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THE pH DEPENDENCE OF TRANSIENT CHANGES IN THE CURVATURE OF THE PURPLE MEMBRANE *
Author(s) -
Czégé József,
Reinisch Lou
Publication year - 1991
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.1751-1097.1991.tb02112.x
Subject(s) - photoexcitation , curvature , ionic bonding , exponential function , transient (computer programming) , exponential decay , chemistry , absorption (acoustics) , bending , molecular physics , ultrafast laser spectroscopy , membrane , scattering , amplitude , atomic physics , chemical physics , analytical chemistry (journal) , laser , optics , physics , thermodynamics , ion , excited state , quantum mechanics , geometry , mathematical analysis , mathematics , organic chemistry , chromatography , computer science , operating system , biochemistry
– We have observed transient changes in the curvature of purple membrane fragments upon photoexcitation as a function of the pH of the suspending medium. The room temperature suspensions have low ionic strengths, and the bending is observed by changes in the scattered light at 320 nm. The photoexcitation is from a 20 ns laser pulse at 532 nm. We use a simple first‐order approximation to subtract any changes in the scattered light associated with transient absorption changes during the photocycle. The resultant scattering curves are then fitted to the sum of three fundamental bending processes. Each process has an exponential rise, an exponential decay and an amplitude. We model two of the processes as transient forces correlated with the charge motion during the photocycle. The third process is probably cuased by local changes in the pH as the protein pumps protons. However, this is not proved rigorously. Additional experiments are proposed.