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Time‐course and stoichiometry of light‐induced proton release and uptake during the photocycle of bacteriorhodopsin
Author(s) -
Grzesiek Stephan,
Dencher Norbert A.
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)81045-6
Subject(s) - pyranine , bacteriorhodopsin , proton , chemistry , stoichiometry , ionic strength , membrane , kinetics , proton transport , photochemistry , analytical chemistry (journal) , chromatography , aqueous solution , biochemistry , physics , quantum mechanics
The kinetics and stoichiometry of light‐induced proton release in purple membrane suspensions have been investigated using the pH‐indicator dye pyranine and single‐turnover flash spectroscopy at a time resolution of 0.1 μs. The number of protons detected by pyranine is inversely proportional to the buffering power of the medium and 1.1 ± 0.2 protons are released per photocycling bacteriorhodopsin molecule (pH 7.0, 20°C). At high ionic strength (250 mM KCl) and higher phosphate buffer concentrations (1 mM) the proton release lags slightly behind the formation of the intermediate M‐412 and proton reuptake by the purple membrane parallels the slow decay process of M‐412 or the decay of O‐640.