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'membranes' in keywords Facet   Publication Year 1975  [X]
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1Author    Hans GrulerRequires cookie*
 Title    Chemoelastic Effect of Membranes  
 Abstract    The elastic theory of a uniaxial membrane in an asymmetric environment predicts a spontaneous splay deformation. This spontaneous curvature of the membrane is discussed by the intrinsic splay of the membrane molecules (e. g. wedge shaped molecules) and their polar orientation. The chemoelastic effect is the polar orientation induced by the asymmetric environment in connection with the intrinsic splay. This effect is also discussed for polyelectrolytes where a small change of pH (~0.1) can lead to a spontaneous curvature of 104 cm-1. The actual shape of red blood cells can be explained by the spontaneous splay and a change in environment induces the change in shape of these cells. A model is proposed for two conical bodies swimming in a uniaxial membrane which interact with each other through elastic coupling. The force between the bodies can be either attractive or repulsive. As an example of this model clustering of proteins is discussed. 
  Reference    (Z. Naturforsch. 30c, 608—614 [1975]; received June 18 1975) 
  Published    1975 
  Keywords    Membrane, Elasticity, Erythrocyte, Enzyme Coupling 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0608.pdf 
 Identifier    ZNC-1975-30c-0608 
 Volume    30 
2Author    N. Puppala, S. S. BrodyRequires cookie*
 Title    Interactions between Retinal and Phospholipids in Monomolecular Films at Acid pH  
 Abstract    The surface properties of mixed monomolecular films of retinal and phospholipids (p. lipids) are measured as a function of mole fraction at a nitrogen-water interface. An acid pH of 6.0 is maintained in the aqueous phase. Before irradiation the surface potential A V for 9-cis retinal, 11-cis retinal, phosphatidyl serine (PS) and phosphatidyl ethanolamine (PE), at j t = 12 dyn/cm, are 490 mV, 645 mV, 548 mV and 375 mV, respectively. Before irradiation, A 0 for 9-cis and 11-ds are 58 Ä2 and 48 A2, respectively. Experimentally measured isotherms are compared with theo­ retically calculated isotherms. In case of mixed films of retinal and PS the experimental isotherms are greater than theoretical, while mixed films of retinal and PE are smaller than theoretical. A maximum value for the difference between theoretical and experimental areas are obtained at (retinal) / (p. lipid) = 0 .1 . Retinal and p. lipid do not appear to form a Schiff base, charge transfer or any other type of complex at pH 6. A eutectic type mixture between retinal and p. lipid may occur on the surface. A light induced change in A V of —130 mV is observed in the case of 11-cis and PE. The significance of these findings with respect to visual excitation is considered. 
  Reference    (Z. Naturforsch. 30c, 478—483 [1975]; received October 4 1973/October 21 1974) 
  Published    1975 
  Keywords    ) Vision, Retinal, Monolayers, Photobiology, Membranes 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0478.pdf 
 Identifier    ZNC-1975-30c-0478 
 Volume    30 
3Author    HansW. Ulrich, EltzienRequires cookie*
 Title    Lysolecithin Induced Membrane Alterations in Thymocytes Effects of Lysophosphatides Possessing A djuvant and Immuno-Suppressive Activities on Cell Agglutination by Concanavalin A  
 Abstract    The effects of lysolecithin and of 2 synthetic ether-desoxy lysolecithin analogs, containing alkyl residues of 16 or 12 carbon atoms, on the agglutination kinetics of calf and rabbit thymocytes by concanavalin A (Con A) were investigated. Unlike the natural lysolecithin, these synthetic analogs are resistant to metabolism by membrane associated enzymes. It was found that pretreat­ ment of thymocytes with lysolecithin or with the C16-analog leads to slightly increased agglutination rates. The C12-analog, in contrast, significantly inhibits thymocyte agglutination by Con A. More­ over, a comparison of these results with lysophosphatide effects on the agglutinability of erythro­ cytes of various species revealed that the inhibitory effect of the short-chain phosphatide is rather specific for thymocytes. The finding that long-and short-chain lysophosphatides, which have pre­ viously been shown to react as adjuvants or immunosuppressants, respectively, induce adserve alterations in thymocyte membranes indicates that these substances may affect the immune response by changing the membrane properties of immune competent cells. Concerning the nature of these membrane alterations it was shown that lysolecithin did not affect the number of Con A receptors per cell nor the affinity of lectin binding. It is therefore concluded that the lysophosphatide in­ duced alterations of Con A agglutinability can not be caused by an uncovering or covering of lectin-receptors. 
  Reference    (Z. Naturforsch. 30c, 785 [1975]; received June 30 1975) 
  Published    1975 
  Keywords    Thymocytes, Membranes, Lysolecithin, Concanavalin A, Agglutination 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0785.pdf 
 Identifier    ZNC-1975-30c-0785 
 Volume    30