Symmetrical dipeptide supramolecular monomer based on bipyridine as well as preparation method and application of symmetrical dipeptide supramolecular monomer

Abstract

The invention discloses a symmetric dipeptide supramolecular monomer based on bipyridine as well as a preparation method and application of the symmetric dipeptide supramolecular monomer based on bipyridine, and the symmetric dipeptide supramolecular monomer based on bipyridine is formed by connecting glycine-alanine dipeptide and chain alkoxy ether or dendronized alkoxy ether to bipyridine by taking bipyridine as a skeleton, and carrying out self-assembly in an aqueous solution to form the supramolecular polymer. The supramolecular polymer can realize polypeptide supramolecular self-assembly and dynamic regulation and control of supramolecular chirality through coordination and de-coordination with different metal ions, and also can realize adjustment of the average particle size of an assembly system through structural change of metal ion coordination so as to change the fluorescence property of the assembly system; meanwhile, the reversible temperature-sensitive phenomenon of the assembly in an aqueous solution is realized by adjusting the dendronized alkoxy ether, and the influence of temperature response on the chirality of the assembly is investigated.

Description

Technical Field

[0001] This invention belongs to the field of polymer compound technology, specifically relating to a symmetrical dipeptide supramolecular monomer based on bipyridine, its preparation method, and its application. Background Technology

[0002] Peptide self-assembly is a dynamic process based on the interaction between amino acid molecules to form ordered nanostructures. Stimulus-response refers to the dynamic behavior of peptide molecules sensing and dynamically responding to changes in the external environment under specific chemical or physical conditions, thereby regulating the dynamic behavior of self-assembly structure or function. This dynamic response enables controllable regulation of structure and function, showing great potential in drug delivery, biosensing, and tissue engineering. By regulating the chiral assembly of peptide molecules, structurally stable and functionally diverse chiral nanomaterials can be prepared. Metal ion-induced peptide self-assembly, through metal coordination, regulates the conformation and assembly behavior of peptides, endowing materials with dynamic responsiveness, catalytic activity, or mechanical properties. In the biomedical field, metal ion-induced peptide formation of specific structures is used to design drug carriers, achieving controlled drug release and targeted delivery. In materials science, biomaterials with special properties can be prepared. Although some progress has been made in the study of metal ion-induced peptide self-assembly, some challenges remain. For example, the assembly process of metals and peptides is complex, and their folding structure is difficult to precisely regulate and predict. Furthermore, how to achieve efficient and stable assembly of peptide self-assembly systems and improve their performance in biomedical applications are also current problems. Summary of the Invention

[0003] The purpose of this invention is to provide a symmetrical dipeptide supramolecular monomer based on bipyridine, its preparation method, and its application. The symmetrical dipeptide supramolecular monomer is composed of a bipyridine backbone, with glycine-alanine dipeptide and chain-like alkoxy ethers or dendritic alkoxy ethers linked to the bipyridine. The alanine moiety in the dipeptide provides the chiral center, the bipyridine has the ability to coordinate with metal ions, the alkoxy ether moiety provides hydrophilicity, and the dendritic alkoxy ether moiety also has thermosensitive properties, enabling the symmetrical dipeptide supramolecular monomer to coordinate with metal ions and have temperature-responsive properties. Furthermore, the symmetrical dipeptide supramolecular monomer based on bipyridine self-assembles into a supramolecular polymer, and forms a polypeptide supramolecular chiral polymer by coordinating with metal ions.

[0004] To achieve the above objectives, this invention proposes a symmetrical dipeptide supramolecular monomer based on bipyridine, wherein the symmetrical dipeptide supramolecular monomer based on bipyridine is any one of the following: (L)BPY-AG-TEG, (L)BPY-AG-G1, or (D)BPY-AG-G1, with the following specific structural formulas: .

[0005] This invention also provides a method for preparing a symmetrical dipeptide supramolecular monomer based on bipyridine, comprising the following steps: (1) Under alkaline conditions, alanine protected by tert-butoxycarbonyl, glycine methyl ester hydrochloride, 1-hydroxybenzotriazole, and N,N-diisopropylethylamine were dissolved in dichloromethane, and then 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was added to carry out a condensation reaction to obtain compound A. (2) A methanol solution of compound A and a lithium hydroxide monohydrate solution were mixed and hydrolyzed to obtain compound B; (3) Compound B, alkoxy ether, dichloromethane and 4-dimethylaminopyridine were mixed and then 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was added to carry out esterification reaction to obtain compound C; (4) A solution of compound C in dichloromethane and trifluoroacetic acid were mixed and reacted to obtain compound D; (5) Under alkaline conditions, compound D is dissolved in tetrahydrofuran solution and added to tetrahydrofuran solution of 2,2'-bipyridine-5,5'-dicarboxylic acid chloride to obtain the symmetrical dipeptide supramolecular monomer based on bipyridine.

[0006] Preferably, the alanine in step (1) includes L-alanine and D-alanine. The molar ratio of alanine, glycine methyl ester hydrochloride, and 1-hydroxybenzotriazole is 1:1.0-1.2:1.1-1.3. The molar ratio of alanine to N,N-diisopropylethylamine is 1:1.5 to 2.0; The molar ratio of alanine to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1.1 to 1.3; The ratio of alanine to dichloromethane is 1 mmol: 8–10 mL.

[0007] Preferably, the volume fraction of methanol in the methanol aqueous solution in step (2) is 75-85%; The molar ratio of compound A to lithium hydroxide monohydrate is 1:2 to 2.2; The ratio of compound A to the methanol aqueous solution is 1 mmol: 3-5 mL.

[0008] Preferably, in step (3), the alkoxy ether is triethylene glycol monoethyl ether or dendritic alkoxy ether G1. When the alkoxy ether in step (3) is triethylene glycol monoethyl ether, the molar ratio of compound B to the alkoxy ether is 1.0:1.1-1.2, and the molar ratio of compound B to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1.0-2.0. When the alkoxy ether in step (3) is dendritic alkoxy ether G1, N,N-dimethylformamide is added to step (5) for amidation reaction. The molar ratio of compound B to the alkoxy ether is 1.2:0.9-1.1, and the molar ratio of compound B to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1.0-1.5. The ratio of compound B to dichloromethane is 1 mmol: 20–30 mL; The molar ratio of compound B to 4-dimethylaminopyridine is 3 to 4:1.

[0009] Preferably, in step (4), the molar volume ratio of compound C to dichloromethane in the dichloromethane solution of compound C is 1.1–1.8 mmol: 5–9 mL; The molar ratio of compound C to trifluoroacetic acid is 1.1–1.8:25–35.

[0010] Preferably, the pH value of the alkaline conditions in step (5) is 8 to 10; The molar volume ratio of the 2,2'-bipyridine-5,5'-dicarboxylic acid chloride and tetrahydrofuran solution is 0.5–0.8 mmol: 20–35 mL; The molar volume ratio of compound D to tetrahydrofuran solution is 1.2–1.5 mmol: 9–10 mL; The molar ratio of compound D to 2,2'-bipyridine-5,5'-dicarboxylic acid chloride is 1.2–1.8:0.06–0.6; The molar ratio of compound D to N,N-dimethylformamide is 1.2–1.8 mmol: 2–3 mL.

