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  • 1995-1999  (4,710)
  • 1985-1989
  • 1880-1889
  • 1995  (4,710)
  • Polymer and Materials Science  (4,710)
  • 101
    Electronic Resource
    Electronic Resource
    Synthesis and properties of fiber-grade poly(trimethylene terephthalate) (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 230 (1995), S. 179-187 
    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: Poly(trimethylenterephthalat) wurde durch Umesterung von Dimethylterephthalat und Polykondensation im halbtechnischen Maßstab hergestellt. Als Katalysator für beide Reaktionsschritte wurde Titantetrabutylat eingesetzt. Die erhaltenen Polymeren mit gewichtsmittleren Molekulargewichten von bis zu 70000 können aus der Schmelze versponnen werden und zeigen, im Gegensatz zu mit Titanverbindungen hergestelltem Poly(ethylenterephthalat), einen bemerkenswerten Weißheitsgrad. Die Mark-Houwink-Parameter in 1,1,2,2-Tetrachlorethan/Phenol-Lösung (1 : 1, w/w) wurden mit Kalibrierung durch statische Lichtstreuung bestimmt. Die MVI-Werte (235°C, 1,2 kg) lagen typischerweise zwischen 20 und 30 mL/10 min bei Polymeren mit einer gewichtsmittleren Molmasse von 50000-60000 g mol-1.
    Notes: Poly(trimethylene terephthalate) was synthesized on a semi-technical scale following the trans-esterification route. Ester exchange as well as polycondensation were catalyzed by titanium tetrabutylate. The polymer formed shows a remarkable degree of whiteness, contrary to poly(ethylene terephthalate) when synthesized with the aid of titanium compounds. Polymers having molar masses up to 70000 (weight average) were obtained suitable for melt spinning. The Mark-Houwink parameters for solutions in 1,1,2,2-tetrachloroethane/phenol (1 : 1, w/w) were determined using static light scattering as a calibration. The melt volume index (235°C, 1.2 kg) was typically in the range 20-30 mL/10 min for a polymer having a weight-average molar mass of 50000-60000 g mol-1.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052300113
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  • 102
    Electronic Resource
    Electronic Resource
    Effect of substitution of monoester by diester on titanium-magnesium catalyst properties in propene polymerization (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 61-67 
    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: Mit dem Monoester Ethylbenzoat als internem Elektronendonor komplexierte Titan-Magnesium-Katalysatoren (TMC) können mit TiCl4 und Dibutylphthalat zum Diester-Komplex umgesetzt werden. Aktivität und Stereospezifität der direkt mit dem Diester hergestellten und der modifizierten TMC sind bei der Polymerisation von Propylen annähernd gleich. Die Oberfläche und Porenstruktur beider TMC-Typen und deren Zusammenhang mit der jeweiligen Katalysatoraktivität wurde untersucht.
    Notes: Titanium-magnesium catalysts (TMC), containing monoester (ethyl benzoate) as internal donor, can be transferred to the diester TMC by the treatment with TiCl4 and dibutyl phthalate. The activity and the stereospecificity of the transferred TMC in propylene polymerization are close to those of TMC prepared directly in the presence of diester. The surface area and the porous structure of both types of TMC were studied and the correlation with the activity of these catalysts is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052310106
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  • 103
    Electronic Resource
    Electronic Resource
    Photopolymerization of styrene and methyl methacrylate using macro photoinitiators. Synthesis and characterization of PS-PEG-PS or PMMA-PEG-PMMA block copolymers (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 123-133 
    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: Makrophotoinitiatoren aus Poly(ethylenglykol) (PEG) mit Benzoylxanthat-Segmenten wurden durch Reaktion der PEG-Xanthate mit Benzoylchlorid hergestellt. Diese Makrophotoinitiatoren mit PEGs unterschiedlicher Molekulargewichte wurden eingesetzt, um durch lichtinduzierte radikalische Polymerisation von Styrol und Methyl-methacrylat Blockcopolymere mit inneren PEG-Segmenten zu synthetisieren. Der Ein-fluß der Konzentration der Reaktanden und der Polymerisationszeit auf die Ausbeute und die Viskosität der Blockcopolymeren wurde untersucht. Die Blockcopolymeren wurden durch fraktionierte Fällung und IR-, UV- und 1H-NMR-Spektroskopie charakterisiert.
    Notes: Macro photoinitiators based on poly(ethylene glycol)s (PEG) bearing benzoyl xanthate moieties were synthesized by the reaction of PEG xanthates with benzoyl chloride. These macro photoinitiators possessing PEGs of different molecular weights were used in the photoinduced radical polymerization of styrene (S) and methyl methacrylate (MMA) to yield block copolymers having an inner-PEG segment. The influence of the concentration of reactants and polymerization time on the yield and intrinsic viscosities of block copolymers were also investigated. Characterization of block copolymers was carried out by fractional precipitation and IR, UV and 1H NMR spectroscopic methods.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052310111
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  • 104
    Electronic Resource
    Electronic Resource
    Preparation and characterization of polymer dispersed liquid crystal films using photosensitive polymers (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 109-121 
    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: Die Flüssigkristalle 4-Butyl-N-(4-methoxybenzyliden)anilin (MBBA) und 4-Butyl-N-(4-ethoxybenzyliden)anilin (EBBA) wurden synthetisiert. Die hydrophilen Monomeren 2-Hydroxyethylmethacrylat (HEMA) und Acrylsäure (Aa) wurden eingesetzt, um die polymere Matrix für Flüssigkristalle zu bilden, die dispergieren und einen Polymer-Flüssigkristall-Film (PDLC) bilden, Um solche PDLC-Filme herzustellen, wurden MBBA, EBBA oder die kommerziellen Flüssigkristalle ZLI-2444, 2452, 2459 und BDH-E7 mit HEMA, Aa und photoempfindlichen Stoffen gemischt und mit UV-Licht bestrahlt. Das elektrooptische Verhalten und die Mikrostruktur der PDLC-Filme wurden mit einem He-Ne-Laser bzw. mit der Rasterelektronenmikroskopie (SEM) untersucht. Die Effekte der UV-Bestrahlung und des Monomerverhältnisses auf das Verhalten der PDLC-Filme wurden ebenso untersucht wie die Reproduzierbarkeit und die Speicherstabilität der Filme.
    Notes: 4-Butyl-N-(4-methoxybenzylidene)aniline (MBBA) and 4-butyl-N-(4-ethoxybenzylidene)aniline (EBBA) liquid crystals were synthesized. To investigate the applications of hydrophilic monomers and polymers on the field of polymer dispersed liquid crystal (PDLC) films, 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (Aa) were selected as monomers for the polymer matrix. To prepare the PDLC films, MBBA, EBBA, and commercial liquid crystals ZLI-2444, 2452, 2459 and BDH-E7 were mixed with HEMA, Aa and photosensitive materials and then irradiated by UV light. The electrooptical behavior and the microstructure of the PDLC films were investigated by He-Ne laser and scanning electron microscopy (SEM), respectively. The effects of UV-light irradiation and monomer ratio on the electrooptical behavior of PDLC films, and the reproducibility and storage stability of the PDLC films were investigated.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052310110
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  • 105
    Electronic Resource
    Electronic Resource
    Investigation of primers reducing the pink-ring formation in multilayer printed circuit boards (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 91-108 
    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: Mit einem schnellen und einfachen Vorversuch wurde die Fähigkeit von unterschiedlich zusammengesetzten Grundierungen zur Reduzierung der “pink-ring”-Defekte in mehrschichtigen gedruckten Leiterplatten untersucht. Mischungen von Silanen mit multifunktionellen Silanol-Gruppen (Vernetzer) und 3-Glycidoxypropyl-trimethoxysilan (Silan A) oder N-(2-Aminoethyl)-3-aminopropyl-trimethoxysilan (Silan B) erwiesen sich als wirksam zur Reduzierung der “pink-rings”. Die Mischungen von Silan A mit aromatischen Vernetzern zeigten bessere Ergebnisse als andere Grundierungsformulierungen, was teilweise dem geringeren Anteil an hydrophilen Gruppen und der besseren Verteilung in den Filmen zugeschrieben wurde. Die besten Resultate wurden mit einer Grundierung mit Siloxan-Verbindungen erhalten. On-line Untersuchungen bestätigten die Ergebnisse der Vorversuche und demonstrierten die Durchführbarkeit des entwickelten Vortests zur Bewertung der Wirkung der Grundierungen. FT-IR-Spek-troskopie und Thermogravimetrie-untersuchungen zeigten, daß die auf die Kupfero-xide aufgebrachten Grundierungen sowohl die Vernetzungsreaktion fördern als auch die thermooxidative Stabilität der Epoxy/CuO-Systeme verbessern.
    Notes: A rapid and easy screening test was applied to assess the capability of various formulated primers to reduce the defect of pink rings in multilayer printed circuit boards. The mixtures of silanes with multifunctional silanol groups (crosslinkers) and 3-glycidoxypropyl-trimethoxysilaneSystematic name: 3-(2,3-Epoxypropoxy)propyl-trimethoxysilane. (referred to as silane C) or N-(2-aminoethyl)-3-aminopropyl-trimethoxysilaneSystematic name: 3-[N-2-aminoethyl]aminopropyl-trimethoxysilane. (silane B) were proved to be effective in reducing the pink rings. The performance of the mixed silanes using silane A and crosslinkers with aromatic groups were better than other formulated primers which was partly attributed to less amounts of hydrophilic groups and better integrity in the primer films. A developed primer consisting of siloxane compounds had the best performance. The online test confirmed the results from the screening test and demonstrated the feasibility of the designed screening test in assessing the performance of primers. The results of FTIR spectroscopy and thermogravimetric analyses confirmed that the effective primers coated on the copper oxides could improve the curing reaction and the thermal oxidative stability of the epoxy/CuO system.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052310109
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  • 106
    Electronic Resource
    Electronic Resource
    Differentialkalorimetrische untersuchungen an chloriertem polyethylen und chloriertem polyvinylchlorid (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 161-169 
    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: In the amorphous region (chlorine ≥ 30 wt.-%), chlorinated polyethylene (PE-C) which was prepared by chlorination in solution shows a continuous rise of the glass temperature Tg with increasing chlorine content. This Tg-percent chlorine function was compared with the Tg-percent chlorine function of PVC-C. It could be shown that the Δcp data as a function of the chlorine content measured at Tg has a maximum at 50 wt.-% chlorine in the case of PE-C and at 60 wt.-% chlorine in the case of PVC-C.
    Notes: Durch Chlorieren in Lösung hergestelltes Polyethylen (PE-C) zeigt im amorphen Bereich (Chlorgehalt ≥ 30 Gew.-%) eine kontinuierliche Erhöhung der Glastemperatur Tg mit steigendem Chlorgehalt. Diese Tg-Chlorgehalt-Funktion wurde verglichen mit der Tg-Chlorgehalt-Funktion des PVC-C. Es wurde festgestellt, daß die Δcp-Werte, gemessen bei Tg, in Abhängigkeit vom Chlorgehalt ein Maximum aufweisen, und zwar bei 50 Gew.-% Chlor für PE-C und bei 60 Gew.-% Chlor für PVC-C.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052310114
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  • 107
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    Announcements (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 213-213 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052310118
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  • 108
    Electronic Resource
    Electronic Resource
    Mitteilungen/Announcements (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 230 (1995), S. 205-205 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052300115
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  • 109
    Electronic Resource
    Electronic Resource
    Sulfonated polyurethane ionomers in solution (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 25-33 
    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: Die Viskosität verdünnter Lösungen in Wasser oder DMF von Polyurethan-Ionomeren mit Natriumsulfopropylgruppen an den Urethan-Stickstoffatomen wurde untersucht. Bei Temperaturen zwischen 25 und 60°C zeigte sich ein Polyelektrolyteffekt, der auch nach Zugabe von Natriumchlorid erhalten blieb. Dies läßt sich durch Coulombsche Wechselwirkungen zwischen den Ladungsträgern und eine Tendenz zur Aggregation in separierten Domänen (begünstigt durch die spezifische molekulare Architektur der Polymeren) erklären.
    Notes: Aqueous and DMF-diluted solutions of polyurethane ionomers with sodium propanesulfonated groups at urethanic nitrogen atoms were studied by viscometry. A polyelectrolyte effect was evidenced at temperatures between 25 and 60°C, and it was preserved when NaCl was added to solutions.The coulombic interactions between charged groups and a tendency to aggregation in separated domains (favoured by specific molecular architecture of polymers) explain the observed solution properties.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052310103
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  • 110
    Electronic Resource
    Electronic Resource
    Increasing of the adhesive properties of poly(propylene) by surface modification (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 69-77 
    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: Es wurde der Einfluß der Oberflächenbehandlung auf die Hydrophilie und die freie Oberflächenenergie (FSE) von isotaktischem Polypropylen (iPP) untersucht. Es wurde festgestellt, daß bereits ein- bis zweiminütige UV-Bestrahlung ausreicht, um die FSE zu erhöhen. Unter dem zusätzlichen Einfluß von PCl3 auf die Polymeroberfläche wird die FSE um 29% im Vergleich mit unmodifiziertem iPP erhöht. Die Adhäsionsarbeit steigt dabei um den Faktor sechs. Die FSE wächst durch die Anwendung von starken Oxidationsmitteln in wäßriger Lösung. Die FSE des iPP ändert sich mit der Zeit nach der Oberflächenbehandlung nur unwesentlich.
