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THE ELECTROCHEMICAL PROTON GRADIENT IN THE PHOTOSYNTHETIC PURPLE SULPHUR BACTERIUM CHROMATIUM VINOSUM
Author(s) -
Davidson Victor L.,
Knaff David B.
Publication year - 1982
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1982.tb04415.x
Subject(s) - chromatium , antiporter , electrochemical gradient , chemistry , electrochemistry , electrochemical potential , proton , analytical chemistry (journal) , ion , potassium , proton transport , ion transporter , inorganic chemistry , photosynthesis , membrane , chromatography , biochemistry , electrode , organic chemistry , physics , quantum mechanics
Cells of the photosynthetic purple bacterium Chromatium vinosum generate a transmembrane electrochemical proton gradient (δμ H+ H+ ) on illumination. The steady state values of the two components of δμ H+ m+ , δpH and the membrane potential (δψ) have been measured as a function of both the pH and ion composition of the external medium. While δψ and δpH vary considerably as the external pH is varied from 5.5 to 7.5, the magnitude of δμ H+ h+ remains relatively constant over this pH range. δψ is relatively unaffected by the ion composition of the medium but δpH and δμ H+ H+ both vary considerably depending upon the cation present in the medium. The use of specific ionophores to eliminate either δpH or δψ results in changes in the magnitude of the other component. The δpH values determined here were used to predict the direction of Tl + flux via the potassium‐proton antiport and to demonstrate the reversibility of this antiport.