Biopolymers and cell. 2003; 19 (1): 43 - 63

UV spectra of pyrimidine bases and nucleosides in the context of methylsubstitution and interaction with amino acid carboxylic group

A. V. Stepanyugin, I. M. Kolomiets', A. L. Potyahaylo, S. P. Samijlenko, D. M. Hovomn

UV spectra of pyrimidine nucleotide bases, nucleosides, a number of their derivatives and analogues were investigated in anhydrous DMSO. Effects of interaction with neutral and deprotonated carboxylic group of amino acids on the UV spectra were traced. It was established that methylation of pyrimidine bases at the positions 1 and 5 leads to the 5—12 nm bathochromic shift of the absorption bands. The majority of the Cyt derivatives excluding m³Cyt and isoCyt were shown to interact specifically with neutral carboxylic group. Interactions with deprotonated carboxylic group is characteristic of Ura, Thy and their derivatives, except chx¹Ura, s²Ura and dU. The conclusion was drawn that substitution at the positions I and 5 is accompanied by a decrease of a complex formation ability with the both forms of carboxylic groups, but substitution at the position 5 strengthens interaction with neutral carboxylic group but decreases interaction with carboxylate-ion. Biological significance of the results obtained is discussed.