    Notes: The applied surface modification methods aim at an increase of the hydrophilicity and the free surface energy (FSE) of isotactic poly(propylene) (iPP).It was shown that for this purpose it is possible to use UV irradiation during 1-2 min, depending on the distance of the source of irradiation from the polymer surface [50, resp. 100 mm]. By the simultaneous effect of phosphorus trichloride (PCl3) and UV irradiation on the polymer surface the FSE was increased by 29% compared to the unmodified polymer and the mechanical work of adhesion was six times the original value. It was found that the application of strong oxidizing agents, such as potassium permanganate (PPM) and ammonium peroxodisulfate (APS), resulted in an increase of the FSE of iPP by 16 to 19%. The efficiency of the modification depends on the time of the modification by aqueous solutions of the oxidizers, as well as on the concentration of the solution. The FSE of iPP modified by UV irradiation does not change with the time after the modification.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052310107
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  • 111
    Electronic Resource
    Electronic Resource
    The synthesis of pyridyl-substituted polyurethanes and copolyurethanes (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 171-186 
    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: Durch Polyaddition von Diphenylmethan-4,4′-diisocyanat oder Dicyclohexylmethan-4,4′-diisocyanat mit 2-Methyl-2-(4-pyridyl)propan-1,3-diol (MPyP) wurden neue reaktive Polyurethane hergestellt, deren Struktureinheiten mit Pyridinringen substituiert sind. Copolyurethane aus diesem Diol wurden in einem Ein- bzw. Zweistufenprozeß in Substanz oder in Diglyme-Lösung hergestellt, wobei als Comonomere Hexan-1,6-diol (HD), α,ω- Dihydroxypoly(oxyethylen)e mit verschiedenen Molekulargewichten (POE 400,1000 und 2000) oder α,ω-Dihydroxypoly(oxypropylen) (PPO 400) eingesetzt wurden. Die erhaltenen Pyridin-substituierten Polyurethane und Copolyurethane wurden durch 1H-NMR- und 13C-NMR-Spektroskopie und durch die Grenzviskosität [λ] charakterisiert. Die Pyridineinheiten wurden acidometrisch (HClO4) bestimmt. Die Reaktivität der OH-Gruppen in MPyP bezüglich der Isocyanat-Gruppe wurde charakterisiert, indem die Geschwindigkeitskonstante der Reaktion von MPyP mit Phenylisocyanat bestimmt wurde. Der erhaltene Wert von 2,45 · 10-3 dm3 mol-1 s-1 (25°C) liegt um eine Größenordnung höher als die Geschwindigkeits-konstante für die Addition von Hexan-1,6-diol. Diese Differenz wurde mit einem katalytischen Mechanismus bei der Addition von MPyP interpretiert.
    Notes: New reactive polyurethanes with structure units substituted with pyridine rings were prepared by the polyaddition reaction of diphenylmethane-4,4′-diisocyanate or dicyclohexylmethane-4,4′-diisocyanate with 2-methyl-2-(4-pyridyl)propane-1,3-diol (MPyP). Copolyurethanes based on this diol were synthesized by a one- or two-step procedure carried out in bulk or diglyme solution using hexane-1,6-diol (HD), α,ω-dihydroxypoly(oxyethylene)s of various molecular weights (POE 400, 1000 and 2000) or α,ω-dihydroxypoly(oxypropylene) (PPO 400) as comonomers.Pyridyl-substituted polyurethanes and copolyurethanes were characterized by their 1H and 13C NMR spectra and limiting viscosity numbers [η]. The pyridine units were determined acidimetrically (HClO4). The reactivity of the OH groups of the pyridine diol towards NCO groups was characterized by determining the rate constants of its reaction with phenyl isocyanate. The obtained value of 2.45 × 10-3 dm3 mol-1 s-1 (25°C) was by an order of magnitude greater than the rate constant for the addition of hexane-1,6-diol. This difference was interpreted in terms of a catalytic mechanism for the addition of MPyP.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052310115
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  • 112
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    Are microencapsulated antioxidants a feasible technology?Paper presented at the “16th International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 14-17, 1994. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 232 (1995), S. 13-25 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We consider the possibility of stabilising a polymer by using a low-molecular-weight, mobile and soluble antioxidant, trapped in a small volume fraction of encapsulating material so that it is released into the surrounding polymer to compensate for consumption or loss. Two models are discussed. In the “matrix” model, the additive is dissolved in an encapsulant and its release is controlled entirely by the diffusion coefficient in the encapsulant. In the “balloon” model, the pure additive is surrounded by a wall of encapsulant, through which it permeates into the surrounding polymer. Modelling of the two cases allows the required diffusion or permeation coefficients to be calculated for any chosen loss time. It is found that purely diffusion-controlled loss would require improbably low diffusion coefficients, whereas the required permeabilities for balloon models are accessible. It is difficult to imagine a system for which the temperature coefficient of loss rate would be low enough to allow elevated temperature processing without loss of the additive.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052320102
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  • 113
    Electronic Resource
    Electronic Resource
    Diffusion von wasserdampf durch feinschichtharze (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 233 (1995), S. 47-58 
    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: Thin, plane plates of a defined thickness were cast from two types of gelcoat resins (isophthalic acid neopentylglycol (UP) and vinylester resin (PHA) based on bisphenol A) as a model for a gelcoat or topcoat layer of a glass fibre-reinforced laminate. The effect of undercuring as well as of resin dilution with styrene on the water vapor permeation through these plates was examined. In both cases the dilution of the resin results in an obvious increase of permeability. Undercuring (curing degrees of about 97%) and subsequent extraction of residual styrene monomer increases the water vapor permeability in the UP, on the other hand a light drop of the permeation coefficient was registered in the case of PHA. The results are discussed in connection with the different kinetics of the curing reactions in both resin types.
    Notes: Als Modell für die Gelcoat- oder Topcoatschicht eines glasfaserverstärkten Laminates wurden dünne, planparallele Platten definierter Dicke aus zwei Gelcoatharztypen (Isophthalsäure-Neopentylglykol- (UP) und Phenacrylat-Harz (PHA) auf Basis von Bisphenol A) gegossen, und es wurde der Einfluß der Unterhärtung sowie der Harzverdünnung mit Styrol auf die Wasserdampfdurchlässigkeit dieser Platten untersucht. Die Harzverdünnung führt in beiden Fällen zu einem evidenten Anstieg der Permeationskoeffizienten P. Die Unterhärtung (Aushärtungsgrade um 97%) und anschließende Extraktion des nicht auspolymerisierten Styrols läßt beim UP die Permeabilität von Wasserdampf ebenfalls ansteigen, beim PHA wurde dagegen ein leichtes Sinken des Permeationskoeffizienten verzeichnet. Die Ergebnisse werden im Zusammenhang mit den Unterschieden in der Kinetik der Aushärtungsreaktion beider Harztypen diskutiert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052330105
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  • 114
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    Mechanical behaviour of PS/PVC blends compatibilized with block-graft copolymers based on poly(styrene-block-butadiene)Dedicated to Prof. Dr. W. Borchard on the occasion of his 60th birthday (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 233 (1995), S. 77-87 
    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: Blends aus Polystyrol (PS) und Polyvinylchlorid (PVC) sind aus thermodynamischen Gründen unverträglich und weisen deshalb nur schlechte mechanische Eigenschaften wie mangelnde Schlagzähigkeits- und Reißdehnungswerte auf. Der Grund hierfür liegt in der Natur der Grenzfläche solcher unverträglicher, heterogener Polymer-Blends. Hohe Grenzflächenspannungen und eine geringe Phasenadhäsion führen zu groben Phasenmorphologien, die kinetisch und thermodynamisch instabil sind. Jedoch gelingt es mit maßgeschneiderten Block-Pfropfcopolymeren P(S-b-(B-g-CHMA, MMA)) auf Basis von Styrol/Butadien-Blockcopolymeren P(S-b-B), auf die Polycyclohexylmethacrylat (PCHMA) oder Polymethylmethacrylat (PMMA) radikalisch ge-pfropft wurden, die Phasenmorphologien drastisch zu verfeinern, was zu einem duktilen Verhalten der modifizierten Blends führt. So steigt die Schlagzähigkeit von modifizierten gegenüber nicht modifizierten PS/PVC-Blends um den Faktor 10 und bewegt sich damit im Bereich von zähmodifiziertem PS.Elektronenmikroskopische Untersuchungen (TEM, REM) beweisen, daß die drastisch verbesserten Eigenschaften der modifizierten PS/PVC-Blends auf einer Grenzflächenselektivität der Block-Pfropfcopolymeren und einer ausgezeichneten Phasenanbindung beruhen.
    Notes: Blends composed of polystyrene (PS) and polyvinylchloride (PVC) are incompatible due to unfavourable interactions. Consequently, their mechanical properties such as impact strength and elongation at break are only very poor. The key to successfully influence the properties of such heterogeneous blends lies in the control of the interface. High interface tensions and an insufficient phase adhesion often lead to coarse phase morphologies which are thermodynamically and kinetically unstable. However, with radically synthesized, tailor made block-graft copolymers P(S-b-(B-g-CHMA, MMA)) based on a styrene/butadiene two-block copolymer P(S-b-B) which are grafted with poly(cyclohexylmethacrylate) (PCHMA) or poly(methylmethacrylate) (PMMA), the phase morphology can be markedly refined and the blends surprisingly show ductile behaviour. Thus, the impact strength of so modified PS/PVC 1 : 1 blends is about ten times higher than in the unmodified case and is thereby similar to impact modified PS.Electron microscopy (SEM, TEM) reveals that the modified PS/PVC blends owe their improved mechanical properties to the interface selectivity of the block-graft copolymers and therefore to a superior phase adhesion.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052330107
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    Triazine-based polymers, 3Part 2 cf.20.. Synthesis and characterization of polyamines (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 233 (1995), S. 121-131 
    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: Eine Serie von 16 Polyaminen auf Triazinbasis wurde mittels Grenzflächenpolykondensation synthetisiert. Als Monomere wurden verschiedene Dichlortriazinderivate sowie Diaminverbindungen verwendet. Der Einfluß von Temperatur, Reaktionszeit, Monomerkonzentration, Art des organischen Lösungsmittels sowie Art der Base auf die reduzierte spezifische Viskosität und die Ausbeute an Polyamin wurde untersucht. Löslichkeiten, Glastemperaturen und thermogravimetrische Daten der Produkte wurden bestimmt. Über die dynamisch-mechanische Thermoanalyse von zwei Polyaminen wird berichtet.
    Notes: A series of 16 triazine-based polymines was synthesized by interfacial polycondensation, using various dichlorotriazine derivatives and diamines as monomers. The effect of the reaction parameters temperature, reaction time, concentration of monomers, type of organic solvent and type of base on the reduced specific viscosity and yield of polyamines was investigated. Solubilities, glass transition temperatures and thermogravimetric data were determined. Dynamic-mechanical thermal analyses of two polyamines are reported.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052330111
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    Synthesis and characterization of low-viscosity fluoropolyether-based segmented oligomers (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 47-60 
    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: Es wurden sechs oligomere Polyole synthetisiert und charakterisiert. Die Oligomeren waren aus strukturell gleichen Perfluorpolyether-Ketten, aber mit unterschiedlichen Endgruppen aus Hydroxygruppen enthaltenden hydrogenierten Segmenten aufgebaut. Zur Synthese der Polyole wurde der Fluorpolyetherdiol-Precursor (ZDOL) mit Epoxiden oder Dibromalkanen verethert. Die Reaktion mit Epoxiden führte direkt zu den Polyolen, während mit Dibromalkanen zunächst die fluorierten Dibromderivate erhalten wurden, die mit Malonat und durch anschließende Reduktion in die Polyole umagewandelt wurden. Die Viskosität der Oligomeren wurde bestimmt, und der Einfluß von Temperatur, Lösungsmittelkonzentration sowie Gehalt an Hydroxyendgruppen auf die Viskosität wurde ermittelt. Die außergewöhnlich niedrige Glastemperatur und Viskosität sowie die gute Mischbarkeit mit gängigen Lösungsmitteln machen diese Polyole als Harze für hochfeste Beschichtungen interessant.
