[Interaction of DNA molecules with divalent platinum coordination complexes. II. Effect of the nature and location of ligands in the first platinum coordination sphere].

The interaction of DNA molecule with some coordination compounds of the divalent platinum: cis-DDP, trans-DDP, [(NH3)4Pt]Cl2 and K2PtCl4 was studied. It was shown that the transition of the cis-DDP, trans-DDP, and [PtCl4]2- to aquo-complexes is necessary for their binding with DNA in solution. It was shown that the labile chloride groups are responsible for the formation of the energetically strong binding. The distance between chloride groups in cis-DDP is optimal for incorporation of two groups of DNA bases into the first coordination sphere of platinum. The complexes are also stabilized with phosphate in the external coordination sphere of platinum. The sterical non-conformity between the DNA structure and positions of chloride groups and the orientation of the amino groups in trans-DDP are the main obstructions for the formation of bidentate DNA-trans-DDP complexes. The existence of more than two vacant positions for binding with DNA in [PtCl4]2- does not stabilise the complex. The compound [(NH3)4Pt]Cl2 cannot produce coordination bonds with DNA, because its first coordination sphere is completed with amino groups; it interacts with DNA, forming principally different complexes.