title: Transition of a liquid crystalline phosphatidylcholine bilayer to the gel phase in a vesicle reduces the internal aqueous volume.
abstract: The liquid crystalline to gel phase transition in phospholipid bilayers is associated with a marked reduction in the area per phospholipid molecule. Geometric considerations based on published data suggest that this decrease in molecular area is accompanied by a reduction in the internal aqueous volume trapped within a unilamellar bilayer vesicle. This volume reduction, which depends upon the shape of the vesicle, is shown to be between 23 and 60 percent. We have observed a 25 to 30 percent reduction in the internal aqueous volume of unilamellar vesicles about 700 A in diameter formed from dipalmitoylphosphatidylcholine using the self-quenching of 6-carboxyfluorescein trapped within this compartment.
mesh_terms: D005452:Fluoresceins; D005782:Gels; D007700:Kinetics; D008051:Lipid Bilayers; D008954:Models, Biological; D008968:Molecular Conformation; D011663:Pulmonary Surfactants; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D005452:Fluoresceins; D005782:Gels; D008051:Lipid Bilayers; D011663:Pulmonary Surfactants; C024098:6-carboxyfluorescein