Action spectrum for reorientations in bacteriorhodopsin of purple membrane in suspension

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) trimer 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. Disrupting the protein–lipid contact during the illumination with light of wavelength in ranges of (410–470 nm) and (610–720 nm) has resulted in emergence of distinct dielectric dispersion at 0.06–0.08 MHz which is comparable to the size of bR trimer 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 trimer inside PM. Changes in rotational diffusion of bR trimer upon blue and red light illumination can influence the three dimensional data storage based on bR, which may implicate bR in bioelectronics.