DNA destruction under the influence of VUV radiation

Abstract

In the work were investigated the effect of vacuum ultraviolet (VUV) radiation (&lambda;=147 nm, 173 nm) on the DNA of microscopic fungi spores of the species <i>Rhodotorula colostri</i>, <i>Aurobasidium pullulans</i> (colored and uncolored types), <i>Cladosporium herbarum</i> containing different types of protective pigments. The DNA molecules inside the spores (in vivo) and isolated from them (in vitro) were irradiated. The results of electrophoresis showed, that VUV irradiation leads to the appearance of light DNA fragments with sizes 100-750 base pairs, as well as high molecular weight fragments containing more than 20 000 base pairs. The greatest features were observed during the irradiation of <i>Rhodotorula colostri</i> DNA: 1) were formed longer fragments (100-750 base pairs); 2) at &lambda;=172 nm threshold effect was observed: DNA destruction appeared starting from radiation energies of 35 mJ/cm² during in vivo irradiation and, starting from radiation energies of 20 mJ/cm², during in vitro irradiation; 2) when irradiated at the wavelength &lambda;=147 nm, the relative destruction of DNA increased, while for other types of the spores it fell. These features can be explained by the presence in <i>Rhodotorula colostri</i> spores of carotene capable of exercising both the properties of the antioxidant and to produce reactive radicals. When irradiated at a wavelength of &lambda;=173 nm in vivo and in vitro, each type of spore had the same characteristic features, which may indicate a small effect on DNA of free water molecules photolysis products. When irradiated at the wavelength &lambda;=147 nm, the influence of melanin was observed: in melanin containing spores the results in vivo and in vitro exposure had the same characteristic features, in the spores without melanin- differed. In the first case, this can be explained by a smaller concentration of reactive radicals due to VUV radiation absorption by melanin, in the second - participation in the DNA destruction of free water molecules photolysis products. A common feature of the electrophoresis results was the presence of long DNA fragments of about 20,000 base pairs in all types of spores. The brightness of these fragments correlated with the DNA destruction degree.