Biopolymers and cell. 2005; 21 (5): 440 - 445

Stacking self-association of cytosine and its manifestation in optical spectra

I. A. Petrushko, M. I. Sukhoviya

Geometrical and optical characteristics of cytosine stacking complexes have been studied by means of multi-configurational method in the frame of semiempirical Hamiltonian AM1 with full geometry optimization. An analysis of the bond lengths, spatial angles, vibration frequencies and electronic spectra in cytosine monomer, dimer and tetramer shows the changes in all aforementioned physical characteristics upon the complexing. The calculation predicts a high-frequency shift of the NH₂-group valence vibrations. Intensity distribution of the electronic spectra bands of different cytosine complexes strongly depends on the number of molecules in the complex. A biophysical significance of the received results is discussed.

Key words: cytosine complexes, physical characteristics, theoretical study.