. In some embodiments, the lipid-based carrier (or lipid nanoformulation) comprises about 30-60 mol% (e.g., about 35-55 mol%, or about 40-50 mol%) of the ionizable lipid including the lipid compounds described herein, about 0-30 mol% (e.g., 5-25 mol%, or 10-20 mol%) phospholipid, about 15-50 mol% (e.g., 18.5-48.5 mol%, or 30-40 mol%) sterol, and about 0-10 mol% (e.g., 1-5 mol%, or 1.5-2.5 mol%) PEGylated lipid. In some embodiments, the lipid-based carrier comprises a payload (e.g., an RNA molecule described herein) that is formulated in a lipid nanoparticle, wherein the lipid nanoparticle comprises about 30-60 mol% (e.g., about 35-55 mol%, or about 40-50 mol%) of the ionizable lipid including the lipid compounds described herein, about 0-30 mol% (e.g., 5-25 mol%, or 10-20 mol%) phospholipid, about 15-50 mol% (e.g., 18.5-48.5 mol%, or 30-40 mol%) sterol, and about 0-10 mol% (e.g., 1-5 mol%, or 1.5-2.5 mol%) PEGylated lipid. In some embodiments, the encapsulation efficiency of the payload may be at least 70%. 1602179968.1 56 Attorney Docket No.: F2001-7001WO(VL99001-W1) In some embodiments, molar ratios of ionizable lipid / sterol / phospholipid (or another structural lipid) / PEG-lipid / additional components is varied in the following ranges: ionizable lipid (25-100%); phospholipid (DSPC) (0-40%); sterol (0-50%); and PEG lipid (0-5%). In some embodiments, the lipid-based carrier comprises a payload (e.g., an RNA molecule described herein) that is formulated in a lipid nanoparticle, wherein the lipid nanoparticle comprises molar ratios of ionizable lipid / sterol / phospholipid (or another structural lipid) / PEG-lipid / additional components in the following ranges: ionizable lipid (25-100%); phospholipid (DSPC) (0-40%); sterol (0-50%); and PEG lipid (0-5%). In some embodiments, the encapsulation efficiency of the payload may be at least 70%. In some embodiments, the lipid-based carrier (or lipid nanoformulation) comprises, by mol% or wt% of the total lipid components, 50-75% ionizable lipid (including the lipid compound as described herein), 20-40% sterol (e.g., cholesterol or derivative), 0 to 10% non- cationic-lipid, and 1-10% conjugated lipid (e.g., the PEGylated lipid). In some embodiments, the lipid-based carrier comprises a payload (e.g., an RNA molecule described in) that is formulated in a lipid nanoparticle, wherein the lipid nanoparticle comprises, by mol% or wt% of the total lipid components, 50-75% ionizable lipid (including the lipid compound as described herein), 20-40% sterol (e.g., cholesterol or derivative), 0 to 10% non-cationic-lipid, and 1-10% conjugated lipid (e.g., the PEGylated lipid). In some embodiments, the encapsulation efficiency of the payload may be at least 70%. In some embodiments, the lipid-based carrier (or lipid nanoformulation) comprises (i) an RNA molecule; (ii) a cationic lipid comprising from 50 mol% to 65 mol% of the total lipid present in the lipid-based carrier; (iii) a non-cationic lipid comprising a mixture of a phospholipid and a cholesterol derivative thereof, wherein the phospholipid comprises from 3 mol% to 15 mol% of the total lipid present in the lipid-based carrier and the cholesterol or derivative thereof comprises from 30 mol% to 40 mol% of the total lipid present in the lipid- based carrier; and (iv) a conjugated lipid comprising 0.5 mol% to 2 mol% of the total lipid present in the particle. In some embodiments, the lipid-based carrier (or lipid nanoformulation) comprises (i) a RNA molecule; (ii) a cationic lipid comprising from 50 mol % to 85 mol % of the total lipid present in the lipid-based carrier; (iii) a non-cationic lipid comprising from 13 mol % to 49.5 mol % of the total lipid present in the lipid-based carrier; and (d) a conjugated lipid comprising from 1602179968.1 57 Attorney Docket No.: F2001-7001WO(VL99001-W1) 0.5 mol % to 2 mol % of the total lipid present in the lipid-based carrier. In some embodiments, the phospholipid component in the mixture may be present from 2 mol% to 20 mol%, from 2 mol% to 15 mol%, from 2 mol% to 12 mol%, from 4 mol% to 15 mol%, from 4 mol% to 10 mol%, from 5 mol% to 10 mol%, (or any fraction of these ranges) of the total lipid components. In some embodiments, the lipid-based carrier (or lipid nanoformulation) is phospholipid-free. In some embodiments, the sterol component (e.g. cholesterol or derivative) in the mixture may comprise from 25 mol% to 45 mol%, from 25 mol% to 40 mol%, from 25 mol% to 35 mol%, from 25 mol% to 30 mol%, from 30 mol% to 45 mol%, from 30 mol% to 40 mol%, from 30 mol% to 35 mol%, from 35 mol% to 40 mol%, from 27 mol% to 37 mol%, or from 27 mol% to 35 mol% (or any fraction of these ranges) of the total lipid components. In some embodiments, the non-ionizable lipid components in the lipid-based carrier (or lipid nanoformulation) may be present from 5 mol% to 90 mol%, from 10 mol% to 85 mol%, or from 20 mol% to 80 mol% (or any fraction of these ranges) of the total lipid components. The ratio of total lipid components to the payload (e.g., an encapsulated therapeutic agent such as an RNA molecule) can be varied as desired. For example, the total lipid components to the payload (mass or weight) ratio can be from about 10:1 to about 30:1. In some embodiments, the total lipid components to the payload ratio (mass / mass ratio; w / w ratio) can be in the range of from about 1:1 to about 25:1, from about 10:1 to about 14:1, from about 3:1 to about 15:1, from about 4:1 to about 10:1, from about 5:1 to about 9:1, or about 6:1 to about 9:1. The amounts of total lipid components and the payload can be adjusted to provide a desired N / P ratio, for example, N / P ratio of 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or higher. Generally, the lipid-based carrier (or lipid nanoformulation’s) overall lipid content can range from about 5 mg / ml to about 30 mg / mL. Nitrogen:phosphate ratios (N:P ratio) is evaluated at values between 0.1 and 100. The efficiency of encapsulation of a payload such as an RNA molecule, describes the amount of the RNA molecule that is encapsulated or otherwise associated with a lipid nanoformulation (e.g., liposome or LNP) after preparation, relative to the initial amount provided. The encapsulation efficiency is desirably high (e.g., at least 70%, at least 80%, at least 90%, at least 95%, or close to 100%). The encapsulation efficiency may be measured, for example, by comparing the amount of RNA molecule in a solution containing the liposome or 1602179968.1 58 Attorney Docket No.: F2001-7001WO(VL99001-W1) LNP before and after breaking up the liposome or LNP with one or more organic solvents or detergents. An anion exchange resin may be used to measure the amount of RNA molecule in a solution. Fluorescence may be used to measure the amount of RNA molecule in a solution. For the lipid-based carrier (or lipid nanoformulation) described herein, the encapsulation efficiency of an RNA molecule may be at least 50%, for example 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%. In some embodiments, the encapsulation efficiency may be at least 70%. In some embodiments, the encapsulation efficiency may be at least 80%. In some embodiments, the encapsulation efficiency may be at least 90%. In some embodiments, the encapsulation efficiency may be at least 95%. Route of administration An RNA molecule described herein is introduced into a cell, tissue or subject by any suitable route. Administration to a target cell or tissue (e.g., ex vivo) may be by methods known in the art such as transfection, e.g., transient or stable transfection using reagents (e.g., liposomal, calcium phosphate) or physical means (e.g., electroporation, gene gun, microinjection, microfluidic fluid shear, cell squeezing). Other methods are described, e.g., in Rad et al.2021. Adv. Mater.33:2005363, which is incorporated herein by reference. Administration to a subject, e.g., a mammal, e.g., a human subject, may be by parenteral (e.g., intravenous, intramuscular, intraperitoneal, subcutaneous, or intracranial) route; by topical administration, transdermal administration or transcutaneous administration. Other suitable routes include oral, rectal, transmucosal, intranasal, inhalation (e.g., via an aerosol), buccal (e.g., sublingual), vaginal, intrathecal, intraocular, transdermal, intraendothelial, in utero (or in ovo), intrapleural, intracerebral, intraarticular, topical, intralymphatic. Also included is direct tissue or organ injection (e.g., to liver, eye, skeletal muscle, cardiac muscle, diaphragm, muscle or brain). Applications The RNA molecule described herein can be used in therapeutic or health applications for a subject, e.g., a human or non-human animal. Although the descriptions of pharmaceutical compositions provided herein are principally directed to pharmaceutical compositions which are suitable for administration to humans, it will be understood by the skilled artisan that such 1602179968.1 59 Attorney Docket No.: F2001-7001WO(VL99001-W1) compositions are generally suitable for administration to any other animal. The subject can be any animal, e.g., a mammal, e.g., a human or non-human mammal. In embodiments, the subject is a vertebrate animal (e.g., mammal, bird, fish, reptile, or amphibian). In embodiments, the subject is a human. In embodiments, the method subject is a non-human mammal. In embodiments, the subject is a non-human mammal is such as a non-human primate (e.g., monkeys, apes), ungulate (e.g., cattle, buffalo, sheep, goat, pig, camel, llama, alpaca, deer, horses, donkeys), carnivore (e.g., dog, cat), rodent (e.g., rat, mouse), or lagomorph (e.g., rabbit). In embodiments, the subject is a bird, such as a member of the avian taxa Galliformes (e.g., chickens, turkeys, pheasants, quail), Anseriformes (e.g., ducks, geese), Paleaognathae (e.g., ostriches, emus), Columbiformes (e.g., pigeons, doves), or Psittaciformes (e.g., parrots). In embodiments, the subject is an invertebrate such as an arthropod (e.g., insects, arachnids, crustaceans), a nematode, an annelid, a helminth, or a mollusk. In some embodiments, an RNA molecule described herein is provided at a dose of about 0.1-100 mg / kg of RNA. In some embodiments, an RNA molecule described