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  • Polymer and Materials Science  (14)
  • Atomic, Molecular and Optical Physics  (2)
  • General Chemistry  (2)
  • Aldimines, unsaturated  (1)
  • Wiley-Blackwell  (19)
  • 1990-1994  (19)
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  • Wiley-Blackwell  (19)
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  • 1
    Digitale Medien
    Digitale Medien
    Enkephalin analogues containing β-naphthylalanine at the fourth position (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 179-196 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: To examine the importance of the aromatic side chains of enkephalin on opiate activity, we report the synthesis and conformational analysis of a series of analogues related to enkephalin with β-naphthylalanine in place of phenylalanine at the fourth position. Three linear analogues (Tyr-D-Ala-Gly-(L and D)-β Nal(1)-Leu-NH2 and Tyr-D-Ala-Gly-β Nal(2)-Leu-NH2) were initially synthesized to examine the effect of the substitution on biological activity. The increased activity of these peptides at the μ-opiate receptor, compared to native Leu-enkephalin, prompted us to examine the more conformational constrained analogues, Tr-c[D-A2bu-Gly-(L and D)-β Nal(1)-Leu], incorporating a α,γ-diaminobutyric acid at the second position and cyclization to the carboxylic end of the leucine. These two cyclic analogues provide insight into the necessity for the L chirality of the aromatic residue at position 4. The Tyr-c[D-A2bu-Gly-L-β Nal(1)-Leu] analogue is highly potent and displays a slight preference for the μ receptor. The conformational analysis indicates that despite the high flexibility of the tyrosine side chain, the aromatic rings of the tyrosine and naphthylalanine are relatively distant from each other. The presence of two intramolecular hydrogen bonds help maintain the conformation of the 14-membered backbone ring that keeps the side chains directed away from each other. These findings are in agreement with our model of an extended structure required for μ selectivity and a folded form with close aromatic ring placement for δ selectivity.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360290123
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  • 2
    Digitale Medien
    Digitale Medien
    Sur une tentative d'unification des théaories quantiques de la cancèrisation par les polyacènes: I. Thèorie des règions M, L, et B (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 461-486 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This study is a unified approach to quantum theories of polyacen carcinogenesis. Part I discusses the M, L, and B regions theory. Although the M region of polyacens is much less reactive than is the K region, the chemical reactivity of these two regions parallels each other. Consequently, the K-L Pullman's theory may be reformulated by replacing the K region by the M region. The M-L regions theory improves all the quantum structure-carcinogenic activity relationships obtained previously in the K-L framework. Moreover, it would appear that in these correlations, the most important role is played by nonconcerted electrophilic reactions. We suggest that the M-L modified Pullman's theory and the Bay (B) region theory, proposed by Jerina et al., are related to different steps of the metabolic activation mechanism leading to ultimate carcinogen: the first step for the Pullman's theory and the carbocation step for the theory of the Bay region. We have termed the “M, L and B regions theory” as this unified approach to the problem of polyacens carcinogenesis.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560380308
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  • 3
    Digitale Medien
    Digitale Medien
    Molecular-weight distributions in the thermally initiated emulsion polymerization of styrene (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 405-414 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In both thermal emulsion polymerization of styrene in the temperature range 60-80 °C, and peroxodisulfate-initiated polymerization at 60 °C, weight-average to number-average molecular-weight ratios (M̄w/M̄n) approach 1,5 when potassium octadecanoate is used as emulsifier. A low activation energy for thermal initiation (≈66,0 kJ/mol) was deduced which may indicate a catalytic effect of the emulsifier during the thermal initiation process. Participation of the emulsifier is probably attributed to a transfer of one of two monomer radicals, produced thermally, to the emulsifier, with subsequent desorption to the aqueous phase, leaving one radical in the polymerization locus.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1991.021920220
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  • 4
    Digitale Medien
    Digitale Medien
    Perfluorinated anion exchange membranes: Preparation and preliminary tests of dialysis (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1407-1412 
