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. 1986 Nov;83(21):8152–8156. doi: 10.1073/pnas.83.21.8152

Isotope effect on electron transfer in reaction centers from Rhodopseudomonas sphaeroides

M Y Okamura 1, G Feher 1
PMCID: PMC386885  PMID: 16593776

Abstract

Previous ENDOR studies on reaction centers from Rhodopseudomonas sphaeroides have shown the presence of two hydrogen-bonded protons associated with the primary, ubiquinone, acceptor QA. These protons exchange with deuterons from solvent 2H2O. The effect of this deuterium substitution on the charge-recombination kinetics (BChl)2+QA- → (BChl)2QA has been studied with a sensitive kinetic difference technique. The electron-transfer rate was found to increase with deuterium exchange up to a maximum Δk/k of 5.7 ± 0.3%. The change in rate was found to have an exchange time of 2 hr, which matched the disappearance of the ENDOR lines due to the exchangeable protons. These results indicate that these protons play a role in the vibronic coupling associated with electron transfer. A simple model for the isotope effect on electron transfer predicts a maximum rate increase of 20%, which is consistent with the experimental results.

Keywords: bacterial photosynthesis, vibronic coupling, hydrogen bonding, kinetics

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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