Membranes temperature dependence

Torres-Pereira, J. M. G. Sang, H. W. W. E Theuvenet, A. P. R. Kraayenhof, R. Electric surface charge dynamics of chloroplast thylakoid membranes. Temperature dependence... 

Membranes are commonly rated for their chlorine tolerance in ppm-hours, simply the product of the concentration and the contact time. Tolerance is temperature dependent. 

Carriers and channels may be distinguished on the basis of their temperature dependence. Channels are comparatively insensitive to membrane phase transitions and show only a slight dependence of transport rate on temperature. Mobile carriers, on the other hand, function efficiently above a membrane phase transition, but only poorly below it. Consequently, mobile carrier systems often show dramatic increases in transport rate as the system is heated through its phase transition. Figure 10.39 displays the structures of several of these interesting molecules. As might be anticipated from the variety of structures represented here, these molecules associate with membranes and facilitate transport by different means. 

In accordance with observed data, this model shows that water flux increases linearly with applied pressure AP, decreases with higher salt concentration through its impact on osmotic pressure Jt, increases with a smaller membrane thickness I, and increases with temperature through the temperature dependence of the water permeability P . The model also demonstrates that the solute or salt flux J, increases linearly with applied pressure AP, increases with higher salt concentration c , increases with a smaller membrane thickness I, and increases with temperature through the temperature dependence of the solute permeability Pj. Polarization, as described early in this section, causes the wall concentration c to exceed the bulk concentration ci,. 

Diffusion-mediated release of root exudates is likely to be affected by root zone temperature due to temperature-dependent changes in the speed of diffusion processes and modifications of membrane permeability (259,260). This might explain the stimulation of root exudation in tomato and clover at high temperatures, reported by Rovira (261), and also the increase in exudation of. sugars and amino acids in maize, cucumber, and strawberry exposed to low-temperature treatments (5-10°C), which was mainly attributed to a disturbance in membrane permeability (259,262). A decrease of exudation rates at low temperatures may be predicted for exudation processes that depend on metabolic energy. This assumption is supported by the continuous decrease of phytosiderophore release in Fe-deficient barley by decreasing the temperature from 30 to 5°C (67). 

This expression can be modified to apply directly to any of various techniques used to measure the interaction parameter, including membrane and vapor osmometry, freezing point depression, light scattering, viscometry, and inverse gas chromatography [89], A polynomial curve fit is typically used for the concentration dependence of %, while the temperature dependence can usually be fit over a limited temperature range to the form [47]... 

Liu, S.C., Fairbanks, G., and Palek, J. (1977) Spontaneous reversible protein cross-linking in the human erythrocyte membrane. Temperature and pH dependence. Biochemistry 16, 4066. 

Salgado, V.L., M.D. Herman, and T. Narahashi. 1989. Interactions of the pyrethroid fenvalerate with nerve membrane sodium channels temperature dependence and mechanism of depolarization. Neurotoxicology 10 1-14. 

Figure 15. Temperature dependence of absorption spectrum of the viologen bilayer membrane having biphenyl chromophore, CnBphCfV 2Br in water.

The initial hydration rate v and the equilibrium hydration amount were obtained as parameters reflecting the hydration behavior of LB films (see Figure 8). Temperature dependencies of the hydration behavior (v0and W ) of 10 layers of DMPE (Tc = 49 °C) LB films are shown in Figure 9. Large W and v0 values were observed only around the phase transition temperature (7C) of DMPE membranes. Thus, DMPE LB films were hydrated only near the Tc, but not in the solid state below the Tc and in the fluid state above the Tc. This indicates that the... 

Strambini and Galley have used tryptophan anisotropy to measure the rotation of proteins in glassy solvents as a function of temperature. They found that the anisotropy of tryptophan phosphorescence reflected the size of globular proteins in glycerol buffer in the temperature range -90 to -70°C.(84 85) Tryptophan phosphorescence of erythrocyte ghosts depolarized discontinuously as a function of temperature. These authors interpreted the complex temperature dependence to indicate protein-protein interactions in the membrane. 

Booij, K. Hofmans, H.E. Fischer, C.V. van Weerlee, E.M. 2003a, Temperature-dependent uptake rates of nonpolar organic compounds by semipermeable membrane devices and low-density polyediy-lene membranes.Ewviww. Sci. Technol. 37 361—366. 

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