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'Lipid Bilayers' in keywords
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2001 (1)
1979 (2)
1Author    M. Ohga, F. M. Ostafa, A. Hmed, A. A. YoussefRequires cookie*
 Title    Dielectric Permittivity and AC Conductivity Investigation for the New Model Lipid Bilayer Material: (CH2)io(NH3)2CdCl4  
 Abstract    Differential thermal scanning of the new lipid-like bilayer material (CH2)io(NH3)2CdCl4 showed two structural phase transitions, with onset temperatures at T2 = (359 ± 2) K and 7, = (415± 1) K. Permittiv­ ity measurements were performed between room temperature and 450 K at 60-100 kHz. A step-like rise in permittivity at T2, associated with an order-disorder transition, is attributed to chain melting. Two anomalies at (413 ± 1) K and (430 ± 3) K, showing thermal hysteresis of -8 and 10 K, respectively, in­ dicate first order transitions which are associated with crystalline phase change. The AC conductivity follows an Arrhenius-type relation with the activation energy A£ varying with the frequency / according to the relation AE = A£0 [1 -exp where AE0,f0 and a are 0.95 eV, 52 Hz and 0.11, respectively. The frequency dependent conductivity follows the power law a= C 7dc + ßcov, with 0.3 <s < 1.5 for hopping conduction of hydrogen and/or chloride ions in the high temperature range, and localized hopping and/or orientational motion predominating temperatures lower than 413 K. Variations of B and s with temperature are discussed. PACS No. 76, 77 
  Reference    Z. Naturforsch. 56a, 568—578 (2001); received April 26 2001 
  Published    2001 
  Keywords    Phase Transitions, AC Dielectric Permittivity, Two-dimensional Materials, Lipid Bilayers 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0568.pdf 
 Identifier    ZNA-2001-56a-0568 
 Volume    56 
2Author    J. Luisetti, H. Möhwald, H. J. GallaRequires cookie*
 Title    Spectroscopic and Thermodynamic Studies of Chlorophyll Containing Monolayers and Vesicles Part II: Chlorophyll a and Pheophytin a Aggregation on DMPC Vesicles  
 Abstract    Absorption and fluorescence experiments on pheophytin and chlorophyll containing lipid bilayer vesicles are reported. Pheophytin aggregates on the vesicles are established from an additional red shifted band (at 695 nm) in the absorption spectrum. These aggregates contain pheophytin in an arrangement with the molecular planes of the porphyrin rings being parallel and cover about 10% of the vesicle surface. The lipid phase dissolves pheophytin up to a molar ratio of 15% above the lipid phase transition. This solubility limit decreases hardly on solidification of the lipid. For chlorophyll a containing vesicles the aggregates are not observed in the absorption spectrum. The chlorophyll solubility is about equal to that of pheophytin. This suggests that the phase separa­ tion indicated from fluorescence measurements at temperatures below the lipid phase transition does not lead to the formation of strongly bound chlorophyll aggregates. In tro d u c tio n 
  Reference    Z. Naturforsch. 34c, 406—413 (1979); received January 25 1979 
  Published    1979 
  Keywords    Lipid Bilayers, Chlorophyll, Phase Separation, Absorption Spectroscopy, Fluorescence Spectroscopy 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0406.pdf 
 Identifier    ZNC-1979-34c-0406 
 Volume    34 
3Author    R. Hosemann, J. Loboda-Čačković, H. Č. Ačković, S. F. Ernandez-Berm, F. J. Údez, Baltá-CallejaRequires cookie*
 Title    Structure of Cerebrosides. II. Small Angle X-Ray Diffraction Study of Cerasine  
 Abstract    Cerasine having a molecular weight of 800 differs chemically from phrenosine only in the hy­ droxyl group attached to the fatty acid tail which is replaced by a hydrogen atom. Nevertheless, remarkable differences between both cerebrosides are detected in the lamellae periodicities. In the range of 23 — 66 °C just one single (instead of two) structure with a sim ilar subcell to the triclinic one component of phrenosine is detected. Between 66 and 87 °C three new components (instead of one in phrenosine) appear. Two of the structures are sim ilar to the two phrenosine-components at low tem perature and the tilt angles of their chains with respect to the basal planes can explain the stabilizing capacity of the 201 and 301 netplanes o f the paraffin-like subcells respectively. These lattice planes are parallely aligned to the surfaces o f the lamellae. The long period of 58 A of component II cannot be explained in such a way. This period persits upto 105 °C and coexists from 87 °C with a new com ponent showing a 40 A -periodicity, which cannot either be explained in the above manner. Paracrystalline distortions of the arrangem ent of the bilayers can be justified by orientational disorder of the galactose heads. 
  Reference    Z. Naturforsch. 34c, 1121—1124 (1979); received July 6 1979 
  Published    1979 
  Keywords    Cerebrosides, Lipid Bilayers, X-Ray Diffraction, Long Period, Paracrystalline Distortions 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-1121.pdf 
 Identifier    ZNC-1979-34c-1121 
 Volume    34