An Investigation into the Mechanisms of DNA Strand Breakage by Direct Ionization of Variably Hydrated Plasmid DNA Export

@article{citeulike:3452023, abstract = {Abstract: The mechanisms by which ionizing radiation directly causes strand breaks in DNA were investigated by comparing the chemical yield of DNA-trapped free radicals to the chemical yield of DNA single strand break (ssb) and double strand break (dsb), as a function of hydration (). Solid-state films of plasmid pUC18, hydrated to 2.5 < < 22.5 mol, were X-irradiated at 4 K, warmed to room temperature, and dissolved in water. Free radical yields were determined by EPR at 4 K. With use of the same samples, Gel electrophoresis was used to measure the chemical yield of total strand breaks, which includes prompt plus heat labile ssb; G'total(ssb) decreased from 0.092 ± 0.016 mol/J at = 2.5 to 0.066 ± 0.008 mol/J at = 22.5. Most provocative is that at = 2.5 the yield of total ssb exceeds the yield of trapped deoxyribose radicals: G'total(ssb) - G'sugar(fr) = 0.06 ± 0.02 mol/J. Nearly 2/3 of the strand breaks are derived from precursors other than radicals trapped on the deoxyribose moiety. To account for these nonradical precursors, we hypothesize that strand breaks are produced by two one-electron oxidations at a single deoxyribose residue within an ionization cluster.}, address = {Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642, and Department of Radiology, University of California at San Diego, La Jolla, California 92093-0610}, author = {Purkayastha, S. and Milligan, J. R. and Bernhard, W. A.}, citeulike-article-id = {3452023}, citeulike-linkout-0 = {http://dx.doi.org/10.1021/jp065489i}, citeulike-linkout-1 = {http://pubs.acs.org/doi/abs/10.1021/jp065489i}, doi = {10.1021/jp065489i}, journal = {J. Phys. Chem. B}, keywords = {damage, dna, radiation, water}, month = {December}, number = {51}, pages = {26286--26291}, posted-at = {2008-10-26 21:33:24}, priority = {2}, title = {An Investigation into the Mechanisms of DNA Strand Breakage by Direct Ionization of Variably Hydrated Plasmid DNA}, url = {http://dx.doi.org/10.1021/jp065489i}, volume = {110}, year = {2006} }

TY - JOUR ID - citeulike:3452023 L3 - citeulike-article-id:3452023 N2 - Abstract: The mechanisms by which ionizing radiation directly causes strand breaks in DNA were investigated by comparing the chemical yield of DNA-trapped free radicals to the chemical yield of DNA single strand break (ssb) and double strand break (dsb), as a function of hydration (). Solid-state films of plasmid pUC18, hydrated to 2.5 < < 22.5 mol, were X-irradiated at 4 K, warmed to room temperature, and dissolved in water. Free radical yields were determined by EPR at 4 K. With use of the same samples, Gel electrophoresis was used to measure the chemical yield of total strand breaks, which includes prompt plus heat labile ssb; G'total(ssb) decreased from 0.092 ± 0.016 mol/J at = 2.5 to 0.066 ± 0.008 mol/J at = 22.5. Most provocative is that at = 2.5 the yield of total ssb exceeds the yield of trapped deoxyribose radicals: G'total(ssb) - G'sugar(fr) = 0.06 ± 0.02 mol/J. Nearly 2/3 of the strand breaks are derived from precursors other than radicals trapped on the deoxyribose moiety. To account for these nonradical precursors, we hypothesize that strand breaks are produced by two one-electron oxidations at a single deoxyribose residue within an ionization cluster. IS - 51 JF - J. Phys. Chem. B AD - Department of Biochemistry and Biophysics, University of Rochester, Rochester, New York 14642, and Department of Radiology, University of California at San Diego, La Jolla, California 92093-0610 EP - 26291 TI - An Investigation into the Mechanisms of DNA Strand Breakage by Direct Ionization of Variably Hydrated Plasmid DNA VL - 110 SP - 26286 KW - damage KW - dna KW - radiation KW - water AU - Purkayastha, S AU - Milligan, JR AU - Bernhard, WA PY - 2006/12/28/ UR - http://dx.doi.org/10.1021/jp065489i ER -