[0011] This invention also provides the application of a symmetrical dipeptide supramolecular monomer based on bipyridine in the preparation of peptide supramolecular chiral materials, fluorescent probe materials, and drug controlled-release materials.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a symmetrical dipeptide supramolecular monomer based on bipyridine. It uses bipyridine as a backbone, linking a glycine-alanine dipeptide and a chain-like alkoxy ether or a dendritic alkoxy ether to the bipyridine. The alanine moiety in the dipeptide provides the chiral center, the alkoxy ether moiety provides hydrophilicity, and the bipyridine has the ability to coordinate with metal ions, allowing the symmetrical dipeptide supramolecular monomer to coordinate with metal ions to form a polypeptide supramolecular chiral polymer. The dendritic alkoxy ether moiety also has thermosensitive properties, giving the symmetrical dipeptide supramolecular monomer a temperature-responsive characteristic.

[0013] The symmetrical dipeptide supramolecular monomers based on bipyridine prepared in this invention self-assemble into supramolecular polymers in aqueous solution. The supramolecular polymers can achieve supramolecular self-assembly and dynamic regulation of supramolecular chirality through coordination and discoordination with different metal ions. Furthermore, the average particle size of the assembled system can be adjusted by structural changes in metal ion coordination, thereby altering its fluorescence properties. Simultaneously, the reversible thermosensitive phenomenon of the assemblies in aqueous solution can be achieved by adjusting the dendritic alkoxy ethers, and the influence of temperature response on the chirality of the assemblies can be investigated.

[0014] The supramolecular monomer based on bipyridine dipeptide prepared in this invention provides a theoretical basis for constructing stimulus-responsive biomimetic chiral peptide materials and developing functional polymers with dual regulation of metal ions and temperature, and expands the application of supramolecular systems in other fields such as drug carriers and fluorescent probes. Attached Figure Description

[0015] Figure 1 Compound 1-a in Example 1 of this invention is... d 6-CDCl3 1 H NMR spectrum; Figure 2 Compound 1-b in Example 1 of this invention is... d 6-CDCl3 1 H NMR spectrum; Figure 3 Compound 1-c1 in Example 1 of this invention is... d 6-CDCl3 1 H NMR spectrum; Figure 4 The compound (L)BPY-AG-TEG in Example 1 of this invention is... d 6-DMSO 1 H NMR spectrum; Figure 5 The compound (L)BPY-AG-TEG in Example 1 of this invention is... d 6-DMSO 13 C NMR spectrum; Figure 6This is the high-resolution mass spectrum of compound (L)BPY-AG-TEG in Example 1 of this invention; Figure 7 The CD spectrum (top) and UV-Vis spectrum (bottom) of H2O solutions containing compound (L)BPY-AG-TEG with different metal ions in Example 1 of this invention are as follows: (a) Cu 2+ b). Ni 2+ ;c). Ba 2+ ;d). Ag + ;e). Zn 2+ ); Figure 8 The CD spectrum (top) and UV-Vis spectrum (bottom) of the H2O solution of compound (L)BPY-AG-TEG after adding the metal ion chelating agent EDTA in Example 1 of this invention are as follows: (a) Cu 2+ b). Ni 2+ ); Figure 9 This is the fluorescence spectrum of compound (L)BPY-AG-TEG added to H2O solutions with different metal ions in Example 1 of this invention; Figure 10 The compound (L)BPY-AG-TEG in Example 1 of this invention is reacted with Cu 2+ Compare the scanning electron microscope (SEM) images before and after (Fig. a. SEM image of (L)BPY-AG-TEG, Fig. b. SEM image of (L)BPY-AG-TEG with Cu). 2+ (Scanning electron microscope image after assembly) Figure 11 Compound 1-c2 in Example 2 of this invention is... d 6-DMSO 1 H NMR spectrum; Figure 12 The compound (L)BPY-AG-G1 in Example 2 of this invention is... d 6-DMSO 1 H NMR spectrum; Figure 13 The compound (L)BPY-AG-G1 in Example 2 of this invention is... d 6-DMSO 13 C NMR spectrum; Figure 14 This is the high-resolution mass spectrum of compound (L)BPY-AG-G1 in Example 2 of this invention; Figure 15 The compound (D)BPY-AG-G1 in Example 2 of this invention is... d 6-DMSO 1 H NMR spectrum; Figure 16 The compound (D)BPY-AG-G1 in Example 2 of this invention is... d 6-CDCl3 13 C NMR spectrum; Figure 17 This is the high-resolution mass spectrum of compound (D)BPY-AG-G1 in Example 2 of this invention; Figure 18 The CD spectrum (top) and UV spectrum (bottom) of compound (L)BPY-AG-G1 in Example 2 of this invention with different metal ions (the latter being the metal ion in the ratio, and the metal ion ratios in subsequent figures are all set according to this) in H2O. Figure 19 The CD spectrum (top) and UV spectrum (bottom) of compound (L)BPY-AG-G1 with different proportions of metal ions in H2O solution in Example 2 of this invention are as follows: (a) Ni 2+ b) Cu 2+ ;c). Ag + ;d). Ba 2+ ;e). Zn 2+ ); Figure 20 The following are the CD spectra (top) and UV spectra (bottom) of compound (L)BPY-AG-G1 with different anionic metal salts in H2O solution in Example 2 of this invention: (a) Cu 2+ b) Ba 2+ c). Zn 2+ ); Figure 21 The CD spectrum (top) and UV spectrum (bottom) of compound (L)BPY-AG-G1 in H2O solution after adding the metal ion chelating agent EDTA in Example 2 of this invention are as follows: (a) Cu 2+ b). Ni 2+ ); Figure 22 This is the CD spectrum of the enantiomer of compound BPY-AG-G1 in H2O in Example 2 of the present invention; Figure 23 These are the CD (top) and UV (bottom) spectra of compound (D)BPY-AG-G1 with different proportions of metal ions in H2O solution in Example 2 of this invention: (a) Ni 2+ b) Cu 2+ ;c). Ag + ;d). Ba 2+ ;e). Zn 2+ ); Figure 24This is a fluorescence change diagram of the compound (D)BPY-AG-G1 solution under the influence of different metal ions in Example 2 of the present invention; Figure 25 This is a particle size distribution diagram of the compound (L)BPY-AG-G1 solution under the influence of different metal ions in Example 2 of the present invention; Figure 26 The compound (L)BPY-AG-G1 and Cu in Example 2 of this invention 2+ Comparison of magnified scanning electron microscope images before and after coordination: (a) BPY-AG-G1; (b) BPY-AG-G1 and Cu. 2+ Coordination; c) BPY-AG-G1 and Cu 2+ (Enlarged view of coordination region); Figure 27 This is a graph showing the temperature-sensitive response change of compound (L)BPY-AG-G1 in Example 2 of this invention; Figure 28 This is a turbidity curve of the compound (L)BPY-AG-G1 solution in Example 2 of the present invention at different temperatures; Figure 29 The compound (L)BPY-AG-G1:Ni in Example 2 of this invention 2+ CD spectra of 2:1 at different temperatures. Detailed Implementation

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Example 1

[0018] A method for preparing a symmetrical dipeptide supramolecular monomer based on bipyridine includes the following steps: When the alanine is L-alanine and the alkoxy ether is triethylene glycol monoethyl ether, the reaction steps are as follows: .

[0019] In the reaction formula, compound 1-a is compound A, compound 1-b is compound B, compound C is compound 1-c1, and compound D is compound 1-d1.

