Membrane undulation

A typical force curve showing the specific avidin-biotin interaction is depicted in figure Bl.20.10. The SFA revealed the strong influence of hydration forces and membrane undulation forces on the specific binding of proteins to membrane-bound receptors [81]. 

The most successful continuum description of membrane elasticity, dynamics, and thermodynamics is based on the smectic bilayer model (for examples of different versions and applications of this approach see Ref. 76-82 and references therein). We introduce this model in conjunction with the question of membrane undulations. 

We have shown that postulating short-A softening of the i-modes of membrane undulations, which can explain the low-voltage low-thinning instability, is consistent with observed equilibrium properties of membranes. This finding supports the hypothesis but obviously does not prove it. 

The steps of apoptosis are distinct from those of necrosis which is a nonprogramed form of cell death in response to injury, in which the cell swells and bursts, causing inflammation. Apoptosing cells form a tight sphere and their membranes undulate, resulting in bulges that form blebs. The nuclear membrane breaks, and endonucleases clip chromosomes where the DNA is exposed from protective proteins. This occurs at 180-base... 

The membrane undulates slightly as it scrapes the carpeting of his room, and the eye occasionally blinks and swivels in his direction. It is a wild, exotic sapphire eye—utterly alien with long gray eyelashes. 

For an external pressure pext, the membranes undulations minimize the Gibbs free energy, based on the enthalpy ... 

There is only one case in which the thermal undulations of a membrane can be evaluated analytically, namely when one membrane undulates in a harmonic potential. Let us assume that the position, along the z direction, of each point of the membrane is described by the function u(x,y), with u(x,y) = 0 corresponding to a non undulating membrane (see Fig. B.l). 

Vesicles (Latin vesicula, bladder) are sealed, extremely thin (< 10 nm), often spherical membraneswhich enclose aqueous or other solvent volumes of approximately 10 -10 nm. Aggregation numbers are in the order of 10 -10. The monomers are held together by the same solvophobic effects which produce micelles, and solvation forces together with membrane undulations prevent crystallization. The state of the vesicle membrane is therefore also essentially of a fluid character. Supramolecular ordering within vesicle membranes is negligible. 

Pfeiffer, W., Konig, S., Legrand, J.F., Bayerl, T., Richter, D. and Sackmann, E. (1993) Neutron spin-echo study of membrane undulations in lipid multibilayers. Europhys. Lett., 23,457-462. 

Instability of Membrane Undulations Under an Applied Voltage... 

Vesicles have molecular masses in the order of 10 -10 daltons. Van der Waals attraction between such gigantic solutes is very large. Nevertheless, vesicles do not precipitate but stay in solution, because the ultrathin membranes undulate. 

Takeda T, Kawabata Y, Seto H, Komura S, Ghosh SK, Nagao M, Okuhara D (1999) Neutron spin-echo investigations of membrane undulations in complex fluids involving amphiphiles. J Phys Chem Solids 60(8-9) 1375-1377... 

In the following contribution the development of a new evaluation theory for X-ray diffraction diagrams of biomembranes and other lamellar systems is presented. This theory is more com-prehensive than other theories applied hitherto, once statistical lattice distortions, distortions of the lattice-cell, membrane undulations and deferent interspatial electron densities as writ as Lorentz correction are considered... 

Some authors discuss the effect of perfectly correlated membrane undulations on the scattering diagram We improve this approach by adopting the general case of partidly correlated membrane undulations (4.3). 

As long as the radial extension of 1st is mudi smaller than Oa bz [0, is the std.dev. of (a)] the Lorentz factor l/b will be a reasonable proximation for (1.12), but in the general case it is invalid and we have to know the exact three-dimensional form of 1st ih reciprocal space in order to evaluate lexp. Before we evaluate the general three-dimensional expression of via Qgx, we will demonstrate an additional effect of membrane undulations on the integral (1.12). For the sake of simplicity we assume stacks consisting of only one vesicle with a deltalike distribution of inter-membrane distances. In Chaps. 2 and 3 Igx was restricted to a delta-cylinder around the hz-axis and as a consequence, all our knowledge of membrane structure was based on the projection of the vesicle-layer density onto the z-axis ... 

Figure 9.1 Videomicrographs of a flaccid giant lipid vesicle (12 microns diameter), a red blood cell (7 microns diameter) and a neutrophil (8 microns diameter). All these capsules are bounded by the lipid bilayer membrane. Some information about the material properties, in particular bending stiffiiess and intrinsic curvature is obtained from microscopic observation of membrane undulations, but the full range of material behavior is obtained by aspirating individual vesicles or cells by micropipet.

---