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Published on: November 10, 2016
[Theoretical study of the hypochromic effect in polynucleotides]
Abstract:
The first UV-absorption band hypochromicity of poly(dA)-poly(dT), poly(dG)-poly(dC), poly(dA), poly(dT), poly(dG), poly(dC), is calculated with the help of the perturbation theory. The wave functions of the bases are computed by Pariser--Parr--Pople's method taking into account all the singly excited configurations. The results obtained show a good correlation between the theoretical and experimental values of hypochromicity. A considerable influence of the vaccum electron transitions on the hypochromicity of polynucleotides is revealed. The origin of the hypochromic effect in the double-stranded polynucleotides is investigated. It is shown that intrastrand interactions between the bases make the main contribution to hypochromicity (60-76%), while the contribution of the Watson-Crick pairs is small (2-12%). The essential part of hypochromicity (22-28%) is due to the interstrand interactions between the bases which are not coupled by hydrogen bonds. The discussion of the experimental data shows that the present theoretical investigation could serve as a basis for correct treatment of experimental results.
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