MODULATION BY IONIC STRENGTH AND SUPERHELICITY OF BENZO[a]PYRENE DIOL EPOXIDE INDUCED DNA ALKYLATION AND UNWINDING

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Superhelical and partially relaxed SV40 DNA were reacted in vitro with (+)7{beta}, 8{alpha}-dihydroxy-9{alpha},10{alpha}-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BaP diol epoxide). The modified DNA contained N{sup 2} guanine and N{sup 6} adeninte hydrocarbon adducts in the ratio 86:14. Superhelical SV40 DNA was approximately 6% more susceptible to modification than partially relaxed viral DNA. Counterions inhibited DNA alkylation by up to 90%, Mg{sup 2+} being 50-fold more effective than Na{sup +}. The sensitivity of covalent binding to helix stability is consistent with a reaction complex in which BaP diol epoxide is intercalated. The superhelical density of the modified DNA substrates was determined electrophoretically relative to partially ... continued below

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Gamper, Howard B.; Straub, Kenneth; Calvin, Melvin & Bartholomew, James C. January 1, 1980.

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Superhelical and partially relaxed SV40 DNA were reacted in vitro with (+)7{beta}, 8{alpha}-dihydroxy-9{alpha},10{alpha}-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BaP diol epoxide). The modified DNA contained N{sup 2} guanine and N{sup 6} adeninte hydrocarbon adducts in the ratio 86:14. Superhelical SV40 DNA was approximately 6% more susceptible to modification than partially relaxed viral DNA. Counterions inhibited DNA alkylation by up to 90%, Mg{sup 2+} being 50-fold more effective than Na{sup +}. The sensitivity of covalent binding to helix stability is consistent with a reaction complex in which BaP diol epoxide is intercalated. The superhelical density of the modified DNA substrates was determined electrophoretically relative to partially relaxed standards and an unwinding angle for the hydrocarbon adducts was calculated. The angle was dependent upon the superhelicity of the DNA molecule and ranged from 330{sup o} to 30{sup o}. This data indicates that the modified base pairs are disrupted and, in the presence of torsional strain, act as centers for the further denaturation of up to 8 adjacent base pairs. In the absence of such strain the alkylation sites have an ordered structure with the attached hydrocarbon probably oriented in the minor or major groove of the helix.

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25 p.

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  • Journal Name: Proceedings of the National Academy of Science of the USA; Journal Volume: 77; Journal Issue: 4

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  • Report No.: LBL-10402
  • Grant Number: DE-AC02-05CH11231
  • DOI: 10.1073/pnas.77.4.2000 | External Link
  • Office of Scientific & Technical Information Report Number: 1030567
  • Archival Resource Key: ark:/67531/metadc847069

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  • January 1, 1980

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  • May 19, 2016, 3:16 p.m.

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  • July 26, 2016, 5:52 p.m.

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Gamper, Howard B.; Straub, Kenneth; Calvin, Melvin & Bartholomew, James C. MODULATION BY IONIC STRENGTH AND SUPERHELICITY OF BENZO[a]PYRENE DIOL EPOXIDE INDUCED DNA ALKYLATION AND UNWINDING, article, January 1, 1980; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc847069/: accessed June 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.