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  • Polymer and Materials Science  (30)
  • liposomes  (2)
  • 1985-1989  (27)
  • 1960-1964  (5)
  • 1920-1924
  • 1
    Electronic Resource
    Electronic Resource
    Phospholipase C and the physical states of polar head groups of lipids (1987)
    Springer
    The journal of membrane biology 96 (1987), S. 187-191 
    Details
    ISSN: 1432-1424
    Keywords: phospholipase C ; liposomes ; fluorescence study ; local dielectric property ; rotational freedom
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Activity of phospholipase C fromClostridium perfringens on liposomes made fromsn-3-phosphatidylcholine, dimyristoyl (DMPC), dipalmitoyl (DPPC) or distearoyl (DSPC) was measured at various temperatures and was correlated with their gel/liquid-crystalline phase transitions (T c : 23, 41.5, 52°C for DMPC, DPPC, DSPC, respectively). In all cases, the activity of phospholipase C was high in the gel phases of the substrates and was almost zero in their liquid-crystalline phases. Fluorescence depolarization measurements of N-dansyl-sn-3-phosphatidylethanolamine (DPE) and 1,6-diphenyl-1,3,5-hexatriene (DPH) incorporated into the liposomes showed that both the head group and the alkyl chains of the lipids were immobilized in the gel phases but were highly mobile in the liquid-crystalline phase. These results indicate that the rotational mobility of lipids (both of the head groups and the alkyl chains) was not a major factor in the phospholipase C reaction. It is inferred that some electrostatic and/or hydrophobic interactions might play important roles in regulation of the phospholipase C activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869244
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  • 2
    Electronic Resource
    Electronic Resource
    Local dielectric properties around polar region of lipid bilayer membranes (1985)
    Springer
    The journal of membrane biology 85 (1985), S. 225-231 
    Details
    ISSN: 1432-1424
    Keywords: dielectric constant ; fluorescence study ; liposomes ; calcium effect ; phase transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Local dielectric constant was evaluated from the Stokes shifts of fluorescence spectra ofl-α-dansylphosphatidylethanolamine (DPE) incorporated into liposomes made of synthetic phosphatidylcholine (dipalmitoyl or distearoyl) or bovine brain phosphatidylserine. The evaluation was established as follows. First, the Stokes shift of DPE was assured to follow Mataga-Lippert's equation and was a function of the dielectric constant and the refractive index in some standard organic solvents. Second, the change of the refractive index did not contribute much to the change in the Stokes shift. Third, the time resolved fluorescence depolarization of DPE in liposomes showed that the cone wobbling diffusion was rapid relative to the fluorescence lifetime and therefore that the dielectric relaxation did not affect the evaluation of the constant in the polar region of membranes. We then investigated the characteristics of the local dielectric constant in the polar region of the lipid bilayer and found that the dielectric constant varies between 4 and 34 depending upon calcium binding and also gel/liquid-crystal phase transition. Such large changes of the local dielectric constant were further correlated with the dynamic structure of lipid bilayer membranes measured by conventional fluorescence depolarization techniques. The large changes of dielectric constant around the polar region suggest that electrostatic interactions at this region can be altered 10-fold by such ionic or thermotropic factors and therefore that local dielectric properties can play crucial roles in membrane functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871517
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  • 3
    Electronic Resource
    Electronic Resource
    Ca2+ binding cyclic octapeptides having an alternating sar and a hydrophobic amino acid in the sequence (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1235-1246 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclic octapeptides having alternating Sar and hydrophobic amino acid sequences, such as cyclo[Lys(Z)-Sar-Leu-Sar-Leu-Sar-Leu-Sar] (C8KL), cyclo[Glu(OMe)-Sar-Lys(Z)-Sar-Leu-Sar-Leu-Sar] (C8KE), and cyclo[Lys(Suc)-Sar-Leu-Sar-Leu-Sar-Leu-Sar][C8K(Suc)L, Suc represents succinic acid], were synthesized. These cyclic octapeptides formed a complex selectively with Ca2+. Upon complexation, trans peptide bonds of Sar residues were isomerized to cis peptide bonds. C8KL and C8KE showed very similar characteristics of Ca2+ binding, extraction of Ca2- from an aqueous solution to a chloroform solution, and Ca2+ transport through a liquid chloroform membrane. C8KL transported Ca2+ across the lipid bilayer membrane above the phase-transition temperature, while C8KE and C8K(Suc)L did not. Therefore, the transport of Ca2+ through the lipid bilayer membrane is very sensitive to the hydrophobicity of the carrier molecule.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280705
