Intramolecular H atom abstraction from the sugar moiety by thymine radicals in oligo- and polydeoxynucleotides.
Hydroxyl radical addition to uracil (U) has been suggested to lead to strand breaks in polyuridylic acid, an occurrence attributed in part to H atom abstraction by .U-OH radicals from the ribose moiety [D.G.E. Lemaire et al., Int. J. Radiat. Biol. 45, 351-358 (1984)]. We have investigated this particular reaction by means of the hydroxyl radical-induced products of thymine (T), pT, TpT, TpTpT, polythymidylic acid (poly-T), (T + dR) poly-dA.poly-T, and a mixture of T and 2-deoxyribose (dR). The major monomeric product of .T-OH in TpT, TpTpT, poly-T, and poly-dA.poly-T was found to be 5-hydroxy-6-hydrothymine (H-T-OH), while that in T, pT, and T plus dR was thymine glycol (HO-T-OH). These results indicated that the intramolecular H atom abstraction from a nearby sugar (in this case, deoxyribose) moiety by base radicals, i.e., .T-OH, occurs in oligo- and polydeoxynucleotides of T. In poly-T, the yield of H-T-OH is not much greater than in TpT or TpTpT, indicating that the abstraction of an H atom from the sugar moiety of a nucleotide subunit further than two nucleotides along the chain may not be significant. Additionally, a corresponding decrease in the yield of HO-T-OH with an increase in the yield of H-T-OH suggests that the formations of these two types of thymine products are competitive.
Karam
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Center for Radiation Research, National Bureau of Standards, Gaithersburg, Maryland 20899.
Dizdaroglu
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Simic
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MG
D003037:Cobalt Radioisotopes; D003855:Deoxyribose / Q000528:radiation effects*; D015226:Dinucleoside Phosphates / Q000528:radiation effects*; D005720:Gamma Rays; D006859:Hydrogen; D011071:Poly T / Q000528:radiation effects*; D011067:Poly dA-dT / Q000528:radiation effects; D011089:Polydeoxyribonucleotides / Q000528:radiation effects*; D012996:Solutions; D013938:Thymidine Monophosphate / Q000528:radiation effects*; D013941:Thymine / Q000528:radiation effects*; D013942:Thymine Nucleotides / Q000528:radiation effects*; D014867:Water
D003037:Cobalt Radioisotopes; D015226:Dinucleoside Phosphates; D011089:Polydeoxyribonucleotides; D012996:Solutions; D013942:Thymine Nucleotides; D014867:Water; C017758:thymidylyl-(3'-5')-thymidine; D011071:Poly T; D011067:Poly dA-dT; D013938:Thymidine Monophosphate; D003855:Deoxyribose; D006859:Hydrogen; D013941:Thymine