Membrane metastability

The possible existence of highly polarized metastable states in biological model membranes has led us to a preliminary model for specific interactions in membranes (14). We have assumed that biomolecules are capable of nonlinear polarization oscillations, when they are sufficiently excited by metabolic energy or by external means, e.g. electric fields. Restricting to the case of two interacting molecules for simplicity, the dynamics of the system is given by a set of nonlinear differential equations for the polarization P. of the molecule i ... 

Dependence of the lifetime of foam bilayers on the concentration of dissolved surfactant. The stability of foam, emulsion and membrane bilayers can be characterised by their mean lifetime r which is the time elapsing form the moment of formation of a bilayer with a given radius until the moment of its rupture. Obviously, this is a kinetic characteristic of the bilayer stability and can only be applied to thermodynamically metastable bilayers. 

Ffe. 5.11 TLie MM forms of rhodopsin (R) are in equilibrium with their parent compound Ml and the progeny Mill. The equilibnum between the metastates, Ml, Mila, and Mllb, are attained within a few milliseconds after illumination. The Ml/Mlla transition is accompanied by the intramolecular translocation of the Schiff-base proton to GlullS, located in a region close to the lipid membrane. The subsequent Mlla/Mllb transition is dependent on proton uptake from the aqueous phase and occurs in a watersxposed area. Fast binding of the G protein, transducin, occurs only with Mllb.(Reproduced from ref. 58 with permission of Elsevier Science.)... 

Finally, interest in zirconia membranes has increased in recent years. Zirconia exhibits three well-defined phases in the order of increasing temperature the monoclinic, tetragonal and cubic phases. However, it has been suggested that a low-temperature metastable tetragonal phase exists in contrast to the high-temperature tetragonal phase [Cot, 1991 Colomban and Bruneton, 1992]. For pure zirconia membranes, it appears that the following phase uansitions occur [Stevens, 1986 Colomban and Bruneton, 1992] ... 

Membrane structural properties may depend strongly on the thermal history of the material, affecting, in turn, the transport properties. Following exposure of the ionomeric membrane to different thefmal/hydration conditions, a range of metastable structures could arise, each associated with a different water content, cluster size, and cluster connectivity. Consequently, as discussed below, thermal pretreatment effects... 

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