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  • 4
    Electronic Resource
    Electronic Resource
    Reactivity of N-alkylated cyclic iminoether salts having vinyl groups, 2Part 1: cf.9. Polymerization and copolymerization of 2-isopropenyl-3-methyl-2-oxazolinium salts (1986)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 1807-1817 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 3-Methyl-2-isopropenyl-2-oxazolinium salts (4a, b) were prepared by alkylation of 2-isopropenyl-2-oxazoline (2). Their preparation is much easier than that of their vinyl analogues, 3-methyl-2-vinyl-2-oxazolinium salts, which cannot be isolated due to their high tendency to polymerization. 4a, however, was found, to show a low tendency toward radical and anionic polymerization, but it can be smoothly radically copolymerized with some vinyl monomers. The copolymerization parameters of 4a were determined and discussed in comparison with those of 2.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1986.021870801
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  • 5
    Electronic Resource
    Electronic Resource
    13C NMR study of O-(2-hydroxypropyl)cellulose (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 61-70 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The proton-decoupled signal of methyl carbons of O-(2-hydroxypropyl)cellulose (HPC) (1b, m ≥ 1) was found to be split into two peaks. The results of experiments on lanthanide shift and the dependence of the relative intensities of both peaks on the molecular weight of poly(oxypropylene) [poly(propylene oxide)] (PPO) indicated that the low-field peak results from the terminal hydroxypropyl groups and the high-field peak from the inside oxypropylene units. From the ratio between the intensities of the two peaks and the molar substitution (MS) (average number of oxypropylene units per anhydroglucose (AHG) unit), the degree of substitution (DS) (average number of hydroxyl groups substituted per AHG unit) was calculated. This new method could be applied to samples of low-MS to which the conventional method based on the 1H NMR technique alone was inapplicable. From the analysis of 13C NMR spectra of HPC samples differing in MS, an authentic structural picuture of the HPC molecule could be proposed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021860107
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  • 6
    Electronic Resource
    Electronic Resource
    Characteristics of rectifying devices with thin films of polyphthalocyanine (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 2693-2701 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chemically and thermally stable thin films of polyphthalocyanine were prepared by a simple evaporation-polymerization method. The rectifying characteristics of metal/semiconductor/metal (MSM) type sandwich devices with the film were studied. A Schottky type device metal (Cu, Al, Ti)/polyphthalocyanine/Cu shows reproducible rectifying characteristics when Ti is selected as a counter electrode. The reproducibility is improved by pre-oxidation treatment of the surface of Cu substrate. Best electric parameters for the device are as follows: rectifying ratio = 14; threshold potential difference = 0,61 V; saturation current = 2,5 · 10-6 A · cm-2; barrier height = 0,75 eV; diode ideality parameter = 4,23. Doping of five kinds of quinones [p-benzoquinone (p-BQ), tetrabromo-p-benzoquinone (p-TBBQ) tetrachloro-p-benzoquinone (p-TCBQ) tetrachloro-o-benzoquinone (o-TCBQ) 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ)] and 2,5-cyclohexadien-1,4-diylidenedimalodinitrile (TNCR) in thin films of polyphthalocyanine affected electrocharacteristics in some cases. The diode ideality parameter decreases to 2,17 at 0,90 · 10-6 mol · cm-1 of p-TBBQ, and the rectifying ratio increases to about fourteen times by doping p-TBBQ and p-TCBQ. The doped device shows a rectifying response up to 1 kHz.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021901103
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  • 7
    Electronic Resource
    Electronic Resource
