Phase transition membrane

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. 

Hypothermia—Indirect cryodestruction Metabolic uncoupling Energy deprivation Ionic imbalance Disruption of acid-base balance Waste accumulation Membrane phase transitions Cytoskeletal disassembly Frozen State—Direct cryodestruction Water solidification Hyperosmolality Cell-volume disruption Protein denaturation Tissue shearing Intracellular-ice propagation Membrane disruption Microvascular Thawed State Direct effects... 

Li, L., Braiteh, F.S., and Kurzrock, R., Liposome-encapsulated curcumin in vitro and in vivo effects on proliferation, Apopf. Signal. Angiogen. Cancer, 104, 1322, 2005. Socaciu, C., Jessel, R., and Diehl, H.A., Competitive carotenoid and cholesterol incorporation into liposomes effects on membrane phase transition, fluidity, polarity... 

Wisniewska, A., Y. Nishimoto, J. S. Hyde, A. Kusumi, and W. K. Subczynski. 1996. Depth dependence of the perturbing effect of placing a bulky group (oxazoline ring spin labels) in the membrane on the membrane phase transition. Biochim. Biophys. Acta 1278 68-72. 

Selected entries from Methods in Enzymology [vol, page(s)] Aspartate transcarbamylase [assembly effects, 259, 624-625 buffer sensitivity, 259, 625 ligation effects, 259, 625 mutation effects, 259, 626] baseline estimation [effect on parameters, 240, 542-543, 548-549 importance of, 240, 540 polynomial interpolation, 240, 540-541,549, 567 proportional method for, 240, 541-542, 547-548, 567] baseline subtraction and partial molar heat capacity, 259, 151 changes in solvent accessible surface areas, 240, 519-520, 528 characterization of membrane phase transition, 250,... 

One possible such mechanism for fixing a pattern is to have a phase transition. For example, if the pattern is in terms of a distribution of large molecules on the outer membrane surface, as in the Fucus-like models discussed here, then a membrane phase transition from a more liquid-like to a more crystal-like state of the membrane could essentially immobilize the membrane bound species and freeze in the pattern. In fact several hours after fertilization in Fucus the lability (rotatability) of the polar axis significantly decreases. Indeed this freezing of the Fucus patterning is not easily explained in terms of a Turing mechanism since the rotational symmetry of the Fucus egg, as discussed previously, implies that the electrical polarity is not stable (or more precisely is marginally stable) to polar axis rotation. 

An explanation for this gel formation is sought in the phase transition behavior of span 60. At the elevated temperature (60 °C) which exceeds the span 60 membrane phase transition temperature (50 °C) [154], it is assumed that span 60 surfactant molecules are self-assembled to form a liquid crystal phase. The liquid crystal phase stabilizes the water droplets within the oil. However, below the phase transition temperature the gel phase persists and it is likely that the monolayer stabilizing the water collapses and span 60 precipitates within the oil. The span 60 precipitate thus immobilizes the liquid oil to form a gel. Water channels are subsequently formed when the w/o droplets collapse. This explanation is plausible as the aqueous volume marker CF was identified within these elongated water channels and non-spherical aqueous droplets were formed within the gel [153]. These v/w/o systems have been further evaluated as immunological adjuvants. 

Laggner P. Nonequilibrium phenomena in lipid-membrane phase-transitions. J. Phys. IV 1993 3 259-269. 

A. Channels are sensitive to membrane phase transitions, while carriers function efficiently only above a membrane phase transition. 

Membrane phase transitions are particularly relevant to lyophilization (Oliver et al., 2001). Eor concreteness (but without loss of generality), we discuss this issue in the context of dipalmitoylphosphocholine (DPPC)... 

One important factor when drying yeast cells is intracellular trehalose. The intracellular trehalose content is considered a critical determinant of stress tolerance in yeast (Nishida et al., 2004). Trehalose is a nonreducing a-linked disaccharide commonly found in any hydrobiotic organisms. When phospholipid membranes are dried, the temperature at which the gel to hquid crystal phase transition occurs increases (Crowe et al., 1984). It has been shown that trehalose interacts with model membranes during drying and lowers the dry membrane phase transition temperature (Crowe et al., 1986). 

Sun, W.Q., Irving, T.C., and Leopold, A.C., The role of sugar, vitrification and membrane phase transition in seed desiccation tolerance. Physiol. Plant, 90,621,1994. 

Electroformed GUVs have proved to be a unique system for visualizing the effects of lipid membrane phase transitions on a dosed single bilayer. In addition, DMPC GUVs have been used in studies of interdigitated phase formation, induced by ethanol and temperature variations [22]. 

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