Influence of Toluene on the Bending Elastic Properties of Giant Phosphatidylcholine Vesicles

AOT-Vesicles Produced at the Oil-Water Interface

Vesicles can be found in many applications like drug delivery or as models for cell membranes. It is often necessary to produce vesicles which are easy to adjust in size and which can be filled with different types of ingredients. In this publication we used phase transfer techniques in to form well defined vesicles. The synthesis of these particles occurred in three different steps. First, a water phase was covered by an oil phase containing surfactants. A water-in-oil emulsion was then added to the oil phase. In the third step the phase transfer was stimulated by sedimentation or centrifugation processes. In a series of experiments we measured the vesicle sizes and encapsulation efficiencies. Giant vesicles, formed by sedimentation processes had typical sizes between 1–10 μm. Smaller vesicles between 100–500 nm were observed after centrifugation processes. With both methods we could produce vesicles with encapsulation amounts about 10%.

Electroformation of giant vesicles from an inverse phase precursor

We discuss a simple modification of the well-known method of giant vesicle electroformation that allows for a direct addition of water-soluble species to the phospholipid bilayers. Using this modified method, we prepare phospholipid vesicles decorated with chitosan, a water-soluble polysaccharide currently investigated for potential pharmacological applications. We find that the method allows this polysaccharide with primary amino groups on every glucose subunit to be tightly bound to the membrane, rather than simply being encapsulated.

Diacylglycerol-rich domain formation in giant stearoyl-oleoyl phosphatidylcholine vesicles driven by phospholipase C activity

We have studied the effect of phospholipase C from Bacillus cereus and Clostridium perfringens (alpha-toxin) on giant stearoyl-oleoyl phosphatidylcholine (SOPC) vesicles. Enzyme activity leads to a binary mixture of SOPC and the diacylglycerol SOG, which phase separates into a SOPC-rich bilayer phase and a SOG-rich isotropic bulk-like domain embedded within the membrane, as seen directly by phase contrast microscopy. After prolonged enzymatic attack, all bilayer membranes are transformed into an isotropic pure SOG phase as characterized by fluorescence microscopy, differential scanning calorimetry, fluorescence anisotropy measurements, and small angle x-ray scattering. These domains may have biological relevance, serving as storage compartments for hydrophobic molecules and/or catalyzing cellular signaling events at their boundaries. Furthermore, in the early stages of asymmetric enzymatic attack to the external monolayer of giant vesicles, we observe a transient coupling of the second-messenger diacylglycerol to membrane spontaneous curvature, which decreases due to enzyme activity, before domain formation and final vesicle collapse occurs.

NMR elastometry of fluid membranes in the mesoscopic regime

In solid-state 2H NMR of fluid lipid bilayers, quasielastic deformations at MHz frequencies are detected as a square-law dependence of the nuclear spin-lattice (R(1Z)) relaxation rates and order parameters (S(CD)). The signature square-law slope is found to decrease progressively with the mole fraction of cholesterol and with the acyl chain length, due to a stiffening of the membrane. The correspondence to thermal vesicle fluctuations and molecular dynamics simulations implies that a broad distribution of modes is present, ranging from the membrane size down to the molecular dimensions.