QUANTUM CALCULATIONS OF ELECTRONIC ABSORPTION SPECTRA OF TYROSINE IN VARIOUS MICROENVIRONMENT CONDITIONS
The study of the physicochemical regularities of the impact of high-energy radiation on biological and chemical systems of varying complexity is not only of fundamental, but also of certain practical interest. The influence of the local microenvironment of tyrosine on its ability to interact with optical radiation of the high-energy part of the electromagnetic spectrum with a wavelength of less than 210 nm is analyzed by computer chemistry methods. As an object of study, we chose a simple protein that does not have an obligatory oligomeric organization - bovine serum albumin. The absence of any additional inclusions and prosthetic groups allowed us to significantly simplify the analyzed system. The electronic absorption spectra were calculated using the ZINDO/S spectral approximation taking into account configuration interactions. As key parameters, we took the oscillator strength (UV oscillator strength) and the change in the electron spin during the transition (UV-spin) It was found that in each of the presented indicators, there is a shift in the intensity and absorption maxima due to a shift in the electron density both inside the tyrosine molecule and the entire tripeptide, which is evidenced by a change in the lengths of bonds Ca - benzene ring, benzene ring - hydroxyl group. This suggests that the relocation of lone oxygen pairs to the conjugated п-electron system of the benzene ring of tyrosine leads to very significant wave shift deviations and changes in absorption intensity. The expansion of the spectral range of studies in the field of vacuum ultraviolet will provide information on the fundamental mechanisms of the biological action of ionizing radiation during their interaction with protein systems.