FURTHER CHARACTERIZATION OF ANESTHETIC-TREATED PURPLE MEMBRANES |
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Authors: | nathalie,Henry ,Normand,Beaudoin ,Johanne,Baribeau Franç ois,Boucher |
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Affiliation: | Centre de Recherche en Photobiophysique, Universitédu Québec àTrois-Rivières, Trois-Rivères, Québec, G9A 5H7 Canada |
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Abstract: | Abstract— The absorption maximum of bacteriorhodopsin is shifted from 568 nm to 480 nm when halogenated volatile anesthetics (enflurane; halothane) are added to purple membranes. Analysis of the rate of formation of this new species upon addition of the anesthetic and of the back-formation of native bacteriorhodopsin upon its removal indicate that in purple membranes, the dark-adapted chromophore is much less reactive than its light-adapted counterpart. Lipid-soluble molecules thus have a lower accessibility to the dark-adapted chromophore. In addition, activity of the 480 nm bacteriorhodopsin was investigated. Flash and steady-state photolysis experiments reveal that this blue shifted chromophore has full photochemical activity. It has a meta-intermediate absorbing maximally at 380 nm. The photocycle ofBR–480 is mainly characterized by a slow decay of the "O" intermediate, enabling the direct observation of the branching reaction between the "M" intermediate and the parentBR–480 pigment. |
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