Pascaly, Matthias and Yoo, Jae and Barton, Jacqueline K. (2002) DNA Mediated Charge Transport: Characterization of a DNA Radical Localized at an Artificial Nucleic Acid Base. Journal of the American Chemical Society, 124 (31). pp. 9083-9092. ISSN 0002-7863. doi:10.1021/ja0202210. https://resolver.caltech.edu/CaltechAUTHORS:20160210-155947915
Full text is not posted in this repository. Consult Related URLs below.
Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20160210-155947915
Abstract
DNA assemblies containing 4-methylindole incorporated as an artificial base provide a chemically well-defined system in which to explore the oxidative charge transport process in DNA. Using this artificial base, we have combined transient absorption and EPR spectroscopies as well as biochemical methods to test experimentally current mechanisms for DNA charge transport. The 4-methylindole radical cation intermediate has been identified using both EPR and transient absorption spectroscopies in oxidative flash-quench studies using a dipyridophenazine complex of ruthenium as the intercalating oxidant. The 4-methylindole radical cation intermediate is particularly amenable to study given its strong absorptivity at 600 nm and EPR signal measured at 77 K with g = 2.0065. Both transient absorption and EPR spectroscopies show that the 4-methylindole is well incorporated in the duplex; the data also indicate no evidence of guanine radicals, given the low oxidation potential of 4-methylindole relative to the nucleic acid bases. Biochemical studies further support the irreversible oxidation of the indole moiety and allow the determination of yields of irreversible product formation. The construction of these assemblies containing 4-methylindole as an artificial base is also applied in examining long-range charge transport mediated by the DNA base pair stack as a function of intervening distance and sequence. The rate of formation of the indole radical cation is ≥107 s-1 for different assemblies with the ruthenium positioned 17−37 Å away from the methylindole and with intervening A−T base pairs primarily composing the bridge. In these assemblies, methylindole radical formation at a distance is essentially coincident with quenching of the ruthenium excited state to form the Ru(III) oxidant; charge transport is not rate limiting over this distance regime. The measurements here of rates of radical cation formation establish that a model of G-hopping and AT-tunneling is not sufficient to account for DNA charge transport. Instead, these data are viewed mechanistically as charge transport through the DNA duplex primarily through hopping among well stacked domains of the helix defined by DNA sequence and dynamics.
Item Type: | Article | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
Related URLs: |
| |||||||||
ORCID: |
| |||||||||
Additional Information: | © 2002 American Chemical Society. Received February 13, 2002. Revised Manuscript Received May 24, 2002. Publication Date (Web): July 12, 2002. We are grateful to the NIH for financial support (GM49216). M.P. also thanks the Deutscher Akademischer Austauschdienst for a postdoctoral fellowship. In addition, we thank Prof. E. D. A. Stemp and Prof. S. Rajski for valuable discussions and S. Delaney for experimental assistance. | |||||||||
Funders: |
| |||||||||
Issue or Number: | 31 | |||||||||
DOI: | 10.1021/ja0202210 | |||||||||
Record Number: | CaltechAUTHORS:20160210-155947915 | |||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20160210-155947915 | |||||||||
Official Citation: | DNA Mediated Charge Transport: Characterization of a DNA Radical Localized at an Artificial Nucleic Acid Base Matthias Pascaly, Jae Yoo, and Jacqueline K. Barton Journal of the American Chemical Society 2002 124 (31), 9083-9092 DOI: 10.1021/ja0202210 | |||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | |||||||||
ID Code: | 64394 | |||||||||
Collection: | CaltechAUTHORS | |||||||||
Deposited By: | George Porter | |||||||||
Deposited On: | 19 Feb 2016 17:54 | |||||||||
Last Modified: | 10 Nov 2021 23:30 |
Repository Staff Only: item control page