The effect of dolichol on the permeability properties of phosphatidylcholine bilayers

The permeability of liposomes to water, glucose, Ca2+ and alkaline cations was monitored by recording the change in absorbance at 450 nm using a rapid reaction stopped-flow spectrophotometer. Liposomes were prepared with egg phosphatidylcholine and concentrations of dolichol ranging from 0.1% to 9% (w/w). Net permeability of phosphatidylcholine bilayers to alkaline cations was induced by the incorporation of dolichol. This effect was not observed in the case of non-charged solutes like glucose or in that of alkaline earth cations such as calcium. Permeation of K+ was significantly increased above the phase transition temperature. These results suggest that dolichols may play a role in biological membranes, besides the well-known glycosyl carrier function in the biosynthesis of glycoproteins.