    Iodine-poly(vinyl alcohol) interactions, 2Part 1: cf.6. Anomalous slow quenching of the chromophore after extraction of free iodine with carbon tetrachloride (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 549-557 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An equilibrium blue colored solution containing poly(vinyl alcohol) (PVA)-iodine-boric acid was prepared at 5°C. With increasing PVA concentration, at the same concentration of iodine, the absorption band of the chromophore I5- (λmax = 650 nm, band D) linearly increased and the intensities of the bands for both I- (λmax = 226 nm, band A) and I3- (λmax = 290 nm, band B) decreased. The band due to another iodide species (λmax = 355 nm, band C), tentatively assigned to I3- · I2, remained unchanged. Three solutions with different PVA concentration were then extracted with the same volume of carbon tetrachloride to remove I2 present in the system. It was found that the chomophore due to I5- gradually decays with repeated extractions. After one extraction the change of the absorbance of I5- with time was measured at 5°C. In the system with a high PVA concentration the chromophore recovers the equilibrium within three days without losing much intensity, while in the systems with lower PVA concentration recovering of equilibrium takes more than four days with a considerable loss of chromophore. In the latter case, free I2 extracted is supplied by the decomposition of polyiodide ions to I-. Analysis of the rate of re-equilibration of iodine species revealed two reaction processes: one is a reaction involving free iodine species in an aqueous environment and the other is a slow reaction involving the polyiodide ions bound in a PVA cage.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021860310
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  • 8
    Electronic Resource
    Electronic Resource
    Iodine-poly(vinyl alcohol) interactions, 4Part 3: cf.20.. Stoichiometry of iodine/iodide in the polyiodide ion bound in the cage of poly(vinyl alcohol) (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 939-950 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Aqueous poly(vinyl alcohol) (PVA)-iodine-boric acid solution was treated with anion exchange resin and the system involving only the cage complex was isolated. The system was then extracted with carbon tetrachloride, and I2 and I-, which were released from the complex, were separated and pooled in the carbon tetrachloride and the aqueous layers, respectively. From the absorption spectra of the layers the amounts of I2 and I- were determined. The ratio I2/I- was found to be approximately 2,0, which corresponds to the I2/I- stoichiometry in the complex. This result suggested that the major species bound in the PVA cage are pentaiodide ions, i.e., I5- with linear configuration and/or I2· I3- with distorted chain structure. Judging from the resonance Raman spectrum of the PVA-iodine solution that had been revealed before, it was concluded that the two absorption bands of the complex at λmax = 650 and 355 nm are ascribed to the I5- and I2 · I3- ions, respectively.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021900503
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of the order parameter in cholesteric liquid crystalline phase cellulose derivatives solutions by refractometry (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 33 (1987), S. 3019-3036 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The macroscopic order parameter S in the cholesteric liquid crystalline phase of hydroxypropyl cellulose (HPC) and ethyl cellulose (EC) solutions was calculated using refractive index data. Haller's extrapolation approach was used. The S calculated was compared with the S predicted from Doi's theory. The calculated values of S for HPC and EC solutions were in the range of 0.4-0.8 within our experimental range, and agreed with the predicted values of S obtained with Doi's theory. This result suggests that Haller's approach is valid for determining S for liquid crystalline solutions of HPC and EC, despite the scattering of the data at higher temperatures.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070330834
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of chemical structure on low-temperature modulus for UV-curable polybutadiene acrylates as an optical fiber coating material (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 1161-1171 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relationship between chemical structure and low-temperature modulus of ultraviolet(UV)-radiation-cured optical-fiber coating materials has been investigated. The coating materials are low-viscosity liquid compounds consisting of a 1,4-polybutadiene diacrylate oli-gomer, a monomer, and a photoinitiator. Dynamic mechanical test results show that low-temperature modulus and glass transition temperature (Tg) are affected by the monomer structure and monomer concentration in the coating material in cases where the same oligomer is used. With increasing alkyl group chain length of the alkylacrylate monomer, the Tg value is shifted to lower temperatures. Low-temperature modulus increases with increasing monomer concentration in the coating material. Low-temperature excess optical losses of coated fibers have been found to be closely related to low-temperature modulus of the coating.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080240606
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