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Electronic absorption and emission spectra of nucleic acids and their components: Some questions of theory and experiment

1980; Wiley; Volume: 17; Issue: 2 Linguagem: Inglês

10.1002/qua.560170214

1097-461X

V.I. Danilov, V. I. Pechenaya, N. V. Zheltovsky,

Metal complexes synthesis and properties

Abstract The results of calculations of the transition energies and polarization in nucleotide bases performed by the CNDO / S CI method are compared with experimental data for long‐wavelength and vacuumabsorption bands. The calculations and the analysis of experimental data testify to the existence of n − π* transitions in the first absorption bands of the bases. The study of double‐stranded polynucleotides and DNA hypochromism based on the theoretical electronic characteristics of the bases and perturbation theory is performed. The role of stacking and complementary interactions within the hypochromic effect is cleared up. Two mechanisms for the shift of the fluorescence band maximum are investigated: two‐proton transfer along H bonds and excimer formation. The study of H‐bond potential curves shows the disadvantage of two‐proton phototautomerism in the nucleotide base pairs in contrast to model systems. The possibility of excimer state formation in stacked homo‐ and heterodimers of nucleotide bases is shown within the extended‐Hückel treatment. The nature of excimer minimum for the excited‐state potential curve is analyzed.