Mechanic assays of synthetic lipid membranes based on micropipette aspiration

Redox Reactions in Lipid Membranes as a Model for Primordial Energy-Conserving Systems

International Astronomical Union Colloquium ◽

10.1017/s0252921100014950 ◽

1997 ◽

Vol 161 ◽

pp. 437-442

Author(s):

Salvatore Di Bernardo ◽

Romana Fato ◽

Giorgio Lenaz

Keyword(s):

Experimental Evidence ◽

Lipid Membranes ◽

Energy Supply ◽

Redox Reactions ◽

Living Systems ◽

Asymmetric Distribution ◽

Conservation Of Energy ◽

Asymmetrical Distribution ◽

Energy Conserving ◽

Living Organisms

AbstractOne of the peculiar aspects of living systems is the production and conservation of energy. This aspect is provided by specialized organelles, such as the mitochondria and chloroplasts, in developed living organisms. In primordial systems lacking specialized enzymatic complexes the energy supply was probably bound to the generation and maintenance of an asymmetric distribution of charged molecules in compartmentalized systems. On the basis of experimental evidence, we suggest that lipophilic quinones were involved in the generation of this asymmetrical distribution of charges through vectorial redox reactions across lipid membranes.

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Observation of Concanavalin-A receptors on hydrated planar erythrocyte membrane film by in situ electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100076640 ◽

1983 ◽

Vol 41 ◽

pp. 608-609

Author(s):

Neng-Bo He ◽

S.W. Hui

Keyword(s):

Lipid Bilayers ◽

Erythrocyte Membrane ◽

Lipid Membranes ◽

Surface Film ◽

Biological Membranes ◽

Electron Microscopic Observation ◽

Electron Microscopic ◽

Black Lipid Membranes ◽

Fine Mesh ◽

Planar Films

Monolayers and planar "black" lipid membranes have been widely used as models for studying the structure and properties of biological membranes. Because of the lack of a suitable method to prepare these membranes for electron microscopic observation, their ultrastructure is so far not well understood. A method of forming molecular bilayers over the holes of fine mesh grids was developed by Hui et al. to study hydrated and unsupported lipid bilayers by electron diffraction, and to image phase separated domains by diffraction contrast. We now adapted the method of Pattus et al. of spreading biological membranes vesicles on the air-water interfaces to reconstitute biological membranes into unsupported planar films for electron microscopic study. hemoglobin-free human erythrocyte membrane stroma was prepared by hemolysis. The membranes were spreaded at 20°C on balanced salt solution in a Langmuir trough until a surface pressure of 20 dyne/cm was reached. The surface film was repeatedly washed by passing to adjacent troughs over shallow partitions (fig. 1).

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Direct visualization of phase-separated domains in lipid membranes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100082315 ◽

1978 ◽

Vol 36 (2) ◽

pp. 290-291

Author(s):

S. W. Hui ◽

T. P. Stewart

Keyword(s):

Lipid Membranes ◽

Structural Information ◽

Freeze Fracture ◽

Biological Molecules ◽

Vacuum Drying ◽

Direct Visualization ◽

X Ray Diffraction ◽

Electron Microscopic ◽

X Ray ◽

Hydrocarbon Chains

Direct electron microscopic study of biological molecules has been hampered by such factors as radiation damage, lack of contrast and vacuum drying. In certain cases, however, the difficulties may be overcome by using redundent structural information from repeating units and by various specimen preservation methods. With bilayers of phospholipids in which both the solid and fluid phases co-exist, the ordering of the hydrocarbon chains may be utilized to form diffraction contrast images. Domains of different molecular packings may be recgnizable by placing properly chosen filters in the diffraction plane. These domains would correspond to those observed by freeze fracture, if certain distinctive undulating patterns are associated with certain molecular packing, as suggested by X-ray diffraction studies. By using an environmental stage, we were able to directly observe these domains in bilayers of mixed phospholipids at various temperatures at which their phases change from misible to inmissible states.

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A Novel Reconstitution Method for Inducing the Formation of Regular 2-Dimensional Arrays of Membrane Proteins and Lipids

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100102845 ◽

1988 ◽

Vol 46 ◽

pp. 152-153 ◽

Cited By ~ 1

Author(s):

A. Engel ◽

A. Holzenburg ◽

K. Stauffer ◽

J. Rosenbusch ◽

U. Aebi

Keyword(s):

Membrane Proteins ◽

Flow Rate ◽

Lipid Membranes ◽

Functional Characterization ◽

Dimensional Structure ◽

Electron Crystallography ◽

Peltier Element ◽

Protein Ratio ◽

Precise Control ◽

3 Dimensional

Reconstitution of solubilized and purified membrane proteins in the presence of phospholipids into vesicles allows their functions to be studied by simple bulk measurements (e.g. diffusion of differently sized solutes) or by conductance measurements after transformation into planar membranes. On the other hand, reconstitution into regular protein-lipid arrays, usually forming at a specific lipid-to-protein ratio, provides the basis for determining the 3-dimensional structure of membrane proteins employing the tools of electron crystallography.To refine reconstitution conditions for reproducibly inducing formation of large and highly ordered protein-lipid membranes that are suitable for both electron crystallography and patch clamping experiments aimed at their functional characterization, we built a flow-dialysis device that allows precise control of temperature and flow-rate (Fig. 1). The flow rate is generated by a peristaltic pump and can be adjusted from 1 to 500 ml/h. The dialysis buffer is brought to a preselected temperature during its travel through a meandering path before it enters the dialysis reservoir. A Z-80 based computer controls a Peltier element allowing the temperature profile to be programmed as function of time.

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What do nanometer molecular trajectories tell us about heterogeneous cell surface domaines?

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100140300 ◽

1995 ◽

Vol 53 ◽

pp. 786-787

Author(s):

Watt W. Webb

Keyword(s):

Cell Surface ◽

Lipid Membranes ◽

Surface Proteins ◽

Protein Diffusion ◽

Coated Pits ◽

Cell Surface Proteins ◽

Membrane Heterogeneity ◽

Fluorescence Photobleaching Recovery ◽

Photobleaching Recovery ◽

Plasma Membrane Heterogeneity

Plasma membrane heterogeneity is implicit in the existence of specialized cell surface organelles which are necessary for cellular function; coated pits, post and pre-synaptic terminals, microvillae, caveolae, tight junctions, focal contacts and endothelial polarization are examples. The persistence of these discrete molecular aggregates depends on localized restraint of the constituent molecules within specific domaines in the cell surface by strong intermolecular bonds and/or anchorage to extended cytoskeleton. The observed plasticity of many of organelles and the dynamical modulation of domaines induced by cellular signaling evidence evanescent intermolecular interactions even in conspicuous aggregates. There is also strong evidence that universal restraints on the mobility of cell surface proteins persist virtually everywhere in cell surfaces, not only in the discrete organelles. Diffusion of cell surface proteins is slowed by several orders of magnitude relative to corresponding protein diffusion coefficients in isolated lipid membranes as has been determined by various ensemble average methods of measurement such as fluorescence photobleaching recovery(FPR).

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