    Notes: Six oligomeric polyols having a common perfluoropolyether chain end-capped by different hydrogenated segments containing hydroxylic groups were synthesized and their properties described. The general scheme for the synthesis of these polyols involved the etherification of the fluoropolyether diol precursor (ZDOL) with epoxides or dibromoalkanes. The former reaction gave directly the polyolic derivatives, while the latter yielded the fluorinated dibromoderivative which could be converted to polyols through the reaction with malonate and final reduction.The viscosity of these oligomers was measured and its dependence on temperature, solvent concentration and hydroxylic end-groups content was established. The exceptionally low Tg and viscosity together with the good miscibility with common solvents make these polyols very interesting as “resins” suitable for high-solid coatings.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1995.052310105
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    Masthead (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350101
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    Contrasting solution conformations of peptides containing α,α-dialkylated residues with linear and cyclic side chains (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 11-20 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational properties of α,α-dialkylated amino acid residues possessing acyclic (diethylglycine, Deg: di-n-propylglycine, Dpg; di-n-butylglycine, Dbg) and cyclic (1-amino-cycloalkane-1-carboxylic acid, Acnc) side chains have been compared in solution. The five peptides studied by nmr and CD spectroscopy are Boc-Ala-Xxx-Ala-OMe, where Xxx = Deg(I). Dpg (II), Dbg (III), Ac6c (IV), and Ac7c (V). Delineation of solvent-shielded NH groups have been achieved by solvent and temperature dependence of NH chemical shifts in CDCl3 and (CD3)2SO and by paramagnetic radical induced line broadening in pepiide III. In the Dxg peptides the order of solvent exposure of NH groups is Ala(1) 〉 Ala(3) 〉 Dxg(2), whereas in the Acnc peptides the order of solvent exposure of NH groups is Ala(1) 〉 Acnc(2) 〉 Ala(3). The nmr results suggest that Acnc peptides adopt folded β-turn conformations with Ala(1) and Acnc(2) occupying i + 1 and i + 2 positions. In contrast, the Dxg peptides favor extended C5 conformations. The conformational differences in the two series are clearly borne out in CD studies. The solution conformations of peptides I-III are distinctly different from the β-turn structure observed in crystals. Low temperature nmr spectra recorded immediately after dissolution of crystals of peptide II provide evidence for a structural transition. Introduction of an additional hydrogen-bonding function in Boc-Ala-Dpg-Ala-NHMe (VI) results in a stabilization of a consecutive β-turn or incipient 310-helix in solution. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350103
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    The helix-coil transition in polypeptides: A microscopic approach. II (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 75-84 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the framework of an earlier constructed model [N. S. Ananikyan et al. (1990) Biopolymers, Vol. 30. pp. 357-367], some analytical estimates for the correlation length and degree of helicity near the transition point were obtained in the case of an arbitrary topology of hydrogen bond closing (Δ). It was shown that the Zimm-Bragg cooperativity parameter σ is determined by the set of (Δ-1) amino acid residues and so is nonlocal. An analytic expression for cooperatively parameters in a heteropolypeptide chain was obtained and numerical calculations showed that in case of heteropolypeptide with random primary structure the nonlocality of cooperativity parameter influenced the temperature dependence of helicity degree. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350108
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    A small-angle x-ray scattering study of alginate solution and its Sol-Gel transition by addition of divalent cations (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 227-238 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The small-angle x-ray scattering (SAXS) technique has been applied to investigate solution and gel structures of alginate in the absence and presence of two divalent cations: Ca(II) and Cu(II). We have observed a broad maximum in the scattering curve, a characteristic of polyelectrolyte, for the purified alginate sample. The scattering maximum disappears in excess of added simple salt and shifts toward the higher angle region with increasing alginate concentration. Concentration dependence of the position and intensity of the maximum follows power law relations with exponents close to those predicted by theory. Data analysis shows an increase in correlation length ξ and cross-sectional diameter d0, of polymer chains upon gelation and suggests that a dimeric structure is adopted in the junction zone, consistent with the “egg-box” model previously proposed. In the Ca(II)-alginate system, the molecular parameters ξ and d0 are found to have good correlation with the macroscopic properties of gelation, such as gel point determined by viscosity measurements. However, for the Cu(II)-alginate system there is no clearly transitional behavior observed in ξ and d0, implying that the junction zone may be replaced by a more uniformly distributed site binding of Cu(II) ions to the carboxyl groups of both mannuronate and guluronate residues, in confirmation of previous 13C-nmr results. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350211
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    Some properties of acid-reassembled tropomyosin (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 239-244 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preference for parallelism of the two chains in tropomyosin coiled coils is thought to result from interchain salt bridges. To examine this idea, studies are presented of tropomyosin molecules reassembled from chaotropic solvents in acid solution, where cross-links cannot exist. The acid-reassembled molecules are appreciably less disulfide cross-linkable in acid than native molecules, a result explainable if some antiparallel dimers indeed form at low pH. Physical studies (backbone- and tyrosine-region CD and intrinsic viscosity) indicate that refolding in acid yields a molecular population demonstrably different in tyrosine-region CD from native, but having comparable (but not identical) helix content, thermal stability, and dimensions. Moreover, the refolding in acid after either thermal or chaotropic-solvent denaturation yields the same final state, arguing that it is an equilibrium state. All these results are consistent with, but do not prove, that the acid-reassembled population includes an appreciable fraction (2/3) of antiparallel coiled-coil dimers. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350212
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    Chain conformation in polyretropeptides: Quantum mechanical and empirical force field calculations on 2,6,8-trioxo-3,5,9-triazadecane, a model compound for poly(retro-glycine) (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 257-269 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report here our results on semiempirical AM1 calculations for the conformational preferences of 2,6,8-trioxo-3,5,9-triazadecane, a model compound for polymers made of retropeptide units. We have evaluated the effect of applying symmetry constraints between chemically equivalent torsion angles. These results suggest that preferred conformations around the —NH—CH2—NH— group are quite independent from those on the —CO—CH2—CO— unit, so all possible combinations generate the complete set of energy minima for the model compound.We have analyzed the implications of the different minimum energy conformation in an infinite chain model and we have explored the conformational space of regular polyretropeptides. This shows a close relation to that of regular polypeptides but with significant differences arising from the change of orientation of the peptide units along the polymer molecule. The energy calculations also support previously proposed models for the crystal structure of the simplest polyretropeptide, poly(retro-glycine). Finally, we discuss the consequences of retropeptide-peptide copolymerization as well as the expected conformations for regular alternate terpolymers. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350302
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    Two-dimensional motion of DNA bands during pulsed-field gel electrophoresis. II. Effect of field angle (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 307-317 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In pulsed-field gel electrophoresis, megabase DNAs are well separated if the angle θ between the two electric fields is 120° but not if θ = 90°. To elucidate the molecular basis for this observation, we measured the instantaneous position (x, y) and velocity (vx, vy) of a band of G-DNA (670 kb) while the field switched direction, for 90° ≤ θ ≤ 102°. For θ = 120° and long pulse period T. The band retraced the last segment of the preceding pulse before moving in- the new field direction. The retracing wax done at a velocity much greater than the average forward velocity. For θ = 90°, rather than retrace itself, the path during one pulse appeared to originate from a point beyond that reached in the previous pulse, end the velocity showed only a brief backward spike.A Monte Carlo simulation that included tube-length fluctuations and hernias was carried out for a model DNA chain moving through a three-dimensional network of interconnected pores, with parameters corresponding to the DNA size, agarose concentration, and field strength of the experiments, Both the xy path and the instantaneous velocities of the simulation were in excellent agreement with experiment for 90° ≤ θ ≤ 120°. When the field changed direction in the simulation, hernias often advanced from both ends in the new field direction. In the 120° case, those near the erstwhile trailing segments of the chain soon established superiority because chain tension and a component of the new field aided their growth. For θ = 90° and long T, however, segments from the head end were more likely to continue to lead because there was often an excess of relaxed segments there, and no component of the field aided either end. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350306
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    Topological features of human chorionic gonadotropin (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 343-345 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350309
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    Biopolymer-surfactant interaction. I. Kinetics of binding of cetyltrimethyl ammonium bromide with carboxymethyl cellulose (Na Salt) (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 533-541 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of binding of the cationic surfactant cetyltrimethyl ammonium bromide with the Na salt of carboxymethyl cellulose was studied by the electrometric method using cetyltrimetlyl ammonium+ (CTA+) ion-selective polyvinyl chloride membrane electrode. The binding process followed the first-order kinetics and occurred in three stages. Its affinity increased with increasing CTA bromide concentration and decreased with ionic strength. The activation process comprised moderate Ea≠ and ΔH≠ and negative ΔS≠ for all three stages with a ΔH≠ 〈 TδS≠ trend proving it to be entropy controlled. The ΔG≠ values followed the trend ΔG1≠ 〈 ΔG2≠ 〈 ΔG3≠ (in accordance with k1 〉 k2 〉 k3). The enthalpies (ΔH≠) and entropies (ΔS≠) of activation followed a systematic and interdependent trend. The multiple-stage binding kinetics is grossly comparable with the kinetics of binding of proteins to solid surfaces. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360350512
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    The “cratic correction” and related fallacies (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 595-602 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The “cratic correction” for removing the contribution of translational motion from standard free energies and entropies of chemical reactions is examined. Although removal of translational effects is useful in interpreting free energy and entropy changes in molecular terms, this particular correction does not do so. No basis for it is found in thermodynamics or statistical mechanics. The appropriate correction for center-of-mass translational motion is derived from classical statistical mechanics. However, the importance of recognizing the proper molecular meaning of the remaining free energy is stressed. In any case, this latter correction, however legitimate, is shown to be futile, since it has long been recognized from classical statistical mechanics that all terms involving momenta (thermal wavelength terms)  - be they classified as translational, rotational, vibrational, or whatever - necessarily cancel out informing the standard free energy change of any chemical reaction from the constituent standard chemical potentials. © 1995 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350605
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    Conformational properties of the proline region of porcine neuropeptide Y by CD and 1H-NMR spectroscopyTaken in pan from the Ph. D. dissertation of Shao Song Chu, The University of Kansas (1992). (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 583-593 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We synthesized porcine neuropeptide Y (pNPY) N-terminal fragments by solid-phase synthesis techniques and analyzed them for solution Conformational properties by CD and 1H-nmr spectroscopy. The analogues pNPY1-9 and pNPY1-14 displayed CD spectra indicative of random structures and showed no evidence for induced α-helical structures in trifluoroethanol (TFE) up to 50%. However, the CD spectra of pNPY1-9 suggested a Conformational shift in tetrahydrofuran. Although in aqueous solution the CD spectra of pNPY1-21 indicated random structures with induction of only a small percentage of α-helix in aqueous TFE, pNPY1-25 displayed 13% a-helical structure in aqueous solution that increased to 40 and 41% by the addition of TFE and methanol, respectively. The nmr spectra of pNPY1-9 and the proline region of pNPY1-25 indicated extended structures with all-trans conformers at Pro5 and Pro8 for pNPY1-9 and at Pro5, Pro8, and Pro13 for pNPY1-25; in each case the Tyrl-Pro2 amide bond was in both cis and trans conformations. However, observed nuclear Overhauser effect correlations and UN exchange experiments indicated an α-helical segment in pNPY1-25 initiated by Pro 13 and extending from residues 14 to 25. Thus, the N-terminal polyproline region of NPY has no propensity to fold into a regular secondary structure, although Pro 13 is a helix initiator, a result consistent with the proposed role of this amino acid in the NPY structural model. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bip.360350604
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    The energy of formation of internal loops in triple-helical collagen polypeptides (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 607-619 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sequence-dependent local destabilization in the interior of the collagen triple helix has been evaluated by means of conformational energy computations. Using a model poly(Gly-Pro-Pro) triple helix as the reference state, a method was developed for generating local loops, i.e., internal deformations, and analyzing their conformations. A seven-residue Gly-Pro-Pro-Gly-Pro-Pro-Gly fragment was replaced by the Gly-Pro-Ala-Gly-Ala-Ala-Gly sequence in one, two, or all three of the strands of the loop region. A set of loop conformations was generated in which the ends of the loop were initially fixed in the triple-helical structure. The potential energy of the entire deformed triple helix was then minimized, resulting in a variety of structures that contained deformed loops. The conformations of the triple helices at the two ends of the loops remained essentially unchanged in many of the low-energy conformations. In numerous high-energy conformations, however, the triple-helical segments were also partially or totally disrupted. The minimum-energy conformations of the whole structures were compared in terms of rms deviations of atomic coordinates with respect to the original triple helix, and of the shapes of the loops (using a distance function derived from differential geometry). Three new geometrical parameters - stretch S, kink K, and unwinding U - were defined to describe the changes in the overall orientation of the triple helices at the two ends of the loop. It is shown that, when the number of Pro residues in a short fragment is reduced, the triple helical structure can accomodate internal loops (i.e., distortions) within a 5 kcal/mol cutoff from the essentially unperturbed triple helical structure. For structures with a Gly-Pro-Ala-Gly-Ala-Ala-Gly sequence in all three strands, the probability of finding conformations with internal loops is small, i.e., 0.06. Internal loops affect the overall orientation of these structures, as measured by the helix-distortion parameters S, K, and U. © 1995 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360360101
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    Observation of unfreezable water in aqueous solution of globule protein by microwave dielectric measurement (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 9-16 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A freezing process analyzed by the dielectric method on aqueous solution of albumin has revealed water structure around protein molecule. A relaxation peak due to bound water attached on the protein surface around 100 MHz at room temperature was found. It could be seen commonly in globule proteins. Another peak due to a different kind of unfreezable water was found around 1 GHz at -6°C. The amount of this water is estimated as 0.36 g water/g protein and in good agreement with that obtained by differential scanning calorimetry and nmr measurements. The water molecules form a shell layer around the protein molecule. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bip.360360103
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    An evaluvation of discrete and continuum search techniques for conformational analysis of side chains in proteins (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 53-70 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methodology for calculation of side-chain conformations in proteins is evaluated. The role and impact of corrections to idealized rotameric structures are considered, by incorporating methods for torsional optimization into rotamer-packing algorithms. Off-rotamer corrections given by continuum torsional optimization improve, over simpler rotamer-packing procedures, the accuracy with which the conformations of side chains of buried amino acids can be predicted. The analogy between protein side-chain calculations and spin systems is explored by adapting spin simulation methods to side-chain packing algorithms. Implementations of mean-field and heat-bath algorithms for side-chain packing are described and their performance tested. The procedures introduced here address the combinatorial problem in an efficient and reasonably effective manner, as evidenced by analysis of their convergence properties. Application of refined protocols yields overall prediction accuracies of 80% for χ1 and 68percnt; for χ1,2 pairs for a test set of 60 proteins, using a 40° cutoff to define correct placement. For buried amino acids (defined as having less than 30% relative solvent accessibility) the prediction accuracies increase to 88percnt; for χ1 and 79percnt; for χ1,2 pairs. The influence of the form of the potential energy function is studied by comparing results obtained with 12-6 and 9-6 potentials. The 9-6 form leads to more accurate results. Detailed comparison with previous work is presented, and the effect of combinatorial packing steps is shown to be important for all but the smallest proteins. © 1995 John Wiley & Sons, Inc.
