Forces between curved mica surfaces across a brine swollen lamellar phase (CTAB/hexanol/Brine) have been measured. The bilayers oriented spontaneously parallel to the mica surfaces. The force-distance curves show regimes where brine is continuously expelled from between the lamellae, and regimes in which bilayers are ejected over a few seconds. We have investigated the effect on the forces of moving in the phase diagram at constant bulk repeat distance, as well as along the dilution line. We found that the force necessary to squeeze out bilayers becomes smaller as the system approaches the transition to the bicontinuous phase (Lα/L3), i.e. on increasing the hexanol content. Dynamic effects are observed and may be explained in terms of hydrodynamic coupling of the bilayers with the solvent. They may produce surprising behaviors : on decompressing the phase, lamellae are systematically ejected. The equilibrium state of the system is discussed. The data is consistent with the 1/d2 profile calculated by Helfrich for the undulation forces [1]. Least square fits of the data to 1/d2 gives bilayer curvature modulus values of the order of 5.5 ± 3 kB T.

We have observed anomalously enhanced self- (tracer) diffusion in systems of polymerlike breakable micelles. We argue that it provides the first experimental realization of a random walk for which the second moment of the jump-size distribution fails to exist (‘‘Levy flight’’). The basic mechanism is the following: Due to reptation, short micelles diffuse much more rapidly than long ones. As times goes on, shorter and shorter micelles are encountered by the tracer, and hence the effective diffusion constant increases with time.

The authors present a self-diffusion study of long cylindrical micelles of lecithin in an organic solvent. The results are compared with those obtained for similar micelles of CTAB (cethyltrimethylammonium bromide) in brine. Qualitatively they observe a similar behaviour for both systems. The measured self-diffusion coefficient D_s has a power law dependence on the surfactant concentration. However, the exponent, which is salinity-dependent in the CTAB system, is constant and in good agreement with a theory for living polymers in the lecithin system. In the case of very elongated lecithin and CTAB micelles, D_s becomes independent of surfactant concentration.

We have studied swollen lamellar phases into which the basic myelin protein can be incorporated. Lamellar spacing thermal fluctuations were analysed with quasi-elastic light scattering. The results are consistent with the existence of a strong steric repulsion between the bilayers due to the thermal undulations of these bilayers. They show that the bilayers bending elastic modulus is significantly increased by the presence of small amounts of the protein.

The Folch-Pi proteolipid is the most abundant structural protein from the central nervous system myelin. This protein-lipid complex, normally insoluble in water, requires only a small amount of water for solubilization in reverse micelles of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) in isooctane. The characterization of the proteolipid-free and proteolipid-containing micelles was undertaken by light scattering and fluorescence recovery after fringe pattern photobleaching (FRAPP) experiments. Quasi elastic light scattering (QELS) was carried out at a high (200 mM) AOT concentration, at low water-to-surfactant mole ratio (Wo = 7) and at increasing protein occupancy. Two apparent hydrodynamic radii, differing tenfold in size, were obtained from correlation functions. The smaller one (RaH = 5.2 nm) remains constant and corresponds to that measured for protein-free micelles. The larger one increases linearly with protein concentration. In contrast, FRAPP measurements of self-diffusion coefficients were found unaffected by the proteolipid concentration. Accordingly, they have been performed at constant protein/surfactant mole ratios. The equivalent RH, extrapolated to zero AOT concentration for protein-free reverse micelles (2.9 nm) and in the presence of the proteolipid (4.6 nm), do not reveal the mode of organization previously suggested by QELS measurements. The complex picture emerging from this work represents a first step in the characterization of an integral membrane protein in reverse micelles.