title: Surface changes induced by osmotic shrinkage on large unilamellar vesicles.
abstract: Osmotic shrinkage changes the surface properties of dipalmitoylphosphatidylcholine large unilamellar vesicles depending on the phase state of the bilayer. In the gel state, shrinkage produces an increase in the adsorption of hydrophobic dyes, such as Merocyanine 540 (MC540) monomers, toluidine and anilinonaphthalene sulfonic acid (TNS, ANS). In the fluid state, shrinkage does not affect the bilayer surface when gradients between the inner and the outer compartments below 0.2-0.25 M NaCl (higher concentration outside) are applied. Larger differences in concentrations produce an increase in packing as inferred from the desorption of the MC monomers. Kinetic experiments show that the surface changes correlate with the volume decrease produced by the water extrusion from the vesicle interior. It is interpreted that the decrease of water content compels the vesicles to a state in which defects at the membrane surface are likely to occur when the bilayer is in the gel state.
authors.affiliation: Química General e Inorgánica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina.
authors.forename: E A
authors.initials: EA
authors.lastname: Disalvo
authors.forename: A M
authors.initials: AM
authors.lastname: Campos
authors.forename: E
authors.initials: E
authors.lastname: Abuin
authors.forename: E A
authors.initials: EA
authors.lastname: Lissi
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism; D004396:Coloring Agents / Q000378:metabolism; D004161:Diphenylhexatriene / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes / Q000378:metabolism; D005782:Gels / Q000378:metabolism; D007700:Kinetics; D008051:Lipid Bilayers / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism*; D009391:Nephelometry and Turbidimetry; D009995:Osmosis / Q000502:physiology*; D010316:Particle Size; D011744:Pyrimidinones / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D013053:Spectrophotometry; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000378:metabolism
chemical_list: D004396:Coloring Agents; D005452:Fluoresceins; D005456:Fluorescent Dyes; D005782:Gels; D008051:Lipid Bilayers; D008081:Liposomes; D011744:Pyrimidinones; D014867:Water; D004161:Diphenylhexatriene; D015060:1,2-Dipalmitoylphosphatidylcholine; C024098:6-carboxyfluorescein; D012965:Sodium Chloride; C003954:merocyanine dye