MATHEMATICAL-MODELING OF PIRIMIDINE PHOTODIMERIZATION IN POLYNUCLEOTIDES

Three models of the interaction of UV radiation with one-chain pirimid ine polynucleotide with a consideration of two possible types of conta cts between closest bases (two types of initial dimers) and phenomenon of the excitation energy delocalization with/without the inclusion of the photodimers into the delocalization area are presented. The consi deration of the two types of contacts and the inclusion of the photodi mers into the delocalization area are made for the first time. In the frame of the models, which differ by the character of the excitation e nergy transfer to the photodimer, the dynamics of the photodimer accum ulation in the polynucleotide under radiation and the dependence of th e stationary concentration of the photodimers on the length of the del ocalization were investigated for different types of the initial dimer s without the heat equilibrium between initial dimers. It is shown tha t the inclusion of the photodimers into the delocalization area result s in significant decrease of the equilibrium concentration of the phot odimers. The consideration of the heat equilibrium between initial dim ers does not break the effect. The proposed models with the energy tra nsfer to the photodimer may describe the photoprocesses in the DNA of spores and some bacterium, which are highly resistant to the UV radiat ion.