    Details
    ISSN: 0887-624X
    Schlagwort(e): radiochemical grafting ; anion exchange membrane ; acid dialysis ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Using the preirradiation technique a kinetic study of the grafting of the 4-vinyl pyridine (V4P) and an aliphatic ammonium monomer (ALAM) onto the copolymer film of ethylene-tetrafluoroethylene (ETFE) has been performed. The influence of dose, temperature, and concentration of monomer, reticular agent, and inhibitor were investigated. The results are discussed on the basis of the interactions between monomer diffusibility and viscosity of the medium. The characteristics of some membranes were determined. Their applicability to the recovery of acid by dialysis is demonstrated.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1992.080300720
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  • 5
    Digitale Medien
    Digitale Medien
    The electrical conductivity of cellulose HYPHAN® and its complexes (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 212 (1993), S. 13-18 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die elektrische Leitfähigkeit (σ) von Cellulose-HYPHAN® und seinen Komplexen mit Cr3+, Mn2+, Mo5+ und Hg2+ wurde im Temperaturbereich 25-510°C bestimmt. Die Aktivierungsenergie wurde aus der Abhängigkeit von log σ von der reziproken Temperatur berechnet. Die Ergebnisse zeigen, daß die Leitfähigkeit mit steigender Temperatur zunimmt und dabei zwei Maxima durchläuft. Das erste Maximum läßt sich dem Wassergehalt zuordnen, während das zweite mit dem thermischen Abbau der Cellulose-Kette zusammenhängt. Die Werte der Aktivierungsenergie lassen darauf schlieäen, daß sich beim Erhitzen die Halbleitereigenschaften der Komplexe verbessern.
    Notizen: The electrical conductivity, σ, of cellulose HYPHAN® and its complexes with Cr3+, Mn2+, Mo5+ or Hg2+ was measured from room temperature to 510°C. The activation energy, ΔE, of the samples was calculated from log σ against 1/T curves. The results show that the electrical conductivity increases by temperature with two maximum peaks. The first peak is attributed to the moisture content, while the second one is attributed to the thermal degradation of the cellulose chain. The values of the activation energy indicate that the samples change from low semiconductor to high semiconductor property with heating.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1993.052120102
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  • 6
    Digitale Medien
    Digitale Medien
    Conformational studies of stereoisomeric 14-membered cyclic enkephalin analogues containing 1-naphthyialanine at the fourth position: Chirality effect of leucine at the fifth position on biological activity and receptor selectivity (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 877-898 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In order to study structure-activity relationships of enkephalin-related analogues, we report the biological activity and conformational analysis of four 14-membered cyclic enkephalin analogues with β-(1-naphthyl)alanine in place of phenylalanine at the fourth position, Tyr-c[D-A2bu-Gly-(L and D)-βNal(1)-(L and D)-Leu]. The L-βNal(1)-containing analogues display higher activity at both the μ and δ receptors than the corresponding analogues with the L-Phe residue. In contrast to the linear enkephalins, the cyclic analogues with the D-βNal(1) residue are also active at the μ receptor since the relative spatial arrangement of functional groups required for biological activity is achieved by the constrained nature of the cyclic molecules. A comparison of the findings from the conformational analysis and biological assays establishes that relatively extended structures, in which the two aromatic side chains are oriented in opposite directions with a ∼ 14Å separation, is required for activity at the μ receptor. On the other hand, folded conformations with nearly parallel orientations and a close proximity ( 〈 10Å) of the aromatic rings of the Tyr and βNal(1) residues are required for activity at the δ receptor. It should be noted that the overall structures and thus the biological profiles of the 14-membered cyclic enkephalin analogues are strongly dependent on the conformation of the second residue. The folded conformations with parallel orientation of the two aromatic side chains of Tyr-c [D-A2bu-Gly-L-βNal (1)-D-Leu] is stabilized by an interaction between the Tyr phenolic OH proton and βNal(1) C*O groups. This analogue, which shows the highest activity at both the μ and δ receptors among the four stereoisomers studied, displays an increase of the fraction of the side-chain χ1 = t conformer for the βNal(1) residue. It is concluded that the incorporation of the D-Leu residue at the fifth position increases the relative fraction of the folded conformations with parallel orientation of the aromatic side chains, and hence enhances activity at the δ receptor as compared to the corresponding L-Leu containing analogue.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360310708
