title: Osmotic stress induces a phase transition from interdigitated gel phase to bilayer gel phase in multilamellar vesicles of dihexadecylphosphatidylcholine.
abstract: We have investigated the effects of poly(ethylene glycol) (PEG) on the structure and phase behavior of multilamellar vesicles of dihexadecylphosphatidylcholine (DHPC-MLVs) using an X-ray diffraction method. At low concentrations of PEG-6K (MW = 7500), DHPC-MLVs were in an interdigitated gel (L(beta)I) phase, a gel phase with interdigitated hydrocarbon chains. At around 24% (w/v) PEG 6K, a phase transition from the L(beta)I phase to a bilayer gel phase occurred in the DHPC-MLVs, and above this concentration, they were in a bilayer gel phase. On the other hand, ethylene glycol (EG), the monomer of PEG, did not induce this phase transition in the DHPC-MLVs. A mechanism of this phase transition is proposed and discussed; a decrease in the repulsive interaction between the head groups of the phospholipids in the bilayer gel phase with an increase in PEG concentration, which is due to a decrease in the cross-sectional area of the head group region by osmotic stress, may be the main reason for this phase transition.
authors.affiliation: Department of Physics, Faculty of Science, Shizuoka University, 836 Oya, Shizuoka 422, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hatanaka
authors.forename: K
authors.initials: K
authors.lastname: Kinoshita
authors.forename: M
authors.initials: M
authors.lastname: Yamazaki