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    Design and characterization of a model αβ peptide (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 109-120 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CD and nmr spectroscopy were used to compare the conformational properties of two related peptides. One of the peptides, Model AB, was designed to adopt a helix-turn-extended strand (αβ) tertiary structure in water that might be stabilized by hydrophobic interactions between two leucine residues in the amino-terminal segment and two methionine residues in the carboxyl terminal segment. The other peptide, AB Helix, has the same amino acid sequence as Model AB except that it lacks the-Pro-Met-Thr-Met-Thr-Gly segment at the carboxyl-terminus. Although the carboxyl-terminal segment of Model AB was found to be unstructured, its presence increases the number of residues in a helical conformation, shifts the pKas of three ionizable side chains by 1 pH unit or more compared to an unstructured peptide, stabilizes the peptide as a monomer in high concentrations of ammonium sulfate, increases the conformational stability of residues at the terminal ends of the helix, and results in many slowly exchanging amide protons throughout the entire backbone of the peptide. These results suggest that interactions between adjacent segments in a small peptide can have significant structure organizing effects. Similar kinds of interactions may be important in determining the structure of early intermediates in protein folding and may be useful in the de novo design of independently folding peptides. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360360202
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  • 133
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    Bioactive peptides: Conformational studies of [TYR4] cyclolinopeptide A (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 453-460 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid state conformational analysis of [Tyr4] cyclolinopeptide A has been carried out by x-ray diffraction studies. The crystal structure of the monoclinic form, grown from a dioxane-water mixture [a = 9.849 (5) Å, b = 20.752 (4) Å, c = 16.728 (5) Å, β = 98.83 (3)°, space group P21, Z = 2], shows the presence of five intramolecular N-H- O=C hydrogen bonds, with formation of one C17 ring structure, one α-turn (C13), one inverse γ-turn (C7), and two β-turns (C10, one of type III and one of type 1). The Pro1-Pro2 peptide unit is cis (ω = 5°) all others are trans. The structure is almost superimposable with that of cyclolinopeptide A. The rms deviation for the atoms of the backbones is on the average 0.33 Å. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360360408
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    Conformationally readdressed CCK-B/δ-opioid pepitide ligands (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 439-452 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sequence of a cholecystokinin (CCK) related peptide was modified to obtain analogues, which intereact selectively either with CCK-B, or with δ-opioid receptors. Two kinds of peptides were designed, namely, the cyclic peptides of the H-Tyr-cyclo(D-Pen-Gly-Trp-L-/D-3-transmecaptoproline)-Asp-Phe-NH2 sequence (compounds 1a and 1b, respectively), and the linear peptides of the H-Tyr-D-Val-Gly-Trp-L/D-3-trans-methylmercaptoproline-Asp-Phe-NH2 sequence (compounds 2a and 2b, respectively). The only difference between the chemical structures of the linear analogues compared to the cyclic ones is that one covalent bond has been eliminated and a sulfur atom is replaced by a methyl group. Molecular modeling showed that, among low-energy conformers of cyclic compounds 1, there are three-dimensional structures compatible to the model for δ- receptor- bound conformer, suggested earlier[G. V. Nikiforovich. V. J. Hruby. O. Prakash, and C. A. Gehrig (1991) Biopolymers. vol. 31. pp. 941-955]. Results of binding assays fully supported the rationale for the design of compounds 1 and 2. The cyclic analogue 1a has Ki values of 4.5 and 〉 5000 n M at δ- and μ-opioid receptors, respectively; IC50 values of 3000 n M for both CCK-A and CCK-B receptors, whereas its linear counterpart 2a has ki values of 462 and 229 nM at δ- and μ-opioid receptors, respectively; and IC50 values of 1.6 and 〉 10.000 nM for CCK-A and CCK-B receptors, respectively. The results of this study demonstrate a possibility to redirect a peptide sequence that interacts with one type of receptors (CCK-B receptors) toward interaction with another type (δ-opioid receptors) belonging to a different physiological system. This redirection could be performed by changing the conformational properties of the peptide with very minimal changes in its chemical structure. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360360407
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  • 135
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    Conformation of cyclobradykinin by nmr and distance geometry calculations (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 461-472 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of the head-to-tail cyclic analogue of bradykinin in DMSO was investigated by nmr. Three sets of resonances were detected and fully assigned. These were attributed to the presence of three stable conformers, two of which were exchanging on the nmr time scale. A fourth, incomplete set of resonances was detected but not assigned. The three major conformers differ in the conformation at the three X-Pro bonds present.From nuclear Overhauser effect spectroscopy (NOESY) spectra, three sets of interproton distances were derived and used in NOE-restrained distance geometry calculations. The resulting structures were refined by energy minimization to yield families of structures. Conformer I is characterized by the presence of two type VIb β-turns between Arg1 and Gly4 and between Phe5 and Phe8. The first β-turn is present also in conformer II, while an inverse γ-turn bridging Pro3 is the most pronounced structural feature of conformer III. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360360409
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  • 136
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    Conformation of parathyroid hormone antagonists by CD, nmr, and molecular dynamics simulations (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 485-495 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of two highly potent parathyroid hormone (PTH) antagonists was investigated in water/2, 2, 2-trifluoroethanol mixtures. The two peptides are derived from the sequence (7-34) of PTH and of PTH-related protein (PTHrP) and have a D-Trp replacing Gly in position 12. In the analogue derived from PTHrP, Lys11 was replaced by Leu to remove the residual agonist activity. The study was conducted by CD and two-dimensional proton magnetic resonance spectroscopy, and the nuclear Overhauser effects found were utilized in restrained distance geometry and molecular dynamics simulations.Both peptides adopt a helical C-terminal conformation, which seems more stable in the case of the PTHrP analogue. A type II′ β-turn centered around D-Trp12 and Lys13 is present inboth structures. © 1995 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360360411
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    Intramolecular electronic energy transfer in peptides carrying naphthalene and protoporphyrin molecules: A spectroscopic and conformational statistics investigation (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 497-510 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Short linear peptides, carrying an AA spacer in the backbone chain (AA = Aib or Ala),and naphthalene(N) and protoporphyrin IX(P) covalently bound to ∊-amino groups of lysine side chains, were synthesized. The general formula is Boc-Leu-Leu-Lys(P)-(AA)n-Leu-Leu-Lys(N)-OtBu, with n = 0-2. The photophysical behavior of these compounds was investigated in water/methanol 75/25(v/v) solution by steady-state and time-resolved fluorescence experiments. Quenching of excited naphthyl chromophore lakes place by electronic energy transfer to the porphyrin ground state, and proceeds on a time scale of 3-8 ns, while a minor and slower(≈45 ns) fluorescence lifetime measures the decay of the exciplexes. The results were compared with those earlier obtained with the P(Ala)nN peptides(n = 0-4) in methanol solution, showing that addition of water does not significantly alter the dynamic relaxation behavior of the systems investigated, but affects the dissipation mechanism of the energy transferred to P. Quenching efficiencies from both fluorescence intensity and fluorescence lifetime measurements follow a different trend as the number of AA units increases, depending on whether AA = Aib or Ala, indicating that there are differences in the structural features of the two series of peptides. Consistently, CD spectral results suggest that the former compounds attain ordered conformations, possibly of the 310-helical type, while the latter populate α-helical structures to an extent depending on the chain length. The ir data in dilute CD3OD or CDCl3 solution confirm this conclusion in that there is an increased percentage of intramolecular H bonds in the P(Aib)nN as compared to the corresponding P(Ala)nN peptides. The photophysical results can be well described by a long-range dipole-dipole interaction model, provided the separation distances distribution and mutual orientation of N and P groups are taken into account. The need of using the angular relationships between the probes implies that interconversion among conformational substates of chromophores linkages is slow on the time scale of the transfer process, very likely because of both the amide bond in the linkages and the bulkiness of the donor-acceptor pair. © 1995 John Wiley & Sons, Inc.
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  • 138
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    Conformational analysis of dolastatin 10: An nmr and theoretical approach (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 525-538 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A solution conformational analysis of dolastatin 10, a powerful antineoplaslic agent, has been carried out by means of nmr techniques and theoretical calculations. 1H mono- and bidimensional nmr experiments, as well as 1H-13C heterocorrelated spectra, have been performed on CD2Cl12 solutions. The most interesting nmr data is a huge shielding of the aCH (25) proton of the Dov residue, suggesting the presence of an interaction between the N-terminal and the aromatic C-terminal ends of the molecule.The possibility of a head-to-tail intermolecular association having been discarded, the presence of a series of preferred folded conformation has been hypothesized. Conformational theoretical analysis supports the nmr hypothesis of a folded peptide-like molecule, and a series of possible conformers in good agreement with the experimental data have been analyzed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360360414
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  • 139
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    Synthesis and biological evaluation of novel NK-1 tachykinin receptor antagonists: The use of cycloalkyl amino acids as a template (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 511-524 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the course of a program aimed at synthesizing novel, potent NK-1 tachykinin receptor antagonists, we developed upon a bioactive model by comparing the low energy structures of a series of peptide and nonpeptide Substance P antagonists. The comparison was based on the super imposition of the aromatic rings, assuming that the rest of the molecule behaves predominantly as a template to arrange the key aromatic groups in the right spatial position. A series of 2-aminocyclohexane carboxylic acid analogues were then selected as the best templates for reproducing the postulated bioactive structure, leading to several pseudo-peptides with interesting biological activity. According to the molecular modeling, these compounds exhibit a neat parallel facing of the indolyl and naphthyl groups at about 3 Å distance. Ultraviolet absorption and steady state fluorescence measurements support this conclusion, showing a linear correlation between the spectral properties and the binding affinity of these analogues. Stacking of the indole ring with naphthalene gives rise to a complex characterized by a well-defined molar extinction coefficient. Consistently, steady state and lifetime fluorescence measurements suggest that the quenching process is ascribable to ground-state interactions between the chromophores. Implications of the π stacking propensity of aromatic groups in the biological activity of the compounds examined are briefly discussed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360360413
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  • 140
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    Conformation and interactions of bombolitin I analogues with SDS micelles and phospholipid vesicles: CD, fluorescence, two-dimensional NMR and computer simulations (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 473-484 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bombolitins are five structurally related heptadecapeptides acting at the membrane level able to lyse erythrocytes and liposomes and to enhance the activity of phospholipase A 2(PLA2). In the presence of SDS or phospholipid vesicles bombolitins are able to form amphiphilic α-helical structures and this property seems to be the major determinant of bioactivity. In order to test the model of interaction between bombolitin I and membranes, an analogue was synthesized in which all the lysines were replaced by arginines: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Ile - Arg - Ile - Thr - Thr - Met - Leu - Ala - Arg - Ile - Gly - Arg - Val - Leu - Ala - His - Val - NH}_{\rm 2}$$ \end{document}([Arg2,9,12, Ile10] bornbolitin I). The design ofthis sequence allowed the synthesis of a second analogue through a specijic postsynthetic dansylation at the ∊-amino group qf a lysine residue replacing the original leucine residue at position 7. The, first analogue was, fiilly characterized by CD and two-dimensional nmr in the presence of SDS or phospholipid vesicles. The peptide, folds into an amphiphilic α-helical confbrrnation with the helical segment spanning the central part of the sequencefrom Ile3 to His16. This behavior is identical to that observed for the native sequence. The replacement of Iysine residues by arginine hus no detectable effect on the conformational prderence of the peptide chain. By CD and fluorescence spectroscopy measurements, the fluorophore-containing analogue [Arg2,9,12, Lys7(∊-dansyl)] bombolitin I also folded into the α-helical conformation in the presence of SDS micelles or phospholipid vesicles. In particular, the dansyl fluorophore, which is located approximately in the middle of the apolar surface ojthe amphiphilic helix, is clearly buried in a hydrophobic environment when the peptide is bound to phospholipid vesicles. These findings support the hypothesis that the peptide helices are oriented parallel to the vesicle surface. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bip.360360410
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    Molecular dynamics in sodium poly (L-glutamate) aqueous solutions analyzed by means of the stretched exponential decay of the williams-watts function (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 539-545 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The high-frequency dielectric dispersions of the sodium salt of poly(L-glutamic acid) aqueous solutions in the frequency range from 1 to 1000 MHz have been analyzed by means of the Cole-Davidson relaxation function in the frequency domain and by means of the Williams-Watts relaxation function in the time domain. The analogies between the two descriptions are discussed on the basis of the analysis carried out by Lindsey and Patterson and the connections between the dipole-dipole correlation function based on the kinetic model for polyion dynamics proposed by Skinner and the Williams-Watts nonexponential decay function are briefly discussed. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bip.360360415
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  • 142
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    Thermodynamics of melting of the circular dumbbell d〈pCGC-TT-GCG-TT〉 (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 701-710 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational behavior of DNA minihairpin loops is sensitive to the directionality of the base pair that closes the loop. Especially tailored circular dumbbells, consisting of a stem of three Watson-Crick base pairs capped on each side with a minihairpin loop, serve as excellent model compounds by means of which deeper insight is gained into the relative stability and melting properties of hairpin loops that differ only in directionality of the closing pair: C-G vs G-C. For this reason the thermodynamic properties of the circular DNA decamers 5′-d〈pCGC-TT-GCG-TT〉-3′(I) and reference compounds 5′-d〈pGGC-TT-GCC-TT≤-3′(II) and 5′-d(GCG-TC-CGC)-3′(III) are studied by means of nmr spectroscopy. MoleculesIandIIadopt dumbbell structures closed on both sides by a two-membered hairpin hop. At low temperatureIconsists of a mixture of two slowly exchanging forms, denotedL2L2andL2L4. The low-temperatureL2L2form is the fully intact minihairpin structure with three Watson-Crick C-G base pairs. The high-temperature form,L2L4,contains a partially disrupted closing G-C base pair in the 5′-GTTC-3′ loop, with the cytosine base placed in a syn orientation. The opposite 5′-CTTG-3′ loop remains stable. A study of the noncircular hairpin structureIIIshows similar conformational behavior for the 5′-GTTC-3′ loop as found inIa syn orientation for C(6) and two slowly exchanging imino proton signals for G(3). The melting point Tm of IIwas estimated to lie above 365 K. The Tm value of the duplex stem and the 5′-CTTG-3′ loop of theL2L4form ofIis 352 ± 2 K. The ΔH° is calculated as -89 ± 10 kJ/mol. The Tm value determined for the individual residues of the 5′-GTTC-3′ loop lies 4°-11° lower. The enthalpy ΔH° of melting the thymine residues in the 5′-GTTC-3′ loop is calculated to be -61± 7 kJ/mol. Thermodynamic data of the equilibrium between the slowly exchanging two- and four-membered loop conformers of I reveal an upper limit for ΔH° of +30 kJ/mol in going from a two-memberedto a four-membered loop, in agreement with the enthalpy difference of +28 k.j/mol between the two loops at the Tm midpoint. For hairpin III the upper limit for ΔH° going from a two-membered to a four-membered loop amounts to ±21 kJ/mol. The mutual exchange rate between the L2 and L4 form in III is estimated as 13.6 s-1. Our results clearly suggest that small four-way DNA junctions(model for immobilized Holliday junctions) can be designed that consist of a single DNA strandthat features -CTTG-caps on three of the four arms of the junction. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bip.360360604