[0020] The specific synthesis steps are as follows: Synthesis of compound 1-a: Boc-Ala-OH (tert-butoxycarbonyl-protected L-alanine) (2.00 g, 10.57 mmol), glycine methyl ester hydrochloride (H-Gly-OMe∙HCl) (1.62 g, 11.58 mmol), 1-hydroxybenzotriazole (HOBt) (1.71 g, 12.63 mmol), and N,N-diisopropylethylamine (DIEA) (2.42 g, 18.72 mmol) were dissolved in 80 mL of dry dichloromethane (DCM), purged with nitrogen, and stirred in an ice bath for 30 min. Then, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) (2.42 g, 12.63 mmol) was added, purged with nitrogen again, and stirred in an ice bath overnight. After the reaction was complete as detected by TLC (DCM / MeOH, 40 / 1, v / v), the reaction was stopped, washed with 10% KHSO4 solution, and the lower organic phase was dried over anhydrous Na2SO4. The solvent was evaporated by filtration, and the sample was loaded onto silica gel and purified by column chromatography (DCM / MeOH, 50 / 1, v / v) to give 2.2892 g of a pale yellow transparent oil, with a yield of 83.50%. Compound 1-a was dissolved in… d In 6-CDCl3, nuclear magnetic resonance imaging was performed, such as... Figure 1 As shown. 1 H NMR (400 MHz, d 6-CDCl3): δ =1.38 (d, 3H, J=5.6 Hz, CH3), 1.45 (s,9H, CH3), 3.76 (s, 3H, CH3), 4.03-4.06 (m, 2H, CH2), 4.21-4.23 (m, 1H, CH), 4.98 (s, 1H, NH), 6.68 (s, 1H, NH).

[0021] Synthesis of compound 1-b: Compound 1-a (2.2892 g, 8.53 mmol) was dissolved in 30 mL of a methanol-water mixture (4:1, v / v). Lithium hydroxide monohydrate (LiOH) (0.7331 g, 17.07 mmol) was added at room temperature. After reacting for 1.5 h, TLC (DCM / MeOH, 20 / 1, v / v) confirmed complete reaction. The reaction was stopped, methanol was distilled off, and the pH was adjusted to 3-4 with 10% KHSO4 solution. Ethyl acetate was added for extraction. The organic phase was dried over anhydrous Na2SO4, filtered, and evaporated to dryness to give 1.5782 g of a white solid, yield 73.10%. Compound 1-b was dissolved in... d In 6-CDCl3, nuclear magnetic resonance imaging was performed, such as... Figure 2 As shown. 1HNMR (400 MHz, d 6-CDCl3): δ =1.40 (d, 3H, J=4.8 Hz, CH3), 1.47 (s, 9H, CH3), 3.52 (s, 2H, CH2), 4.03-4.17 (m, 1H, CH), 4.37 (s, 1H, NH), 5.27 (s, 1H, NH),7.02 (s, 1H, OH).

[0022] Synthesis of compound 1-c1: Compound 1-b (0.5 g, 2.03 mmol) and triethylene glycol monoethyl ether (TEG) (0.435 g, 2.44 mmol) were weighed and added to a 250 mL round-bottom flask. 50 mL of DCM was added to the flask, followed by 4-dimethylaminopyridine (DMAP) (0.074 g, 0.609 mmol). A magnetic stir bar was added, and the nitrogen was displaced by a water pump. The mixture was stirred in an ice bath for 30 min, and then EDC·HCl (0.547 g, 3.045 mmol) was added. The nitrogen was displaced again by a water pump, and the mixture was kept in an ice bath overnight. TLC was used to detect the completeness of the reaction (DCM / MeOH, 20 / 1, v / v). Once complete, the reaction was stopped, and the magnetic stir bar was removed. The mixture was washed and extracted with 10% KHSO4 solution, dried over anhydrous Na2SO4, filtered, and the DCM in the reaction solution was removed by rotary evaporation to obtain the crude product. After adding 1.2 g of silica gel for sample loading, the sample was purified by column chromatography (PE / EA, 1 / 3, v / v) to give 0.7035 g of a colorless oil, with a yield of 85.30%. Compound 1-c1 was dissolved in... d In 6-CDCl3, nuclear magnetic resonance imaging was performed, such as... Figure 3 As shown. 1 HNMR (400 MHz, d 6- CDCl3): δ =1.23-1.24 (t, 3H, CH3), 1.40 (d, 3H, CH3), 1.47(s, 9H, CH3), 3.54-3.73 (m, 12H, CH2), 4.10-4.11 (m, 2H, CH2), 4.25(m, 1H,CH), 4.33 (t, 2H, CH2), 5.06 (s, 1H, NH), 6.74 (s, 1H, NH).

[0023] Synthesis of compound 1-d1: Compound 1-c1 (0.7035 g, 1.73 mmol) was added to a 100 mL round-bottom flask. 7 mL of DCM was added to the flask, followed by the dropwise addition of trifluoroacetic acid (TFA) (3.946 g, 34.61 mmol). A magnetic stir bar was then added, and the mixture was stirred in an ice bath for 20 min. The ice bath was then removed, and the mixture was stirred at room temperature for 1.5 h. TLC was used to detect the completeness of the reaction (DCM / MeOH, 30 / 1, v / v). Once complete, the reaction was stopped, and 30 mL of methanol was added and stirred for 30 min to terminate the reaction. The MeOH in the reaction mixture was removed by rotary evaporation to obtain 0.7035 g of a colorless oil, with a yield of 100.00%.

[0024] Synthesis of compound (L)BPY-AG-TEG: 2,2'-bipyridine-5,5'-dicarboxylic acid chloride (0.16 g, 0.5694 mmol) was dissolved in 35 mL of anhydrous tetrahydrofuran solution (THF) and stirred under nitrogen protection. Compound 1-d1 (0.7035 g, 1.73 mmol) was dissolved in 10 mL of anhydrous THF, and the pH was adjusted to approximately 9 by adding an appropriate amount of N,N-diisopropylethylamine (DIEA). The N2 was replaced by a water pump, and the THF solution containing compound 1-d1 was added dropwise to the tetrahydrofuran solution containing 2,2'-bipyridine-5,5'-dicarboxylic acid chloride. The reaction was carried out at room temperature for 48 h. After the reaction was completed, the magnetic oscillator was removed, and the THF in the reaction solution was removed by rotary evaporation. 30 mL of DCM was added, and the pH was adjusted to weakly acidic with a 10% KHSO4 aqueous solution. The organic phase was extracted and dried with anhydrous Na2SO4. After filtration, the DCM was removed by rotary evaporation. The crude product was purified by LH-20 dextran gel column chromatography (eluent: DCM) to obtain 0.1232 g of red solid, which was (L)BPY-AG-TEG, with a yield of 19.08%.

[0025] Dissolve compound (L)BPY-AG-TEG in d In 6-DMSO, 1 H NMR and 13 C NMR detection such as Figure 4 and Figure 5 As shown. 1 H NMR (400 MHz, d6- DMSO): δ =1.03 (t, 6H, CH3), 1.34 (d, 6H, CH3), 3.40-3.55 (m, 20H, CH2), 3.81 (t, 4H, CH2), 4.03-4.11 (m, 8H, CH2), 4.53 (q, 2H,CH), 8.43 (d, 2H, CH), 8.86 (d, 4H, CH, NH), 9.12 (d, 4H, CH, NH). 13 C NMR ( d 6-DMSO): δ =15.57, 18.24, 49.29, 64.29, 65.99, 68.63, 69.65, 70.18, 70.23,70.29, 120.89, 130.38, 137.17, 149.31, 156.81, 164.85, 170.27, 173.22. HRMS(ESI) calcd for C 38 H 56 N6O 14 [M+H] + 821.3927, found 821.3960.

