By fluorescence and phase properties of a 1-acyl-2-[8-(2-anthroyl)-octanoyl]-sn-glycero-3-phosphocholine probe, the influence of the chromophore on the phase transition of bacteriorhodopsin–lipid vesicles was investigated. It was observed that removal of the chromophore led to the down-shifting of the phase transition temperatures. The temperatures corresponding to the beginning and ending of the gel–liquid phase transition were also influenced. This demonstrated that the liquid phase is reached more easily when the chromophore is bleached. The results indicate that removal of the chromophore alters the protein–lipid interactions. It is suggested that this alteration might be related to the change in the lipid molecular packing.
