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  • 1
    Electronic Resource
    Electronic Resource
    The journal of membrane biology 90 (1986), S. 157-161 
    ISSN: 1432-1424
    Keywords: phase transition ; phospholipids ; alcohols ; anesthetics ; regular solution theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effect of 1-alkanols upon the main phase-transition temperature of phospholipid vesicle membranes between gel and liquid-crystalline phases was not a simple monotonic function of alkanol concentration. For instance, 1-decanol decreased the transition temperature at low concentrations, but increased it at high concentrations, displaying a minimal temperature. This concentration-induced biphasic effect cannot be explained by the van't Hoff model on the effect of impurities upon the freezing point. To explain this nonlinear response, a theory is presented which treats the effect of 1-alkanols (or any additives) on the transition temperature of phospholipid membranes in a three-component mixture. By fitting the experimental data to the theory, the enthalpy of the phase transition ΔH * and the interaction energy, ɛ AB * between the additive and phospholipid molecules may be estimated. The theory predicts that when ɛ AB * 〉2 (where ɛ AB * = ɛAB,/RT o,T o being the transition temperature of phospholipid), both maximum and maximum transition temperatures should exist. When ɛ AB * = 2, only one inflection point exists. When ɛ AB * 〈 2, neither maximum nor minimum exists. The alkanol concentration at which the transition temperature is minimum (X min) depends on the ɛ AB * value: the larger the ɛ AB * values, the smaller theX min. When ɛ AB * is large enough,X min values become so small that the plot ΔT vs.X shows positive ΔT in almost all alkanol concentrations. The interaction energy between 1-alkanols and phospholipid molecules increased with the increase in the carbon chain-length of 1-alkanols. In the case of the dipalmitcylphosphatidylcholine vesicle membrane, the carbon chain-length of 1-alkanols that caused predominantly positive ΔT was about 12.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 13 (1981), S. 913-923 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cell membranes consist of lipid bilayers in which proteins are embedded. Many cell functions are carried out at the cell boundary which interface with water. Here we describe the response to an anesthetic of a lipid bilayer and of an enzyme separately. While both systems are markedly affected by anesthetics at appropriately high concentrations, the result at the clinical concentrations seems best explained as principally an effect on the protein somewhat accentuated by its presence in the lipid bilayer. Thus the lipoprotein complex seems to have the properties of the protein alone, except with somewhat greater induced sensitivity due to the lipid matrix in which it is immersed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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