[0026] 1.1 Study on the metal ion-induced chirality of compound (L)BPY-AG-TEG The chiral effect of symmetrical dipeptide supramolecular monomers based on bipyridine mainly originates from the conformational change induced by the coordination interaction between metal ions and bipyridine ligands. At the molecular level, like Cu... 2+ Zn 2+ Once such metal ions coordinate with bipyridine groups, the conformation of symmetrical dipeptide monomers will change significantly, and this conformational change will drive the supramolecular monomers to arrange in an orderly manner, thus exhibiting the formation of chiral supramolecular structures at the nanoscale. The chiral center of the dipeptide itself and the conformational locking after the coordination of metal ions and bipyridine groups are the two key factors that generate the chiral effect.

[0027] Circular dichroism (CD) spectroscopy was used to study the metal ion-induced chiral effect of the symmetrical dipeptide supramolecular monomer based on bipyridine. In the absence of metal ions, the synthesized symmetrical dipeptide supramolecular monomer exhibited a strong negative peak at 200-243 nm and two positive peaks at 255 nm and 293 nm, indicating that the symmetrical dipeptide supramolecular monomer possesses a certain chiral conformation in solution. The addition of Cu... 2+ Ni 2+Following the addition of Cu, CD spectroscopy revealed a significant weakening of the positive Cotton effect at 248-320 nm corresponding to π-π stacking interactions, and a significant weakening of the negative Cotton effect at 230 nm corresponding to peptide amide absorption. This indicates that the addition of Cu... 2+ Ni 2+ The supramolecular chirality is significantly weakened (e.g.) Figure 7 (As shown in a and b). This is because the supramolecular structure is altered due to the coordination of the bipyridine group and amide bond with the metal ion.

[0028] Further research into the effect of metal ion concentration on chiral effects reveals that as the concentration of metal ions (Cu) increases, the chiral effect becomes more pronounced. 2+ and Ni 2+ As the concentration increases, the CD signal initially weakens and then gradually stabilizes, indicating an optimal metal-to-ligand ratio of 1:2. Analysis revealed that after the addition of metal ions, the UV spectrum showed a weakening absorption peak at 275 nm and a double peak at 310-325 nm. This change in the UV spectrum corresponds to the CD curve, further confirming that the chiral effect changes after the assembly coordinates with the metal ions.

[0029] like Figure 7 As shown, by comparing and analyzing the effects of different metal ions on this chiral effect, it can be found that Cu 2+ and Zn 2+ Ag + Ba 2+ The chiral induction ability is completely different; at the same concentration, Cu 2+ The induced circular dichroism (CD) spectrum shows a shift of approximately 15 nm towards longer wavelengths in the 275 nm-325 nm peak position. This is because Cu... 2+ The Zn ligand forms a planar tetragonal coordination configuration with the bipyridine ligand. 2+ It prefers to form a tetrahedral configuration, Ag + Ba readily forms linear dicoordination. 2+ These readily form polymer chains or layered structures with eight to nine coordination groups. Studies show that different coordination geometries and coordination strengths of different metal ions can induce supramolecular structures with different chiral orientations and strengths, thus enabling the precise design of chiral materials.

[0030] Adding the metal ion chelating agent ethylenediaminetetraacetic acid (EDTA) can chelate different metals (e.g., Ag) in the same proportion. + Ba 2+ Zn 2+ Cu 2+ Ni 2+The influence of bispyridine-based symmetrical dipeptide supramolecular monomers on metal ions. EDTA, a widely used multidentate ligand, primarily affects metal ions by forming stable chelates, thereby regulating the activity and chemical behavior of metal ions in solution. Because EDTA molecules contain multiple carboxyl and amino functional groups, these groups can bind with various metal ions such as Cu. 2+ Ni 2+ Zn 2+ When chelates with six- or five-membered ring structures are formed, this strong coordination ability allows EDTA to effectively reduce the free concentration of metal ions, thereby weakening the direct force of metal ions on the supramolecular assembly system.

[0031] When EDTA is added to a solution containing metal ions, not only does the coordination state of the metal ions change significantly, but the overall chiral characteristics of the solution are also significantly affected. This is because metal ions typically act as templates or bridges in the process of chiral supramolecular assembly, and the introduction of EDTA disrupts the original metal-ligand complexation mode, leading to a weakening or even reversal of the chiral signal. Figure 7 As shown in a and b, Cu was added to the H2O solution of (L)BPY-AG-TEG. 2+ Ni 2+ The chiral signal changes significantly with two metal ions, but reverts to its original state without metal ions upon the addition of EDTA. This change in chiral signal is attributed to the stronger coordination of EDTA with metal ions, which extracts the coordinated metal ions from the assembly. Therefore, in studying the metal ion-induced self-assembly of bipyridine dipeptide amphiphilic supramolecular monomers, EDTA serves as an important regulatory tool. It not only reveals the crucial role of metal ions in the assembly mechanism but also provides experimental evidence for understanding the dynamic regulation of chiral expression.

[0032] 1.2 Study on metal ion-induced fluorescence spectroscopy of compound (L)BPY-AG-TEG By detecting the changes in fluorescence spectra of symmetrical dipeptide supramolecular monomers based on bipyridine before and after the addition of different metal ions, information on changes in molecular aggregate structure can be obtained, thereby revealing the molecular mechanism of metal ion-induced self-assembly.

[0033] Symmetric dipeptide supramolecular monomers based on bipyridine, with the addition of metal ions (such as Cu) 2+ Ni 2+ Zn 2+ Ba 2+ and Ag + The change in fluorescence intensity led to further discussion of its self-assembly. First, H2O was selected as the solvent to prepare (L)BPY-AG-TEG solutions with a concentration of 0.05 mg·mL⁻¹.-1 Five H₂O solutions with a molecular weight ratio of 1:2 to each metal ion were prepared. Fluorescence spectroscopy was used, with a scanning range of 400-550 nm and an excitation wavelength of 330 nm. The six prepared solutions were measured sequentially. Figure 7 As shown, the fluorescence intensity of the compound was enhanced after coordination with metal ions.

[0034] Different metal ions exhibit a certain selectivity in their effect on fluorescence intensity due to differences in their electronic structure and coordination geometry. For example... Figure 9 As shown, Cu 2+ and Ni 2+ Due to the characteristics of its d-orbital electrons, it typically induces strong spin-orbit coupling, thereby promoting intersystem crossing and indirectly enhancing fluorescence emission; while Zn 2+ and Ba 2+ The fluorescence efficiency is improved primarily through electrostatic interactions and steric effects to stabilize the supramolecular assembly. When the assembly coordinates with Ag⁺, a linear two-coordinate structure is formed. This coordination allows the flexible peptide chain and bipyridine ring of the ligand to form a rigid planar structure, significantly reducing energy dissipation (non-radiative transitions) caused by intramolecular vibrations and rotations, thus releasing more excited-state energy in the form of fluorescence. In addition, the introduction of metal ions may induce self-assembly of the dipeptide supramolecular structure, forming a highly ordered nanostructure. This self-assembly process not only enhances the π-π stacking interactions between molecules but may also reduce non-radiative decay by restricting molecular vibrations and rotations, ultimately achieving a significant increase in fluorescence intensity. The unique chemical structure of the bipyridine dipeptide supramolecular structure and the diversity of metal ions provide rich possibilities for the regulation of its fluorescence properties and also lay a theoretical foundation for the development of novel functional materials.

