title: The extent of transmembrane phospholipid movement in mixed phosphatidylcholine-phosphatidylserine vesicles.
abstract: A hypothesis of rapid coupled translocation of egg phosphatidylcholine and bovine brain phosphatidylserine across a mixed vesicle membrane was tested. Homogeneous preparations of sonicated phospholipid vesicles containing four different compositions of the above two phospholipids were prepared. Trinitrobenzene-sulfonate derivatization of vesicle-phosphatidylserine was used to determine the outside-inside ratio of this phospholipid. No change in the ratio was observed over a 2-hr period. The transmembrane distribution of phosphatidylcholine was quantitated using 600 MHz 1H NMR; this distribution was found to be identical after a 24-hr incubation at pH 5 or pH 8. Thus, rapid exchange of phosphatidylcholine for phosphatidylserine is not observed under the conditions of these experiments.
mesh_terms: D007700:Kinetics; D008081:Liposomes; D008563:Membrane Lipids / Q000502:physiology*; D010713:Phosphatidylcholines / Q000502:physiology*; D010718:Phosphatidylserines / Q000502:physiology*; D013010:Sonication
chemical_list: D008081:Liposomes; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D010718:Phosphatidylserines