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Effects of the Photooxidant on DNA-Mediated Charge Transport

Williams, Tashica T. and Dohno, Chikara and Stemp, Eric D. A. and Barton, Jacqueline K. (2004) Effects of the Photooxidant on DNA-Mediated Charge Transport. Journal of the American Chemical Society, 126 (26). pp. 8148-8158. ISSN 0002-7863. doi:10.1021/ja049869y.

[img] PDF (HPLC profiles of dG and d^(CP)G oxidation by photoexcited thionine anaerobically. HPLC profiles of nucleoside mixtures obtained from enzymatic digestion of irradiated ^(CP)G-containing DNA assemblies functionalized with Rh, Ru, and AQ, ...) - Supplemental Material
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A direct comparison of DNA charge transport (CT) with different photooxidants has been made. Photooxidants tested include the two metallointercalators, Rh(phi)_2(bpy‘)^(3+) and Ru(phen)(bpy‘)(dppz)^(2+), and three organic intercalators, ethidium (Et), thionine (Th), and anthraquinone (AQ). CT has been examined through a DNA duplex containing an A_6-tract intervening between two 5‘-CGGC-3‘ sites with each of the photooxidants covalently tethered to one end of the DNA duplex. CT is assayed both through determination of the yield of oxidative guanine damage and, in derivative DNA assemblies, by analysis of the yield of a faster oxidative trapping reaction, ring opening of N^2-cyclopropylguanine (d^(CP)G) within the DNA duplex. We find clear differences in oxidative damage ratios at the distal versus proximal 5‘-CGGC-3‘ sites depending upon the photooxidant employed. Importantly, nondenaturing gel electrophoresis data demonstrate the absence of any DNA aggregation by the DNA-bound intercalators. Hence, differences seen with assemblies containing various photooxidants cannot be attributed to differential aggregation. Comparisons in assemblies using different photooxidants thus reveal characteristics of the photooxidant as well as characteristics of the DNA assembly. In the series examined, the lowest distal/proximal DNA damage ratios are obtained with Ru and AQ, while, for both Rh and Et, high distal/proximal damage ratios are found. The oxidative damage yields vary in the order Ru > AQ > Rh > Et, and photooxidants that produce higher distal/proximal damage ratios have lower yields. While no oxidative DNA damage is detected using thionine as a photooxidant, oxidation is evident using the faster cyclopropylguanosine trap; here, a complex distance dependence is found. Differences observed among photooxidants as well as the complex distance dependence are attributed to differences in rates of back electron transfer (BET). Such differences are important to consider in developing mechanistic models for DNA CT.

Item Type:Article
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URLURL TypeDescription Information
Stemp, Eric D. A.0000-0003-2098-4214
Barton, Jacqueline K.0000-0001-9883-1600
Additional Information:© 2004 American Chemical Society. Received January 8, 2004. Publication Date (Web): June 11, 2004. We are grateful to the NIH for their financial support of this work. We are also grateful to JSPS (C.D.) and UNCF-Merck Science Research Initiative (T.T.W.) for fellowship support.
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Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
UNCF-Merck Science Research InitiativeUNSPECIFIED
Issue or Number:26
Record Number:CaltechAUTHORS:20160209-122559989
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Official Citation:Effects of the Photooxidant on DNA-Mediated Charge Transport Tashica T. Williams, Chikara Dohno, Eric D. A. Stemp, and Jacqueline K. Barton Journal of the American Chemical Society 2004 126 (26), 8148-8158 DOI: 10.1021/ja049869y
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64336
Deposited By: George Porter
Deposited On:09 Feb 2016 21:19
Last Modified:10 Nov 2021 23:29

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