[0035] 1.3 Morphological comparison of compound (L)BPY-AG-TEG before and after coordination with metal ions The self-assembly behavior of bispyridine-based symmetrical dipeptide supramolecular monomers in aqueous solution and the influence of metal ions on monomer morphology were investigated. Scanning electron microscopy (SEM) was used to observe the surface morphology and three-dimensional structural features of the samples. The samples required gold sputtering and observation under high vacuum conditions were necessary. SEM revealed the morphological changes of bispyridine-based symmetrical dipeptide supramolecular monomers before and after metal ion induction, thus laying a solid experimental foundation for understanding the influence of metal coordination on the self-assembly process.

[0036] First, prepare a 0.05 mg / mL solution. -1 (L)BPY-AG-TEG H2O solution and (L)BPY-AG-TEG H2O solution with Cu 2+A 1:2 molecular weight mixture of aqueous and supramolecular monomers was prepared. 5 μL of this solution was dropped onto a silicon wafer and allowed to air dry. The wafer was then characterized using scanning electron microscopy (SEM) to observe the assemblies formed by the supramolecular monomers in the solution and their interaction with Cu. 2+ Changes in size and morphology after coordination. For example... Figure 8 As shown, the aqueous solution of (L)BPY-AG-TEG reacts with metal ions Cu 2+ After combination, the morphological changes were clearly revealed by scanning electron microscopy. Using high-resolution imaging technology, it was clearly observed that (L)BPY-AG-TEG molecules without added metal ions exhibited a blocky structure in aqueous solution, with a rough surface and large particle size. However, in Cu... 2+ In the presence of ions, (L)BPY-AG-TEG molecules respond rapidly, and these aggregates exhibit a network or leaf vein-like morphology.

[0037] Furthermore, scanning electron microscopy images revealed a significant increase in the surface roughness of these aggregates, indicating a further adjustment in the molecular packing pattern. This phenomenon may originate from Cu. 2+ The strong coordination between the ion and the bipyridine group in the (L)BPY-AG-TEG molecule causes a redistribution of weak interactions such as hydrogen bonds and van der Waals forces between molecules, thereby driving changes in the self-assembly process.

[0038] Example 2 A method for preparing a symmetrical dipeptide supramolecular monomer based on bipyridine includes the following steps: When the alanine is L-alanine and the alkoxy ether is dendritic alkoxy ether G1, the reaction steps are as follows: .

[0039] In the reaction formula, compound 1-a is compound A, compound 1-b is compound B, compound C is compound 2-c2, and compound D is compound 2-d2.

[0040] The specific synthesis steps are as follows: The synthesis steps of compounds 1-a and 1-b are the same as those of compounds 1-a and 1-b in Example 1.

[0041] Synthesis of compound 1-c2: Compound 1-b (0.55 g, 2.233 mmol) and dendritic alkoxy ether G1 (G1-OH) (1.19 g, 1.861 mmol) were dissolved in 50 mL of DCM. DMAP (0.068 g, 0.56 mmol) was added, and nitrogen was purged. After stirring in an ice bath for 30 min, EDC·HCl (1.50 g, 2.792 mmol) was added, and nitrogen was purged again. The mixture was stirred in an ice bath overnight. TLC analysis (DCM / MeOH, 30 / 1, v / v) indicated complete reaction. After washing and extraction with 10% KHSO4 solution, the mixture was dried over anhydrous Na2SO4, filtered, and the solvent was evaporated. The sample was then purified by column chromatography (PE / EA, 1 / 3, v / v) after silica gel loading, yielding 1.2883 g of a colorless oil, with a yield of 78.83%. Compound 1-c2 was dissolved in... d Nuclear magnetic resonance imaging (NMR) was performed in 6-DMSO, such as... Figure 11 As shown. 1 H NMR (400MHz, d 6-DMSO) δ: 1.11 (t, 9H, CH3), 1.16 (d, 3H, J=4.8 Hz, CH3), 1.36 (s, 9H,CH3), 3.16−3.59 (m, 36H, CH2), 3.66 (s, 2H, CH2), 3.82 (t, 6H, CH2), 3.96-4.01(m, 1H, CH), 5.02 (s, 2H, CH2), 6.68 (s, 2H, Ar-H), 6.96 (s, 1H, NH), 8.26(s, 1H, NH).

[0042] Synthesis of compound 1-d2: Compound 1-c2 (1.1 g, 1.2528 mmol) was dissolved in 7 mL of DCM, and TFA (2.8568 g, 25.0552 mmol) was added dropwise. The mixture was stirred in an ice bath for 20 min, then the ice was removed, and the mixture was stirred at room temperature for 6 h. TLC analysis (DCM / MeOH, 30 / 1, v / v) showed that the reaction was complete. The reaction was terminated by adding 30 mL of methanol and stirring for 30 min. The product was evaporated to dryness to give 1.1 g of a colorless oil, with a yield of 100.00%.

[0043] Synthesis of compound (L)BPY-AG-G1: 2,2'-bipyridine-5,5'-dicarboxylic acid chloride (0.16 g, 0.5694 mmol) was dissolved in 35 mL of anhydrous THF and stirred under nitrogen protection. Separately, compound 1-d2 (1.1 g, 1.2528 mmol) was dissolved in 10 mL of anhydrous THF, and the pH of the solution was adjusted to approximately 9 by adding an appropriate amount of N,N-diisopropylethylamine (DIEA), followed by purging with nitrogen three times. Subsequently, the (L)1-d2 solution was slowly added dropwise to the 2,2'-bipyridine-5,5'-dicarboxylic acid chloride solution, and the reaction was carried out at room temperature in the dark for 60 h.

[0044] After the reaction was complete, 2 mL of anhydrous N,N-dimethylformamide (DMF) was added to the system, and nitrogen was purged again. The reaction was continued at room temperature for 24 h. Most of the volatile solvent was removed by rotary evaporation under reduced pressure. The residue was adjusted to a weakly acidic pH (pH≈5–6) with 10% KHSO4 aqueous solution, and then extracted with 20 mL of DCM to obtain the organic phase. The organic phase was dried over anhydrous Na2SO4, filtered, and then the DCM was removed by rotary evaporation under reduced pressure. The crude product was purified by LH-20 dextran gel chromatography (eluent: DCM) to give 0.1222 g of a red solid, with a yield of 12.35%, yielding compound (L)BPY-AG-G1.

[0045] Dissolve compound (L)BPY-AG-G1 in d In 6-DMSO, 1 H NMR and 13 C NMR detection, respectively as follows Figure 12 and Figure 13 As shown. 1 H NMR (400 MHz, d 6-DMSO): δ 1.08 (t, 18H, CH3), 1.38 (d, 6H, J=6Hz, CH3), 3.41−3.58 (m, 60H, CH2), 3.69 (t, 12H, CH2), 3.93 (s, 4H, CH2), 4.05(t, 12H, CH2), 4.55-4.60 (m, 2H, CH), 5.03(s, 4H, CH2), 6.68 (s, 4H, Ar-H), 8.53 (d, 2H, J=7.6 Hz, CH), 8.90 (d, 4H, J=6 Hz, NH, CH), 9.18 (d, 4H, J=10Hz, NH, CH). 13 C NMR ( d6- DMSO): δ =15.55, 18.22, 41.34, 49.29, 65.99, 68.86,69.47, 69.67, 70.20, 70.28, 70.33, 70.43, 107.53, 120.85, 131.63, 137.13,137.77, 149.31, 152.59, 156.83, 164.83, 170.15, 173.22. HRMS (ESI) calcd forC 84 H 133 N6O 32 [M+H] + 1737.8959, found 1737.9026.

