EVIDENCE THAT CHARGE MOTION WITHIN BACTERIORHODOPSIN DEPENDS ON SOLVENT VISCOSITY

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Abstract
Abstract— It is shown that glycerol in the bathing solutions of a bacteriorhodopsin model membrane slows the photoresponse. The early stage of the photoresponse is only slightly affected while the later stage is appreciably retarded. These results are in agreement with previous measurements by other investigators on the temporal behavior of the photoreaction cycle in viscous bathing solutions. Data is fit to an equation of the form τ=A ηm exp(Δ/kT) where t is a time constant characterizing the photoresponse, τ is the viscosity of the bathing solution and Δ is the activation energy for the thermally driven process.