[Interaction of DNA molecules with divalent platinum coordination complexes. II. Effect of the nature and location of ligands in the first platinum coordination sphere]. / Issledovanie vzaimodeistviia molekuly DNK s koordinatsionnymi soedineniami dvukhvalentnoi platiny. II. Vliianie prirody i raspolozheniia ligandov v pervoi koordinatsionnoi sfere platiny.

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.

[Study of the interaction of a DNA molecule with coordination compounds of divalent platinum. I. Effect of cis-diaminodichloroplatinum on molecular parameters of DNA in solution]. / Issledovanie vzaimodeistviia molekuly DNK s koordinatsionnymi soedineniiami dvukhvalentnoi platiny. I. Vliianie tsis-diaminodikhlorplatiny na molekuliarnye parametry DNK v rastvore.

DNA interaction with cis-diaminodichloroplatinum (cis-DDP in solutions of different ionic strength was studied by flow birefringence, viscometry, circular dichroism. Though cis-DDP is not an electrolyte, electrostatic interactions are important for binding of cis-DDP with DNA probably for transporting cis-DDP to a macromolecule. The charges aqua-complex is formed by cis-DDP. The complexation being dependent on the platinum/DNA ratio in solution. Along with the increase of platinum concentration, it forms first the complexes with phosphate groups, then with bases without destruction of the DNA secondary structure. The next type of complex formation is accompanied by the local destruction of the hydrogen bonds and stacking interactions. And when the Pt/DNA ratio grows high enough, DNA is denatured. It is suggested that the stability of the complex is provided by nitrogen groups of the bases incorporated in the platinum first coordination sphere. The phosphate DNA groups play the role of counterions in the external coordination sphere.