[0046] When the alanine is D-alanine and the alkoxy ether is dendritic alkoxy ether G1, the reaction steps are as follows: .

[0047] In the reaction formula, compound 2-a is compound A, compound 2-b is compound B, compound C is compound 2-c, and compound D is compound 2-d.

[0048] The specific synthesis steps are as follows: The synthesis steps of compounds 2-a and 2-b are the same as those of compounds 1-a and 1-b in Example 1; the synthesis steps of compounds 2-c and 2-d are the same as those of compounds 2-c2 and 2-d2 described above.

[0049] Synthesis of compound (D)BPY-AG-G1: 2,2'-bipyridine-5,5'-dicarboxyl chloride (0.16 g, 0.5694 mmol) was dissolved in 35 mL of anhydrous THF and stirred under nitrogen protection. Separately, compound 2-d (1.2 g, 1.4247 mmol) was dissolved in 10 mL of anhydrous THF, and the pH of the system was adjusted to approximately 9 with the addition of an appropriate amount of DIEA, followed by the addition of 2 mL of anhydrous DMF. The entire reaction system was subjected to three vacuum-nitrogen purgings to ensure an inert atmosphere. Subsequently, the THF solution containing compound 2-d was slowly added dropwise to the above acyl chloride solution, and the reaction was stirred at room temperature in the dark for 68 h.

[0050] After the reaction was complete, most of the volatile solvent was removed by rotary evaporation under reduced pressure. The residue was adjusted to a weakly acidic pH (pH ≈ 5–6) with a 10% KHSO4 aqueous solution, and then extracted with 20 mL of DCM to obtain the organic phase. The organic phase was dried over anhydrous Na2SO4, filtered, and the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by LH-20 dextran gel column chromatography (eluent: pure DCM) to give 0.0543 g of a red solid, with a yield of 5.03%.

[0051] Dissolve compound (D)BPY-AG-G1 in d In 6-DMSO, 1 H NMR detection, such as Figure 15 As shown; compound (D)BPY-AG-G1 dissolves in d In 6-CDCl3, 13C NMR detection was performed, such as... Figure 16 As shown. 1 H NMR (400 MHz, d 6-DMSO): δ 1.07 (t, 18H, CH3), 1.38 (d, 6H, J=15.6 Hz, CH3), 3.40−4.58 (m, 90H, CH 2, CH), 5.03(s, 4H, CH2), 6.68 (s, 4H, Ar-H), 8.52 (d, 2H, J=8 Hz, CH), 8.89 (d,4H, J=5.6 Hz, NH, CH), 9.17 (d, 4H, J=10 Hz, NH, CH). 13 C NMR ( d 6- CDCl3): δ =11.10, 18.13, 40.51, 48.22, 65.59, 66.16, 67.88, 68.71, 68.76, 68.78, 69.47,69.50, 69.63, 69.75, 70.77, 71.28, 107.07, 120.08, 127.81, 129.45, 129.87,137.63, 151.69, 156.39, 164.38, 168.35, 171.41. HRMS (ESI) calcd forC 84 H 133 N6O 32 [M+H] + 1737.8959, found 1737.8972.

[0052] Compounds (L)BPY-AG-G1 and (D)BPY-AG-G1 are L-configuration and D-configuration, respectively.

[0053] 2.1 Chiral Study Based on Bipyridine Dipeptide Supramolecular Monomer The effects of different metal ions on compound (L)BPY-AG-G1 were investigated using circular dichroism spectroscopy. A 0.02 mg / mL solution was prepared. -1 aqueous solutions, such as Figure 18 As shown, (L)BPY-AG-G1 exhibits a negative peak at 230 nm and a very broad positive peak at 291 nm. The negative peak is due to the absorption of the polypeptide amide, while the positive peak is due to the π-π stacking effect of the bipyridine.

[0054] The compound (L)BPY-AG-G1 is a supramolecular monomer with metal coordination ability. This supramolecular monomer contains two pyridine groups (as metal coordination sites) and two amino acid residues, and can self-assemble into a dynamic supramolecular structure through non-covalent interactions (such as metal coordination, hydrogen bonding, and π-π stacking). When it reacts with metal ions (such as Cu), it... 2+ Ni 2+ After coordination with (etc.), its supramolecular assembly mode and chirality may change, thereby affecting the circular dichroism spectrum.

[0055] like Figure 18 As shown, Ni is added 2+ Subsequently, CD spectroscopy revealed an enhanced positive peak at 263 nm corresponding to the stacking effect, a significant negative peak at 316 nm, and a significant enhancement of the positive peak at 340 nm. This indicates the presence of Ni. 2+ The supramolecular chirality was significantly enhanced after the addition of Cu. 2+ Subsequently, CD spectroscopy revealed a significant decrease in the positive peak at 291 nm corresponding to the stacking effect, and a significant decrease in the negative peak at 230 nm corresponding to the peptide amide absorption effect. This indicates that the addition of Cu... 2+ The supramolecular chirality is significantly weakened afterward. Compared to other metal ions, Ag... + Ba 2+ Zn 2+ The effect on this molecule is relatively small. This demonstrates that the addition of metal ions can affect the chirality of the system, with different metal ions exhibiting different coordination modes.

[0056] The CD spectra of the same metal ion at different proportions were studied. The CD signal intensity of compound (L)BPY-AG-G1 molecule increased with Ni. 2+ The addition of [Ni] gradually enhances the effect in [(L)BPY-AG-G1]:[Ni 2+ The signal strength is greatest when the ratio of ] to 2:1. 2 +When the signal strength of the CD is increased further, it actually decreases (e.g., Figure 19 As shown in figure a), this illustrates the relationship between (L)BPY-AG-G1 and Ni. 2+ It forms an octahedral structure. Conversely, as Cu... 2+ The addition of CD signal strength gradually weakens, when it reaches [(L)BPY-AG-G1]: [Cu 2+ When the ratio is 1:5, the signal attenuation is greatest (e.g., Figure 19 (as shown in b). Figure 19 As shown in a, d, and e, different equivalents of Ag were added respectively. + Ba 2+ Zn 2+ The impact on the CD signal is relatively small, which may be related to the volume of different metal ions themselves. The addition of metal ions (such as Cu) 2+ Ni 2+ After (etc.), the UV spectrum also showed corresponding changes, with the positive peak at 300 nm decreasing and the positive peak at 320 nm increasing, further confirming that the monomer coordinated with metal ions, thereby causing a change in its chiral effect.

[0057] To eliminate the influence of anions on the above studies, perchlorate metal salts were used to prepare a solution with a 1:1 ratio of metal ions to (L)BPY-AG-G1 molecules for circular dichroism spectroscopy. As shown in Figure 20, the effects of different anion metal salts on the BPY-AG-G1 molecules were almost identical, indicating that the coordination between (L)BPY-AG-G1 molecules and metal ions mainly depends on the properties of the molecule itself and the metal ions, while the anions have a relatively small impact on the coordination process and the chiral properties of the assembly.

[0058] To further investigate the intelligent regulation of supramolecular assemblies coordinated with metal ions, EDTA, a chelating agent with stronger binding ability to metal ions, was selected as a competing ligand. EDTA's chemical structure enables it to coordinate with metal ions, forming a cyclic structure with multiple coordinate bonds; this structure is generally quite stable. Adding EDTA to an aqueous solution containing metal ions (L)BPY-AG-G1 causes it to compete with the (L)BPY-AG-G1 molecule for metal ions, resulting in a change in the chiral signal.

