The luminescence of guanine molecules in the gas phase under the electron beam


Background. Information about the physical structure of molecules is necessary for understanding of the role of primary physical processes in ensuring the functioning of biological systems and for identification of the mechanisms of influence of the various environmental factors. Among these factors, special attention is given to natural and artificial radiation. The interaction of high-energy radiation with living cells, mostly does not lead directly to degradation of biopolymer molecules, in particular, to the breaking of covalent bonds in the primary structure of nucleic acids. This feature performs secondary electrons, which are produced in great quantity in biological matter. 
Materials and methods. Optical method of investigation was used in experiments. The gas phase of guanine molecules was formed by heating of guanine polycrystalline powder in a separate metal container. The temperature at which the research was conducted was 390 K. The electron beam was formed by three-electrode gun with tungsten cathode. 
Results. The luminescence spectra of isolated guanine molecules in the wavelength region from 200 nm to 500 nm under the beam of slow electrons were obtained. Near 19 spectral bands and lines were observed in the spectrum. Spectral bands were identified based on existing literature data. Experimentally was found that 100 eV energy electrons effectively destroy the guanine molecule with producing of atomic hydrogen. The phenomenon of transmutation of nucleic acid base is observing. 
Conclusion. The interaction of slow electrons with guanine molecules in the gas state is accompanied by the occurrence of a complicated emission spectrum in the range of 200-500 nm, which is indicative of an intense fragmentation of molecules. The emission spectrum of guanine is formed by processes of dissociative excitation of molecules, dissociative excitation with ionization, and excitation of electronic levels of the initial molecule. The obtained data can be used to estimate radiation changes in DNA and RNA molecules upon internal β irradiation of bioobjects

Keywords: electron beam, vapor filled cell, guanine, spectrum, spectral bands, fragments