Action Spectrum for Reorientations in Bacteriorhodopsin of Purple Membrane in Suspension

Résumé

Abstract In the present study, the dependency of purple membrane (PM) dielectric responses on the wavelength of light in the range 380–750 nm has showed meaningful changes about the rotation of PM in suspension and about the rotation of bacteriorhodopsin (bR) trimmer inside PM, as well. The action spectrum of PM random walk substantiates the existence of two states of bR. One of them (blue edge-state) lies at the blue edge and the other (red edge-state) at the red edge of the visible absorption of bR. The results might bear on correlation of these bands to some bR photocycle intermediates or bR photoproducts. The results implicate the protein-chromophore interactions that eventually underlie protein-lipid interactions. Disrupture of the protein-lipid contact during illumination with light of wavelength in the range 410–470 nm as well as 610–720 nm has resulted in emerging of distinct dielectric dispersion at 0.06–0.08 MHz, and which is comparable to the size of bR trimmer or monomer. The work reports on the chromatic adaptation of bR in view of the dielectric spectral parameters of PM. It aimed to explore a correlation seemingly found between the light wavelength and the relaxations of bR trimmer inside PM. Changes in rotational diffusion of bR trimmer upon blue and red light illumination can influence the three dimensional data storage based on bR, which may implicate bR in bioelectronics.

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