PubMed · 8193194
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
B M Borovik, E V Popov. [Structural ordering model biomembrane].. https://pubmed.ncbi.nlm.nih.gov/8193194/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The intermolecular interactions and microscopic miscibility of the lipid bilayers of single component and binary mixtures with high content of saturated fatty acids were investigated by 2H- and 31P-NMR for phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and cardiolipin (CL). Their glycerol backbones were selectively deuterated by biosynthesis and chemical synthesis. Deuterium quadrupole splittings and phosphorus chemical shift anisotropies provided the consistent information for the molecular miscibility of each phospholipids. PE was found to be completely miscible with PG and CL. Since deuterium quadrupole splittings and phosphorus chemical shift anisotropy are identical for two components in the mixed bilayer, the dynamic structure from the glycerol backbone to phosphate group should be uniform in the binary mixture of these phospholipids. In contrast to PE, PC was not fully miscible with PG and CL at molecular resolution. The dynamic structure from the glycerol backbone to phosphate group is different for two components in the binary mixed bilayers. In the case of the mixed bilayers of PC and PE, both phospholipids are microscopically immiscible with each other. Thus, while PE, PG and CL can adapt to a new situation to form a uniform dynamic structure in mixed bilayers, PC has no ability for adaptation. The molecular miscibility in lipid bilayers was shown to depend on the molecular species and the nature of the molecular interactions. The biological significance of this result was discussed.
The interactions of retinol with vesicles of dioleoylphosphatidylcholine of varying radii were studied. The rate constants of dissociation of retinol from bilayers (k(off)) and the equilibrium partition constants (Keq) of retinol into bilayers of different sized vesicles were measured. The rate constants for association of retinol with vesicles were calculated from the expression Keq = k(on)/k(off). k(off) was 10-fold faster in the smallest versus the largest vesicles tested. K(on) was also somewhat faster in vesicles with small radii, but the effect on k(off) was more pronounced, leading to an overall higher affinity for retinol of bilayers in large vesicles. The thermodynamic parameters of the dissociation reaction were studied in vesicles with 0.025, 0.1, and 0.4 microns diameter. The enthalpy of activation decreased while the entropy of activation of the dissociation of retinol from bilayers increased as the vesicles become larger. It is suggested that restructuring of lipid-lipid interactions within the bilayer play a role in determining the rate by which retinol is solvated off bilayers. Overall, the data indicate that the rates by which retinol moves between different cell types in vivo may depend on the geometry of cellular surfaces.
The structural properties of lipid films, made from a squalene/butanol solution containing varying amounts (0-15 mg/ml) of egg phosphatidylcholine and deposited on a thin metallic silver layer, were investigated using surface plasmon resonance (SPR) spectroscopy. Optical parameters (thickness, refractive index and extinction coefficient) of such supported self-assembled lipid membranes were obtained from a theoretical analysis of the experimental SPR curves. The mass of the lipid membrane and the area and volume occupied by one lipid molecule were also calculated. The results were consistent with the formation of durable and homogeneous lipid bilayers on the solid substrate, and indicated similarities in structural properties between the present lipid bilayers and freely suspended and Langmuir-Blodgett bilayer membranes. Such bilayers represent a simple model for biological membranes, as well as providing a means of immobilizing proteins for various practical applications, including receptor-based sensors and molecular devices. The results confirm the value of the SPR technique for investigating the properties of thin biomolecular dielectric films deposited on a metal surface.