[Theoretical study of the hypochromic effect in polynucleotides].
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.
D001665:Binding Sites; D006860:Hydrogen Bonding; D008433:Mathematics; D009690:Nucleic Acid Conformation; D011119:Polynucleotides; D013056:Spectrophotometry, Ultraviolet
D011119:Polynucleotides
Teoreticheskoe izuchenie gipokhromnogo effekta v polinukleotidakh