FURTHER CHARACTERIZATION OF ANESTHETIC‐TREATED PURPLE MEMBRANES

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.