Study of the reactive excited-state dynamics of delipidated bacteriorhodopsin upon surfactant treatments

Abstract

The dynamics of the reactive excited-state of bacteriorhodopsin treated with various surfactants have been investigated through the measurement of pump-probe absorption spectra. Upon excitation of bR at 570 nm in the presence of ionic surfactants CTAB and SDS, the lifetime of the reactive excited-state of the all-trans protonated Schiff base, probed at 460 nm, was observed to increase up to 20%, whereas an insignificant change was observed upon addition of neutral surfactant C6E2. Measurements of steady-state absorption spectra, fluorescence, and circular dichroism indicated that the bR suspensions retain their trimeric configuration with partial delipidation. This removal of lipids causes a structural alteration and the varied excited-state dynamics. (C) 2012 Elsevier B. V. All rights reserved.