Lysis tension

Above some electroporation threshold, the transmembrane potential cannot be further increased, and can even decrease due to transport of ions across the membrane [91, 95]. The phenomenon of membrane electroporation can also be understood in terms of tension. If the total membrane tension exceeds the lysis tension c ys, the vesicle ruptures. This corresponds to building up a certain critical transmembrane potential, = Pc- According to Eqs. (7.3) and (7.4), this porahon potenhal Pc depends on the inihal membrane tension Co as previously reported [59, 89, 90, 96, 97]. The crihcal hansmembrane potenhal for cell membranes is about IV (e.g., [98, 99]). 

In vivo heme is released into the plasma by erythrocyte lysis in the form of hemoglobin and by tissue trauma in the form of myoglobin, and both heme proteins are quickly oxidized to their ferric heme forms (methemoglobin and metmyoglobin) at the oxygen tension found in tissue capillary beds. 

In their natural environment, bacterial cells need to adapt to a wide range of osmotic conditions. Escherichia coli cells exposed to hypo-osmotic shock respond by a rapid release of cellular osmolytes such as proline, potassium glutamate, trehalose, and ATP. This ability prevents the cells from lysis by decreasing the turgor pressure on the challenge of a sudden shift in osmolarity. Bacterial MS channels, MscL and MscS (Fig. la and b), are major components of adaptation mechanisms to hypo-osmotic shock. Being located in the cytoplasmic membrane, MscL and MscS are activated by an increase of membrane tension... 

The critical transmembrane potential for the latter was found to be in the range 8-lOV [111]. This value is significantly higher than the critical potenhal of IV reported for fluid membranes [59, 98, 99]. Thus, membranes in the gel phase can sustain higher tensile stresses (see Eqs. (7.3) and (7.4)). This is also confirmed by micropipette aspiration experiments showing that fluid-phase dimyristoylphos-phahdylcholine membranes undergo lysis at tensions around but... 

Fig. 6 Plot of membrane tension t as a function of dilation for a wide range of copolymer amphiphiles as extracted from MD simulations. The computational models, derived from systematic coarse-graining (black symbols), show nearly the same dilational behavior marked by the solid line. The slope of the line, ka, is very close to experimental measurements performed on giant vesicles 0colored symbols). Experimental data for a dimyristoyl phosphatidylcholine lipid membrane are also shown. The point of membrane lysis as observed experimentally for selected lipid and polymersome systems is also shown in the plot with green and red stars, respectively. Reprinted by permission from Macmillan Publishers Ltd Nature Materials, Ref. [85], copyright (2004)...

Considerable work has been directed at characterizing halohydrins of the alkenes of lipids. The treatment of tissues with hypochlorous acid and subsequent lipid chlo-rohydrin production has been associated with biological consequences, including erythocyte and endothelial cell lysis, as well as decreased contractile tension in cardiac papillary muscle preparations (Carr et al. 1997 Iwase et al. 1997). Early studies by Winterbourne showed monounsaturated and polyunsaturated fatty acids, either... 

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