The Formation and Properties of Bilayers Containing Lipids Extracted from Bovine Erythrocytes

The formation and the properties of bimolecular membranes separating two aqueous phases have been studied using some single and mixed lipids extracted from bovine erythrocytes by means of column chromatography. Phosphatidyl ethanolamine and phosphatidyl serine were found to give very stable membranes, whose capacitances were 0.39 and 0.33 vF/cm2 respectively. The membranes formed from phosphatidyl choline were less stable, the capacitance being 0.33 pF/cm2. Using sphingomyelin or non-phosphorus-containing neutral lipids composed of cholesterol ester, triglyceride, diglyceride and cholesterol it was almost impossible to form thin membranes. The addition of the neutral lipid fractions to the phosphatidyl choline or to the sphingomyelin markedly improved the stability of bimolecular membranes, giving values of 0.29 to 0.34 vF/cm2 for membrane capacitances. This fact implies that the neutral lipids when mixed with phospholipids play a part in the mechanical stability of cell membranes. Distinct differences in membrane stability were observed between phosphatidyl choline extracted from egg and that from bovine erythrocytes. Analytical data of fatty acid carbon chain constitution were also presented for phosphatidyl choline and phosphatidyl ethanolamine. I