[0059] Prepare 2 mg·mL -1 Add 80 μL of EDTA solution to the above system, as follows: Figure 21As shown, after the addition of EDTA, the chiral signal of (L)BPY-AG-G1 reverted to the state without metal ions, indicating that the introduction of EDTA extracts the metal ions coordinated with the assembly, leading to the dissociation of the original metal coordination structure. This phenomenon suggests that EDTA can act as an effective coordination competitor in the coordination system of (L)BPY-AG-G1 and metal ions, thereby regulating the assembly process of (L)BPY-AG-G1. Therefore, in the study and application of metal ion-induced self-assembly of bipyridine dipeptide supramolecular monomers, EDTA can be used to achieve dynamic regulation of supramolecular chirality.

[0060] Next, circular dichroism spectroscopy was used to investigate the chirality of (D)BPY-AG-G1. When circularly polarized light passes through the chiral molecule, due to the molecule's chiral structure, there is a difference in absorption between left-handed and right-handed circularly polarized light. This difference leads to the generation of the CD signal. The D and L configurations are chiral isomers, and their molecular structures are mirror images of each other in spatial arrangement; therefore, they exhibit mirror symmetry in circular dichroism spectroscopy. (Prepared at 0.02 mg / mL) -1 aqueous solutions, such as Figure 22 As shown, the D-configuration and L-configuration of BPY-AG-G1 exhibit a clear mirror-symmetry relationship in their CD spectra. The D-configuration shows a strong positive peak at 230 nm and a negative peak near 290 nm. Similarly, the signal at 230 nm is due to the absorption of the peptide amide, while the signal near 290 nm is due to the π-π stacking of the bipyridine.

[0061] The same, such as Figure 23 As shown, the D-configuration BPY-AG-G1 aqueous solution, upon the addition of Ni 2+ Later, an increase in chirality was observed, with the negative peak at 304 nm weakening and the negative peak at 325 nm significantly strengthening. The CD signal also appeared in [(D)BPY-AG-G1]:[Ni 2+ The strength is greatest when the ratio of Cu to Cu is 2:1; conversely, the strength decreases when Cu is added. 2+ Afterwards, the positive peak at 230 nm weakened significantly, and the negative peak at 290 nm weakened significantly, indicating that the addition of Cu... 2+ The supramolecular chirality also weakened, and with Cu 2+ The CD signal strength gradually weakens upon addition, until [BPY-AG-G1]: [Cu 2+ When the ratio of Ag to 5 is 1:5, the signal attenuation is greatest. Compared to other metal ions, Ag... + Ba 2+ Zn 2+The impact on this molecule is relatively small. This is consistent with the CD change in the L configuration, indicating that although the L and D configurations are enantiomers and mirror images of each other in chiral structure, the BPY-AG-G1 molecules in both configurations have the same coordination sites, namely the two N atoms in the bipyridine group. These N atoms can form coordinate bonds with metal ions. When coordinating with metal ions, they exhibit the same coordination mode, and the effect of chiral differences on coordination is negligible.

[0062] 2.2 Study on Metal Ion-Induced Fluorescence Spectroscopy and Particle Size of Symmetric Dipeptide Supramolecular Monomers Based on Bipyridine Metal coordination not only affects supramolecular assembly patterns but also alters electronic transition behavior, thereby influencing fluorescence properties. This involves the monomer reacting with metal ions (such as Cu). 2+ Ni 2+ The coordination of (etc.) can induce structural changes in supramolecular aggregates, and the resulting system should have an increased particle size, while exhibiting significant fluorescence quenching.

[0063] The effects of different metal ions on (L)BPY-AG-G1 were investigated using fluorescence spectroscopy. A 0.1 mg·mL⁻¹ solution was prepared. -1 An aqueous solution, simultaneously prepared with metal ions (Ni 2+ Cu 2+ Ag + Ba 2+ Zn 2+ Five solutions in a 2:1 ratio were used. The excitation wavelength was 330 nm, and the scanning wavelength range was 400-600 nm with a slit width of 10 nm. Fluorescence data were collected and plotted at this wavelength (e.g.,...). Figure 24 (As shown). It was found that the fluorescence intensity of this compound decreased at 461 nm. Ni 2+ and Cu 2+ The decrease is most pronounced in Ni. This is because when metal ions coordinate with the N atom of bipyridine, a stable metal-ligand complex is formed, altering the electronic structure and thus reducing fluorescence intensity; this is a static quenching mechanism. 2+ and Cu 2+ It has strong coordination ability and can form a more stable structure with (L)BPY-AG-G1 than other complexes, thereby exacerbating the quenching of fluorescence.

[0064] Using the above solution, the average particle size of the assembly was further determined using a particle size analyzer. Its particle size distribution diagram (e.g.) Figure 25 As shown in the figure, the average particle size of the (L)BPY-AG-G1 solution is 159.0 nm, which is similar to that of Ni. 2+ After coordination, the wavelength is 186.3 nm, which is similar to that of Cu. 2+After coordination, the particle size was 188.9 nm, and the PDI values ​​were all less than 1, indicating a relatively uniform particle size distribution. The particle size increased significantly after coordination with metal ions. This is because the metal ions, in conjunction with the supramolecular monomers, form larger supramolecular assemblies. The formation of these assemblies increases intermolecular interactions, leading to increased particle size. As the average particle size of the assemblies increases, the fluorescence quenching phenomenon becomes more pronounced, further clarifying the reason for the decreasing trend in fluorescence intensity.

[0065] 2.3 Morphology of supramolecular monomers based on bipyridine dipeptides Prepare 0.02 mg·mL -1 (L)BPY-AG-G1 solution and Cu 2+ A 2:1 mixed solution was prepared, and approximately 5 μL of the solution was dropped onto a silicon wafer and allowed to air dry. The two solutions were then characterized using a scanning electron microscope (SEM) to observe the assemblies formed by the supramolecular monomers in the solution and their interaction with Cu. 2+ Changes in size and morphology after coordination. For example... Figure 26 As shown, scanning electron microscopy revealed that the (L)BPY-AG-G1 assembly exhibited a blocky fibrous structure with a rough surface and a wide diameter distribution. The addition of Cu... 2+ Afterwards, the morphology of the assembled body is similar, but the diameter is significantly increased, forming a distinct single left-handed helix with a fibrous structure with a pitch of about 140 nm.

[0066] The formation of the left-handed helix is ​​directly related to the L-chirality of the dipeptide, Cu 2+ Coordination makes the helical conformation of individual fibers more pronounced and occupies more space, thus increasing their diameter. This indicates that the role of metal ions is mainly to regulate and strengthen the internal structure of the assembly, rather than to change its original self-assembly mode.

[0067] 2.4 Thermosensitive Response Study of Symmetric Dipeptide Supramolecular Monomers Based on Bipyridine The dendritic alkoxyether units in the supramolecular compound (L)BPY-AG-G1 exhibit thermosensitive properties, with their response mechanism closely related to the phase transition temperature (LCST). At room temperature, the solution remains transparent. When the temperature exceeds the LCST, the dendritic alkoxyether structure undergoes a conformational change. Due to the collapse and aggregation of the dendritic alkoxyethers, they self-assemble into larger assemblies. This phase transition directly leads to a decrease in the solution's transmittance, macroscopically manifested as a change from a clear to a turbid state. The entire response process is reversible; the system returns to its initial transparent state upon cooling.

