DNA CONFORMATIONAL CHANGE PRODUCED BY THE SITE-SPECIFIC INTERSTRAND CROSS-LINK OF TRANS-DIAMMINEDICHLOROPLATINUM(II)

The DNA distortion produced by the interstrand cross-link of trans-diamminedichloroplatinum-(II) has been described by means of gel electrophoresis, chemical probes, and molecular mechanics modeling. Synthetic double-stranded oligodeoxyribonucleotides of varying lengths (19-22 base pairs) were synthesized that contained a unique site-specific interstrand cross-link within their central sequence d(TGCT)/d(AGCT) between complementary guanine and cytosine residues. We find that the platinated deoxyriboguanosine residue adopts syn conformation. The duplex is distorted on both sides of the cross-link, but the bases are still paired. The distortion introduces some flexibility into the helix. In addition, the double helix is unwound and bent toward the major groove.