[Oligonucleotides with peptide internucleotide linkage. A novel class of modified oligonucleotides].

Oligonucleotide analogues with replacement of one or more internucleotide phosphodiester linkages with glycine, L- and D-alanine residues have been synthesized (C3'-NH-C(O)-CH(X)-NH-C(O)-C4', X = H, (S)-CH3 and (R)-CH3). The stability of the duplexes formed by the modified oligonucleotides and their wild-type complements have been studied. Incorporation of glycine and L-alanine residues have been shown to substantially decrease the stability the modified duplexes in comparison with that of the wild-type ones (DeltaT(m) approximately -2 degrees C per modification), while the analogs with D-alanine-containing linkages appeared to form duplexes with increased stability (DeltaT(m), approximately +0.2 degrees C per modification).