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    Anomalous temperature fluorescence quenching of N-Trp terminal peptides (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 723-733 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photophysics of Trp-containing peptides is extremely affected by the position of the indole ring with respect to the substituents. In this work an unusual temperature fluorescence quenching behavior is presented. The N-tryptophan terminal peptides (N- Trp) show an increase of the static emission intensity as rising the temperature from 10 to about 40°C. The anomaly is typical of the N-Trp terminal peptides since neither tryptophan (Trp) nor glycyl-tryptophan (Gly-Trp) and alanyl-tryptophan (Ala-Trp) show the same trend; a similar behavior is not detected in the C-tryptophan terminals. The other important features are the wavelength and pH dependence of the effect. The anomaly is in fact detected only at neutral pH and for excitation wavelength near the red edge of the UVB absorption band of indole. An interpretation of the anomaly is suggested, though more sophisticated techniques are needed to better focus the problem; the model proposed involves the superimposition of a ground state effect (the temperature-induced equilibrium shift from the zwitterionic to the anionic form of the peptides) and an excited state mechanism. At present no unique interpretation can be provided about the excited state mechanism that favors the anomaly and some suggestions are discussed. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bip.360360606
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    Influence of sample pH on the conformational backbone dynamics of a pseudotripeptide (H-Tyr-TicΨ[CH2-NH] Phe-OH) incorporating a reduced peptide bond: An NMR investigation (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 735-749 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present paper we investigate the influence of sample pH on the conformational and dynamical properties of the pseudotripeptide H-Tyr-TicΨ[CH2NH]Phe-OH(TIP[Ψ]:Tic: l, 2, 3, 4,-tetrahydroisoquinoline-3-carboxylic acid) using various one- and two-dimensional nmt techniques in conjunction with molecular modeling. Studies were conducted at three different pH levels-corresponding to the zwitterionic peptide containing a formal positive charge(pH 3. 1).the deprotonated molecule(pH 9. 1), and a situation at neutral pH(pH 7. 2) involving both protonated and deprotonated states of the reduced peptide bond. Analysis of the one-dimensional1H-nmr spectra reveals that in solution TIP[Ψ]is in slow dynamic exchange between conformations containing cis and trans configurations of the Tyr-Tic bond. An nmr pH dependence study of the cis:trans ratio indicated that the exchange process was governed by the protonation state of the reduced bond amine. From the nmr data, reduced peptide bond pKavalues of 6. 5 and 7. 5 were determined for the cis and trans conformers, respectively. It was concluded that conformations containing a trans Tyr-Tic bond are stabilized at law pH by an intramolecular hydrogen bond between the Tyr carbonyl and the reduced peptide bond protonated amine. This observation was corroborated by molecular mechanics investigations that revealed low energy trans structures compatible with nmr structural data, and furthermore, were consistently characterized by the existence of a strong N+ H-O= C interaction closing a seven-membered cycle. The dynamics of cis-trans isomerization about the Tyr-Tic peptide bond were probed by nmr exchange experiments. The selective presaturation of exchanging resonances carried out at several temperatures between 50 and 70°C allowed the determination of isomerization rate constants as well as thermodynamic activation parameters. ΔG≠ values were in close agreement with the cis → trans energy barrier found in X-Pro peptide fragments (∼83 kJ/mol).A large entropic barrier determined for the trans → cis conversion of TIP[Ψ](5. 7 JK-1 mol-1 at pH 3. 1; 6. 5 JK-1 mol-1 at pH 9. 1) is discussed in terms of decreased solvent molecular ordering around the conformers possessing a trans Tyr-Tic bond. Evidence that the neutral form of the reduced peptide bond gains rigidity upon protonation was obtained from relaxation measurements in the rotating frame. TJp measurements of several protons in the vicinity of the reduced peptide bond were made as a function of spin-lock field. Quantitative analysis of the relaxation data indicated that chemical shift fluctuations in the 10-4-10-5s range were more pronounced in the case of deprotonated TIP[Ψ]. Results of molecular dynamics simulations in addition to 3Jαβ coupling constant measurements support the experimentally observed greater flexibility in the C-terminal region of TIP[Ψ]. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bip.360360607
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    A molecular mechanics/continuum reaction field investigation of the interactions between polar amino acid side chains in water and organic solvents (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 765-780 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An integrated procedure that computes in a consistent way both the intermolecular interaction energies and the solvation energies is reported. It interfaces the Sum of Interactions Between Fragments Ab initio computed molecular mechanics and the Langlei-Claverie continuum reaction field procedures. These two methodologies formulate the interaction energy as a sum of separate electrostatic, polarization, dispersion, and repulsion terms; the first two are computed with the help of distributed charges, dipoles, and quadrupoles derived from the ab initio SCF or MP2 molecular wave fundctions of individual solutes. This computational procedure will be used to estimate the solvent contribution to the interaction energy between polar amino acids side chains. We will consider, on the one hand, the terminal fragments of the side chains of aspartate and glutamate - namely the acetate anion and its protonated counterpart, acetic acid - and on the other hand, the terminal fragments of the cationic residues lysine, histidinium, and arginine, as represented by methylammonium, imidazolium, and methylguanidinium cations, respectively. The deprotonated counterpart of imidazolium, imidazole, is also investigated. With water as a solvent, and for each of the three anion-cation complexes investigated, the total energy value DE (intermolecular + solvation) of the associated ion pair is only slightly larger (≈ 5 kcal/mol out of ≈ 170) than that of the fully dissociated arrangement and has a virtually flat dependence as a function of intermolecular separation. The associated complex has an enhanced stability in DMSO, a trend accented in chloroform and carbon tetrachloride. In water, the acetic acid-imidazole complex is less than 1 kcal/mol more stable than the dissociated pair. Energy balances, taking into account the experimental values of protonation energies of acetate and imidazole, indicate that the acetate-imidazolium complex is more stable than its nonzwitterionic counterpart, acetic acid-imidazole in water. In carbon tetrachloride, by contrast, the two complexes are of similar stabilities in terms of internal energies. When we consider free instead of internal energies of solvation, the three organic solvents stabilize the complex between the neutral molecules. The investigation of the interaction of two methylguanidiniums in the polar solvents suggests that the solvation energy of a complex, larger than that of the two isolated entities, could be able to overcome their electrostatic repulsion. This results in a small preference in favor of the complex. Implications of the findings of this study, and future prospects of applications to molecular recognition and conformational studies of oligopeptides and possibly proteins, are discussed. © 1995 John Wiley & Sons, Inc.
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    The conformation of an alamethicin in methanol by multinuclear NMR spetroscopy and distance geometry/simulated annealing (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 781-792 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution conformation of the antibiotic peptide alamethicin was investigated using multi-nuclear spectroscopy and the distance geometry/simulated annealing algorithms from the program DSPACE. 1H-, 13C-, and 15N-nmr chemical shifts and homonuclear 1H coupling constants suggest that the molecule is flexible in the vicinity of Gly-11 and Leu-12. The temperature dependence of the amide proton chemical shifts indicates that there is flexibility in the middle of the 20 residue peptide and provides evidence that, at the very N-terminus, the molecule adopts a 310-helical conformation. The large differences in the 13C chemical shifts of the pro-R and pro-S methyls of the α-aminoisobutyric acid residues were used to constrain those residues to the right-handed helical conformation in the distance geometry/simulated annealing algorithms. A family of 24 structures was generated but did not converge to a common conformation when superimposed over the entire polypeptide sequence. The molecules did converge to a helical conformation over residues 1-10 and residues 13-18. The lack of convergence when the entire lengths of the molecules are superimposed is explained by the flexibility of the peptide near Gly-11/Leu-12. The results suggest that the protein consists of two helices connected by a flexible “hinge.” The flexibility of the molecule is discussed with respect to the macrodipole model of voltage gating. © 1995 John Wiley & Sons, Inc.
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    1H-nmr studies on the structure of a new thionin from barley endosperm (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 751-763 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new thionin from barley, ω-hordothionin, has been shown to exist in aqueous solution as a mixture of two different isoforms in a 3:2 ratio, as revealed by a complete analysis of its two-dimensional 1H-nmr spectra. The conformational heterogeneity arises frtm cis-trans isomerism ahout the Phe 12-Pro 13 peptide bond, where the major, form corresponds to the cis conformation. The complete assignment of chemical shifts and nuclear Overhaiiser effects (NOES) of the two isoforms allow a detailed comparative analysis of their conformational properties, even though a complete calculation of their solution structures is not possible because of a somewhat limited number of NOE constraints. Structures for the two isomers could be modeled, however, on the basis of the high structural homology between ω-hordothionin and related γ-thionins, and under the conditions of satisfying all observed experimental data. The two isoforms adopt practically identical global folds and the structural changes imposed by cis-trans isomerization are confined to the region proximal to Pro 13. The cis-trans isomerism occurs in a conserved loop connecting the first β-strand of the triple-stranded antiparallel β-sheet and the α-helix. A comparative analysis of the sequences of this loop in the different thionins suggests that the cis-trans equilibrium about the X-Pro peptide bond depends on the size of the side chain of X (X = Gly in γ-thionins and Phe in ω-thionin). The structural homology of this new thionin with γ-thionins as well as with some scorpion toxins and insect defensins suggests that these proteins may share a common mode of functional activity. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 148
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    Structure of two microcystins: Refinement with nuclear overhauser effects and ensemble calculations (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 811-828 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ensemble calculations employing restraints developed from 1H-nmr were used to examine the conformational states of the two microcystins LR and LY. Despite the fast “flip-flop” dynamics about the N-methyl-dehydroalanine residue and adjacent residues, the main conformational characteristics of the cyclic heptapeptides consist of a compact ring formed by five of the seven amino acid residues with expulsion of a dipeptide portion out of the plane and the unnatural C20 β-amino acid (2S. 3S. 8S, 9S)-3-amino-9-methoxy-2, 6, 8-trimethyl-10-phenyldeca-4. 6-dienoic acid pointing upward from the ring. This structure of microcystin LR shows high degrees of similarity with the energy-minimized structure of nodularin, a cyclic pentapeptide of identical inhibitory potency against protein phosphatases 1 and 2A. Comparison of these structures with those of the less toxic LY variant and with the structurally unrelated okadaic acid, known as potent inhibitor of the protein phosphatases 1 and 2A, allowed us to propose a rational binding mode of this structural diverse set of natural inhibitors. © 1995 John Wiley & Sons, Inc.
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    Dielectric study of the cooperative order-disorder transition in aqueous solutions of schizophyllan, a triple-helical polysaccharideContribution No. 115 from the Microcalorimetry Research Center, Faculty of Science, Osaka University. (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 803-810 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Schizophyllan exists in aqueous solution as a triple helix, which is intact at room temperature. Its aqueous solution forms some ordered structure at low temperatures but undergoes a sharp transition to a disordered structure as the temperature is raised. The transition temperature Tc is about 7 and 18°C for H2O and D2O solutions, respectively. This transition was followed by time-domain reflectometry to investigate dynamic aspects of the transition. In addition to a major peak around 10 GHz, the dielectric dispersion curve of a 20 wt % schizophyllan in D2O exhibited a small peak around 100 MHz below Tc and around 10 MHz above Tc. The major peak is due to bulk water, whereas the 100 MHz peak is assigned to “bound” or “structured” water, and that around 10 MHz to side-chain glucose residues. However, unlike usual bound water reported for biopolymer solutions, this “structured” water disappears abruptly when the temperature becomes close to Tc without accompanying a conformational transition of the main chain. The above assignment is consistent with the structure of the ordered phase derived from previous static data that it consists of side-chain glucose residues along with nearby water molecules surrounding the helix core that are interacting with each other loosely through hydrogen bonds, and spreads radially only a layer of one or two water molecules but a long distance along the helix axis. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    Introduction (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 3-4 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360370103
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    Peptide science (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 1-2 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360370102
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    Synthesis of large peptides in solution (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 17-28 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360370105
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    100 Years lock-and-key concept: Are peptide keys shaped and guided to their receptors by the target cell membrane? (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 5-16 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ideas developed in the Membrane Compartments Theory which allow a quantitative prediction of receptor preference are discussed in terms of our present knowledge of opioid and neurokinin receptor structure. Furthermore, conformations of regulatory peptides interacting with artificial lipid membranes are compared with those of chemically constrained molecules that react selectively with different receptor classes. Striking similarities in the topochemistry of molecules with similar activity were observed. The membrane-induced topomers were almost congruent with the artificial topomers that are selectively recognized by the same receptors. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    Editorial (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 55-55 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.360370202
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  • 155
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    Masthead (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360370201
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  • 156
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    Design and synthesis of nonpeptide peptidomimetic inhibitors of renin (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 29-53 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The desire to replace the amide backbone of renin inhibitors with a new scaffold led us to explore vinylogous amides (enaminones). An initial attempt proved unsuccessful, a result explained after the fact via docking experiments. Based on this lesson, we designed a different vinylogous amide scaffold which incorportated one or more pyrrolinone rings into the backbone. Three of the four compounds gave IC50s in the 0.6 to 18 μM range. These compounds did not inhibit HIV-1 protease. Taken together, the results reported herein provide insights into the role of hydrogen bonding and steric interactions for binding to renin. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bip.360370106
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    Design and development of a vasoactive intestinal peptide analog as a novel therapeutic for bronchial asthma (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 57-66 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analogs of vasoactive intestinal peptide (VIP) were synthesized and screened as bronchodilators with the ultimate goal of enhancing the potency and extending the duration of action of the native peptide. Several design approaches were applied to the problem. First, the amino acid residues required for receptor binding and activation were identified. A model of the active pharmacophore was developed. With knowledge of the secondary structure (NMR) of the peptide, various analogs were synthesized to stabilize α-helical conformations. Having achieved a level of enhanced bronchodilator potency, our approach then concentrated on identification of the sites of proteolytic degradation and synthesis of metabolically-stable analogs. Two primary cleavage sites on the VIP molecule were identified as the amide bonds between Ser25-Ile26 and Thr7-Asp8. This information was used to synthesize cyclic peptides which incorporated disulfide and lactam ring structures. Analog work combined the best multiple-substitution sites with potent cyclic compounds which resulted in identification of a cyclic lead peptides. This compound, Ro 25-1553, exhibited exceptionally high potency, metabolic stability, and a long duration of action and may be an effective therapeutic for the treatment of bronchospastic diseases. © 1994 John Wiley & Sons, Inc.
