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Charge equilibration between two distinct sites in double helical DNA.
Proc Natl Acad Sci U S A. 2004 Jul 20; 101(29):10511-6.PN

Abstract

DNA assemblies containing a pendant dipyridophenazine complex of Ru(II) along with two oxidative traps, a site containing the nucleoside analog methylindole (5'-GMG-3') and a 5'-GGG-3' site, have been constructed to explore long-range charge transport through the base pair stack. With these chemically well defined assemblies, in combination with the flash/quench technique, formation of the methylindole cation radical and the neutral guanine radical is monitored directly by using transient absorption spectroscopy, and yields of oxidative damage are quantitated biochemically by gel electrophoresis. In these assemblies the base radicals form with a rate of > or =10(7) s(-1). The rate of base radical formation does not change upon the addition of a second radical trap, the 5'-GGG-3' site; however, the yield of methylindole oxidation is significantly lower. This observation indicates that the 5'-GGG-3' site is effective in competing for the migrating charge and provides a second trapping site. Switching the orientation of the two trapping sites does not affect the yield of oxidized products at either site. Therefore, in DNA both forward and reverse charge transport occur so as to provide equilibration across the duplex on a timescale that is fast compared with trapping at a particular site. Further evidence of charge equilibration results from incorporating an intervening base-stacking perturbation and monitoring the fate of the injected charge. These experiments underscore the dynamic nature of DNA charge transport and reveal the importance of considering radical propagation in both directions along the DNA duplex.

Authors+Show Affiliations

Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

15247417

Citation

Delaney, Sarah, et al. "Charge Equilibration Between Two Distinct Sites in Double Helical DNA." Proceedings of the National Academy of Sciences of the United States of America, vol. 101, no. 29, 2004, pp. 10511-6.
Delaney S, Yoo J, Stemp ED, et al. Charge equilibration between two distinct sites in double helical DNA. Proc Natl Acad Sci USA. 2004;101(29):10511-6.
Delaney, S., Yoo, J., Stemp, E. D., & Barton, J. K. (2004). Charge equilibration between two distinct sites in double helical DNA. Proceedings of the National Academy of Sciences of the United States of America, 101(29), 10511-6.
Delaney S, et al. Charge Equilibration Between Two Distinct Sites in Double Helical DNA. Proc Natl Acad Sci USA. 2004 Jul 20;101(29):10511-6. PubMed PMID: 15247417.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Charge equilibration between two distinct sites in double helical DNA. AU - Delaney,Sarah, AU - Yoo,Jae, AU - Stemp,Eric D A, AU - Barton,Jacqueline K, Y1 - 2004/07/09/ PY - 2004/7/13/pubmed PY - 2004/8/27/medline PY - 2004/7/13/entrez SP - 10511 EP - 6 JF - Proceedings of the National Academy of Sciences of the United States of America JO - Proc. Natl. Acad. Sci. U.S.A. VL - 101 IS - 29 N2 - DNA assemblies containing a pendant dipyridophenazine complex of Ru(II) along with two oxidative traps, a site containing the nucleoside analog methylindole (5'-GMG-3') and a 5'-GGG-3' site, have been constructed to explore long-range charge transport through the base pair stack. With these chemically well defined assemblies, in combination with the flash/quench technique, formation of the methylindole cation radical and the neutral guanine radical is monitored directly by using transient absorption spectroscopy, and yields of oxidative damage are quantitated biochemically by gel electrophoresis. In these assemblies the base radicals form with a rate of > or =10(7) s(-1). The rate of base radical formation does not change upon the addition of a second radical trap, the 5'-GGG-3' site; however, the yield of methylindole oxidation is significantly lower. This observation indicates that the 5'-GGG-3' site is effective in competing for the migrating charge and provides a second trapping site. Switching the orientation of the two trapping sites does not affect the yield of oxidized products at either site. Therefore, in DNA both forward and reverse charge transport occur so as to provide equilibration across the duplex on a timescale that is fast compared with trapping at a particular site. Further evidence of charge equilibration results from incorporating an intervening base-stacking perturbation and monitoring the fate of the injected charge. These experiments underscore the dynamic nature of DNA charge transport and reveal the importance of considering radical propagation in both directions along the DNA duplex. SN - 0027-8424 UR - https://www.unboundmedicine.com/medline/citation/15247417/Charge_equilibration_between_two_distinct_sites_in_double_helical_DNA_ L2 - http://www.pnas.org/cgi/pmidlookup?view=long&pmid=15247417 DB - PRIME DP - Unbound Medicine ER -