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

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.