herein imparts a biological effect of the effector, e.g., expression of a therapeutic polypeptide, on a host cell, tissue or subject over a time period of at least 2, at least 3, at least 4, at least 5, at least 6 days, or at least a week. In some embodiments, an RNA molecule described herein imparts a biological effect of the effector, e.g., expression of a therapeutic polypeptide, on a host cell, tissue or subject over a time period of at least 1 cell division of the host cell. In embodiments, an RNA molecule described herein can be used to deliver an effector, e.g., an effector described herein, to a cell, tissue or subject. In embodiments, an RNA molecule described herein can be used to modulate (e.g., increase or decrease) a biological parameter in a cell, tissue or subject. The biological parameter may be an increase or decrease in gene expression of a subject gene in a target cell, tissue or subject. In some embodiments, an RNA molecule described herein increases or decreases a biological activity in a target cell, wherein the biological activity comprises cell growth, cell metabolism, cell signaling, cell movement, specialization, interactions, division, transport, homeostasis, osmosis, or diffusion. In some embodiments, the cell is an animal cell, e.g., a mammalian cell, e.g., a human cell. 1602179968.1 60 Attorney Docket No.: F2001-7001WO(VL99001-W1) In embodiments, an RNA molecule described herein can be used to treat a cell, tissue or subject in need thereof by administering the RNA molecule described herein to such cell, tissue or subject. In embodiments, the RNA molecule delivers an effector to a cell. EXAMPLES Example 1: Synthesis of Se-modified NTP Precursor This example demonstrates the synthesis of Se-modified nucleoside triphosphate (NTP) precursor for use in the synthesis of Se-modified NTPs. First, a general starting material for each of the above-mentioned Se-modified bases was synthesized as follows (FIG.1): 1. To a solution of Compound 1001 (50 g, 265.71 mmol, 1 eq) and triethylamine (TEA) (53.77 g, 531.41 mmol, 73.97 mL, 2 eq) in dichloromethane (DCM) (500 mL) was added methanesulfonyl chloride (MsCl) (39.57 g, 345.42 mmol, 26.74 mL, 1.3 eq) dropwise at 0 °C under N2. Then the mixture was stirred at 25 °C for 0.5 hour. The reaction can also proceed for 3 hours. Thin-layer chromatography (TLC) indicated Compound 1001 was consumed completely and one new spot formed. The reaction mixture was washed by aq.NaHCO3(200 mL * 2) and brine (200 mL * 2). The organic layer was dried over Na2SO4and concentrated to give Compound 1002 (70 g, crude) as yellow oil. 2. A solution of KOH (29.08 g, 518.28 mmol, 3 eq) in H2O (230 mL) was added dropwise into a mixture of Compound 1002 (46 g, 172.76 mmol, 1 eq) in dioxane (350 mL) at 0 °C. The mixture was stirred at 25 °C for 12 hours. Liquid chromatography-mass spectrometry (LC-MS) showed Compound 1002 was consumed completely and the desired mass was detected. The pH was adjusted to 3 by adding 2 M HCl under ice bath. The acidic solution was concentrated in vacuum to afford a solid, then it was triturated with acetone (300 mL) and heated to 65 °C for 1 hour. The mixture could also be heated to 70 °C. The acetone was decanted and filtered. The remaining solid was triturated 2 more times and each time the boiling 1602179968.1 61 Attorney Docket No.: F2001-7001WO(VL99001-W1) acetone was decanted and filtered. The combined clear filtrate was concentrated in vacuum to give Compound 1003 (32 g, crude) as yellow oil. 3. To a solution of Compound 1003 (32 g, 170.05 mmol, 1 eq) in DCM (320 mL) were added imidazole (18.52 g, 272.08 mmol, 1.6 eq) and tert-butyl(chloro)diphenylsilane (TBDPS-Cl) (56.09 g, 204.06 mmol, 52.22 mL, 1.2 eq) at 0 °C. The mixture was stirred at 20 °C for 12 hours. The reaction can also be performed at 25 °C for 2 hours. LC-MS showed Compound 1003 was consumed completely and the desired mass was detected. The reaction mixture was added to water (100 mL) and extracted with DCM (50 mL * 3). The organic layer was dried over Na2SO4and then concentrated to give the crude product. The residue was purified by flash silica gel chromatography to give Compound 1004 (60 g, 140.65 mmol, 82.71% yield) as light yellow oil. 4. To a solution of Compound 1004 (55 g, 82.05 mmol, 1 eq) in methanol (MeOH) (100 mL) and tetrahydrofuran (THF) (500 mL) was added NaBH4 (12.19 g, 205.12 mmol, 2.5 eq) at 0 °C slowly under N2. After addition, the mixture was stirred at 0 °C for 1 hour under N2. This reaction can also be performed at 25 °C for 2 hours. LC-MS showed Compound 1004 was consumed completely and one main peak with desired mass was detected. H2O (150 mL) was added to the reaction mixture slowly, and then it was stirred at 0 °C for 0.5 hour. The mixture was then extracted with ethyl acetate (EtOAc) (100 mL * 3). The combined organic layers were dried over Na2SO4, filtered, and concentrated under reduced pressure to give Compound 1005 (30 g, crude) as white gum. 5. To a solution of Compound 1005 (50 g, 116.11 mmol, 1 eq), 4- Dimethylaminopyridine (DMAP) (1.42 g, 11.61 mmol, 0.1 eq) and TEA (47.00 g, 464.46 mmol, 64.65 mL, 4 eq) in DCM (500 mL) was added MsCl (39.90 g, 348.34 mmol, 26.96 mL, 3 eq) dropwise at 0 °C under N2, then the mixture was stirred at 0 °C for 0.5 hour. The reaction can also be performed at 25 °C for 1 hour. LC-MS showed Compound 1005 was consumed and the desired mass was detected. The reaction mixture was washed by aq.NaHCO3(100 mL * 3) and brine (100 mL * 3). The organic layer was dried over Na2SO4and then concentrated to give Compound 1006 (60 g, crude) as yellow oil. 1602179968.1 62 Attorney Docket No.: F2001-7001WO(VL99001-W1) 6. To a suspension of selenium powder (12.42 g, 153.38 mmol, 2 eq) in ethanol (EtOH) (300 mL) was added NaBH4 (11.61 g, 306.75 mmol, 4 eq) slowly under N2 at 0 °C. The reaction mixture was stirred at 25 °C until the color of the reaction mixture changed from black to colorless, and then the mixture of Compound 1006 (45 g, 76.69 mmol, 1 eq) in THF (150 mL) was added to the mixture dropwise under 25 °C, then the mixture was stirred at 60 °C for 12 hours. LC-MS showed Compound 1006 was consumed completely and the desired mass was detected. The reaction mixture was partitioned between H2O (200 mL) and EtOAc (100 mL). The organic phase was separated, washed with EtOAc (100 mL * 3), dried over Na2SO4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography to give Compound 1007 (20 g, crude) as yellow oil. 7. To a solution of Compound 1007 (15 g, 31.54 mmol, 1 eq) in DCM (150 mL) was added a mixture of meta-chloroperoxybenzoic acid (m-CPBA) (6.40 g, 31.54 mmol, 85% purity, 1 eq) in DCM (50 mL) at -70 °C. The mixture was stirred at -70 °C for 0.5 hour. The reaction can also be performed for 1 hour. LC-MS showed Compound 1007 was consumed completely and desired mass was detected. The reaction mixture was quenched with saturated aqueous NaHCO3solution (100 mL) and extracted with DCM (100 mL * 2). The combined organic layer was washed with brine (100 mL * 2), dried over Na2SO4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography to give Compound 1008 (12 g, 24.41 mmol, 77.40% yield) as yellow oil. FIG.1 shows the synthesis of generic starting material for Se NTPs. This generalizable starting material (dashed box) can be used to synthesize any Se-modified base. Example 2: Synthesis of Se-modified Adenosine Triphosphate This example demonstrates the synthesis of Se modified adenosine triphosphate (ATP). The following synthetic steps are outlined below and in FIG.2: 1. To a solution of Compound 1007 (15 g, 31.5 mmol, 1 eq) in DCM (200 mL) was added a solution of m-CPBA (9.61 g, 47.3 mmol, 85% purity, 1.5 eq) in DCM (100 mL) dropwise under N2atmosphere at -70 °C, then the mixture was stirred at -70 °C under N2 atmosphere for 1 hour. LC-MS showed Compound 1007 was consumed 1602179968.1 63 Attorney Docket No.: F2001-7001WO(VL99001-W1) completely and desired mass was detected. The reaction mixture was quenched with saturated aqueous NaHCO3 solution (200 mL) and extracted with DCM (100 mL * 3). The combined organic layer was washed with brine (50 mL * 2), dried over Na2SO4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography to give Compound 1008 (13 g, 26.5 mmol, 83.9% yield) as yellow oil. 2. A mixture of Compound 1008 (9 g, 18.3 mmol, 1 eq) in acetic anhydride (Ac2O) (97.8 g, 958 mmol, 90.0 mL, 52.3 eq) was stirred at 100 °C for 1 hour. TLC (Plate 1: Petroleum ether : Ethyl acetate = 0:1) indicated Compound 1008 was consumed completely. The reaction mixture was quenched by saturated aqueous NaHCO3(200 mL) solution at 0 °C, and extracted with EtOAc (50 mL * 3). The combined organic layers were dried over Na2SO4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography to give Compound 2009 (6 g, 11.2 mmol, 61.4% yield) as yellow oil. 3. A mixture of Compound 2009A (1.04 g, 6.75 mmol, 1.2 eq) and bis(trimethylsilyl)acetamide (BSA) (2.29 g, 11.2 mmol, 2.78 mL, 2 eq) in toluene (Tol.) (60 mL) was degassed and purged with N2for 3 times, and then the mixture was stirred at 80 °C for 1 hour under N2 atmosphere until giving a clear solution. Then, to this reaction mixture was added a solution of Compound 2009 (3.00 g, 5.62 mmol, 1 eq) in toluene (30 mL) and trimethylsilyl trifluoromethanesulfonate (TMSOTf) (625 mg, 2.81 mmol, 508 μL, 0.5 eq) at 80 °C under N2 atmosphere and the mixture was stirred at 80 °C for 12 hours under N2atmosphere. TLC (Plate 1: Petroleum ether : Ethyl acetate = 10:1) showed Compound 2009 was consumed completely and LC-MS showed the desired mass was detected. To the reaction mixture was added H2O (100 mL), and then the mixture was extracted with EtOAc (50 mL * 3). The organic layer was dried over Na2SO4and then concentrated to give a residue. The residue was purified by flash silica gel chromatography to give Compound 2010 (650 mg, 1.03 mmol, 18.4% yield) as yellow oil. 4. To a solution of Compound 2010 (650 mg, 1.03 mmol, 1 eq) in THF (6 mL) was added tetra-n-butylammonium fluoride (TBAF) (1 M, 1.55 mL, 1.5 eq) at 20 °C. The mixture was stirred at 20 °C for 0.5 hour. LC-MS showed Compound 2010 was 1602179968.1 64 Attorney Docket No.: F2001-7001WO(VL99001-W1) consumed completely and desired mass was detected. The reaction mixture was concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography to give Compound 2011 (348 mg, 893 μmol, 86.3% yield) as yellow oil. 5. To a solution of Compound 2011 (348 mg, 893 μmol, 1 eq) in THF (4 mL) were added Compound 2011A (557 mg, 2.23 mmol, 2.5 eq) and 2H-tetrazole (113 mg, 1.61 mmol, 1.8 eq) at 20 °C under N2atmosphere. The mixture was stirred at 20 °C for 12 hours under N2 atmosphere. LC-MS showed Compound 2011 was consumed completely and desired mass was detected. Compound 2012 (500 mg, 883.57 μmol, 98.94% yield) in 2 mL THF was obtained as yellow liquid. 