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    Rational design, synthesis, and biological evaluation of novel growth hormone releasing factor analogues (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 67-88 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Since its initial discovery in 1982, growth hormone-releasing factor (GRF) has been the subject of intense investigation. This interest was prompted by the potential application of GRF for Stimulating growth in dwarf humans and for performance enhancement in livestock. Substantial research has been focused upon the development of potent, long-acting analogs as therapeutics. Herein is described a summary of the cumulative efforts of various laboratories endeavoring in this quest. The rationale utilized in GRF analog development is discussed: (1) determination of bioactive core. (2) evaluation of secondary structure, and (3) elucidation of degradation pathways (chemical and enzymatic). Using this information, several series of linear (unnatural and natural sequence) and cyclic GRF analogs were designed, synthesized, and evaluated. Stimulated by the constraints of commercial production, innovative, alternative methods of synthesis were explored: solid-phase, solution-phase, enzymatic, and recombinant. To date, the most promising candidate for drug development is [His1, Val2, Gln8, Ala15, Leu27]-hGRF(1-32)-OH. This natural sequence analog, consisting of rodent and human sequences, incorporates the bioactive core, preferred secondary structure, resistance to chemical and enzymatic degradation: with the added benefit of amenability to large-scale recombinant synthesis. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    Structure-activity studies on magainins and other host defense peptides (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 105-122 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Host defense peptides are widely distributed in nature, being found in species from bacteria to humans. The structures of these peptides from insects, horseshoe crabs, frogs, and mammals are known to have the common features of a net cationic charge due to the presence of multiple Arg and Lys residues and in most cases the ability to form amphipathic structures. These properties are important for the mechanism of action that is thougln to be a nonreceptor-mediated interaction with the anionic phospholipids of the target cell followed by incorporation into the membrane and disruption of the membrane structure. Host defense peptides have been shown to have broad spectrum antimicrobial activity, able to kill most strains of bacteria as well as some fungi, protozoa, and in addition, many types of tumor cells. Specificity for pathogenic cells over host cells is thought to be due to the composition of the cell membranes, with an increased proportion of anionic phospholipids making the pathogen more susceptible and the presence of cholesterol making the host membranes more resistant. Structure-activity relationship studies have been performed on insect cecropins and apidaecins. horseshoe crab tachyplesins and polyphemusins. and the frog magainins. CPFs (caerulein precursor fragments) and PGLa. In general, changes that increased the basicity and stabilized the amphipathic structure have increased the antimicrobial activity: however, as the peptides become more hydrophobic the degree of specificity decreases. One magainin-2 analogue. MSI-78. has been developed by Magainin Pharmaceuticals as a topical antiinefective and is presently in clinical trials for the treatment of infected diabetic foot ulcers. © 1994 John Wiley & Sons, Inc.
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    The development of potent peptide agonists and antagonists for the endothelin receptors (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 89-104 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The endothelins (ETs), sarafotoxins (SRTXs), vasoactive intestinal contractor (VIC), and bibrotoxin are a family of potent vasoconstrictor peptides. All peptides in this family possess 21 amino acids arranged in a unique bicyclic motif formed between cystine bridges in the 1-15 and 3-11 positions. Since the discovery of endothelin-1 (ET-1) in 1988, significant effort has been focused on the understanding of its structure-activity relationships. The identification of endothelin receptor subtypes has led to the discovery/design of potent peptide agonists and antagonists, along with nonpeptide antagonists of endothelin with varying levels of potency and receptor subtype selectivity. In keeping with the theme of this journal, this review will focus only on the development of peptidic-based agonists and antagonists of endothelin in addition to their applications in understanding the physiological and/or pathophysiological role of endothelin and its isopeptides. © 1994 John Wiley & Sons, Inc.
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    Structure-activity relationships of neuropeptide Y analogues with respect to Y1 and Y2 receptors (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 123-142 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Secondary structure investigations, affinities, and activities of neuropeptide Y analogues with respect to the Y1 and the Y2 receptor are reviewed. The results are discussed with respect to the different prerequisites for affinities to both receptor subtypes. The results from a systematic scanning of the hormone using L-alanine and from a large variety of discontinuous and cyclic analogs suggest that two different conformations of neuropeptide Y are adopted at the Y1 and Y2 receptors. Whereas a C-terminal turn structure is suggested for Y1 receptor affinity, an α-helical conformation of the C-terminus is afforded for good binding to the Y2 receptor. © 1994 John Wiley & Sons, Inc.
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    Bradykinin antagonists: Development and applications (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 143-155 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bradykinin (BK) is involved in regulation of every major physiological system and is an initiator or mediator of many pathophysiological conditions. Rapid progress in understanding these aspects of BK biology has come since the discovery of BK antagonists. This article reviews principal points in the history of the kallikrein-kinin field and of kinin biology. The chemistry and development of antagonists for B1 and B2 kinin receptors is discussed. Uses of the antagonists in biomedical research and potential clinical applications are presented. © 1994 John Wiley & Sons, Inc.
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    Editorial (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 176-176 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360370302
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    Masthead (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360370301
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    Concept and progress in the development of RGD-containing peptide pharmaceuticals (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 157-175 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cell adhesion domain, arginine-glycine-aspartic acid (RGD), has been incorporated into synthetic peptides to perform either of two modes of drug action, antagonist or agonist. Short, conformationally constrained peptides have been developed as antagonists for the platelet membrane glycopivtein complex, the integrin αIIbβ3, using cell-based and integrin-based assays. In combination with a comparative molecular modeling study, these results have helped identify common conformalional elements in the pharmacophore of this class of molecules. Peptides are presented that are highly potent, integrin specific, and that possess reduced pharmacological side effects. Also presented is the development of a peptide that modifies, noncovalently, the surfaces of a wide variety of this molecule is evident from its ability to stimulate cell attachment on these surfaces. This is shown to translate into an in vivo activity of faster and more complete tissue integration, and a reduction in foreign body response. © 1994 John Wiley & Sons, Inc.
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    One-bead-one-structure combinatorial libraries (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 177-198 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Combinatorial libraries employing the one-bead-one-compound technique are reviewed. Two distinguishing features characterize this technique. First, each compound is identified with a unique solid support, enabling facile segregation of active compounds. Second, the identity of a compound on a positively reacting bead is elucidated only after its biological relevance is established. Direct methods of structure identification (Edman degradation and mass spectroscopy) as well as indirect “coding” methods facilitating the synthesis and screening of nonpeptide libraries are discussed. Nonpeptide and “scaffold” libraries, together with a new approach for the discovery of a pentide binding motif using a “library of libraries,” are also discussed. In addition, the ability to use combinatorial libraries to optimize initially discovered leads is illustrated with examples using peptide libraries. © 1994 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360370401
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    Novel biopolymers for drug discovery (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 213-219 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid phase synthesis and generation of libraries of “unnatural biopolymers” is described. These polymers are characterized by novel backbones and building blocks, the properties of which may modify their pharmacological and folding properties. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360370305
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    The use of light-directed combinatorial peptide synthesis in epitope mapping (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 199-211 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of light-directed combinatorial peptide synthesis to epitope mapping is described. Photolithography and solid phase peptide synthesis were combined in an automated fashion to assemble arrays containing 1024 peptide sequences on a glass support in ten steps with the precise location of each peptide known. The simultaneous synthesis of two slides containing three arrays of peptidtes each allowed for the independent screening of both a monoclonal antibody (mAb) and its Fab fragment at two different concentrations. A binary synthesis strategy was used to assemble the arrays, resulting in all deletions and truncations possible within the FLRRQFKVVT sequence being present and available for screening. The relative binding interactions of each peptide was determined by incubating the arrays with either mAb D32.39 and goat antimouse immunoglobulin G-FITC or mAb D32.39 Fab-FITC conjugate, followed by scanning the surface for fluorescence with an epifluorescence microscope. The fragment RQFKVVT was found to bind lightly to both the mAb and Fab fragment while tethered to the surface, and was measured to have 0.49 n M affinity in solution. The frame-shifted RRQFKVV sequence was found to have lower affinity both in solution (1.3 m M) and on the surface. The fragment RQFKVV was determined to be responsible for antibody recognition and was found to bind tightly when tethered to the surface, yet exhibited no binding in solution as the free acid, suggesting the requirement of an amidated C-terminus or an additional flunking residue. A deletion analysis revealed that the novel RQFKVT sequence exhibited higher affinity than the RQFKVV sequence while tethered to the surface. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360370304
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    A review of the utility of soluble peptide combinatorial libraries (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 221-240 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This is paper reviews the preparation and use of soluble synthetic combinatorial libraries (SCLs) made up of millions of peptide and nonpeptide sequences for the identification of highly active individual compounds. First presented in 1991. SCLs have been prepared in a number of different lengths and formats, and are composed entirely of L-, D-, and unnatural amino acids. Also, existing peptide libraries have been chemically transformed to yield large diversities of nonpeptidic compounds. This review encompasses the published work from this laboratory using SCLs for the identification of antigenic sequences recognized by monoclonal antibodies, novel peptide agonists and antagonists to opioid receptors, new trypsin inhibitors, novel antibacterials, and compounds that inhibit melittin's hemolytic activity. SCLs offer a fundamental, practical advance in the study of interactions between peptide and nonpeptide sequences and their biochemical or pharmacological targets. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360370306
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    Editorial (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 241-241 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360370402
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    Vibrational optical activity of oligopeptides (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 265-279 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vibrational optical activity (VOA) is a relatively newspectroscopic technique, which has two principal manifestations, ir vibrational CD and vibrational Raman optical activity. Progress in the study of oligopeptides using both of these forms of VOA is reviewed from the perspective of theoretical and instrumental techniques, spectral results, and structural interpretations. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360370405
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    The importance of extended conformations and, in particular, the PII conformation for the molecular recognition of peptides (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 281-292 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Crystallographic, isotopic labeling nmr and transferred nuclear Overhauser effect studies have highlighted the extended conformation as a very important element of secondary structure at the binding site of many peptide/protein complexes including peptide inhibitors-enzymes, B-cell epitopes-antibodies, and T-cell epitopes-major histocompatibility complex (MHC) of class I and II complexes. This paper discusses the peptide ligand conformation consequences of these findings particularly in view of the identification of the PII conformation (left-handed extended polyproline II) in free solution. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360370406
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    Masthead (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360370601
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    Concept and progress in the development of RGD-containmg peptide pharmaceuticals (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 363-363 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cell adhesion domain, arginine-glycine-aspartic acid (RGD), has been incorporated into synthetic peptides to perform either of two modes of drug action, antagonist or agonist. Short, conformationally constrained peptides have been developed as antagonists for the platelet membrane glycoprotein complex, the integrin α11b, β3, using cell-based and integrin-based assays. In combination with a comparative molecular modeling study, these results have helped identify common conformotional elements in the pharmacophore of this class of molecules. Peptides are presented that are highly potent, integrin specific, and that possess reduced pharmacological side effects. Also presented is the development of a peptide that modifies, noncovalently, the surfaces of a wide variety of synthetic materials used in medical implants. The agonist activity of this molecule is evident from its ability to stimulate cell attachment on these surfaces. This is shown to translate into an in vivo activity of faster and more complete tissue integration, and a reduction in foreign body response. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360370506
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  • 176
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    Editorial (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 365-365 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360370602
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  • 177
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    Synthesis and characterization of 3-aryl-2-(polystyryl)cyclopropenones via cyclopropenium ion substitution on polystyrene (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1-6 
    Details
    ISSN: 0887-624X
