title: Alkali-labile sites and post-irradiation effects in single-stranded DNA induced by H radicals.
abstract: Single-stranded phiX174 DNA in aqueous solutions has been irradiated in the absence of oxygen, under conditions in which only H radicals react with the DNA. It was shown that H radical reactions result in breaks, which contribute approximately 10 per cent inactivation. Further, two types of alkali-labile sites are formed. One is lethal and gives rise to single-strand breaks by alkali and is most probably identical with post-irradiation heat damage and contributes about 33 per cent to the inactivation mentioned above. The other consists of non-lethal damage, partly dihydropyrimidine derivatives, and is converted to lethal damage by alkali. This follows from experiments in which the DNA was treated with osmium-tetroxide, which oxidizes thymine to 5,6-dihydroxy-dihydrothymine. Treatment with alkali of this DNA gives the same temperature dependence as found for the non-lethal alkali-labile sites in irradiated DNA. A similar temperature dependence is found for dihydrothymine and irradiated pyrimidines with alkali.
mesh_terms: D000468:Alkalies; D003037:Cobalt Radioisotopes; D003090:Coliphages; D004277:DNA, Single-Stranded / Q000528:radiation effects*; D004279:DNA, Viral / Q000528:radiation effects*; D005720:Gamma Rays; D010100:Oxygen; D012996:Solutions; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000528:radiation effects
chemical_list: D000468:Alkalies; D003037:Cobalt Radioisotopes; D004277:DNA, Single-Stranded; D004279:DNA, Viral; D012996:Solutions; D014867:Water; D010100:Oxygen