6. A mixture of m-CPBA (239 mg, 1.18 mmol, 85% purity, 1.5 eq) in THF (3 mL) was added to a mixture of Compound 2012 (500 mg, 784 μmol, 1 eq) in 2 mL THF at -70 °C under N2atmosphere and the mixture was stirred at 20 °C for 1 hour under N2atmosphere. LC-MS showed Compound 2012 remained and desired mass was detected. Then, a mixture of m-CPBA (79.6 mg, 392 μmol, 85% purity, 0.5 eq) in THF (1 mL) was added to the mixture at -70 °C under N2atmosphere and the mixture was stirred at 20 °C for 0.5 hour under N2atmosphere. LC-MS showed Compound 2012 was consumed completely and desired mass was detected. The reaction mixture was quenched by addition of saturated aqueous Na2SO3(3 mL) solution and saturated aqueous NaHCO3(3 mL) solution, and then diluted with H2O (3 mL) and extracted with EtOAc (3 mL * 3). The combined organic layers were washed with brine (3 mL), dried over Na2SO4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography to give Compound 2013 (275 mg, 473 μmol, 60.3% yield) as yellow oil. 7. A mixture of Compound 2013 (185 mg, 318 μmol, 1 eq) in ammonia (2 M, 10 mL, 62.9 eq) was degassed and purged with N2for 3 times, and then the mixture was stirred at 80 °C for 12 hours under N2 atmosphere. LC-MS showed Compound 2013 was consumed completely and desired mass was detected. The reaction mixture was concentrated to give Compound 2014 (170 mg, crude) as yellow oil. 8. Two batches were set in parallel. To a solution of Compound 2014 (302.5 mg, 538 μmol, 1 eq) in THF (3 mL) and H2O (3 mL) was added HCl (12 M, 0.04 mL, 8.92e-1 1602179968.1 65 Attorney Docket No.: F2001-7001WO(VL99001-W1) eq) at 20 °C. The mixture was stirred at 40 °C for 2 hours. LC-MS showed Compound 2014 remained and desired mass was detected. Then, HCl (12 M, 0.1 mL, 2.23 eq) was added to the mixture, and the mixture was stirred at 40 °C for 12 hours. Two batches were combined for work-up. To the reaction mixture was added TEA to adjust pH to 8, and then the mixture was concentrated under reduced pressure to give a residue. The residue was purified by prep-HPLC (triethylammonium bicarbonate (TEAB) condition; column: Titank C1810um 30*150mm; mobile phase: [50mM TEAB-acetonitrile (ACN)]; gradient:2%-12% B over 20 min) to give Compound 2015 (100 mg, 151 μmol, 14.0% yield, 2.5 TEA salt) as a white solid. 9. To a solution of Compound 2015 (90 mg, 136 μmol, 1 eq, 2.5 TEA salt) in DMF (2 mL) was added a mixture of carbonyldiimidazole (CDI) (33 mg, 204 μmol, 1.5 eq) in DMF (0.3 mL) at 20 °C under N2 atmosphere, and then the mixture was stirred at 20 °C for 1 hour under N2atmosphere. LC-MS showed Compound 2015 remained. Then, CDI (22.0 mg, 136 μmol, 1 eq) was added to the mixture at 20 °C under N2 atmosphere. The mixture was stirred at 20 °C for 1 hour under N2 atmosphere. LC- MS showed Compound 2015 remained. Then, CDI (11.00 mg, 67.9 μmol, 0.5 eq) was added to the mixture. The mixture was stirred at 20 °C for 0.5 hour under N2atmosphere. Then, MeOH (34.8 mg, 1.09 mmol, 43.9 μL, 8 eq) was added to quench excess CDI. The mixture was stirred at 20 °C for 0.5 hour, then N,N-dibutylbutan-1- amine;phosphono dihydrogen phosphate (1 M, 1.36 mL, 10 eq) was added to the mixture and stirred at 20 °C for 12 hours under N2 atmosphere. LC-MS showed Compound 2015 was consumed completely and desired mass was detected. The reaction mixture was diluted with H2O (10 mL). The mixture was purified by DEAE Sephadex A25 column (NH4HCO3 (1M) / water=1:4 to 3:7) to give a crude product, then it was purified by prep-HPLC (TEAB condition, column: Titank C1810um 30*150mm; mobile phase: [50mM TEAB-ACN]; gradient:3%-16% B over 20 min) to give the desired product. The mixture was then loaded to sodium ion exchange resin and eluted with H2O to give target Compound 2036 (22.8 mg, 34.87 μmol, 25.69% yield, 90.7% purity, Na salt) as a white solid. LC-MS (ESI-): m / z 570.0 [M-H]- 1602179968.1 66 Attorney Docket No.: F2001-7001WO(VL99001-W1) HNMR: 1H NMR (400 MHz, D2O) δ = 8.66 (s, 1H), 8.23 (s, 1H), 6.11 - 6.04 (m, 1H), 4.88 (dd, J = 3.6, 7.6 Hz, 1H), 4.65 (t, J = 3.2 Hz, 1H), 4.37 - 4.26 (m, 2H), 3.89 - 3.81 (m, 1H) PNMR: 31P NMR (162 MHz, D2O) δ = -6.02 (d, J = 20.0 Hz, 1P), -11.40 (d, J = 19.2 Hz, 1P), -22.02 (t, J = 19.6 Hz, 1P) FIG.2 shows a representative synthesis scheme for a Se-modified ATP. Example 3: Synthesis of Se-modified Uridine Triphosphate This example demonstrates the synthesis of Se modified uridine triphosphate (UTP). The following synthetic steps are outlined below and in FIG.3: 1. To a solution of 1H-pyrimidine-2,4-dione (2.28 g, 20.34 mmol, 2 eq) in Tol. (60 mL) was added TEA (4.12 g, 40.69 mmol, 5.66 mL, 4 eq) and TMSOTf (18.09 g, 81.37 mmol, 14.70 mL, 8 eq). The mixture was stirred at 25 °C for 1 hour. Then, the above mixture was diluted with DCM (30 mL) and added to Compound 1008 (5 g, 10.17 mmol, 1 eq) in DCM (30 mL) at 0 °C dropwise. Then TEA (4.12 g, 40.69 mmol, 5.66 mL, 4 eq) in Tol. (30 mL) was added to the mixture and the reaction was stirred at 25 °C for 12 hours. TLC showed Compound 1008 was consumed completely and desired spot formed. The reaction mixture was added to water (50 mL) and extracted with EtOAc (30 mL * 3). The organic layer was dried over Na2SO4and then concentrated to give the crude product. The residue was purified by flash silica gel chromatography to give Compound 3009 (2.7 g, 4.61 mmol, 45.33% yield) as yellow oil. 2. To a solution of Compound 3009 (2.7 g, 4.61 mmol, 1 eq) in THF (30 mL) was added TBAF (1 M, 6.92 mL, 1.5 eq). The mixture was stirred at 25 °C for 0.5 hour. LC-MS showed Compound 3009 was consumed and desired mass was detected. The reaction mixture was concentrated to give the residue. The residue was purified by flash silica gel chromatography to give Compound 3010 (1.2 g, 3.46 mmol, 74.96% yield) as yellow oil. 3. Two batches were set in parallel. To a solution of Compound 3010 (500 mg, 1.44 mmol, 1 eq) in THF (10 mL) was added N-ditert-butoxyphosphanyl-N-ethyl- 1602179968.1 67 Attorney Docket No.: F2001-7001WO(VL99001-W1) ethanamine (1.80 g, 7.20 mmol, 5 eq) and 2H-tetrazole (806.97 mg, 11.52 mmol, 1.02 mL, 8 eq) at 20 °C under N2 atmosphere. The mixture was stirred at 40 °C for 12 hours. LC-MS showed Compound 3010 was consumed completely and the desired mass was detected. Compound 3010E (0.75 g, 2.87 mmol, 99.51% yield) in 10 mL THF was obtained as white liquid. The two batch mixture was used directly for the next step. 4. The reaction was set in two batches. A mixture of m-CPBA (570.18 mg, 2.81 mmol, 85% purity, 2 eq) in THF (2 mL) was added to the mixture of Compound 3010E (735 mg, 1.40 mmol, 1 eq) in 9.5 mL THF at -70 °C and the mixture was stirred at 20 °C for 1 hour. LC-MS showed Compound 3010E was consumed completely and the desired mass was detected. The reaction mixture was quenched by the addition of sat.aq. Na2SO3 (1 mL) and sat.aq. NaHCO3 (1 mL), and then diluted with DCM (1 mL) and extracted with DCM (1 mL * 3). The combined organic layers were washed with sat.aq. NaCl (1 mL), dried over Na2SO4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography to give Compound 3010F (845 mg, 1.57 mmol, 55.78% yield) as a white solid. 5. The reaction was set in two batches. To a solution of Compound 3010F (420 mg, 778.62 μmol, 1 eq) in THF (4 mL) and H2O (4 mL) was added HCl (12 M, 64.88 μL, 1 eq) at 20 °C. The mixture was stirred at 40 °C for 12 hours. LC-MS showed desired mass was detected. The two batches were combined and concentrated to give the crude product. The residue was purified by prep-HPLC (TEAB condition; column: YMC-Actus Triart C18150*30mm*5um; mobile phase: [H2O(10mM TEAB)-ACN]; gradient:1%-5% B over 10.0 min) to give Compound 3010G (300 mg, 508.89 μmol, 32.68% yield, 2TEA) as a white solid. 6. The reaction was set in two batches. To a solution of Compound 3010G (135 mg, 229.00 μmol, 1 eq, 2TEA) in DMF (2 mL) was added CDI (66.84 mg, 412.20 μmol, 1.8 eq). The mixture was stirred at 20 °C for 1 hour. LC-MS showed Compound 3010G was consumed. Then, MeOH (58.70 mg, 1.83 mmol, 74.14 μL, 8 eq) was added to quench excess CDI. The mixture was stirred at 20 °C for 0.5 hour, then N,N- dibutylbutan-1-amine;phosphono dihydrogen phosphate (1 M, 2.29 mL, 10 eq) was 1602179968.1 68 Attorney Docket No.: F2001-7001WO(VL99001-W1) added to the mixture and stirred at 20 °C for 12 hours. LC-MS showed Compound 3010G was consumed completely and the desired mass was detected. The two batches of the reaction mixture were combined, and the mixture was diluted with H2O (10 mL). The mixture was purified by DEAE Sephadex A25 column (NH4HCO3(1M) / water = 1 / 4 to 3:7) to give crude product. The crude product was further purified by prep-HPLC (TEAB condition; column: Titank C1810um 30*150mm; mobile phase: [50mM TEAB-ACN]; gradient:1%-10% B over 20 min) to give the desired compound, which was then loaded to sodium ion exchange resin and eluted with H2O to give target Compound 3038 (20.6 mg, 34.44 μmol, 7.52% yield, 95.297% purity, Na) as a white solid. LC-MS (ESI-): m / z 546.9 [M-H]- 1H NMR (400 MHz, D2O) δ = 8.15 (br d, J = 8.0 Hz, 1H), 6.18 (br d, J = 7.6 Hz, 1H), 5.94 (br d, J = 8.0 Hz, 1H), 4.58 - 4.50 (m, 2H), 4.32 - 4.16 (m, 2H), 3.71 (br s, 1H) 31P NMR (162 MHz, D2O) δ = -5.68 - -6.09 (m, 1P), -11.42 (d, J = 19.2 Hz, 1P), - 21.84 (br t, J = 20.0 Hz, 1P) FIG.3 shows a representative synthesis scheme for a Se-modified UTP. Example 4: Synthesis of Se-modified Cytosine Triphosphate This example demonstrates the synthesis of Se modified cytosine triphosphate (CTP). The following synthetic steps are outlined below and in FIG.4: 