Use of resonance energy transfer to monitor membrane fusion.

An assay for vesicle--vesicle fusion involving resonance energy transfer between N-(7-nitro-2,1,3-benzoxadiazol-4-yl), the energy donor, and rhodamine, the energy acceptor, has been developed. The two fluorophores are coupled to the free amino group of phosphatidylethanolamine to provide analogues which can be incorporated into a lipid vesicle bilayer. When both fluorescent lipids are in phosphatidylserine vesicles at appropriate surface densities (ratio of fluorescent lipid to total lipid), efficient energy transfer is observed.

Cell-induced leakage of liposome contents.

Using the principle of relief of self-quenching of carboxyfluorescein [Weinstein, J. N., Yoshikami, S.

Interactions of phospholipid vesicles with rat hepatocytes in vitro. Influence of vesicle-incorporated glycolipids.

We examined the interaction of glycolipid-containing phospholipid vesicles with rat hepatocytes in vitro. Incorporation of either N-lignoceroyldihydrolactocerebroside or the monosialoganglioside, GM1, enhanced liposomal lipid uptake 4-5-fold as judged by the uptake of radioactive phosphatidylcholine as a vesicle marker. Cerebroside enhanced phospholipid uptake only when incorporated into dimyristoyl, but not into egg phosphatidylcholine vesicles.

Effect of fetal calf serum and serum protein fractions on the uptake of liposomal phosphatidylcholine by rat hepatocytes in primary monolayer culture.

We studied the effect of fetal calf serum and serum proteins fractions on the interaction of phospholipid vesicles consisting of phosphatidylcholine, cholesterol and dicetylphosphate (molar ratio 7 : 2 : 1), with rat liver parenchymal cells in a primary monolayer culture. During incubation of such vesicles with fetal calf serum part of the labeled phosphatidylcholine is transferred to a lipoprotein particle similar to the one we identified previously as a derivative of high density lipoprotein (Scherphof, G., Roerdink, F.

Interaction of phospholipid vesicles with rat hepatocytes in primary monolayer culture.

We studied the interaction of positively and negatively charged unilamellar and multilamellar phospholipid vesicles (liposomes) with rat-liver parenchymal cells in primary monolayer culture. Radioactive liposomal phosphatidylcholine was taken up more rapidly and to a larger extent from unilamellar than from multilamellar vesicles. No significant difference in uptake characteristics was observed between vesicles of different charge.

Release of outer membrane fragments from normally growing Escherichia coli.

A complex containing lipopolysaccharides, phospholipids and proteine separated from the medium by gelfiltration on Sephadex G-200 or by centrifugation. Electron microscopy revealed that this material is released as vesicles and membrane fragements. To determine the origin of these fragments, they were compared to outer and cytoplasmic membranes with respect to keto-deoxyoctulosonic acid, phospholipid, and protein content, phospholipid composition, fatty acid composition, protein distribution on sodium dodecyl sulfate-polyacrylamide gels, buoyant density, and content of several membrane marker enzymes.