Isotope effect on electron transfer in reaction centers from Rhodopseudomonas sphaeroides
- 1 November 1986
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 83 (21) , 8152-8156
- https://doi.org/10.1073/pnas.83.21.8152
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 .**GRAPHIC**. .fwdarw. (BCh)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 .DELTA.k/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.This publication has 16 references indexed in Scilit:
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