Electric-Field Effects in 13-Demethyl-11,14-Epoxyretinal-Bacteriorhodopsin Films |
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| Authors: | Paul Kolodner Evgeniy P Lukashev Yuan-chin Ching I Rousso M Sheves |
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| Institution: | Bell Laboratories, Lucent Technologies, Inc., Murray Hill, NJ, USA;Department of Biophysics, Biology Faculty, Moscow State University, Moscow, Russia;Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel |
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| Abstract: | Abstract— We report the results of experiments on the application of electric fields across thin, dry Alms of a bacteriorho-dopsin (BR) analog pigment in which the retinal chro-mophore has been replaced with 13-demethyl-11,14-epoxyretinal. As previously observed in other BR variants with low Schiff-base pK values, this pigment exhibits protonation and deprotonation of the Schiff base under an applied electric field, depending on the initial Schiff-base protonation state or effective pH. At low effective pH, a fast (<200 μs) deprotonation reaction dominates. At high pH, an apparently different mechanism leads to Schiff-base protonation on the time scale of seconds. Comparison of our results with a simple model suggests that the external field causes a shift in the pK of the Schiff base by1–2 pH units. |
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