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  • 1
    Electronic Resource
    Electronic Resource
    Dextran functionalized by 4-nitrophenyl carbonate groups. Aminolysis reactions (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 123-130 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Dextran wurde mit 4-Nitrophenylchloroformat und Pyridin als Katalysator umgesetzt. Die Struktur der modifizierten Dextrane wurde mittels IR-, 1H- und 13C-NMR-Spektroskopie bestimmt. Unter den gewählten Reaktionsbedingungen entstehen nur acyclische Carbonate. Vorversuche zeigten, daß die Reaktion der 4-Nitrophenyl-chloroformat-Gruppen mit verschiedenen Amin-Modellverbindungen stark von der Basizität des Amins abhängt. Die Anbindung der Modellamine Phenethylamin und Tyramin an das modifizierte Dextran war befriedigend. Die Dextran-Phenethylamin-und Dextran-Tyramin-Verbindungen sind gegen heterogene Hydrolyse bei 37°C (pH 9 und pH 1) weitgehend beständig.
    Notes: The modification reaction of dextran with 4-nitrophenyl chloroformate using pyridine as catalyst was studied. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analysis. Under the used experimental conditions only acyclic carbonate groups have been detected. Preliminary experiments have shown that the reaction of 4-nitrophenyl carbonate groups with several model amines is greatly dependent on the basic character of the amine. Model amino-type drugs (phenethylamine and tyramine) were satisfactorily bound to activated dextran with 4-nitrophenyl carbonate groups. The heterogeneous hydrolysis of dextran-phenethylamine or dextran-tyramine adducts showed that no significant hydrolysis takes place under the applied conditions (pH 1 and pH 9, 37°C).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052250111
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  • 2
    Electronic Resource
    Electronic Resource
    Model for colloidal fouling of membranes (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 368-376 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A proposed theoretical model describes colloids deposition on a membrane surface accounting for surface interactions. A mass-transfer equation links the deposition rate to hydrodynamic conditions (permeation and tangential flow through a boundary layer thickness, δ) and to physicochemical properties of the suspension (diffusion, D, and potential barrier between particles, VB). This equation predicts the existence of a critical flux, Jcrit, for ultrafiltration, reverse osmosis, or microfiltration of large-size colloids as: \documentclass{article}\pagestyle{empty}\begin{document}$$ J_{crit} = \frac{D}{\delta}ln \left({\frac{{V_B}}{\delta}} \right) $$\end{document} Some of the trends observed when processing protein solutions are explained by this model. Previous experimental data for various colloids or our data with a clay suspension in the presence of electrolytes are also compared to predictions of our model. It explains the “flux anomaly” for particle sizes between 10 nm and 1 μm.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410218
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  • 3
    Electronic Resource
    Electronic Resource
    CVD of Covalent Compounds and high-Tc superconductors (1995)
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 111-119 
    Details
    ISSN: 0935-9648
    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
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19950070203
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  • 4
    Electronic Resource
    Electronic Resource
    A new class of network-polymeric chiral stationary phases (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 248-256 
    Details
    ISSN: 0899-0042
    Keywords: chiral discrimination ; chiral stationary phase ; network polymer ; DATD ; hydrogen bonding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A strategy based on the use of homo bi- and multifunctional building blocks for the synthesis of a new class of network-polymeric chiral stationary phases has been evaluated. The key steps comprise acylation of N,N′-diallyl-L-tartardiamide (DATD) and reaction with a multifunctional hydrosilane, yielding a network polymer incorporating the bifunctional C2-symmetric chiral selector. Covalent bonding to a functionalized silica takes place during the latter process. Many of these chiral sorbents show interesting enantioselective properties toward a wide variety of racemic solutes under normal-phase (hexane-based) conditions. The retention is mainly caused by the hydrogen-bonding ability of the analyte, which is regulated by mobile phase additives like alcohol or ether cosolvents. The most interesting chiral stationary phases, in terms of broad enantioselectivity, were obtained from O,O′-diaryol-DATD-derivatives, particularly those containing the 3,5-dimethylbenzoyl and the 4-(tert-butyl)benzoyl moieties. Since high column efficiencies can be obtained with these chiral sorbents, an α-value of ca. 1.2 is usually sufficient to produce baseline separation. A large number of neutral as well as acidic or basic drug racemates are resolved without derivatization. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070411
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  • 5
    Electronic Resource
    Electronic Resource
    Enhancement and inhibition of luminol chemiluminescence by phenolic acids (1995)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 10 (1995), S. 175-184 
    Details
    ISSN: 0884-3996
    Keywords: Luminol ; enhanced chemiluminescence ; phenolic acid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: We explored the behaviour of a series of phenolic acids used as enhancers or inhibitors of luminol chemiluminescence by three different methods to determine if behaviour was associated with phenolic acid structure and redox character. All the phenolic acids inhibited chemiluminescence when hexacyanoferrate(III) was reacted with the phenolic acids before adding luminol. The redox character of these compounds was clearly related to structure. When hexacyanoferrate(III)-luminol-O2 chemiluminescence was initiated by phenolic acid-luminol mixtures some phenolic acids behaved as enhancers of chemiluminescence, and others as inhibitors. We propose a mechanism to explain these findings. We found direct relationships between the redox character of the phenolic acids and the enhancement or inhibition of the chemiluminescence of the luminol-H2O2-peroxidase system and we propose mechanism to explain these phenomena.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bio.1170100306