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  • 7
    Digitale Medien
    Digitale Medien
    Modifications of the amide bond and conformational constraints in pseudopeptide analogues (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1135-1148 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have investigated the conformational effects of modifying the amide group in model dipeptides. The N-methyl amide ψ[CO-NMe], N-hydroxy amide ψ[CO-N(OH)], N-amino amide ψ[ CO-N (NH2)], retro amide ψ[ NH-CO], reduced amide in the neutral ψ[CH2-NH] and protonated ψ[CH2-N + H2] state, and hydrazide ψ[CO-NH-NH] have been introduced as surrogates of the amide link in pseudopeptide derivatives of the Pro-Gly or Ala-Gly model dipeptides protected on both termini by an amide group. These compounds have been studied in solution by proton nmr and ir spectroscopy, and in the solid state by x-ray diffraction, giving an extended data set of experimental structural and conformational information on pseudopeptide sequences. The conformational effects depend both on the nature and the position of the modified amide link. Some modifications appear to have no intrinsic conformational induction (N-amino and retro amide), but destabilize any local folded structure by hydrogen-bond breaking. Because of the formation of strong intramolecular interactions, others are capable of stabilizing a β-turn (for example protonated reduced amide), or of inducing a particular local conformation such as a β- or γ-like turn (for example N-hydroxy amide). The particular geometry of the cis N-methyl amide and of the “hydrazino” proline favors the formation of a sharp turn of the main chain. All these structural data are of interest to the design of bioactive peptide mimics. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360330715
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  • 8
    Digitale Medien
    Digitale Medien
    Polymères porteurs de dérivés du glycérol, 10Partie 9: cf. ref.1. Fixation de l'acide naphtyl-1 acétique sur le poly(acide méthacrylique) (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 2947-2964 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Glycidyl (2,3-epoxypropyl) esters are convenient reagents for the fixation of carboxylic acid moieties on polymeric support of the polyacid type. This way of synthesis was applied to 1-naphthylacetic acid on poly(methacrylic acid). Esterification of 1-naphthylacetyl chloride by glycidol (2,3-epoxy-1-propanol) and addition of 1-naphthylacetic acid on epichlorohydrin (1-chloro-2,3-epoxypropane) with subsequent reformation of the oxirane ring have been used for the synthesis of the glycidyl ester but the reaction of the potassium salt of the acid with epichlorohydrin leads to a better yield. Addition of 1-naphthylacetic acid on glycidyl acetate was studied in N,N-dimethylformamide (DMF) and acetonitrile. The best results were obtained in DMF. The reaction is of first order with respect of epoxide, but 2nd order applies when the solvent is acetonitrile. The same reaction conditions as for glycidyl acetate were used for the chemical modification of poly(methacrylic acid) with glycidyl 1-naphthylacetate except that methanol was used as the solvent.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1994.021950822
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  • 9
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of an amphoteric ion-exchange membrane (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 705-713 
    Details
    ISSN: 0887-6266
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: An amphoteric ion-exchange membrane was prepared by chemical grafting of acrylic acid and dimethyl amino-2-ethyl methacrylate on ozonized polyethylene. The effects of the variation of external pH on the physicochemical properties of this membrane were studied (exchange capacity, electrical resistance, water and electrolyte content, and membrane potential). The determination of the mean activity coefficient of the NaCl in the membrane phase using the Donnan equilibrium equation reveals that this coefficient increases with the NaCl concentration in the external solution. Fundamental electrochemical properties of the amphoteric membrane are discussed on the basis of the variation of the membrane selectivity with the external electrolyte concentrations and the pH. The properties at neutral pH are accounted for by a mutual neutralization of some acidic and basic groups in the membrane phase.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/polb.1991.090290609
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  • 10
    Digitale Medien
    Digitale Medien
    Electrical degradation of polypropylene: A study by FTIR microspectroscopy (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 1121-1124 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1992.070460623
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