    Keywords: cyclopropenone ; cyclopropenium ; reactive oligomer ; polystyrene ; Friedel-Crafts ; TGA ; polymeric cyclopropenone ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrophilic substitution of cyclopropenium ions on aromatic polymers offers a unique opportunity to introduce polar functionality in a controlled manner to conventional, nonpolar polymers. Phenylcyclopropenone substituted polystyrene with predictable chemical composition and narrow molecular weight distribution were prepared. Size exclusion chromatography (SEC) analysis demonstrated the absence of branching or crosslinking in these functionalized polystyrenes during electrophilic substitution of the parent homopolymer. 13C-NMR confirmed that the degree of phenylcyclopropenone substitution was both highly efficient and predictable over a broad compositional range. The glass transition temperature (Tg) of the polymers was found to vary linearly with mole % phenylcyclopropenone substitution of the polystyrene. Thermal gravimetric analysis (TGA) indicated that thermal decarbonylation of the appended cyclopropenones occurred at approximately 180°C. Weight loss vs. temperature profiles correlated reasonably well with levels of substitution based on 13C-NMR analysis, confirming that decarbonylation of the calculated cyclopropenone substituents was the predominant thermal decomposition pathway. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330101
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    The structures of low molecular weight glycerin propoxylates: An experimental, semi-empirical, and Monte Carlo study (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 31-47 
    Details
    ISSN: 0887-624X
    Keywords: glycerin ; 1,2,3-propanetriol ; propyelene oxide ; methyloxirane ; propoxylate ; oxypropylene ; oxyalkylene ; propoxylation ; alkoxylation ; alkylene oxide ; semi-empirical ; molecular orbital ; quantum ; MNDO ; PM3 ; molecular mechanics ; MM2 ; hydrogen bonding ; Monte Carlo ; statistical trials ; polyether ; polyol ; triol ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple Monte Carlo model has been developed for calculating the structural features and properties of low molecular weight triols produced by the base-catalyzed propoxylation of glycerin. The model computes the probability of a reaction to a specific oligomer from the local site reactivities of model compounds with an adjustment for the molecular weight of the reacting oligomer. The resulting product array is then used to calculate typical polymer properties such as average molecular weight, polydispersity, and average chain length. Trial rate constants were estimated from the activation energies of MNDO-PM3 semi-empirical molecular orbital theory. For the compounds used to model the oligomer chain end groups, the activation enthalpies were found to be within the ranges reported for experimental values. Although the predicted enthalpies of activation were significantly higher for the alkoxylation directly at glycerin, this was found to be attributable to intramolecular hydrogen bonding in the reactants that was disrupted in the transition states. Although the hydrogen bonding energies were higher than what are normally considered typical, comparison tests showed that the calculated energies agreed well with experimental values of alkoxide anion-alcohol systems. The PM3 rate constants, when used to calculate Monte Carlo probabilities, predicted the isomer distribution of the four isomeric monopropoxylates with a error of 4%. Optimization of the model reduced this to 0.5%. However, to accurately predict the oligomer distribution of higher molecular weight adducts and other properties, the correction term (M0/Mi)b had to be included, where M0/Mi is the ratio of the molecular weight of glycerin to the molecular weight of the oligomer undergoing alkoxylation, and b is assigned the value 0.7. Although b is empirical, it is consistent with a simple molecular mechanics (MM2) conformational study of the relative availability of the reactive end groups. When the final model was used to simulate the propoxylation of glycerin for a variety of PO/glycerin ratios, it was found to accurately reproduce properties such as primary hydroxyl content, polydispersity, oligomer distribution, and change in the monopropoxylate isomer ratio as a function of bulk PO/glycerin ratio. © 1995 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330104
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    Poly-3-Hydroxyalkanoates containing unsaturated repeating units produced by pseudomonas oleovorans (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1367-1374 
    Details
    ISSN: 0887-624X
    Keywords: poly-β-hydroxyalkanoates ; bacterial polyesters ; Pseudomonas oleovorans ; functional polyesters ; reserve polyesters ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly-3-hydroxyalkanoates (PHAs) containing repeating units with terminal alkene substituents at the 3-position were produced by Pseudomonas oleovorans grown with either 7-octeneoic acid [OA(=)] alone, or 10-undeceneoic acid [UND(=)] alone, or mixtures of UND(=) and either nonanoic acid (NA) or octanoic acid (OA). For the latter, the biomass and PHA yields decreased as the fraction of UND(=) increased in the mixed carbon substrates. Essentially all of the repeating units in the PHA obtained from cells grown with UND(=) alone contained terminal alkene groups, including 3-hydroxy-10-undeceneoate, 3-hydroxy-8-noneneoate, and 3-hydroxy-6-hepteneoate units, but less than half of the units in the PHA from OA(=) had alkene substituents. The PHAs obtained from cells grown with various mixtures of UND(=) and either OA or NA were random copolymers, and the fraction of units with alkene substituents in these polymers increased in proportion to the fraction of UND(=) in the mixed carbon substrates. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330819
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    Miniemulsion polymerization of styrene: Evolution of the particle size distribution (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1381-1389 
    Details
    ISSN: 0887-624X
    Keywords: particle size distribution ; evolution of latex particles ; miniemulsion polymerization; evolution of particle size ; mechanism of miniemulsion polymerization ; particle nucleation in miniemulsion polymerization ; calorimetry, miniemulsion polymerization of styrene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of the miniemulsion polymerization of styrene was investiaged through a combination of calorimetry to monitor the polymerization rate and transmission electron microscopy (TEM) to follow the evolution of the particle size distribution. These techniques proved to be a powerful combination for gaining detailed mechanistic information regarding these polymerizations. Particle size analysis of the latexes withdrawn during the course of the reaction revealed that most of the polymer particles were formed by a relatively low conversion (i.e., 10% conversion). However, nucleation continued well past this point (to 40-60% conversion). In fact, it was observed that nucleation in miniemulsion polymerizations using cetyl alcohol continued past the maximum in the rate of polymerization. As a result of these long nucleation periods, the latex particle size distributions produced from these miniemulsion polymerizations were broader than their conventional emulsion polymerization counterparts, and were negatively skewed with a tail of small particles. The amount of negative skewing of the particle size distributions was found to decrease with increasing initiator (potassium persulfate) concentration. Finally, a correlation was observed between the length of time to the maximum polymerization rate and the breadth of the particle size distribution as reflected in the standard deviation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330822
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    Crowned polyacetylene. I. Synthesis and characterization of poly(4′-ethynylbenzo-15-crown-5) (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1431-1436 
    Details
    ISSN: 0887-624X
    Keywords: poly(4′-ethynylbenzo-15-crown-5) ; Rh complex catalyst ; cation-binding property ; electroconductivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4′-Ethynylbenzo-15-crown-5 (EB15C5) polymerized with high yields in the presence of (bicyclo[2.2.1] hepta-2,5-diene) rhodium(I) chloride dimer and triethylamine as a cocatalyst in chloroform at 30°C. Common catalysts for the polymerization of substituted acetylenes, WCl6 and MoCl5, did not produce any polymer from EB15C5. The structure of the main chain for poly(4′-ethynylbenzo-15-crown-5) (PEB15C5) was determined to be predomi-nantly cis form, based upon the relatively sharp signals attributed to the main chain atoms that was observed in the 1H and 13C NMR spectra. The cation-binding properties of PEB15C5 are very similar to that of poly(4′-vinylbenzo-15-crown-5), and the selectivity is in the order of K+〉 Rb+ ≫ Cs+ ⋙ Na+, Li+. The electrical conductivity of PEB15C5 increased from 1.3 × 10-10 to 1.3 × 10-6 S. cm-1, when the polymer was doped with iodine. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330903
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    Homogeneous polyesters of predetermined length, composition, and sequence: Model synthesis of alternating glycolic-acid-co-(L)-lactic-acid oligomers (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1419-1429 
    Details
    ISSN: 0887-624X
    Keywords: polyester copolymers ; peptide isosterics ; monodisperse polyester copolymers ; engineered sequence polyster copolymers ; exactly sequenced copolyester ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methods for making monodisperse polyester copolymers of predetermined length, com-position, and sequence are reported. Alternating oligomers of (L)-lactic-co-glycolic acid (La-co-Gl), isosteric with polypeptides, are prepared by solution methods of protecting, coupling, and deprotecting alcohol and acid groups. The carboxylic acid is protected by benzyl ester formation and released by hydrogenation. The hydroxyl group is protected as the methoxyethoxyethyl ether and deprotected with sodium iodide and trimethylsilyl chlo-ride. Coupling uses dicyclohexylcarbodiimide. End-capped alternating oligomers containing —(GILa)4— and —(GILa)8— show polymer properties. They are noncrystalline oils that exhibit discernable Tg. The conformation of —GILa— and —LaGl— diads in the polyesters is shown to be similar to isosteric peptide diads —GlyAla— and —AlaGly—. Exactly structured, monodisperse polyesters suggest a chemical parallel to proteins. Designed struc-tural templates combining sheet-form —(Gl)n— and helical —(La)n— segments are at-tractive synthesis targets. The solution preparations reported here can be applied, but it is suggested that biosynthetic methods for introducing single ester units into peptide chains be adapted to synthesize precisely fashioned polyesters. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330902
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  • 183
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    Photoinitiated cationic polymerization using o-phthaldehyde and pyridinium salt (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1461-1464 
    Details
    ISSN: 0887-624X
    Keywords: photopolymerization ; cationic polymerization ; pyridinium salts ; o-phthal-dehyde ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cationic polymerization of cyclohexene oxide (CHO), n-butyl vinylether (BVE), N-vinylcarbazole (NVC), and 4-vinyl cyclohexenedioxide (4-VCHD) is initiated upon UV irradiation (Λinc. = 350 nm) of dichloromethane solution containing N-ethoxy-2-methyl-pyridinium hexafluorophosphate (EMP+PF6) and o-phthaldehyde. A feasible initiation mechanism involves formation of biradical by intramolecular hydrogen abstraction of triplet o-phthaldehyde. Oxidation of these radicals by EMP+ ions yields protons capable of initiating the cationic polymerization. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330907
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    Complex-radical terpolymerization of allylglycidyl ether, maleic anhydride, and methyl methacrylate: Design of self-crosslinking macromolecules (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1447-1454 
    Details
    ISSN: 0887-624X
    Keywords: terpolymerization ; charge transfer complex ; allylglycidyl ether ; maleic anhydride ; methyl methacrylate ; thermo-crosslinking ; photo-crosslinking ; thermal degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical copolymerization of donor-acceptor monomers, i.e., allylglycidyl ether (AGE), maleic anhydride (MA) and methyl methacrylate (MMA) are studied, where binary copolymerization of AGE...MA complex with MMA is obtained. Constants of charge transfer complex formation (Kc) and copolymerization (r1 and r2) are determined by 1H-NMR and Kelen-Tüdöş methods, respectively. It is found that synthesized film-forming terpolymers with free epoxy and anhydride groups on side chain of macro-molecules are being crosslinked easily under the effect of temperature and/or UV-ir-radiation. Observed crosslinking effect is proved by the DTA, TGA, and IR spectroscopic analyses. It is shown that complex-radical terpolymerization is very convenient method for the designing of reactive functional macromolecules of linear structure with self-crosslinking properties which can serve as a basis for the use in photolithographic applications. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330905
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    Macromolecular synthesis from saccharic lactones. Polyaddition of D-glucaro- and D-mannaro- 1,4:6, 3-dilactones with diisocyanates and hydrolyzability of the resulting polyurethanes having dilactone rings in the main chains (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1495-1503 
    Details
    ISSN: 0887-624X
    Keywords: saccharic acid ; dilactone ; polyaddition ; polyurethane ; diisocyanate ; deg-radation ; hydrolysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyaddition of saccharic acid dilactones prepared from D-glucose and D-mannitol, D-glu-caro-, and D-mannaro-1,4:6,3-dilactones (1 and 2, respectively), with hexamethylene di-isocyanate (3a) and methyl (S)-2,6-diisocyanatocaproate (3b) was carried out by using dibutyltin dilaurate as a catalyst at 50, 25, and 0°C to give polyurethanes (4 and 5) having dilactone moieties in the main chains. The resulting polymers were found to decompose easily in phosphate buffers under neutral or slightly basic conditions (pH 7 or 8). Therefore, the polyurethanes may be used as novel degradable polymeric materials. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330911
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    Synthesis and polymerization of 1-(2,4,6-tricyanophenylthio)-3-[3,5-bis(n,n-dimethylamino)phenoxy]-2-propyl methacrylate; polymer effect on intramolecular charge-transfer interaction (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1475-1485 
    Details
    ISSN: 0887-624X
    Keywords: methacrylate bearing donor and acceptor moieties ; polymer effect ; intra-molecular charge-transfer interaction ; spacer length ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-[3,5-Bis(N,N-dimethylamino)phenoxy]-ω-(2,4,6-tricyanophenylthio)alkanes (1a-c), where an electron-accepting 2,4,6-tricyanophenylthio group and an electron-donating 3,5-bis(N,N-dimethylamino)phenoxy one are linked with a spacer such as ethylene, trimethylene, and tetramethylene, were prepared in order to examine an effect of the spacer chain length on intramolecular charge-transfer interaction between the 2,4,6-tricyanophenylthio and 3,5-bis(N,N-dimethylamino)phenoxy groups. From the UV-vis spectra measurements of 1a-c, 1-[3,5-bis(N,N-dimethylamino)phenoxy]-3-(2,4,6-tricyanophenylthio)Propane (1b) carrying the trimethylene chain as a spacer was found to have the strongest intramolecular charge-transfer interaction. A new methacrylate-type monomer carrying the 1b unit as a side chain, 1-(2,4,6-tricyanophenylthio)-3-[3,5-bis(N,N-dimethylamino)phenoxy]-2-propyl methacrylate (2), was prepared successfully in 9.2% total yield in seven steps. The monomer 2 homopolymerized in benzene, tetrahydrofuran, acetone, and dimethyl sulfoxide in the presence of 2,2′-azobis(isobutyronitrile) at 60°C to give polymers [poly(2)] with molecular weights of 6,000 to 98,000. An intramolecular charge-transfer interaction in the poly(2) was found to be larger than that in the monomer 2 and to increase with an increase in the degree of polymerization of the poly(2), suggesting that there is an existence of polymer effect other than the polymer effect due to the high local concentration of the donor-acceptor pair. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330909
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    Synthesis and crosslinking of cyano-substituted polyamides and polyimides prepared from 1-(2,2-dicyano-1-hydroxyviyl)-3,5-diaminobenzene, sodium salt (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 381-387 
    Details
    ISSN: 0887-624X
    Keywords: cyano-substituted polyamides and polyimides ; crosslinked polymers ; thermal stability ; malononitrile ; 3,5-dinitrobenzoyl chloride ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,5-Dinitrobenzoyl chloide was condensed with malononitrile in the presence of sodium hydroxide under phase-transfer conditions to afford 1-(2,2-dicyano-1-hydroxyvinyl)-3,5-dinitrobenzene, sodium salt, which was catalytically hydrogenated to the corresponding diamine. The latter was used as starting material for the preparation of unsaturated cyanosubstituted polyamides and polyimides. The polymers were soluble in polar aprotic solvents, dilute sodium hydroxide, and certain strong inorganic and organic acids. Upon curing at 300°C for 65 h, crosslinked polymers were obtained that were stable up to 392-404°C in N2 or air and afforded an anaerobic char yield of 60-71% at 800°C. Their glass transition temperatures as determined by thermal mechanical analysis (TMA) were 221-275°C. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330305
