Distortions induced in double-stranded oligonucleotides by the binding of cis- or trans-diammine-dichloroplatinum(ll) to the d(GTG) sequence

摘要

Conformational changes induced in double-stranded oligonucleotides by the binding of trans- or cis-diamminedichloro platinum(ll) to the d(GTG) sequence have been characterized by means of melting temperatures, electrophoretic migrations in nondenaturing polyacrylamide gels, reactivities with the artificial nuclease Phenanthroline-copper and with chemical probes. The cis-platinum adduct behaves more as a centre of directed bend than as a hinge joint, the induced bend angle being of the order of 25–30°. The double helix is locally denatured over 2 base pairs (corresponding to the platinated 5'G residue and the central T residue) and is distorted over 4 – 5 base pairs. The frans-platinum adduct behaves also more as a centre of directed bend than as a hinge joint, the induced bend angle being of the order of 60°. The double helix is locally denatured over 4 base pairs (corresponding to the immediately 5'T residue adjacent to the adduct and to the three base residues of the adduct).Both the cis- and trans-platinum adducts decrease the thermal stability of the double helix.