Rates of DNA-Mediated Electron Transfer Between Metallointercalators

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Science  26 Jul 1996:
Vol. 273, Issue 5274, pp. 475-480
DOI: 10.1126/science.273.5274.475


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 (∼1010 per second). This rate is independent of the loading of acceptors on the helix, but is sensitive to sequence and π 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.

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