NMR methods are used to study the structure and stability of the duplex formed by the nucleopeptide [Ac- Cys- Gly- Ala-Hse( p(3')dGCATGC)- Ala-OH](2)[S-S], in which the oligonucleotide is self-complementary and the cysteine residues of the two peptide chains form a disulfide bridge; thermal transitions and NMR-derived structural calculations are consistent with a 3-D structure in which the oligonucleotide forms a standard B-DNA helix without significant distortions; the peptide chains are relatively disordered in solution and lie in the minor groove of the DNA helix; this nucleopeptide duplex exhibits a high melting temperature, indicating that peptide - oligonucleotide conjugates containing cysteines are suitable molecules to establish cross-links between DNA strands and stabilize the duplex
