  The goal of the work was to study the role of GC alternative dimmers in the
binding of DNA with Ni (II) ions. The method of ultraviolet difference
spectroscopy has been applied to investigate Ni (II) ions interactions with DNA
extracted from Clostridium perfringens, Mice liver (C3HA line), Calf thymus,
Salmon sperm, Herring sperm, E.coli, Micrococcus luteus and polynucleotides
Poly (dA-dT)xPoly (dA-dT), Poly (dG)x Poly (dC), Poly (dG-dC)xPoly (dG-dC). It
is shown that Ni (II) ions at outer-spherical binding with DNA double helix
from the side of the major groove choose more stable dimmers 3^'-C-G-5^'
  . . 5^'-G-C-3^' and get bound with N7 atoms of both guanines in dimmer
forming G-G interstrand crosslink. It directly correlates to the process of
forming point defects of Watson-Crick wrong pair type (creation of rare
keto-enolic and amino-imino tautomeric forms) and depurinization.