1. To a solution of N-(2-oxo-1H-pyrimidin-4-yl)benzamide (Compound 4008B) (4.38 g, 20.34 mmol, 2 eq) in toluene (60 mL) was added TEA (4.12 g, 40.69 mmol, 5.66 mL, 4 eq) and TMSOTf (18.09 g, 81.37 mmol, 14.70 mL, 8 eq). The mixture was stirred at 25 °C for 1 hour. Then, the mixture was diluted with DCM (30 mL) and added to Compound 1008 (5 g, 10.17 mmol, 1 eq) in DCM (30 mL) at 0 °C dropwise. Then TEA (4.12 g, 40.69 mmol, 5.66 mL, 4 eq) in Tol. (30 mL) was added to the mixture, and the reaction mixture was stirred at 25 °C for 12 hours. TLC showed Compound 1008 was consumed completely and desired spot formed. The reaction mixture was added to water (150 mL), extracted with EtOAc (100 mL * 3). The organic layer was 1602179968.1 69 Attorney Docket No.: F2001-7001WO(VL99001-W1) dried over Na2SO4, concentrated to give the crude product. The residue was purified by flash silica gel chromatography to give Compound 4009 (3.7 g, 5.37 mmol, 52.81% yield) as yellow oil. 2. To a solution of Compound 4009 (3.7 g, 5.37 mmol, 1 eq) in THF (40 mL) was added TBAF (1 M, 8.06 mL, 1.5 eq). The mixture was stirred at 25 °C for 0.5 hour. It can also be stirred for 1 hour. LC-MS showed Compound 4009 was consumed and desired mass was detected. The reaction mixture was concentrated to give the residue. The residue was purified by flash silica gel chromatography to give Compound 4010 (1.46 g, 3.24 mmol, 60.35% yield) as yellow oil. 3. The reaction was set in two batches. To a solution of Compound 4010 (600 mg, 1.33 mmol, 1 eq) and 2H-tetrazole (746.66 mg, 10.66 mmol, 945.14 μL, 8 eq) in THF (10 mL) was added N-ditert-butoxyphosphanyl-N-isopropyl-propan-2-amine (1.85 g, 6.66 mmol, 5 eq) at 20 °C under N2. Then the mixture was stirred at 40 °C for 1 hour. LC-MS showed Compound 4010 was consumed and desired mass was detected. The two batches of the reaction mixture were combined and it was used for the next step directly. Compound 4011 (1.67 g, crude) was obtained as yellow oil in THF (20 mL) and was used directly. 4. To a solution of Compound 4011 (1.62 g, 2.59 mmol, 1 eq) in THF (19.5 mL) was added a solution of m-CPBA (1.05 g, 5.17 mmol, 85% purity, 2 eq) in THF (10 mL) at -70 °C, then the mixture was stirred at 20 °C for 1 hour. LC-MS showed Compound 4011 was consumed and desired mass was detected. The reaction mixture diluted with EtOAc (20 mL) and washed with sat. aq. NaHCO3(20 mL) and sat. aq. NaHSO3(20 mL * 2). Then, the combined organic layers were dried over Na2SO4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography to give Compound 4012 (1.08 g, crude) as yellow oil. 5. To a solution of Compound 4012 (1 g, 1.56 mmol, 1 eq) in DCM (10 mL) was added H3PO4 (610.05 mg, 6.23 mmol, 363.12 μL, 4 eq). The mixture was stirred at 15 °C for 1 hour. LC-MS showed Compound 4012 was consumed completely and desired mass was detected. The reaction mixture was diluted with H2O (10 mL). The mixture was purified by DEAE Sephadex A25 column (NH4HCO3(1M) / water = 1:9 1602179968.1 70 Attorney Docket No.: F2001-7001WO(VL99001-W1) to 3:7) to give crude product, which was further purified by prep-HPLC (TEAB condition, column: Titank C1810um 30*150mm; mobile phase: [50mM TEAB- ACN]; gradient:8%-28% B over 20 min) to give Compound 4013 (330 mg, 444.00 μmol, 28.53% yield, 2.5TEA) as a white solid. 6. Two batches were set in parallel. To a solution of Compound 4013 (150 mg, 201.82 μmol, 1 eq, 2.5TEA) in DMF (2 mL) was added CDI (55 mg, 339.19 μmol, 1.68 eq). The mixture was stirred at 20 °C for 1 hour. LC-MS showed little Compound 4013 remained. Then MeOH (25.87 mg, 807.28 μmol, 32.67 μL, 4 eq) was added to quench excess CDI. The mixture was stirred at 20 °C for 0.5 hour, then N,N- dibutylbutan-1-amine;phosphono dihydrogen phosphate (1 M, 2.0 mL, 9.91 eq) was added to the mixture and stirred at 20 °C for 11.5 hours. LC-MS showed Compound 4014 was detected. The two batches mixture were combined. The reaction mixture was diluted with H2O (10 mL). The mixture was purified by DEAE Sephadex A25 column (NH4HCO3(1M) / water = 1 / 4 to 3:7) to give crude product, then it was purified by prep-HPLC (TEAB condition, column: Titank C1810um 30*150mm; mobile phase: [50mM TEAB-ACN]; gradient:5%-20% B over 20 min) to give Compound 4014 (120 mg, 113.75 μmol, 28.49% yield, 4TEA) as a white solid. 7. A solution of Compound 4014 (120 mg, 113.75 μmol, 1 eq, 4TEA) in NH3.H2O (2 mL) (25%) was stirred at 20 °C for 1 hour. LC-MS showed Compound 4014 was consumed completely and the desired mass was detected. The reaction mixture was diluted with H2O (10 mL). The mixture was purified by prep-HPLC (TEAB condition; column: Titank C1810um 30*150mm; mobile phase: [50mM TEAB- ACN]; gradient:1%-10% B over 20 min) to give the desired compound, then it was loaded to sodium ion exchange resin and eluted with H2O to give target compound 4039 (20.2 mg, 34.27 μmol, 30.13% yield, 96.564% purity, Na) as a white solid. LC-MS (ESI-): m / z 545.9 [M-H]- 1H NMR (400 MHz, D2O) δ = 8.19 (d, J = 7.6 Hz, 1H), 6.25 - 6.03 (m, 2H), 4.56 - 4.41 (m, 2H), 4.30 - 4.14 (m, 2H), 3.69 (br s, 1H) 31P NMR (162 MHz, D2O) δ = -8.54 - -10.27 (m, 1P), -11.64 (br d, J = 19.2 Hz, 1P), - 22.91 (br dd, J = 4.4, 17.6 Hz, 1P) 1602179968.1 71 Attorney Docket No.: F2001-7001WO(VL99001-W1) FIG.4 shows a representative synthesis scheme for a Se-modified CTP. Example 5: IVT with Se-modified (4’Se) NTPs This example demonstrates using in vitro transcription (IVT) to generate partially 4’Se- modified RNA (without a 5’ cap or poly(A) tail) or mRNA (with a 5’ capped and poly(A) tail) of sufficient length and quality for use in cell-based or cell-free translation assays and in vitro nuclease resistance assays. A PCR product comprising double-stranded DNA encoding reporter RNA (e.g. HiBiT and driven by a T7 promoter) was generated by high-fidelity PCR amplification. The PCR product was then used as a template for IVT reactions. The HiBiT reporter is the smaller subunit of a luciferase protein and produces a luminescent signal upon complexation with its cognate subunit, LgBiT. For downstream assays (Examples 7-11), HiBiT RNA and mRNA were produced via IVT reactions using the following DNA sequence: TAATACGACTCACTATAAGGAGAATAAACTAGTATTCTTCTGGTCCCCACAGACTCA GAGAGAACCCGCCACCATGGTCTTCACAGACTACAAAGACGATGACGACAAGGAAC AAAAACTCATCTCAGAAGAGGATCTGGTGAGCGGCTGGAGGCTGTTCAAGAAGATC AGCTAATGATGATGACTCGAGCTGGTACTGCATGCACGCAATGCTAGCTGCCCCTTT CCCGTCCTGGGTACCCCGAGTCTCCCCCGACCTCGGGTCCCAGGTATGCTCCCACCT CCACCTGCCCCACTCACCACCTCTGCTAGTTCCAGACACCTCCCAAGCACGCAGCAA TGCAGCTCAAAACGCTTAGCCTAGCCACAC (SEQ ID NO: 1) The RNA sequence produced from this DNA sequence has a predicted sequence of: AUGGUCUUCACAGACUACAAAGACGAUGACGACAAGGAACAAAAACUCAUCUCA GAAGAGGAUCUGGUGAGCGGCUGGAGGCUGUUCAAGAAGAUCAGCUAAUGA (SEQ ID NO: 2) IVT reactions were assembled using the following conditions in 40 µL reaction volume: a. Buffer: 40 mM Tris-HCl pH 7.9, 2 mM spermidine, and 9 mM MgCl2. 1602179968.1 72 Attorney Docket No.: F2001-7001WO(VL99001-W1) b. Nucleotides: 2 mM NTPs (final for each). a. Unmodified RNA: ATP, CTP, GTP, and UTP b. 25% modified (or SeU) RNA: ATP, CTP, GTP, and SeUTP c. 50% modified (or SeUC) RNA: ATP, SeCTP, GTP, SeUTP d. 75% modified (or SeUCA) RNA: SeATP, SeCTP, GTP, SeUTP c. For reactions meant to generate mRNA, a final concentration of 0.8 mM CleanCap (Trilink BioTechnologies N-7113) was additionally added d. Template: 100-300 ng of PCR product e. Enzyme: AmpliScribe T7 RNA polymerase (LGC Biosearch Technologies).4 µL for each 40 µL reaction. f. Ribonuclease Inhibitor: RiboGuard RNase Inhibitor (40 U / µL) (LGC Biosearch Technologies), added at 1 µL for each 40 µL reaction. Throughout the Examples, a reaction involving 25% modified nucleotides indicates that 25% of the input nucleotides in the IVT reaction are modified, and the remaining nucleotides are not Se-modified. Thus, in the Examples, when one of the four types of nucleotides is Se- modified, the reaction product is referred to as 25% modified RNA; when two of the four types of nucleotides are Se-modified, the reaction product is referred to as 50% Se-modified RNA; and when three of the four types of nucleotides are Se-modified, the reaction product is referred to as 75% Se-modified RNA. Depending on the RNA sequence being transcribed, the percent of nucleotides in the resulting RNA that comprise a structure according to Formula (I) herein may be different from the 25%, 50%, or 75% numbers used in the nomenclature in the Examples. Assembled IVT reactions were incubated for 4 hours at 37˚C. Following IVT, completed reactions were incubated with 1 µL RNase-Free DNase I (1 U / µL) (LGC Biosearch Technologies) for 15 minutes at 37 ˚C to remove residual template, then enriched using CleanNGS DNA and RNA Clean-Up magnetic beads (BulldogBio; CNGS500) using the manufacturer’s supplied protocols for RNAs >200 nt. Reactions were eluted in 15 µL of water before quantification. The products of these IVT reactions were either 5’ triphosphorylated or 5’ capped (reactions assembled in the presence of CleanCap). The product of the IVT reaction lacked a polyA tail. 1602179968.1 73 Attorney Docket No.: F2001-7001WO(VL99001-W1) Next, for mRNA, the 5’ capped RNA molecule was further polyadenylated. Polyadenylation of CleanCap-containing RNA was performed using E. coli Poly(A) polymerase (NEB M0276) according to the manufacturer’s protocol using 4 µg per RNA as input for each 20 µL reaction. Reactions were assembled, mixed, and incubated for 1 hour at 37 ˚C prior to reaction cleanup using CleanNGS DNA and RNA Clean-Up magnetic beads (BulldogBio; CNGS500) using the manufacturer’s supplied protocols for RNAs >200 nt. Reactions were eluted in 15 µL of water before quantification. Analysis of RNA production, quality, and quantity was performed on an Agilent TapeStation 4200 using RNA ScreenTapes and associated reagents (Agilent; 5067-5576). RNA quality and quantity were assessed by band patterning and intensity, respectively. Of note, yields of Se-modified RNA were sensitive to specific reaction conditions. For example, yields of 50% Se-modified RNA (i.e., SeUC) were sensitive to Mg2+concentrations and NTP concentrations, with suitable yields occurring, e.g., at 9 mM Mg2+and 2 mM of each NTP. Example 6: Synthesis of Se-modified uridine phosphoramidite and conversion into Se- modified homopolymer via oligonucleotide chemical synthesis This example demonstrates the synthesis of a Se-modified uridine phosphoramidite and its subsequent use in automated oligonucleotide synthesis. The synthesis of the phosphoramidite is described below and shown in FIG.5B. 1. First, ((3aR,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyldihydrofuro[3,4-d][1,3]dioxol- 4(3aH)-one was reacted with methanesulfonyl chloride (MsCl), in triethylamine (TEA) and DCM, at room temperature for 3 hours. The resultant product was (((3aR,4R,6aR)-2,2-dimethyl-6-oxotetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl methanesulfonate. 