Ea. Disalvo et al., SURFACE CHANGES INDUCED BY OSMOTIC SHRINKAGE ON LARGE UNILAMELLAR VESICLES, Chemistry and physics of lipids, 84(1), 1996, pp. 35-45
Osmotic shrinkage changes the surface properties of dipalmitoylphospha
tidylcholine large unilamellar vesicles depending on the phase state o
f the bilayer. In the gel state, shrinkage produces an increase in the
adsorption of hydrophobic dyes, such as Merocyanine 540 (MC540) monom
ers, toluidine and anilinonaphthalene sulfonic acid (TNS, ANS). In the
fluid state, shrinkage does not affect the bilayer surface when gradi
ents between the inner and the outer compartments below 0.2-0.25 M NaC
l (higher concentration outside) are applied. Larger differences in co
ncentrations produce an increase in packing as inferred from the desor
ption of the MC monomers. Kinetic experiments show that the surface ch
anges correlate with the volume decrease produced by the water extrusi
on from the vesicle interior. It is interpreted that the decrease of w
ater content compels the vesicles to a state in which defects at the m
embrane surface are likely to occur when the bilayer is in the gel sta
te.