生物化学技术

Micropipet aspiration of giant unilamellar vesicles can be used to determine the mechanical properties of area compressibility modulus, bending modulus, and lysis tension of lipid bilayers. In this technique, giant (∼25-�m diameter) single bilayered vesicles are aspirated into a pi ...

Lipid suspensions in aqueous solutions most often form multilamellar vesicles of uniformly spaced bilayers. Interlamellar spacing is determined by the balance of attractive van der Waals (charge fluctuation) and repulsive forces. This balance of forces, as well as membrane elasti ...

Two methods are presented for deforming giant unilamellar vesicles with holographic optical tweezers. The first allows ultrahigh spatial- and temporal-resolution optical tracking of membrane deformations, by using embedded silica microspheres in a giant unilamellar vesi ...

Membrane shape parameters such as curvature, bending elasticity, and lateral tension, are relevant to the lateral organization and function of biomembranes, and may critically influence the formation of lateral clustering patterns observed in living cells. Fluorescence laser ...

Structure of a lipid monolayer can be characterized by its spontaneous shape corresponding to a stress-free state. In the chapter, the rigorous description of monolayer shape in terms of curvature of a Gibbs dividing surface is reviewed, and the notions of the neutral and pivotal surfaces are di ...

Molecular fluctuations are a dominant feature of biomembranes. Cellular functions might rely on these properties in ways yet to be determined. This expectation is suggested by the fact that membrane deformation and rigidity, which govern molecular fluctuations, have been implicat ...

The authors developed a technique to apply high hydrostatic pressure to giant unilamellar vesicles and to directly observe the consequent structural changes with two-photon fluorescence microscopy imaging using high numerical aperture oil-immersion objectives. The data d ...

Osmotic water permeability and solute permeability coefficient are measured using stopped-flow fluorimetry. In a vesicle that behaves as a perfect osmometer, water flux is directly proportional to imposed osmotic pressure, and solute flux is proportional to the chemical gradient ...

Modeling obstructed diffusion is essential to the understanding of diffusion-mediated processes in the crowded cellular environment. Simple Monte Carlo techniques for modeling obstructed random walks are explained and related to Brownian dynamics and more complicated Mon ...

In the postgenomic era, spatially and temporally regulated molecular interactions as signals are beginning to take center stage in the understanding of fundamental biological events. For years, reductionism derived from the “fluid mosaic” model of the cell membrane has portrayed me ...

The single-molecule detection (SMD) of individual fluorophores represents a powerful experimental technique that allows for the observation of individual membrane molecules in their different dynamic states without having to average over a large number of molecules. Spatial ...

The lateral diffusion of lipids is crucial to the biogenesis and function of biological membranes. In this chapter, approaches for observing the lateral diffusion of lipids using fluorescence recovery after photobleaching are described. The procedures described can be carried out ...

Membrane organization, including the presence of domains, can be characterized by measuring lateral diffusion rates of lipids and membrane-bound substances. Magic angle spinning (MAS) yields well-resolved proton nuclear magnetic resonance (NMR) of lipids in biomembranes. Wh ...

The authors’ laboratory has applied a series of different fluorescence assays for monitoring the binding and transport of fatty acids (FA) in model and biological membranes. The authors recently expanded their fluorescent assays for monitoring the adsorption of FA to membranes to a total ...

The fluidity of the lipid matrix of cell membranes is crucial for the mobility of various inclusions like proteins. When the lipid bilayer undergoes phase transition from fluid-to-gel phase, the shear surface viscosity of the membrane diverges, thus hindering the motion of the membrane inc ...

Fourier transform infrared (FTIR) spectroscopy is a powerful, nonperturbing technique that has been used to good effect for the detection and characterization of lipid phase transitions in model and natural membranes. The technique is also quite versatile, covering a wide range of soph ...

Pressure perturbation calorimetry is a rather new technique which serves to measure the temperature-dependent thermal volume expansion of a solute or particle in aqueous dispersion. It can be used to detect thermotropic transitions in lipid systems and to characterize their accomp ...

Differential scanning calorimetry (DSC) is a relatively rapid, straightforward, and nonperturbing technique for studying the thermotropic phase behavior of hydrated lipid dispersions and of reconstituted lipid model or biological membranes. However, because of the diver ...

There is a significant amount of experimental data, obtained predominantly from fluorescence studies, showing that sterol-containing liposomes can exhibit multiple biphasic changes in membrane properties at specific critical mole fractions of sterol such as 20.0, 22.2, 25.0, 33. ...

This chapter describes the major issues thDepartment of Physiat are involved in the statistical thermodynamics of phospholipid membranes at the atomic level. The ingredients going into models of lipid bilayers are summarized: force fields, representation of long-range interac ...