Conformational analysis of the adductcis[Pt(NH3)2{d(GpG)}]+in aqueous solution. A high field (500–300 MHz) nuclear magnetic resonance investigation

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Abstract
A 500, 400 and 300 MHz proton NMR study of the reaction product of cis -Pt(NH 3 ) 2 Cl 2 or cis -[Pt(NH 3 ) 2 (H 2 O) 2 ] (NO 3 ) 2 with the deoxydinucleotide d(GpG): cis -[Pt(NH 3 ) 2 (d(GpG)] + was carried out. Complete assignment of the proton resonances by decoupling experiments and computer simulation of the high field part of the spectrum yield proton-proton and proton-phosphorus coupling constants of high precision. Analysis of these coupling constants reveal a 100Z N (C3′- endo ) conformation for the deoxyribose ring at the 5′-terminal part of the chelated d(GpG) moiety. In Contrast, the 3′-terminal -pG part of the molecule displays the normal behaviour for deoxyriboses: the sugar ring prefers to adopt an S (C2′- endo ) conformation (about 70%). Extra-polating from this model compound, it is that Pt chelation by a -dGpdG- sequence of DNA would require a S to N conformational change of one deoxyribose moiety as the main conformational alteration and lead to a kink in one strand of the double-helical structure of DNA.

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