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  • Video monitoring  (1)
  • phospholipid bilayer  (1)
  • statistical mechanics  (1)
  • 1
    ISSN: 1432-1424
    Keywords: phospholipid bilayer ; phase transition ; phase diagram ; phospholipid binary mixture ; pretransition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Miscibility among phospholipids with different lipid chain-lengths or with different head groups has attracted a number of research efforts because of its significance in biological membrane structure and function. The general consensus about the miscibility of phosphatidylcholines with varying lipid chainlengths appears to be that binary mixtures of phospholipids with a difference of two carbon atoms in the lipid chain mix well at the main phase transition. Miscibility between phosphatidylcholines with differences of four carbon atoms appears to be inconclusive. Previous reports on the phase transition of binary phospholipid mixtures are concerned mainly with multilamellar vesicles and are mostly limited to the main transition. In the present study, unilamellar vesicles were used and miscibility in binary systems between dimyristoyl-, dipalmitoyl- and distearoyl-phosphatidylcholines at pretransition, as well as main transition temperatures was evaluated by constructing phase diagrams. Two methods were used to monitor the phase transitions: differential scanning microcalorimetry and optical absorbance methods. The optical method has the advantage that unilamellar vesicles of dilute phospholipid concentrations can be used. The liquidus and solidus phase boundaries were determined by the onset temperature of heating and cooling scans, respectively, because the completion temperature of a phase transition has no meaning in binary solutions. Dimyristoyl- and distearoyl-phosphatidylcholines. where the difference in the, lipid chain-length is four carbon atoms, mixed well even at pretransition temperature.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1438-8359
    Keywords: Inhalation anesthetics ; Artemia salina ; Motility ; Video monitoring ; Cooperativity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The swimming movement of artemia salina in the artificial sea water was measured by using the video camera system in the absence and presence of anesthetics, i.e. enflurane, halothane, and isoflurane. The movement of artemia looked random at a glance but the obtained distribution curve for the swimming speed was skewed toward the high speed side somewhat resembling a Maxwellian distribution curve seen in the statistics of ideal gases. When anesthetic were added, the distribution curve became sharpened and shifted to the low speed side, which is similar to a behavior of ideal gasses when they are cooled down. The mean swimming-speed was decreased eventually leading to an irreversible death with increasing the anesthetic dose. The activity was analyzed by using the hydrodynamic equation. The ED50, which is a dose that causes a 50% reduction in the activity, of all anesthetics used in this study was quite similar to the MAC values for human. It was also suggested that an interaction between anesthetics and artemia was highly cooperative since the larger Hill coefficients were obtained for all three anesthetics used. (Takasaki T, Tatara T, Suezaki Y, et al.: Effect of inhalation anesthetics on swimming activity of artemia salina. J Anesth 5: 287–293, 1991)
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-8927
    Keywords: Fluid mixtures ; critical solution temperature ; high pressure ; excess volume ; miscibility ; phase diagram ; statistical mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A simple statistical mechanical theory is presented to explain phase diagrams of fluid mixtures with both a lower critical solution temperature and an upper critical solution temperature under pressure. By postulating a temperature dependence for the interaction free energy parameter of the constituent molecules and a pressure dependence for the excess volume, phase diagrams with both lower critical solution temperature, and upper critical solution temperature and their pressure dependence can be reproduced by quadratic surfaces in temperature-concentration-pressure space. The topological aspects of the observed phase diagrams in this space have been related to our theoretical model, and the thermodynamical meaning of the topologies has been interpreted based on our model. Experimental data for the mutual solubility of water and 2-butanol under pressure and that of water and 3-methylpyridine with added salts have been analyzed quantitatively and theoretical parameters are determined.
    Type of Medium: Electronic Resource
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