Reaction of (1R, 2S, 3S)-3-Methylcyclohexanediamineplatinum(II) with DNA : Isolation and Characterization of the Platinum-Nucleotide Adducts by Means of HPLC and NMR Spectroscopy

Abstract

Reaction products of calf thymus DNA with (1R, 2S, 3S)-3-methylcyclohexanediamineplatinum (abbreviated as Pt(RSS-dach)Cl₂) were investigated by enzymatic degradation of the platinated DNA and subsequent HPLC analysis.Five platinated adducts involving d(GpG), d(ApG) and (dG)₂ residues were identified by HPLC after complete digestion using deoxyribonuclease I, nuclease P1, and alkaline phosphatase. The adducts with d(GpG) and d(ApG)consisted of two geometrical isomers, because Pt(RSS-dach)Cl₂ lacks a C₂ symmetry element. The d(GpG) and d(ApG) adducts were intrastrand compounds crosslinked between the N7 atoms of the adjacent purine bases. The two d(GpG) adducts were most abundant and comprised more than 65% of all the platinated adducts. The relative ratio of the two d(GpG) isomers was 3 : 2 for reaction with DNA, whereas the ratio was 1 : 1 for reaction with a single stranded oligonucleotide. The detailed structure of the two d(GpG) adducts is also described based on NMR spectroscopic data.