Mechanisms of membrane protein insertion into liposomes during reconstitution procedures involving the use of detergents. 1. Solubilization of large unilamellar liposomes (Prepared by reverse-phase evaporation) by Triton X-100 octyl glucoside, and sodium cholate
The mechanisms governing the solubilization by Triton X-100, octyl glucoside, and sodium cholate of large unilamellar liposomes prepared by reverse-phase evaporation were investigated. The solubilization process is described by the three-stage model previously proposed for the detergents. In stage I, detergent monomers are incorporated into the phospholipid bilayers until they saturate the liposomes. At this point, i.e., stage II, mixed phospholipid-detergent micelles begin to form. By stage III, the lamellar to micellar transition is complete and all the phospholipids are present as mixed micelles. The turbidity of liposome preparations was systematically measured as a function of the amount of detergent added for a wide range of phospholipid concentrations. The results allowed a quantitative determination of the effective detergent to lipid molar ratios in the saturated liposomes. The monomer concentrations of the three detergents in the aqueous phase were also determined at the lamellar to micellar transitions. These transitions were also investigated by /sup 31/P NMR spectroscopy, and complete agreement was found with turbidity measurements. Freeze-fracture electron microscopy and permeability studies in the sublytic range of detergent concentrations indicated that during stage I of solubilization detergent partitioning between the aqueous phase and the lipid bilayer greatly affects the basic permeability of the liposomes without significantly changing the morphology of the preparations. A rough approximation of the partition coefficients was derived from the turbidity and permeability data. It is concluded that when performed systematically, turbidity measurements constitute a very convenient and powerful technique for the quantitative study of the liposome solubilization process by detergents.
- Research Organization:
- CEN Saclay, Gif-sur-Yvette (France)
- OSTI ID:
- 7241924
- Journal Information:
- Biochemistry; (United States), Vol. 27:8
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CELL MEMBRANES
MATHEMATICAL MODELS
LIPOSOMES
ELECTRON MICROSCOPY
NUCLEAR MAGNETIC RESONANCE
DETERGENTS
PHOSPHORUS 31
PROTEINS
TURBIDITY
ADDITIVES
CELL CONSTITUENTS
EMULSIFIERS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MEMBRANES
MICROSCOPY
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANOIDS
PHOSPHORUS ISOTOPES
RESONANCE
STABLE ISOTOPES
SURFACTANTS
WETTING AGENTS
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