Dynamic Changes of Lipids and Bacteriorhodopsin in DMPC Bilayer Vesicles

Abstract

The “Iodine-Laser Temperature-Jump” (ILTJ) technique with a time resolution from 10-9 s to 100 s has been used to study the interaction of bacteriorhodopsin (BR), reconstituted in dimyristoylphosphatidylcholine (DMPC) vesicles, with the annular lipids. The phase transition behaviour of the bilayer lipids is strongly altered by the presence of BR and a shift of the relaxation processes towards the 5µs time domain could be observed. By monitoring simultaneously spectral changes at 560 mn due to dynamic changes caused by the photocycle of BR and turbidity changes at 350 ± 15 nm due to the mobility changes of the annular lipids we could establish a strong correlation between the annular lipid motion and the protein activity. We conclude that the surface of BR undergoes a “functional important movement” (FIM after Frauenfelder) during its biological activity in the microsecond time range.