title: Binding of radiation-induced phenylalanine radicals to DNA: influence on the biological activity of the DNA and on its sensitivity to the induction of breaks by gamma-rays.
abstract: When an aqueous solution of double-stranded DNA of bacteriophage PM2 containing phenylalanine and saturated with N2O is irradiated with gamma-rays, radiation-induced phenylalanine radicals are bound covalently. Under the conditions used, about 25 phenylalanine molecules may be bound per lethal hit. For single-stranded PM2 DNA, most of the phenylalanine radicals bound are non-lethal. Evidence is presented that, in double-stranded DNA, an appreciable fraction of the single-strand breaks is induced by phenylalanine radicals. Radiation products of phenylalanine and the phenylalanine bound to the DNA decrease the sensitivity of the DNA to the induction of single-strand breaks. There are indications that the high efficiency of protection by radiation products of phenylalanine is due to their positive charge, which will result in a relatively high concentrations fo these compounds in the vicinity of the negatively-charged DNA molecules.
mesh_terms: D001435:Bacteriophages; D003037:Cobalt Radioisotopes; D004279:DNA, Viral / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D010649:Phenylalanine; D011549:Pseudomonas; D011831:Radiation Genetics
chemical_list: D003037:Cobalt Radioisotopes; D004279:DNA, Viral; D010649:Phenylalanine