2. Next, ((3aR,4R,6aR)-2,2-dimethyl-6-oxotetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl methanesulfonate was reacted with potassium hydroxide (KOH) and then aqueous hydrochloric acid (HCl) and propan-2-one to form (3aR,6S,6aR)-6-(hydroxymethyl)- 2,2-dimethyldihydrofuro[3,4-d][1,3]dioxol-4(3aH)-one. 3. (3aR,6S,6aR)-6-(hydroxymethyl)-2,2-dimethyldihydrofuro[3,4-d][1,3]dioxol-4(3aH)- one was then reacted with tert-Butyl(chloro)diphenylsilane (TBDPSCl) and imidazole, in DCM, at room temperature for 5 hours. 1602179968.1 74 Attorney Docket No.: F2001-7001WO(VL99001-W1) 4. The resultant product, (3aR,6S,6aR)-6-(((tert-butyldiphenylsilyl)oxy)methyl)-2,2- dimethyldihydrofuro[3,4-d][1,3]dioxol-4(3aH)-one, was reacted with NaBH4 in THF and methanol, at room temperature for 2 hours, to form (3aR,6S,6aR)-6-(((tert- butyldiphenylsilyl)oxy)methyl)-2,2-dimethyldihydrofuro[3,4-d][1,3]dioxol-4(3aH)- one. 5. Next, (3aR,6S,6aR)-6-(((tert-butyldiphenylsilyl)oxy)methyl)-2,2- dimethyldihydrofuro[3,4-d][1,3]dioxol-4(3aH)-one was reacted with MsCl, TEA, 4- dimethylamipyridine, in DCM, at room temperature for 18 hours. The resultant product was (3aR,6S,6aR)-6-(((tert-butyldiphenylsilyl)oxy)methyl)-2,2- dimethyldihydrofuro[3,4-d][1,3]dioxol-4(3aH)-one. 6. This product was subsequently reacted with selenium (Se), NaBH4, in ethanol / DMF for 3 hours. This reaction can be performed at a temperature between room temperature and 60 °C. 7. The resultant product, (3aR,6S,6aR)-6-(((tert-butyldiphenylsilyl)oxy)methyl)-2,2- dimethyldihydrofuro[3,4-d][1,3]dioxol-4(3aH)-one, was reacted with meta- chloroperoxybenzoic acid (m-CPBA), in DCM, at -78°C, for 1 hour, to form (3aS,4R,6aR)-4-(((tert-butyldiphenylsilyl)oxy)methyl)-2,2- dimethyltetrahydroselenopheno[3,4-d][1,3]dioxole 5-oxide. 8. This product was reacted with uracil, TEA, trimethylsilyl trifluoromethanesulfonate (TMSOTf), in toluene and DCM for 18 hours, to form 1-((3aR,4R,6R,6aS)-6-(((tert- butyldiphenylsilyl)oxy)methyl)-2,2-dimethyltetrahydroselenopheno[3,4- d][1,3]dioxol-4-yl)pyrimidine-2,4(1H,3H)-dione. This reaction can be performed at a temperature ranging from 0 °C to room temperature. 9. Next, 1-((3aR,4R,6R,6aS)-6-(((tert-butyldiphenylsilyl)oxy)methyl)-2,2- dimethyltetrahydroselenopheno[3,4-d][1,3]dioxol-4-yl)pyrimidine-2,4(1H,3H)-dione was reacted with THF and 50% trifluoroacetic acid, at room temperature, for 18 hours. 10. The resultant product, 1-((2R,3R,4S,5R)-3,4-dihydroxy-5- (hydroxymethyl)tetrahydroselenophen-2-yl)pyrimidine-2,4(1H,3H)-dione, was reacted with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane, in pyridine, at room temperature, for 3 hours, to form 1-((6aR,8R,9R,9aS)-9-hydroxy-2,2,4,4- 1602179968.1 75 Attorney Docket No.: F2001-7001WO(VL99001-W1) tetraisopropyltetrahydro-6H-selenopheno[3,2-f][1,3,5,2,4]trioxadisilocin-8- yl)pyrimidine-2,4(1H,3H)-dione. 11. This was reacted with TBDOTf and 2,6-dimethylpyridine, in DCM, at room temperature, for 12 hours, to form 1-((6aR,8R,9R,9aS)-9-((tert- butyldimethylsilyl)oxy)-2,2,4,4-tetraisopropyltetrahydro-6H-selenopheno[3,2- f][1,3,5,2,4]trioxadisilocin-8-yl)pyrimidine-2,4(1H,3H)-dione. 12. Next, 1-((6aR,8R,9R,9aS)-9-((tert-butyldimethylsilyl)oxy)-2,2,4,4- tetraisopropyltetrahydro-6H-selenopheno[3,2-f][1,3,5,2,4]trioxadisilocin-8- yl)pyrimidine-2,4(1H,3H)-dione was reacted with acetic acid, tetra-n- butylammonium fluoride, in THF, at 0 °C, for 0.5 hours. 13. The resultant product, 1-((2R,3R,4S,5R)-3-((tert-butyldimethylsilyl)oxy)-4-hydroxy- 5-(hydroxymethyl)tetrahydroselenophen-2-yl)pyrimidine-2,4(1H,3H)-dione, was reacted with 4,4-Dimethoxytrityl chloride (DMTrCl), in dry pyridine, for 2 hours, to form 1-((2R,3R,4S,5R)-5-((bis(4-methoxyphenyl)(phenyl)methoxy)methyl)-3-((tert- butyldimethylsilyl)oxy)-4-hydroxytetrahydroselenophen-2-yl)pyrimidine- 2,4(1H,3H)-dione. Finally, this product was reacted with 2-cyanoethyl N,N- diisopropylchlorophosphoramidite with N,N-diisopropylethylamine (DIPEA) catalyst to form the selenium-uridine phosphoramidite. The Se-modified uridine phosphoramidite was subsequently used in solid-phase oligonucleotide synthesis. The 1H NMR spectrum for the Se-modified uridine phosphoramidite is shown in FIG.5A. DMSO is the solvent that was used when acquiring this spectrum. 31P NMR (CDCl3) δ: 150.2 (s), 149.7 (s). Standard coupling methods were modulated to improve the coupling efficiency of the selenium-modified uridine phosphoramidite into a fully modified uridine homopolymer. Parameters tested included coupling time, reagent concentration, and cleavage / deprotection protocols. The final products were poly-SeU oligonucleotides of ~30 bases that were tested for enzymatic stability in subsequent examples. 1602179968.1 76 Attorney Docket No.: F2001-7001WO(VL99001-W1) Example 7: Exonuclease stability of Se-modified RNA This example demonstrates the determination of the resistance of 4’ Se-modified RNA to two exonucleases; 1) XRN-1 (New England Biolabs, #M0338) and 2) Exonuclease T (ExoT; New England Biolabs #M0265). This example encompasses resistance to both 5’ - 3’ exonuclease activity (XRN-1) and 3’ - 5’ exonuclease activity (ExoT). 1. 5’ - 3’ exonuclease resistance a. XRN-1 resistance was tested by assembling a combined reaction of unmodified or 75% Se-modified RNA (without a 5’ cap or polyA tail) produced as in Example 5, XRN-1, and a companion enzyme (RppH) to convert the triphosphorylated 5’ end of IVT products into 5’ monophosphate RNAs that are substrates for XRN-1. b. Reactions were set up under the following buffer conditions; 10 mM Tris- HCl, 50 mM NaCl, 10 mM MgCl2, 1 mM DTT, pH 7.9, 1 unit per reaction of XRN-1, 5 units per reaction of RppH, and 50 ng of substrate RNA in 20 µL reaction volume. Reactions were assembled on ice before mixing and incubation at 37˚C for the indicated timepoints shown in FIG.6A. c. Reactions were stopped by the addition of 40 µL of CleanNGS DNA and RNA Clean-Up magnetic beads (BulldogBio; CNGS500) and residual RNA was enriched using the manufacturer’s supplied protocols for RNAs >200 nt. Reactions were eluted in 5 µL of water before quantification via RNA ScreenTape as described in Example 5. d. RNA resistance to XRN-1 was calculated as a ratio of the residual signal intensity of intact RNA at each time point to the signal intensity of input RNA (0 minute timepoint). 2. 3’ - 5’ exonuclease resistance a. ExoT resistance was tested by assembling a combined reaction of unmodified or Se-modified homopolymers produced via chemical synthesis as described in Example 6 with ExoT under manufacturer recommended conditions. Decay was monitored over a total of 60 minutes, and residual RNA was visualized by denaturing polyacrylamide gel electrophoresis (PAGE). 1602179968.1 77 Attorney Docket No.: F2001-7001WO(VL99001-W1) b. Reactions were set up under the following buffer conditions; 20 mM Tris- Acetate, 50 mM KCl, 10 mM magnesium acetate, 1 mM DTT, pH adjusted to pH 7.9, 5 units per reaction of ExoT, and 300 ng of substrate RNA in 20 µL total reaction volume. Reactions were assembled on ice before mixing and incubation at 37˚C for the timepoints shown in FIG.6B, up to 60 minutes. c. Reactions were stopped by the addition of Novex TBE-Urea Sample buffer 2X (ThermoFisher LC6876) and briefly heated to 80˚C before cooling, loading into, and electrophoresis through a denaturing PAGE gel. d. Residual homopolymer was detected by staining with SYBR Gold (ThermoFisher S11494) and quantified by image post processing in ImageJ. Residual RNA signal was compared as a ratio to RNA detected in the input samples (0 minute). The resistance of Se-modified RNA to degradation by both exonucleases is depicted in FIGs.6A and 6B. Whether in long IVT-produced RNA or short chemical RNA oligos, Se incorporation in place of the 4’ oxygen in the RNA conferred considerable protection against both 5’ exonuclease (XRN-1; FIG.6A) and 3’ exonuclease (ExoT; FIG.6B) activity. Example 8: Endonuclease stability of Se-modified RNA This example demonstrates the determination of the resistance of partially 4’ Se-modified RNA to an endonuclease. The endonuclease resistance of 4’ Se-modified RNA was examined in vitro using bovine RNase A as a representative mechanistic example of endonucleolytic decay in human biology. Reactions were assembled under the following conditions: 10 mM Tris-HCl pH 8.0, 250 pg of RNase A (New England Biolabs #T3018), and 300 ng of substrate RNA in 10 µL reaction volume. The following species of RNA were tested in these reactions: unmodified and 75% Se- modified RNA (without a polyA tail), produced by IVT as described in Example 5 above, and unmodified and 100% Se-modified uridine homopolymer, produced by chemical synthesis as described in Example 6 above. Reactions were assembled on ice before mixing and incubation at 37˚C for the timepoints shown in FIG.7A and FIG.7B, up to 60 minutes. 