Petrushko I. Structural changes in nucleobases and 5-bromouridine initiated by low-energy electrons and ultraviolet radiation

The thesis is concerned with comparative study of molecular mechanisms of the low-energy electrons and the long-wave ultraviolet radiation influence on nucleic acids (NA) components. By means of mass-spectrometry with high energy resolution electrons sources, the ionization and dissociation processes of cytosine, uracile and 5-bromouridine were investigated. The dominative decomposition canals of these molecules under the electrons with energies 10^-1-10^1 eV were clarified. It was revealed the resonance fragmentation of 5-bromouridine on electrons with energy below 12 eV occurs via C5-Br and glycosidic bonds cleavage. Infrared absorption spectroscopy was used for the study ultraviolet radiation affect on the films of cytosine, guanine and their complex. Based on an analysis of the experimental data and on quantum-chemical semi-empirical calculations it was shown that, in contrast to electrons, the influence of the UV radiation modifies the intermolecular interactions in NA components without structural damage.