Peptide nucleic acids and synthetic procedures therefor

Abstract

A novel class of compounds, known as peptide nucleic acids, bind complementary ssDNA and RNA strands more strongly than a corresponding DNA. The peptide nucleic acids generally comprise ligands such as naturally occurring DNA bases attached to a peptide backbone through a suitable linker.

Description

[0001] This application is a continuation-in-part of U.S. Ser. No. 108,591, filed Nov. 22, 1993, deriving from Application PCT / EP92 / 01219, filed May 22, 1992, which is a continuation-in-part of the following Danish Patent Applications: No. 986 / 91, filed May 24, 1991, No. 987 / 91, filed May 24, 1991, and No. 510 / 92, filed Apr. 15, 1992. The disclosure the foregoing patent applications is incorporated herein by reference.[0002] This invention is directed to compounds that are not polynucleotides yet which bind to complementary DNA and RNA strands more strongly the corresponding DNA. In particular, the invention concerns compounds wherein naturally-occurring nucleobases or other nucleobase-binding moieties are covalently bound to a polyamide backbone.[0003] Oligodeoxyribonucleotides as long as 100 base pairs (bp) are routinely synthesized by solid phase methods using commercially available, fully automatic synthesis machines. The chemical synthesis of oligoribonucleotides, however, is f...

AI Technical Summary

Benefits of technology

PNAs achieve strong and stable binding to complementary DNA and RNA strands, enabling effective site-specific gene regulation and therapeutic applications with improved stability and membrane penetration.

Problems solved by technology

The chemical synthesis of oligoribonucleotides, however, is far less routine.

However, there are a number of drawbacks associated with triple helix formation.

For example, it can only be used for homopurine sequences and it requires unphysiologically high ionic strength and low pH.

Furthermore, unmodified oligonucleotides are unpractical both in the antisense approach and in the triple helix approach because they have short in vivo half-lives, they are difficult to prepare in more than milligram quantities and, thus, are prohibitively costly, and they are poor cell membrane penetrators.

These problems have resulted in an extensive search for improvements and alternatives.

In order to improve half life as well as membrane penetration, a large number of variations in polynucleotide backbones has been undertaken, although so far not with desired results.

However, the specification provides no example wherein a claimed compound or structure is actually prepared.

However, the application provides no examples directed to the preparation of a claimed oligonucleotide analog and no data confirming the specific binding of an oligonucleotide analog to a target oligonucleotide.

However, such linking has not resulted in satisfactory binding for either double-stranded or single-stranded DNA.

Other problems which resulted from, for example, methylphosphonates and monothiophosphates were the occurrence of chirality, insufficient synthetic yield or difficulties in performing solid phase assisted syntheses.

Furthermore, the oligomers actually produced have rarely been shown to bind to DNA or RNA or have not been examined biologically.

The great majority of these backbone modifications led to decreased stability for hybrids formed between the modified oligonucleotide and its complementary native oligonucleotide, as assayed by measuring Tm values.

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