[0068] The concentration was prepared at 2.5 mg / mL. -1 (L)BPY-AG-G1 aqueous solution. For example... Figure 27As shown, the obtained solution is in a clear state. After the temperature of the solution is increased, it can be observed with the naked eye that the solution gradually becomes turbid. After the solution temperature drops to room temperature, the solution returns to a clear state. Therefore, this indicates that (L)BPY-AG-G1 has a temperature-sensitive response and a high phase transition temperature. It is clear at room temperature and becomes turbid after heating.

[0069] This phase transition process can be repeated multiple times. The turbidity of the solution was further measured using variable-temperature UV-Vis spectroscopy. Figure 28 As shown, within the temperature range of 45℃-70℃, 2.5 mg·mL -1 The LCST of the solution is 52.9 °C. The transmittance of the (L)BPY-AG-G1 solution decreases with increasing temperature, but recovers when the temperature decreases.

[0070] Prepare 0.02 mg·mL -1 (L)BPY-AG-G1:Ni 2+ Changes in a 2:1 solution were observed by measuring circular dichroism chromatogram data at different temperatures. For example... Figure 29 As shown, with increasing temperature, the positive peak at 330 nm gradually decreases, while the negative peak at 316 nm gradually increases, and the CD signal intensity gradually weakens. This phenomenon is attributed to the regulation of the supramolecular self-assembly process by temperature changes, indicating that the supramolecular system has the ability to be precisely controlled by temperature. Its response process exhibits reversible and continuous characteristics, fully demonstrating the controllable and flexible advantages of the supramolecular system in responding to external stimuli.

[0071] 3. Conclusion This invention uses bipyridine as the backbone to link glycine-alanine dipeptides and alkoxy ethers to form supramolecular monomers (L)BPY-AG-TEG, (L)BPY-AG-G1, and (D)BPY-AG-G1 that can coordinate with metal ions. The thermosensitive characteristics of the dendritic alkoxy ether motif endow the supramolecular polymers formed by (L)BPY-AG-G1 and (D)BPY-AG-G1 with temperature responsiveness. The structures of intermediate and target products during synthesis were confirmed using 1H NMR, 1C NMR, and high-resolution mass spectrometry. The supramolecular chirality of the assemblies and their coordination with different metal ions were analyzed using circular dichroism spectroscopy and infrared spectroscopy. Reversible control of the supramolecular chirality of the assemblies was achieved through ligand substitution, making it a potential application in the preparation of metal ion-induced biomimetic peptide supramolecular chiral materials. The structural changes of its coordination with metal ions in solution were studied using fluorescence chromatography and particle size measurement. It was found that the average particle size of the assembled system increases and a significant fluorescence quenching phenomenon occurs. This property is expected to play an important role in the fields of fluorescent probes, bioimaging and biosensing.

[0072] The assembly and its relationship with Cu were studied using scanning electron microscopy. 2+ The morphology after coordination was observed, indicating that metal ions have a regulatory and enhancing effect on the internal structure of the assembly. Simultaneously, the reversible thermosensitive phenomenon of the assembly in aqueous solution was investigated using variable-temperature ultraviolet spectroscopy, demonstrating the reversible control of the assembly state by temperature.

[0073] This invention provides a theoretical basis for constructing stimulus-responsive chiral peptide materials and developing functional polymers with dual regulation by metal ions and temperature, and expands the application of supramolecular systems in other fields such as the research and development of biomimetic chiral peptide materials, drug carriers, and fluorescent probes.

[0074] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A symmetrical dipeptide supramolecular monomer based on bipyridine, characterized in that, The symmetrical dipeptide supramolecular monomer based on bipyridine is any one of the following: (L)BPY-AG-TEG, (L)BPY-AG-G1, or (D)BPY-AG-G1, with the following specific structural formulas: 。 2. A method for preparing a symmetrical dipeptide supramolecular monomer based on bipyridine as described in claim 1, characterized in that, Includes the following steps: (1) Under alkaline conditions, alanine protected by tert-butoxycarbonyl, glycine methyl ester hydrochloride, 1-hydroxybenzotriazole, and N,N-diisopropylethylamine were dissolved in dichloromethane, and then 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was added to carry out a condensation reaction to obtain compound A. (2) A methanol solution of compound A and a lithium hydroxide monohydrate solution were mixed and hydrolyzed to obtain compound B; (3) Compound B, alkoxy ether, dichloromethane and 4-dimethylaminopyridine were mixed and then 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was added to carry out esterification reaction to obtain compound C; (4) A solution of compound C in dichloromethane and trifluoroacetic acid were mixed and reacted to obtain compound D; (5) Under alkaline conditions, compound D is dissolved in tetrahydrofuran solution and added to tetrahydrofuran solution of 2,2'-bipyridine-5,5'-dicarboxylic acid chloride to obtain the symmetrical dipeptide supramolecular monomer based on bipyridine.

3. The preparation method according to claim 2, characterized in that, In step (1), alanine includes L-alanine and D-alanine. The molar ratio of alanine, glycine methyl ester hydrochloride, and 1-hydroxybenzotriazole is 1:1.0-1.2:1.1-1.

3. The molar ratio of alanine to N,N-diisopropylethylamine is 1:1.5 to 2.0; The molar ratio of alanine to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1.1 to 1.3; The ratio of alanine to dichloromethane is 1 mmol: 8–10 mL.

4. The preparation method according to claim 2 or 3, characterized in that, In step (2), the volume fraction of methanol in the methanol aqueous solution is 75-85%. The molar ratio of compound A to lithium hydroxide monohydrate is 1:2 to 2.2; The ratio of compound A to the methanol aqueous solution is 1 mmol: 3-5 mL.

5. The preparation method according to claim 4, characterized in that, In step (3), the alkoxy ether is triethylene glycol monoethyl ether or dendritic alkoxy ether G1. When the alkoxy ether in step (3) is triethylene glycol monoethyl ether, the molar ratio of compound B to the alkoxy ether is 1.0:1.1-1.2, and the molar ratio of compound B to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1.0-2.

0. When the alkoxy ether in step (3) is dendritic alkoxy ether G1, N,N-dimethylformamide is added to step (5) for amidation reaction. The molar ratio of compound B to the alkoxy ether is 1.2:0.9-1.1, and the molar ratio of compound B to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1.0-1.

5. The ratio of compound B to dichloromethane is 1 mmol: 20–30 mL; The molar ratio of compound B to 4-dimethylaminopyridine is 3 to 4:

1.

6. The preparation method according to claim 4, characterized in that, In step (4), the molar volume ratio of compound C to dichloromethane in the dichloromethane solution of compound C is 1.1–1.8 mmol: 5–9 mL; The molar ratio of compound C to trifluoroacetic acid is 1.1–1.8:25–35.

7. The preparation method according to claim 5, characterized in that, The pH value of the alkaline conditions in step (5) is 8 to 10; The molar volume ratio of the 2,2'-bipyridine-5,5'-dicarboxylic acid chloride and tetrahydrofuran solution is 0.5–0.8 mmol: 20–35 mL; The molar volume ratio of compound D to tetrahydrofuran solution is 1.2–1.5 mmol: 9–10 mL; The molar ratio of compound D to 2,2'-bipyridine-5,5'-dicarboxylic acid chloride is 1.2–1.8:0.06–0.6; The molar ratio of compound D to N,N-dimethylformamide is 1.2–1.8 mmol: 2–3 mL.

8. The application of the symmetrical dipeptide supramolecular monomer based on bipyridine as described in claim 1 in the preparation of peptide supramolecular chiral materials, fluorescent probe materials and drug controlled-release materials.

Images