The influence of the lipid on the water permeability of artificial membranes.

The water permeabilities of artificial membranes formed formed from various monoglycerides or phospholipids in alkane solvents have been measured using an osmotic method, and it has been shown that the permeability depends upon the type of lipid used. For monoglycerides, the permeability was found to increase with the unsaturation and decrease with the length of the acyl chain. Membranes formed from either egg phosphatidylcholine or dioleyl phosphatidylcholine had an osmotic permeability coefficient of approx. 35--40 micrometer/s at 25 degrees C; with sphingomyelin as the membrane lipid, the permeability was an order of magnitude lower than that for phosphatidylcholine. It is suggested that the water permeabilities of biological membranes might be partly controlled by the types of lipid present.