1602179968.1 78 Attorney Docket No.: F2001-7001WO(VL99001-W1) Reactions were stopped by the addition of 10 µL Novex TBE-Urea Sample buffer 2X (ThermoFisher LC6876) and briefly heated to 80˚C before cooling. To visualize the levels of intact species, IVT-produced RNAs and chemically synthesized homopolymers were visualized by capillary electrophoresis (TapeStation) and PAGE gel electrophoresis, respectively, as described in Examples 5 and 6 above. The resistance of 75% and 100% Se-modified RNA to degradation by RNase A is depicted in FIG.7A and 7B, respectively. Whether in long IVT-produced RNA or short chemical RNA oligos, Se incorporation in place of the 4’ ribose oxygen conferred considerable protection against a classic endoribonuclease, RNase A. Example 9: Serum stability of Se-modified RNA This example demonstrates the determination of the resistance of partially 4’ Se-modified RNA to the total nuclease content of bovine serum. The total nuclease resistance of selenium- modified reporter RNA, generated via IVT as described in Example 5, was examined in vitro using fetal bovine serum (FBS) as a representative mechanistic example of nucleolytic decay in human serum. Unmodified or modified RNAs were tested for resistance to degradation in dilute serum by incubating RNA in the presence of 0.08% FBS (Life Technologies). FIG.8 shows the results for 75% modified RNA compared to an unmodified control. Stability reactions were assembled by the following method. 1. Each RNA sample for each time point was diluted to 25 ng / µL in water and 2 µL of each sample was placed in separate reaction tubes. 2. Next, 8 µL of 0.08% FBS diluted in Dulbecco’s Modified Eagle Medium (DMEM, Life Technologies) was added to each reaction tube and gently mixed. 3. Samples were incubated at 37˚C for the indicated timepoints shown in FIG.8 (up to 60 minutes). 4. At the end of the time course, 10 µL of 1% SDS was added to the reaction, and each sample was mixed to rapidly stop the reaction prior to enrichment and analysis. Reactions were enriched by the addition of 40 µL of CleanNGS DNA and RNA Clean- Up magnetic beads (BulldogBio; CNGS500) and residual RNA was enriched using the 1602179968.1 79 Attorney Docket No.: F2001-7001WO(VL99001-W1) manufacturer’s supplied protocols for RNAs >200 nt. Reactions were eluted in 5 µL of water before quantification via RNA ScreenTape as described above. RNA resistance to serum nuclease activity was calculated by measuring a ratio of the residual signal intensity of intact RNA at each time point to the signal intensity of input RNA (0 minute timepoint), as described above. The resistance of 75% Se-modified RNA to degradation in serum is depicted in FIG.8. As with purified enzymes (XrnI, ExoT, RNase A), Se incorporation in place of the 4’ ribose oxygen resulted in considerable RNA serum stability relative to unmodified control RNA. Example 10: Base hydrolysis resistance of Se-modified RNA This Example demonstrates the determination of the resistance of partially 4’ Se- modified RNA to base hydrolysis. The resistance of Se-modified RNA to base hydrolysis was examined in vitro using treatment with Mg+2and NaOH to accelerate the natural rate of RNA hydrolysis in water caused by in-line attack. Reactions were performed by incubating 50 ng of RNA in a 5 μL volume with 5 mM MgCl2and 5 mM NaOH at 37˚C for 60 minutes. Hydrolysis was halted by placing samples on ice and adding 5 μL of 500 mM Tris-HCl pH 7.0 and 500 mM EDTA. Samples were mixed with 15 μL SPRI Beads (Bulldog Bio) and 25 μL isoproyl alcohol to bind residual RNA, which were then washed twice with 50 μL 80% (v / v) EtOH in water, dried, and eluted in 5 μL water. Recovered RNA was analyzed using RNA Screen Tape (Agilent) and quantified with TapeStation Analysis Software version 4.1.1 as described above. The resistance of 75% Se-modified RNA to base hydrolysis is depicted in FIG.9. As with purified enzymes (e.g., XRN-I, ExoT, RNase A) and serum (e.g., FBS), Se incorporation in place of the 4’ ribose oxygen resulted in considerable stability in the context of chemical degradation that extends beyond enzymatic degradation. Example 11: Reporter gene expression of Se-modified mRNA This Example demonstrates the determination of translatability of Se-modified RNA, as defined by expression of HiBiT reporter RNA. 1602179968.1 80 Attorney Docket No.: F2001-7001WO(VL99001-W1) mRNA encoding HiBiT was produced via IVT and post-synthesis tailing as described in Example 5 above. To measure HiBiT expression in transfected cells, 30,000 Huh-7 cells were seeded in 100 µL DMEM + 10% FBS in 96-well collagen I-coated plates (STEMCELL Technologies, 100-1056) and incubated overnight at 37°C + 5% CO2. The following day, Lipofectamine MessengerMAX transfection reagent (Thermo Fisher, Invitrogen LMRNA008) was diluted in Opti-MEM I Reduced Serum Medium (Thermo Fisher, 31985070) at a ratio of 0.3 µL of transfection reagent in 5 µL of Opti-MEM I Reduced Serum Medium per well and incubated for 10 min at room temperature. Thereafter, 10 ng of HiBiT mRNA (Se-modified or unmodified) was diluted in an additional 5 µL of Opti-MEM I Reduced Serum Medium. The diluted transfection reagent and the diluted mRNA were mixed 1:1 (10 µL total volume) and incubated for 5 minutes at room temperature, followed by addition of 10 µL of mRNA transfection complex to each well, gently mixed, and incubated for the indicated time points at 37°C + 5% CO2. Transfection complex was removed from the cells 4 hours post transfection and replaced with DMEM + 10% FBS for the remainder of the experiment. After the incubation period, half of the volume of culture supernatant was removed from each well and replaced with Nano-Glo®HiBiT Lytic Reagent per manufacturer’s instructions (Nano-Glo®HiBiT Lytic Detection system, Promega, N3030). Wells containing medium only were used to subtract background signal from experimental values. The plate was incubated for 10 minutes with gentle orbital mixing at room temperature; then the lysates were transferred to 96-well, white bottom plates (Corning, 3917) for 10 minutes to allow for signal stabilization. Luminescence data was acquired on a Glo-Max Discover system (Promega) using an integration time of 0.5. Data is shown as luminescence values minus background signal. As shown in FIG.10, the expression of 75% Se-modified HiBiT mRNA was comparable to that of unmodified mRNA, as defined by similar luminescence at 48 hours post transfection. This result demonstrates that substitution of the 4’O to Se does not eliminate the ability of the corresponding RNA to be translated by ribosomes in cells, resulting in detectable protein production. Example 12: Reporter gene expression of Se-modified mRNA with a secreted NLuc reporter This Example demonstrates the determination of translatability of Se-modified RNA, as defined by expression of a secreted nanoluciferase (NLuc) reporter RNA. 1602179968.1 81 Attorney Docket No.: F2001-7001WO(VL99001-W1) mRNA encoding NLuc with an N-terminal IL2 secretion signal was produced via IVT with Se-modified NTPs as described in Example 5 above. Specifically, either Se-UTP or Se-ATP were substituted in IVT reactions for UTP or ATP, respectively. Thus, both of these molecules are referred to as 25% Se-modified mRNA. Secreted NLuc mRNA was produced via IVT reactions using the following DNA sequence: TAATACGACTCACTATAAGGAGAATAAACTAGTATTCTTCTGGTCCCCACAGACTCA GAGAGAACCCGCCACCATGTACAGGATGCAACTCCTGTCTTGCATTGCACTAAGTCT TGCACTTGTCACGAATTCGGGCGGCGGCGGCGGCATGGTCTTCACACTCGAAGATTT CGTTGGGGACTGGCGACAGACAGCCGGCTACAACCTGGACCAAGTCCTTGAACAGG GAGGTGTGTCCAGTTTGTTTCAGAATCTCGGGGTGTCCGTAACTCCGATCCAAAGGA TTGTCCTGAGCGGTGAAAATGGGCTGAAGATCGACATCCATGTCATCATCCCGTATG AAGGTCTGAGCGGCGACCAAATGGGCCAGATCGAAAAAATTTTTAAGGTGGTGTAC CCTGTGGATGATCATCACTTTAAGGTGATCCTGCACTATGGCACACTGGTAATCGAC GGGGTTACGCCGAACATGATCGACTATTTCGGACGGCCGTATGAAGGCATCGCCGT GTTCGACGGCAAAAAGATCACTGTAACAGGGACCCTGTGGAACGGCAACAAAATTA TCGACGAGCGCCTGATCAACCCCGACGGCTCCCTGCTGTTCCGAGTAACCATCAACG GAGTGACCGGCTGGCGGCTGTGCGAACGCATTCTGGCGTGATAATAGTGATGACTC GAGCTGGTACTGCATGCACGCAATGCTAGCTGCCCCTTTCCCGTCCTGGGTACCCCG AGTCTCCCCCGACCTCGGGTCCCAGGTATGCTCCCACCTCCACCTGCCCCACTCACC ACCTCTGCTAGTTCCAGACACCTCCCAAGCACGCAGCAATGCAGCTCAAAACGCTTA GCCTAGCCACACCCCCACGGGAAACAGCAGTGATTAACCTTTAGCAATAAACGAAA GTTTAACTAAGCTATACTAACCCCAGGGTTGGTCAATTTCGTGCCAGCCACACCCTG GAGCTAGCAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAGCATATGACTAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAA (SEQ ID NO: 3) The RNA sequence produced from this DNA sequence has a predicted sequence of: AGGAGAAUAAACUAGUAUUCUUCUGGUCCCCACAGACUCAGAGAGAACCCGCCAC CAUGUACAGGAUGCAACUCCUGUCUUGCAUUGCACUAAGUCUUGCACUUGUCACG AAUUCGGGCGGCGGCGGCGGCAUGGUCUUCACACUCGAAGAUUUCGUUGGGGAC UGGCGACAGACAGCCGGCUACAACCUGGACCAAGUCCUUGAACAGGGAGGUGUGU CCAGUUUGUUUCAGAAUCUCGGGGUGUCCGUAACUCCGAUCCAAAGGAUUGUCCU GAGCGGUGAAAAUGGGCUGAAGAUCGACAUCCAUGUCAUCAUCCCGUAUGAAGG UCUGAGCGGCGACCAAAUGGGCCAGAUCGAAAAAAUUUUUAAGGUGGUGUACCC UGUGGAUGAUCAUCACUUUAAGGUGAUCCUGCACUAUGGCACACUGGUAAUCGA CGGGGUUACGCCGAACAUGAUCGACUAUUUCGGACGGCCGUAUGAAGGCAUCGCC GUGUUCGACGGCAAAAAGAUCACUGUAACAGGGACCCUGUGGAACGGCAACAAA AUUAUCGACGAGCGCCUGAUCAACCCCGACGGCUCCCUGCUGUUCCGAGUAACCA UCAACGGAGUGACCGGCUGGCGGCUGUGCGAACGCAUUCUGGCGUGAUAAUAGU GAUGACUCGAGCUGGUACUGCAUGCACGCAAUGCUAGCUGCCCCUUUCCCGUCCU 1602179968.1 82 Attorney Docket No.: F2001-7001WO(VL99001-W1) GGGUACCCCGAGUCUCCCCCGACCUCGGGUCCCAGGUAUGCUCCCACCUCCACCU GCCCCACUCACCACCUCUGCUAGUUCCAGACACCUCCCAAGCACGCAGCAAUGCA GCUCAAAACGCUUAGCCUAGCCACACCCCCACGGGAAACAGCAGUGAUUAACCUU UAGCAAUAAACGAAAGUUUAACUAAGCUAUACUAACCCCAGGGUUGGUCAAUUU CGUGCCAGCCACACCCUGGAGCUAGCAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAGCAUAUGACUAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAA (SEQ ID NO: 4) To measure NLuc expression in transfected cells, 10k HUH-7 cells were seeded in 100 µL DMEM + 10% FBS in 96-well collagen I-coated plates and incubated overnight at 37°C + 5% CO2. The following day, Lipofectamine MessengerMAX transfection reagent was diluted in Opti-MEM I Reduced Serum Medium at a ratio of 0.3 µL of transfection reagent in 5 µL of Opti-MEM I Reduced Serum Medium per well and incubated for 10 min at room temperature. Thereafter, 50 ng of NLuc mRNA (Se-modified or unmodified) was diluted in an additional 5 µL of Opti-MEM I Reduced Serum Medium. The diluted transfection reagent and the diluted mRNA were mixed 1:1 (10 µL total volume) and incubated for 5 minutes at room temperature, followed by addition of 10 µL of mRNA transfection complex to each well. Cells were incubated for 4 hours at 37°C + 5% CO2, after which transfection complexes were removed and replaced with 100 μL DMEM + 10% FBS. To analyze secreted NLuc, cell culture media was collected 24, 48, 72, and 96 hours after the transfection was halted. After collecting media, wells were washed twice with 150 μL PBS buffer before replenishing with 100 μL DMEM + 10% FBS. The collected media was analyzed immediately or stored at -20 °C to be measured with each time point after 96 hours. Secreted NLuc was quantified using Nano-Glo® Luciferase Assay System (N1150 , Promega) according to the manufacturer’s protocol. Briefly, 50 μL of Nano-Glo® detection reagent was prepared per sample by mixing Nano-Glo® buffer and substrate at a ratio of 50:1. A diluted stock of samples was prepared by mixing 5 μL of harvested cell culture media in 45 μL ddH2O (final volume 50 μL).50 μL of Nano-Glo® detection reagent was added to each well with a multichannel pipette with mixing. To remove bubbles, 80 μL of each sample was then transferred to 96-well, white bottom plates (Corning, 3917) which was then incubated for 3 min at RT. Luminescence data was acquired on a Glo-Max Discover system (Promega) using an integration time of 0.5. Data is shown as luminescence values minus background signal. 