The peculiarities of complex-formation of cis- and trans-DDP with DNA and synthetic polynucleotides in an interval of concentration 0.003 < r_b < 0.03 (where r_b is relative concentration of a platinum complex) have been investigated by the methods of UV- and CD-spectroscopy.

It is shown that there are extremely rare centers of binding on DNA for both ligands (cis-DDP and trans-DDP), which are localized in GC-rich sites of heterogeneous DNA having certain nucleotide sequences. These ligands are capable strongly influence on the structure of DNA even at rather low concentrations of ligand, which is unexpected result.

The reasons of such serious alterations in DNA structure may differ and while are not determined unequivocally. But its most probable reason can be formation of intra-molecular linkage in DNA and its compactization. The similar phenomena seriously influence secondary and tertiary structure of macromolecule and, as result, on potential of long-range distance interaction between ligands, adsorbed on different sites of DNA.