Rotational dynamics of lipid–detergent mixtures probed by a cyanine dye: a mechanism for vesicle formation

Abstract

Time-resolved fluorescence anisotropy and lifetime measurements on the dye 3,3′-diethyloxadicarbocyanine iodide in phospholipid–deoxycholate and phospholipid–octyl glucoside mixtures have been carried out. Earlier we showed that the different populations of the dye could be resolved by virtue of the difference in their microenvironmental emission behaviour. Rotational dynamics of the dye in detergent–phospholipid mixtures show that gradual removal of detergent from the medium leads to a large increase in rotational correlation time corresponding to formation of large vesicles. The lamellar–micellar transition takes place near the critical micellar concentration (c.m.c.) of the detergents. The present results strongly support the mechanism of stepwise formation of lipid vesicles on removal of detergent that was proposed recently by us.