1602179968.1 83 Attorney Docket No.: F2001-7001WO(VL99001-W1) As shown in FIG.11, the expression of 25% Se-modified NLuc mRNA was detected, as defined by luminescence of secreted NLuc protein at 48 hours post transfection. Together with FIG.10, this result with a distinct reporter further demonstrates that substitution of the 4’O to Se still allows for the corresponding RNA to be meaningfully translated by ribosomes in cells, resulting in detectable protein production. Example 13: Synthesis of Se-modified Guanosine Triphosphate This example demonstrates the synthesis of Se modified guanosine triphosphate (GTP). The following steps are outlined below and in FIG.12. 1. The crude Compound 1008 was dissolved in Ac2O (212 mL) and heated to 100 °C for 1 h. The Ac2O was removed in vacuo. The residue was partitioned between EtOAc and water. The organic phase was washed with saturated aqueous NaHCO3 solution (200 mL) and brine, dried over sodium sulfate, filtered, and concentrated. The crude product was enriched using silica gel chromatography (EtOAc: PE = 1:20) to give Compound 5010c (19.94 g, 82% yield) as pale brown oil. LC-MS m / z: 557.2 [M + 23]+. LC-MS purity (214 nm): 73.6%; tR = 2.415 min. 2. To a solution of 6-chloro-7H-purin-2-amine (6.88 g, 40.68 mmol, 1.3 equiv.) in dry toluene (750 mL) was added BSA (15.88 g, 78.24 mmol, 2.5 equiv), and the mixture was stirred at 95 °C under Ar atmosphere for 1 h. Then a solution of Compound 5010c (16.68 g, 31.29 mmol, 1.0 equiv.) in dry toluene (450 mL) and TMSOTf (8.34 g, 37.55 mmol, 1.2 equiv.) was added slowly at 95 °C in sequence. The reaction was stirred at 95 °C under Ar atmosphere overnight. The mixture was then concentrated under reduced pressure. The residue was poured into aqueous NaHCO3 solution (800 mL) and extracted with EtOAc (3 × 500 mL). The combined organic phase was concentrated under reduced pressure. The crude product was enriched by column chromatography on silica gel (EtOAc: PE = 1:2) to give Compound 5011d (6.64 g, 33% yield) as a light yellow solid.1H-NMR (CDCl3, 400 MHz): δ 8.36 (s, 1H), 7.68-7.63 (m, 4H), 7.49-7.37 (m, 6H), 6.55 (d, J = 3.2 Hz, 1H), 5.42 (brs, 1.4H)(NH2), 4.81 (dd, J = 5.6, 3.2 Hz, 1H), 4.76 (dd, J = 5.6, 3.2 Hz, 1H), 4.08-4.02 (m, 1H), 3.97-3.85 (m, 2H), 1.58 (s, 3H), 1.33 (s, 3H), 1.09 (s, 9H). 3. To a solution of Compound 5011d (6.64 g, 10.33 mmol, 1.0 equiv.) in MeOH (100 mL) was added MeONa (2.96 g, 54.73 mmol, 5.3 equiv.) and 2-mercaptoethanol (3.22 g, 41.31 1602179968.1 84 Attorney Docket No.: F2001-7001WO(VL99001-W1) mmol, 4.0 equiv.). The reaction was stirred at 80 °C overnight. After completion of the reaction, the mixture was adjusted to pH of 7 with HOAc and concentrated under reduced pressure. The residue was enriched by column chromatography on silica gel (DCM:MeOH = 20:1 → 15:1) to give Compound 5012 (4.25 g, 66% yield) as a light yellow solid.. LC-MS m / z: 626.2 [M+H]⁺. LC-MS purity (214 nm): 63.2%; tR = 2.169 min. 4. To a solution of Compound 5012 (4.25 g, 6.80 mmol, 1.0 equiv.) in dry pyridine (50 mL) was added isobutyryl chloride (2.17 g, 20.40 mmol, 3.0 equiv.). The reaction was stirred at room temperature overnight. After completion of the reaction, the mixture was poured into EtOAc (100 mL) and washed with water (2 × 50 mL). The organic phase was concentrated under reduced pressure, and the residue was enriched by column chromatography on silica gel (DCM:MeOH = 15:1) to give Compound 5013 (4.6 g, 97% yield) as a light brown solid. LC-MS m / z: 696.2 [M+H]⁺. LC-MS purity (214 nm): 67.5%; tR = 2.308 min. 5. Compound 5013 (4.3 g, 6.19 mmol, 1.0 equiv.) was dissolved in 80% aqueous HOAc solution (125 g). The reaction was stirred at 80 °C overnight. After completion of the reaction, the mixture was diluted with EtOAc (200 mL) and washed with aqueous NaHCO3 solution (2 × 60 mL). The organic phase was concentrated under reduced pressure and the residue was enriched by reverse-phase column chromatography (60% CH3CN in water (5% NH4HCO3)) to give Compound 5014 (3.8 g, 94% yield) as a light yellow solid. LC-MS m / z: 656.0 [M+H]⁺. LC-MS purity (214 nm): 52.3%; tR= 2.061 min. 6. Compound 5014 (3.8 g, 5.80 mmol, 1.0 equiv.) was dissolved in NH3 / MeOH solution (7 M, 20 mL). The reaction was stirred at 80 °C overnight. After completion of the reaction, the precipitate was filtered and washed with MeOH to give Compound 5015 (3.2 g, 94% yield) as an off-white solid. LC-MS m / z: 586.2 [M+H]⁺. LC-MS purity (214 nm): 57.2%; tR = 1.892 min. 7. To a solution of Compound 5015 (3.2 g, 5.47 mmol, 1.0 equiv.) in dry pyridine (25 mL) were added acetyl chloride (2.15 g, 27.35 mmol, 5.0 equiv.) and DMAP (21 mg, 0.17 mmol, 0.03 equiv.). The reaction was stirred at room temperature overnight. After completion of the reaction, the mixture was diluted with EtOAc (100 mL) and washed with 0.3 N HCl (2 × 50 mL). The organic phase was concentrated under reduced pressure and the residue was enriched by reverse-phase column chromatography (95% CH3CN in water) (followed by silica gel 1602179968.1 85 Attorney Docket No.: F2001-7001WO(VL99001-W1) chromatography, DCM:MeOH = 15:1) to give Compound 5016 (1.92 g, 49% yield) as a light brown solid. LC-MS m / z: 712.0 [M+H]⁺. LC-MS purity (214 nm): 62.2%; tR= 2.103 min. 8. To a solution of Compound 5016 (1.92 g, 2.70 mmol, 1.0 equiv.) in dry THF (30 mL) was added TBAF (1.06 g, 4.05 mmol, 1.5 equiv). The reaction was stirred at room temperature for 5 h. After completion of the reaction, the mixture was diluted with EtOAc (50 mL) and washed with NH4Cl solution (2 × 50 mL). The organic phase was concentrated under reduced pressure and the residue was enriched by Prep-HPLC (HCOOH) to give Compound 5017 (300 mg, 49% yield) as a white solid. LC-MS m / z: 474.1 [M+H]⁺. LC-MS purity (214 nm): 100%; tR= 1.228 min.1H-NMR (DMSO-d6, 400 MHz): δ 12.08 (s, 1H), 11.74 (s, 1H), 8.46 (s, 1H), 6.13 (d, J = 8.4 Hz, 1H), 6.02 (dd, J = 8.4, 3.6 Hz, 2H), 5.70 (t, J = 2.8 Hz, 1H), 5.49 (t, J = 5.4 Hz, 1H), 4.00-3.92 (m, 1H), 3.84-3.76 (m, 1H), 3.70-3.64 (m, 1H), 2.19 (s, 3H), 2.12 (s, 3H), 1.91 (s, 3H). 9. To a solution of Compound 5017 (44 mg, 93 μmol) in dry pyridine (200 μL) and 1,4- dioxane (600 μL) was added a 1 M solution of 2-chloro-4H-1,2,3-dioxaphosphorin-4-one in 1,4- dioxane (112 μmol, 112 μL) at room temperature. After 15 min, a 0.5 M solution of bis(tri-n- butylammonium)pyrophosphate in dry DMF (153 μmol, 306 μL) and tri-n-butylamine (419 μmol, 99.5 μL) were added, and the reaction mixture was stirred for 20 min. A solution of 1% iodine in pyridine / water (98 / 2, v / v) (3.3 mL) was then added. After 5 min excess iodine was decomposed by adding 5% aqueous solution of Na2S2O3(1.4 mL), and the reaction mixture was stirred for 5 min. Water (20 mL) was added, and the reaction mixture was lyophilized. The residue was subjected to reversed-phase chromatography (MeCN / H2O (10 mmol / L NH4HCO3) = 0 / 1~1 / 10, C-18 column, 20 mL / min, UV 254) to give the crude Compound 5018. A DEAE Sephadex column (UniGel-80DEAE) was used to enrich Compound 5018. The column was eluted with (1.0 M TEAB buffer / water = 0 / 1~1 / 4, 15 mL / min, UV 254). Fractions containing Compound 5018 were lyophilized to give Compound 5018 (45 mg, 43.3%) as a white solid. 10. To a solution of Compound 5018 (45 mg, 40.3 μmol) in MeCN (6 mL) was added 28% NH3•H2O (6 mL), and the mixture was stirred overnight at 50°C. LC-MS analysis indicated the total consumption of the starting material. Water (10 mL) was added, and the reaction mixture was lyophilized. The residue was subjected to reversed-phase chromatography (H2O (10 1602179968.1 86 Attorney Docket No.: F2001-7001WO(VL99001-W1) mmol / L NH4HCO3), C-18 column, 20 mL / min, UV 254) to give target Compound 5037 (SeGTP) (22.2 mg, 83.8%) as a white solid.1H-NMR (D2O, 400 MHz): δ 8.03 (s, 1H), 5.79 (d, J = 7.6 Hz, 1H), 4.85-4.77 (m, 1H), 4.49- 4.47 (m, 1H), 4.30-4.24 (m, 1H), 4.19-4.13 (m, 1H), 3.67-3.66 (m, 1H). LC-MS (ESI-): m / z 585.9 [M-H]- PNMR: 31P NMR (162 MHz, D2O) δ = -8.13 (d, J = 12.4 Hz, 1P), -11.51 (d, J = 12.4 Hz, 1P), - 22.52 (t, J = 12.4 Hz, 1P) For all patents, applications, or other reference cited herein, such as non-patent literature and reference sequence information, it should be understood that they are incorporated by reference in their entirety for all purposes as well as for the proposition that is recited. Where any conflict exists between a document incorporated by reference and the present application, this application will control. All information associated with reference gene sequences disclosed in this application, such as GeneIDs or accession numbers (typically referencing NCBI accession numbers), including, for example, genomic loci, genomic sequences, functional annotations, allelic variants, and reference mRNA (including, e.g., exon boundaries or response elements) and protein sequences (such as conserved domain structures), as well as chemical references (e.g., PubChem compound, PubChem substance, or PubChem Bioassay entries, including the annotations therein, such as structures and assays, et cetera), are hereby incorporated by reference in their entirety. Headings used in this application are for convenience only and do not affect the interpretation of this application. 1602179968.1 87