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of the conformational domains of bradykinin by computational methods (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 1 (1995), S. 227-235 
    Details
    ISSN: 1075-2617
    Keywords: Bradykinin ; conformational domains ; conformational search ; molecular mechanics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The AMBER 4.0 force field was used to perform a characterization of the conformational profile of the nonapeptide bradykinin. A thorough conformational search was carried out using molecular dynamics as sampling technique, by computing cycles of high (900 K) and low (300 K) temperature trajectories. A total of 2400 minima were generated and subsequently clustered using the root-mean-square of the backbone dihedral angles as criterium. After the use of a tolerance value of 20deg;, the conformations were clustered in 233 unique conformations with energies up to 40 kcal/mol above the lowest minimum. The analysis of the low-energy conformations indicate that the peptide exhibits a high tendency to adopt a β-turn at the C-terminus and a propensity to adopt a bent structure at the N-terminus. These results are in agreement with the experimental evidence reported in the literature and provide detailed information necessary to understand the conformational preferences of the peptide.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/psc.310010403
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  • 7
    Electronic Resource
    Electronic Resource
    Assay of cholinesterase using a proenhancer of the luminol-H2O2-horseradish peroxidase reaction (1995)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 10 (1995), S. 285-289 
    Details
    ISSN: 0884-3996
    Keywords: Cholinesterase ; luminol ; pro-enhancer ; chemiluminescence ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: 2-Naphthyl acetate acts as a pro-enhancer of the luminol-H2O2-horseradish peroxidase reaction. Cholinesterase hydrolyses the bound acetyl group and produces 2-naphthol, and this compound is an enhancer of the chemiluminescent reaction. We studied the kinetics of chemiluminescent emission and the influence of 2-naphthyl acetate and cholinesterase enzyme concentration. The cholinesterase concentration versus chemiluminescence intensity maximum was linear for cholinesterase between 0 and 181 μU/mL, with a detection limit of 8 μU/mL and a relative standard deviation of 9.5% (n = 3), for a sample containing 90.67 μU/mL of cholinesterase.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bio.1170100505
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  • 8
    Electronic Resource
    Electronic Resource
    Nanofoam porosity by infrared spectroscopy (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 253-257 
    Details
    ISSN: 0887-6266
    Keywords: porosity ; nanofoams ; polyimide ; voids ; infrared spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectroscopy has been used to determine the porosity of polymer nanofoams produced from block copolymers of an aromatic polyimide with either poly(propylene oxide) or poly(α-methyl styrene). It is shown that, with an independent measurement of the film thickness, both the absorption bands and the interference fringes can yield an accurate measure of the void content. The results obtained are in quantitative agreement with density gradient methods. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090330210
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  • 9
    Electronic Resource
    Electronic Resource
    Positron annihilation lifetime study of vapor sorption in polypropylene and polytetrafluoroethylene (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 779-791 
    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: Positron annihilation lifetime (PAL) spectra were measured for two different kinds of polymers: polypropylene (PP) and polytetrafluoroethylene (PTFE), during sorption of vapors of the following molecules: n-hexane, cyclohexane, benzene, methyl methacrylate, acrylic acid, and water. The behavior of ortho-positronium (o-Ps) annihilation parameters: lifetime, τ3, and intensity, I3, can be explained by considering different sorption mechanisms in rubbery and glassy polymers. The mean size of the intermolecular-space holes and the relative free-volume fraction of PP and PTFE were estimated before and during the sorption process from the o-Ps parameters obtained. Sorption of n-hexane, cyclohexane, and benzene in both polymers affect the o-Ps component in a systematic way, for PP τ3 and I3 tend to decrease, while in PTFE, τ3 stay almost constant and I3 diminishes. These effects are interpreted in relation to the different states of the polymers studied: rubbery for PP and glassy for PTFE. In case of methyl methacrylate molecules, the behavior of o-Ps parameters was more complicated. For acrylic acid and water, their associated polarity provokes a diminution in I3, which is explained from the viewpoint of the spur model of positronium formation. Large changes in the mean size and the fraction of free volume, as well as their constant behavior in some cases, were interpreted to be due to positive or negative interactions, respectively, between vapor molecules and PP and PTFE, which could be correlated with the solvent-interaction parameters calculated. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070560703
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  • 10
    Electronic Resource
    Electronic Resource
    Graft copolymerization of dimethylacrylamide onto AFLAS (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 279-281 
    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 method of irradiation grafting of DMAA onto AFLAS (alternating copolymer of tetrafluoroethylene and propylene) films was studied. The effect of the solvent on the grafting yield was determined. As a result, it might be important to evaluate the blood compatibility of the films already grafted by using an in vitro test. Benzene tests seem to be the most adequate for copolymerization. Grafting yield was better in the monomer 40-60% concentration range. The degree of grafting increases proportionally to does rate in gamma ray radiation. The graft copolymerization is terminated via unimolecular mechanism. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070550210
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