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Science 26 July 1996:
Vol. 273. no. 5274, pp. 475 - 480
DOI: 10.1126/science.273.5274.475
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Reports

Rates of DNA-Mediated Electron Transfer Between Metallointercalators

M. R. Arkin, E. D. A. Stemp, R. E. Holmlin, J. K. Barton, * A. Hörmann, E. J. C. Olson, P. F. Barbara *

Ultrafast emission and absorption spectroscopies were used to measure the kinetics of DNA-mediated electron transfer reactions between metal complexes intercalated into DNA. In the presence of rhodium(III) acceptor, a substantial fraction of photoexcited donor exhibits fast oxidative quenching (>3 × 1010 per second). Transient-absorption experiments indicate that, for a series of donors, the majority of back electron transfer is also very fast (sim 1010 per second). This rate is independent of the loading of acceptors on the helix, but is sensitive to sequence and pi  stacking. The cooperative binding of donor and acceptor is considered unlikely on the basis of structural models and DNA photocleavage studies of binding. These data show that the DNA double helix differs significantly from proteins as a bridge for electron transfer.

[Data] On-Line References and Notes

M. R. Arkin, E. D. A. Stemp, R. E. Holmlin, J. K. Barton, Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
A. Hörmann, E. J. C. Olson, P. F. Barbara, Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA.
*   To whom correspondence should be addressed.


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