title: [Structure of the DNA molecule in the course of reparation process after ultraviolet irradiation of E. coli cells].
abstract: Kinetics was studied of DNA degradation, processing and synthesis in the course of post-radiation incubation (irradiation dose 0-2000 erg/mm2). It has been shown that contrary to the endonuclease splitting of DNA strands, DNA degradation requires energy. DNA degradation is not enhanced upon an increase of the irradiation up to 400 erg/mm2 and more and at the incubation duration exceeding 120 min. The degradation involves not more than 40% of the total DNA quantity. It takes place in the absence of resynthesis registered by the incorporation of [3h] thymidine and 32P and dephinylamine reaction. The number of single-strand breaks in DNA (per one E. coli chromosome strans) reaches a maximum value after 120-180 min. of incubation. This maximal value is linearily increased upon an increase of the irradiation dose from 0 to 1200 erg/mm2 and does not change when the dose increases further. The number of single-strand breaks does not exceed 35-50, this value being dependent on the presence of glucose. On the basis of the data obtained a suggestion is put forward that in the course of the reparative degradation of DNA, prolonged (10(4)-10(5) nucleotides) single-stranded regions are formed. Possible role of these 'nicks" in the appearance of mutations is discussed.
mesh_terms: D004260:DNA Repair; D004269:DNA, Bacterial / Q000378:metabolism / Q000528:radiation effects; D004277:DNA, Single-Stranded / Q000378:metabolism / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000378:metabolism / Q000528:radiation effects*; D007700:Kinetics; D011830:Radiation Effects
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded
vernacular_title: Struktura molekuly DNK v khode reparatsionnogo protsessa posle ul'trafioletovogo oblucheniia bakteriĭ E. coli