Proton transfer in the photosynthetic reaction center of Blastochloris viridis |
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Authors: | Kozlova Maria A Juhnke Hanno D Cherepanov Dmitry A Lancaster C Roy D Mulkidjanian Armen Y |
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Affiliation: | A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia. |
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Abstract: | Photosynthetic reaction centers of Blastochloris viridis require two quanta of light to catalyse a two-step reduction of their secondary ubiquinone Q(B) to ubiquinol. We employed capacitive potentiometry to follow the voltage changes that were caused by the accompanying transmembrane proton displacements. At pH 7.5 and 20 degrees C, the Q(B)-related voltage generation after the first flash was contributed by a fast, temperature-independent component with a time constant of approximately 30 micros and a slower component of approximately 200 micros with activation energy (E(a)) of 50 kJ/mol. The kinetics after the second flash featured temperature-independent components of 5 micros and 200 micros followed by a component of 600 micros with E(a) approximately 60 kJ/mol. |
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Keywords: | Photosynthetic reaction center Ubiquinone Proton transfer Capacitive potentiometry Blastochloris viridis Rhodobacter sphaeroides |
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