Evidence of voltage-induced channel opening in Na/K ATPase of human erythrocyte membrane.

Previous studies have shown that human erythrocytes when subjected to a high voltage pulsation, in the microsecond time range, lysed in an isotonic medium. The hemolysis was the result of the colloid osmotic swelling, which, in turn, was caused by the voltage perforation of the red cell membranes. In this work we demonstrate that in a low ionic medium at least 35% of the pores was related to the opening of Na+/K4 ATPase channels.

A fluorescence study with polarised incident light of the compression of phospholipid monolayers spread at the air/water interface: orientation processes in the glycerol region.

Monolayers of phospholipids spread at the air/water interface were studied by means of fluorescence measurements. Using linearly polarised incident light and following the behaviour of a fluorescent covalently-labelled phospholipid (dansylphosphatidylethanolamine) embedded in the monolayer, it was possible to obtain information about the orientation changes at the glycerol level of the phospholipid. When using dipalmitoylphosphatidylcholine as phospholipid, the main orientation of the probe appears unchanged during the phase transition process.

Fluorescence temperature jump relaxations of dansylphosphatidylethanolamine in aqueous dispersions of dipalmitoylphosphatidylcholine during the gel to liquid-crystal transition.

The change of fluorescence of the probe dansylphosphatidylethanolamine embedded in multilamellar liposomes of dipalmitoylphosphatidylcholine was used to investigate the dynamics of the thermotropic gel to liquid-crystalline phase transition by use of the temperature-jump technique. The results are discussed and compared to published observations on the same system in which the phenomenon was reported by turbidity changes.

A fluorescence approach of the determination of translational diffusion coefficients of lipids in phospholipid monolayer at the air-water interface.

In the present work, it is shown that the photobleaching technique as well as experimentation based on fluorescence recovery after bleaching can be extended to monolayers spread at the air-water interface. A mathematical model is derived which allows the determination of translational diffusion coefficients of species diffusing in such a system. Using 12-(9-anthroyl)stearic acid (anthroylstearate) as a fluorescent probe, dispersed either in dipalmitoylphosphatidylcholine or in dipalmitoylphosphatidylglycerol in various conditions of subphase ionic composition and surface pressure of the monolayer, including phase transition domains, we are led to the following conclusions: 1.

A fluorescence study of the binding of cytochrome C to mixed-phospholipid microvesicles : evidence for a preferred orientation of the bound protein.

Kinetic and equilibrium experiments are reported on the binding of the fluorescent probe 1,8-anilino-naphtalene sulfonate (ANS) to microvesicles of natural lecithin containing 10 per cent of an anionic phospholipip (90 : 10 mixtures). Kinetics discriminated between fast binding to the outer leaflet of the bilayer and apparently slow binding to the inner leaflet controlled by the diffusion of the probe across the bilayer. The equilibrium distribution of ANS between the two leaflets was not dependent on the nature of the anionic species and the spectral properties of bound ANS were identical in all cases investigated.

The use of fluorescent probes for studying the interaction of proteins with black lipid membranes.

The number of 1-anilino-8-naphthalene sulphonate (ANS) molecules bound to black phosphatidylcholine (PC) and phosphatidylinositol (PI)-membranes was calculated. The fluorescences change of membrane bound ANS was measured after the additon of positively charged proteins to the same side as ANS. Cytochrome c caused a fluorescence decrease, lysozyme and protamine an increase.