Claims

Attorney Docket No.: F2001-7001WO(VL99001-W1) CLAIMS 1. An RNA molecule comprising a plurality of nucleosides, wherein: at least one nucleoside of the RNA molecule comprises a structure according to Formula (I): ,OH, OMe or F; B is a nucleobase; and the RNA molecule comprises an effector sequence that encodes an effector (e.g., a therapeutic effector).

2. The RNA molecule of claim 1, which is single stranded or double stranded.

3. The RNA molecule of claim 1 or 2, which is linear or circular.

4. The RNA molecule of any of the preceding claims, which has a length of at least 30, at least 40, at least 50, at least 100, at least 150, or at least 200 nucleotides.

5. The RNA molecule of any of the preceding claims, wherein B comprises a canonical nucleobase or a chemically modified nucleobase.

6. The RNA molecule of any of the preceding claims, wherein at least 25%, 50%, 75%, or 99% of the nucleosides of the RNA molecule each independently comprises a structure according to Formula (I).

7. The RNA molecule of any of the preceding claims, wherein the nucleoside comprising the structure of Formula (I) is situated in a coding region. 1602179968.1 88Attorney Docket No.: F2001-7001WO(VL99001-W1) 8. The RNA molecule of any of claims 1-6, wherein the nucleoside comprising the structure of Formula (I) is situated in a polyA tail.

9. The RNA molecule of any of claims 1-6, which comprises a polyA tail, wherein the polyA tail does not comprise any nucleoside having the structure of Formula (I).

10. The RNA molecule of any of the preceding claims, wherein the effector comprises a polypeptide (e.g., a DNA binding protein; an epigenetic modifying factor; an antigen; a hormone; an enzyme; a CRISPR-linked enzyme; a mobile genetic element protein; a gene writer; an antibody; a signaling peptide; a receptor ligand; a receptor; or a clotting factor).

11. The RNA molecule of any of the preceding claims, which is translated when present in a cell.

12. The RNA molecule of any of the preceding claims, which has a half-life of greater than 20, greater than 40, or greater than 60 minutes in the presence of 0.064% fetal bovine serum (FBS) at 37 ˚C, e.g., in an assay of Example 9.

13. An RNA molecule comprising a plurality of nucleosides, wherein: at least one nucleoside of the RNA molecule comprises a structure according to Formula (I): ,OH, OMe or F; B is a nucleobase; and the RNA molecule has a length of at least 20 nucleosides.

14. The RNA molecule of claim 13, which is a mRNA, tRNA, gRNA, saRNA, siRNA, ribozyme, or aptazyme. 1602179968.1 89Attorney Docket No.: F2001-7001WO(VL99001-W1) 15. An RNA molecule that has a length of at least 20 nucleotides and comprises one or more selenoribonucleosides.

16. An RNA molecule that encodes an effector (e.g., a therapeutic effector) and comprises one or more selenoribonucleotides.

17. A pharmaceutical composition comprising an RNA molecule of any of the preceding claims.

18. The pharmaceutical composition of claim 17, wherein the RNA molecule is comprised in a lipid nanoparticle (LNP).

19. The pharmaceutical composition of claim 17, which is substantially free of (e.g., is free of) LNPs.

20. A method of modulating a biological activity in a target cell, the method comprising: contacting a target cell with the RNA molecule of any of claims 1-16 or the pharmaceutical composition of any of claims 17-19, wherein the effector modulates a biological activity in the target cell; thereby modulating the biological activity in the target cell.

21. A method of treating a cell, tissue, or subject in need thereof, the method comprising: administering to the cell, tissue, or subject the RNA molecule of any of claims 1- 16 or the pharmaceutical composition of any of claims 17-19; thereby treating the cell, tissue, or subject. 1602179968.1 90

Images