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    Detection of nanoscale events in dispersed polymer particles containing a charge-transfer fluorescence probe (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 399-405 
    Details
    ISSN: 0887-624X
    Keywords: polystyrene latex ; fluorescence ; solvent diffusion ; staining ; fluorescent probe ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A probe molecule, which shows an unusually large change in fluorescent properties in response to changes in its environment, was introduced into a monodisperse polystyrene latex. Upon addition of low-molecular-weight compounds, the ensuing swelling process of the latex could be followed via the changes in the fluorescence spectrum of the probe molecule. Polymerization reactions of monomers, introduced into the particles, could also be monitored by means of this approach. Using glycidylmethacrylate as the monomer led to the formation of particles in which two distinctly different surroundings could be detected after such a polymerization. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330307
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  • 189
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    Reactions on polymers with amine groups. I. Reactions of vinylpridine polymers and of their model compounds with unsaturated carboxylic acids (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 389-398 
    Details
    ISSN: 0887-624X
    Keywords: chemically modified polymers ; addition reactions ; carboxybetaines ; proton magnetic resonance ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of vinylpyridine polymers with α,β-unsaturated carboxylic acids such as acrylic, methacrylic, crotonic, itaconic, cinnamic, fumaric, and maleic acids were studied. It was found that, when reacted with acrylic, itaconic and fumaric acids. poly(4-vinylpyridine) gave macromolecular betaine products while with maleic acid, betaine as well as the corresponding salt was obtained. Poly(2-vinylpyridine) reacted with the same acids as poly(4-vinylpyridine) gave only the salts. No significant changes were observed with the two polymers when reacted with methacrylic, crotonic, and cinnamic acids. To attempt to rationalize these observations with the two macromolecular tertiary amines, the reactions of 4-methyl and 2-methylpyridines with the same carboxylic acids were investigated. The 1H-NMR methodology was generally applied to elucidate the chemical structure obtained. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330306
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  • 190
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    Blends of bisphenol a polycarbonate and acrylic polymers. I. A chemical reaction mechanism (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 407-414 
    Details
    ISSN: 0887-624X
    Keywords: polycarbonate ; polymethyl methacrylate ; polyglutarimide ; acidolysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemical reaction at high temperature (above 200°C) between PC and PMMA has been very recently highlighted. However, no clear reaction mechanism has been proposed to explain this phenomenon. We suggest a reaction mechanism following two steps. The first step consists of hydrolysis of the ester bonds of the PMMA leading to acid pendant groups. These acids can then either ring close into glutaric anhydride, or acidolyze the carbonate bonds of PC during the second step. At the same time, benzoic acid produced by PC degradation could further react with PMMA or acidolyze the carbonate groups leading to the crosslinking of the system. A satisfactory contact between the reacting units is a key point in the proces. Significant amounts of PC-PMMA copolymer are obtained when the reaction is performed from a miscible system. On the contrary, no reaction occurs during melt mixing. Understanding the process enables us to specify the conditions, in which no chemical reaction takes place. In nonreactive conditions, PC/PMMA blends remain immiscible for several hours at 300°C. The thermodynamic UCST proposed in the literature is just an artifact due to the occurrence of the chemical reaction. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330308
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  • 191
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    Quantitative nuclear magnetic resonance imaging of liquids in swelling polymers (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1795-1806 
    Details
    ISSN: 0887-624X
    Keywords: NMR imaging ; NMR relaxation ; ultra-high molecular weight polyethylene ; Fickian diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The variation of nuclear magnetic resonance (NMR) relaxation parameters (T1, T2) within a polymer during swelling, limits the absolute accuracy with which liquid concentration profiles can be obtained using NMR imaging. In this article a study of the diffusion of decalin into ultra-high molecular weight polyethylene (UHMWPE) is reported. The study illustrates the use of a method of analysis whereby quantitative solvent profiles can be obtained from data influenced by both T1 and T2 contrast effects. A T1 and T2 map are obtained at a point in the uptake of liquid where the greatest range in liquid concentration is obtained at a point in the uptake of liquid where the greatest range in liquid concentration is observed. The intensity of signal corresponding to liquid in the polymer is compared to that of pure liquid in a reference sample, and correlations for T1 and T2 values versus signal intensity are used to deconvolve relaxation contrast, to yield the true liquid concentration. The technique was used to study the effect of degree of crosslinking of UHMWPE on the swelling kinetics and decalin transport within the polymer. A spin-echo imaging technique was used with a recycle delay approximately equal to the average spin-lattice relaxation time of the liquid, and an echo time approximately half the average spin-spin relaxation time. Under these conditions the relaxation contrast was significant, yet the mass uptake data derived from the concentration profiles obtained, using the method of analysis described, agreed well with gravimetric data. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331106
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  • 192
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    LC-Polyimides. XIX. Chiral and thermotropic poly(esterimide)s based on N-(4′-caboxyphenyl)trimellitimide and novel chiral spacers (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 427-439 
    Details
    ISSN: 0887-624X
    Keywords: poly(ester-imide)s ; chiral spacers ; cholesteric phase ; chiral smectic phases ; polycondensation ; Grand-Jean texture ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from commercial S- or R-3-bromo-2-methylpropanol, several new spacer diols were prepared. These spacers were polycondensed with the acid chloride of N-(4′-carboxyphenyl)trimellitimide. The resulting poly(ester-imide)s were characterized by elemental analyses, viscosity measurements, 1H-NMR spectroscopy, DSC- and WAXD-measurements and optical microscopy. The poly(ester-imide)s derived from chiral, aliphatic spacers form layer structures in the solid state, but no liquid crystalline phase. With nonsymmetrical, nonchiral semialiphatic spacers, poly(ester-imide)s were obtained, which form a smectic E or H phase in the solid state, a smectic-A or -C phase in the melt, and a nematic phase, when the spacer possesses an odd number of CH2 groups. The polycondensation of a chiral semialiphatic spacer yielded thermotropic poly(ester-imide)s with either S- or R-configuration. WAXD patterns measured with synchrotron radiation at various temperatures proved that a layer structure exists in the solid state (smectic-E* or H*) and a chiral smectic-A* or -C* phase plus a cholesteric phase in the melt. A 1 : 1 blend of the S- and R-polyesters was also studied, but did not show unusual features. © 1995 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330310
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  • 193
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    Simulation model for the molecular weight distribution in emulsion polymerization (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 441-453 
    Details
    ISSN: 0887-624X
    Keywords: emulsion polymerization ; molecular weight distribution ; mathematical model ; Monte Carlo method ; computer simulation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Monte Carlo simulation model for the kinetics of emulsion polymerization is proposed. In the present model, the formation of each polymer molecule is simulated by the use of only a couple of probability functions; therefore, the calculation can be handled well even on personal computers. It is straightforward to account for virtually any kinetic event, such as the desorption of oligomeric radicals and chain length dependence of kinetic parameters, and as a consequence very detailed information such as the full distributions of the dead polymer molecular weights and the macroradicals among various polymer particles can be obtained. When bimolecular terminations are the dominant chain stoppage mechanism, the instantaneous molecular weight distribution (produced in a very small time interval) becomes broader than that for homogeneous polymerizations due to a higher possibility that short and long polymer radicals react with each other if bimolecular reactions are fast enough. The increase in the polydispersity of the MWD is fairly large, especially when bimolecular termination by disproportionation is significant; however, the gel permeation chromatography (GPC) may not be a suitable analytical technique to detect such broadening since oligomeric peaks may not be observed in the elution curve. The present simulation method provides greater insight into the complicated phenomena of emulsion polymerizations. © 1995 John Wiley & Sons, Inc.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330311
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  • 194
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    Curing of diglycidylamine-based epoxides with amines: Kinetic model and simulation of structure development (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 461-472 
    Details
    ISSN: 0887-624X
    Keywords: reaction mechanism ; curing of epoxides ; theory of structure development ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A complex mechanism of the reaction of diglycidylamine (DGA)-based epoxides with primary amines is described and the kinetic model is developed. The reaction mechanism involves the addition of amine, etherification, and also formation of small cycles and anionic homopolymerization of the epoxide compound including transfer and termination. The polymer structure was theoretically described by distribution of structural fragments determined using the kinetic model. Simulation of the structure evolution during the DGA-aniline reaction at varying molar ratios of reagents and dilution of the system was performed. The effect of the reaction conditions on the distribution of structural fragments, such as branching units and cyclic structures, was determined. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330313
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  • 195
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    Formation and characterization of simple and mixed vesicles based on monomeric and oligomeric phosphate bipolar amphiphiles (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 455-460 
    Details
    ISSN: 0887-624X
    Keywords: bipolar amphiphiles ; bolaamphiphiles ; vesicles ; oligomeric phosphates ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Certain phosphate bipolar amphiphiles, both monomeric (I and II) and polymeric or rather oligomeric (poly-I and poly-II), were used as basic materials for the preparation of simple and mixed vesicles. Specifically, it was found that oligomeric phosphate bipolar amphiphiles form stable vesicles in aqueous media. The same oligomeric bolaamphiphiles in mixture with their monomeric counterparts also form stable mixed vesicles with sonication; they are relatively less stable with the “thin film method.” Furthermore, it was shown that the method of spanning the membrane of didodecylphosphate vesicels with the dipolar amphiphile II is not effective for enhancing stability. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pola.1995.080330312
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  • 196
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    Differences in structure growth in amine curing of diglycidyl ether of bisphenol a and N,N-diglycidylaniline epoxy resins: Bifunctional models (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 473-480 
    Details
    ISSN: 0887-624X
    Keywords: epoxides ; reaction mechanism ; cyclization ; structure development ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of diepoxides, diglycidylaniline (DGA), or diglycidyl ether of Bisphenol A (DGEBA) with aniline was followed using HPLC and SEC. The effect of molar ratio of reagents, dilution of the system, reaction temperature, and the difference between the reaction mechanisms for DGA and DGEBA systems on the reaction kinetics and molecular weight evolution is discussed. Molecular weights of the DGA-aniline polymers were by an order of magnitude lower than those of the DGEBA-aniline polymers due to the formation of small cyclic products in the former case. Also, a reduction in Mn with increasing temperature, dilution, and diluent polarity is brought about by a greater tendency toward cyclization under these conditions. Theoretically calculated molecular weight evolution during the reaction is in satisfactory agreement with the experiment. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330314
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  • 197
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    Synthesis and characterization of bismaleimide-polyurethane crosslinked copolymers (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 481-491 
    Details
    ISSN: 0887-624X
    Keywords: bismaleimide ; polyurethane ; crosslinked copolymer ; FTIR ; solid-state 13C-NMR ; thermal properties ; dynamic mechanical analysis ; morphologies ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of novel crosslinked copolymers of bismaleimide (BMI) and polyurethanes (PU) were prepared by direct copolymerization of BMI monomer and urethane-modified bismaleimide (UBMI). The copolymers were characterized by FT-IR and solid state 13C-NMR. The reaction rate of the BMI monomer can be significantly increased by copolymerization with UBMI. The crosslinked copolymers show good mechanical properties and high thermal stability. Studies on glass transition temperatures and dynamic mechanical properties indicate that the copolymer is a homogeneous system as the polyester-type PU employed. The transmission electron microscopy (TEM) of the copolymer illustrated a one-phase structure of the cured resins when the polyester-type PU was incorporated. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330315
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  • 198
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    Graft polymerization of arcylamide onto LLDPE film by electron beam pre-irradiation in air or argon. I. Influence of dose, grafting temperature, and monomer concentration (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2039-2047 
    Details
    ISSN: 0887-624X
    Keywords: graft polymerization ; grafting rate ; grafting kinetics ; EB-irradiation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linear low density polyethylene (LLDPE) film was irradiated by electron beam in air or argon prior to grafting in aqueous solutions of acrylamide containing 0.05% of Mohr's salt. The grafting kinetics was studied with pre-irradiation doses in the range of 2.5-25 Mrad and in the temperature range of 40-70°C. Grafting rates and final degrees of grafting were higher for LLDPE pre-irradiated in air than for LLDPE pre-irradiated in argon. The overall activation energies for the grafting reaction were dose-dependent. Above 5 Mrad, the overall activation energies were higher for LLDPE pre-irradiated in argon which is interpreted as being due to crosslinking of the LLDPE. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331211
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  • 199
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    Cationic polymerization of 1,3-pentadiene in the presence of alkyl halides (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2087-2090 
    Details
    ISSN: 0887-624X
    Keywords: 1,3-pentadiene ; Cationic Polymerization ; crosslinking ; chain transfer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331216
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    Dehydrofluorination of a copolymer of vinylidene fluoride and tetrafluoroethylene by phase transfer catalysis reaction (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2109-2112 
    Details
    ISSN: 0887-624X
    Keywords: dehydrofluorination ; phase transfer catalyst ; conjugated double bond ; vinylidenefluoride-tetrafluoroethylene copolymer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331302
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