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Effects of strand and directional asymmetry on base-base coupling and charge transfer in double-helical DNA

O'Neill, Melanie A. and Barton, Jacqueline K. (2002) Effects of strand and directional asymmetry on base-base coupling and charge transfer in double-helical DNA. Proceedings of the National Academy of Sciences of the United States of America, 99 (26). pp. 16543-16550. ISSN 0027-8424. http://resolver.caltech.edu/CaltechAUTHORS:ONEpnas02

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Abstract

Mechanistic models of charge transfer (CT) in macromolecules often focus on CT energetics and distance as the chief parameters governing CT rates and efficiencies. However, in DNA, features unique to the DNA molecule, in particular, the structure and dynamics of the DNA base stack, also have a dramatic impact on CT. Here we probe the influence of subtle structural variations on base-base CT within a DNA duplex by examining photoinduced quenching of 2-aminopurine (Ap) as a result of hole transfer (HT) to guanine (G). Photoexcited Ap is used as a dual reporter of variations in base stacking and CT efficiency. Significantly, the unique features of DNA, including the strandedness and directional asymmetry of the double helix, play a defining role in CT efficiency. For an (AT)(n) bridge, the orientation of the base pairs is critical; the yield of intrastrand HT is markedly higher through (A)n compared with (T)(n) bridges, whereas HT via intrastrand pathways is more efficient than through interstrand pathways. Remarkably, for reactions through the same DNA bridge, over the same distance, and with the same driving force, HT from photoexcited Ap to G in the 5' to 3' direction is more efficient and less dependent on distance than HT from 3' to 5'. We attribute these differences in HT efficiency to variations in base-base coupling within the DNA assemblies. Thus base-base coupling is a critical parameter in DNA CT and strongly depends on subtle structural nuances of duplex DNA.


Item Type:Article
Additional Information:Copyright © 2002 by the National Academy of Sciences. This contribution is part of the special series of Inaugural Articles by members of the National Academy of Sciences elected on April 30, 2002. Contributed by Jacqueline K. Barton, November 4, 2002. We gratefully acknowledge the National Institutes of Health for generous financial support of this research (Grant GM49216). We also thank the Natural Sciences and Engineering Research Council of Canada for a postdoctoral fellowship (to M.A.O.).
Subject Keywords:mediated electron-transfer, hole-transport, distance dependence, guanine oxidation, abasic sites, duplex DNA, B-DNA, dynamics, fluorescence, sequence
Record Number:CaltechAUTHORS:ONEpnas02
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:ONEpnas02
Alternative URL:http://dx.doi.org/10.1073/pnas.012669599
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:975
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:17 Nov 2005
Last Modified:26 Dec 2012 08:42

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