EFFECT OF ARTIFICIAL BOUNDARY LIPID ON THE MEMBRANE DYNAMICS OF HUMAN GLYCOPHORIN-CONTAINING LIPOSOME

Membrane dynamics of egg yolk phosphatidylcholine (egg PC) lipid bilayer which contains human glycophorin with an artificial boundary lipid, 1,2-dimyristoylamido-1,2-deoxyphosphatidylcholine (DDPC), were investigated by ESR spin probe technique. 2-Tridecyl-2-(4-hydroxy-4-oxoundecyl)4.4-dimethyl-3-oxazolidinyloxy (5-NS), 2-octyl-2-(7-ethoxy-7-oxoheptyl)-4,4-dimethyl-3-oxazolidinyloxy (8-ENP), and 2-hexyl-2-(11-methoxy-11-oxo-undecyl)-4,4-dimethyl-3-oxazolidinyloxy (12-M NS) were used as the spin probe to measure the fluidity in different regions and depths of the lipid bilayer membrane. Studies on lipid bilayer containing 5-NS revealed that the reconstitution of glycophorin to egg PC bilayer slightly decreased the membrane fluidity in the vicinity of membrane surface. Further addition of DDPC to this liposome brought about further decrease in the fluidity of this region. Liposomes containing 12-MNS revealed, however, that the addition of glycophorin had an opposite effect on the deep hydrophobic domain of the membrane by increasing the fluidity and the addition of DDPC to the liposome makes this domain less fluid. Corresponding changes were observed in the energy of activation for the rotation of 12-MNS during each case.