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  • 1995-1999  (5,277)
  • 1890-1899
  • 1850-1859
  • 1995  (5,277)
  • Polymer and Materials Science  (4,710)
  • Inorganic Chemistry  (567)
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Material
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  • 1995-1999  (5,277)
  • 1890-1899
  • 1850-1859
Year
Keywords
  • 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
    Electronic Resource
    Electronic Resource
    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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  • 170
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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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  • 171
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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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  • 172
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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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  • 173
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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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  • 174
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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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  • 175
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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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    Masthead (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280101
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  • 178
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    Tripodal Triamidostannates as Building Blocks in the Generation of Sn - M-Bonded Heterobimetallics (M = Fe, Ru) (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 29-34 
    Details
    ISSN: 0009-2940
    Keywords: Tripodal ligands ; Triamidostannates ; Metal-metal bonds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By in situ lithiation of the trifunctional amines H3CC(CH2NHSiMe3)3, PhC(CH2NHSiMe3)3, and HC{SiMe2NH(p-Tolyl)}3 and subsequent reaction with SnCl2 the corresponding triamidostannates were obtained. These were coupled with CpM(CO)2Cl (M = Fe, Ru) to yield the M - Sn-bonded heterobimetallics 9-14 of which H3CC(CH2NSiMe3)3SnFe(CO)2Cp (9) was characterized by a single-crystal X-ray structure analysis. Of the in situ-generated amidostannates only [HC{SiMe2N(p-Tolyl)}3Sn][Li(THF)3] (8) could be isolated as a uniform product and characterized analytically and spectroscopically.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19951280105
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  • 179
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    The Structures of [X2Y—N—YX2]+ Cations (X = F, Cl; Y = S, Se). A Comparison of X-ray and ab Initio Studies[1] (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 35-40 
    Details
    ISSN: 0009-2940
    Keywords: Selenium-nitrogen compounds ; Sulfur-nitrogen compounds ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures of cationic species of the series [X2Y—N—YX2]+ (X = F, Cl; Y = S, Se) have been computed ab initio using all electron treatments for first-row elements and sulfur and quasi-relativistic pseudopotentials for Se and Cl. Splitvalence basis sets with polarization and diffuse functions were employed. The MP2 results for the (non-isostructural!) cations [Cl2Se—N—SeCl2]+ (1: Cs) and [F2S—N—SF2]+ (2: C2v) are in excellent agreement with the experimental (X-ray) observations. Both structures represent local minima. A deeper minimum for either of the cations is represented by another C2v isomer which for crystal lattice energy reasons is stable in the isolated state only. The geometries of the hitherto unknown species [Cl2S—N—SCl2]+ (3) and [F2Se—N—SeF2]+ (4) have been assessed by ab initio HF calculations. In analogy to 2, cations 3 and 4 are predicted to prefer C2v symmetry. Therefore, 1 exhibits unusual structural features. According to strictly localized natural bond orbital analysis (NBO), the central nitrogen atoms in 1 and 2 possess two lone pairs of electrons (LP: one sp hybrid and one p orbital). The relatively short Se—N and S—N bond distances in 1 (1.741-1.760 Å) and 2 (1.551 Å) can best be attributed to LP(N)→s̰*(Y—X) negative hyperconjugation (1: Y = Se, X = Cl; 2: Y = S, X = F).
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19951280106
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  • 180
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    Die fördernde Rolle von Phosphinoester-Liganden bei der Synthese neutraler Carben-, Vinyliden- und Allenyliden-Ruthenium(II)-KomplexeHerrn Professor Hubert Schmidbaur zum 60. Geburtstag gewidmet. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 49-62 
    Details
    ISSN: 0009-2940
    Keywords: Ruthenium(II) complexes, octahedral ; Phosphino esters as mono- and bidentate ligands ; Fluxional behaviour ; Carbene complexes ; Vinylidene complexes ; Allenylidene complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vinylidene Transition-Metal Complexes, XXXV[1].  -  The Supporting Role of Phosphino Ester Ligands for the Synthesis of Neutral Carbene, Vinylidene and Allenylidene Ruthenium(II) ComplexesThe reaction of [RuCl2(PPh3)3] (1) with the phosphino esters iPr2P(CH2)nCO2R (2-4) leads to complete (n = 1; R = CH3, C2H5) or partial (n = 2; R =CH3) displacement of the PPh3 ligands and formation of the octahedral ruthenium(II) complexes [RuCl2{k2(P,O)-iPr2PCH2CO2R}2] (5, 6) and [RuCl2(PPh3){k(P)-iPr2PCH2CH2CO2Me}{k2(P,O)-iPr2PCH2CH2CO2Me}] (7). Treatment of 5 with LiBr and LiI affords the dibromo- and diiodoruthenium derivatives 8 and 9. While compound 5 reacts with CO and SO2 by cleavage of one Ru - O bond to yield the 1:1 adducts [RuCl2(L){k(P)-iPr2PCH2CO2Me}{k2(P,O)-iPr2PCH2CO2Me}] (10, 11), the reaction of the dibromo derivative 8 with CO in solution gives the dicarbonyl complex [RuBr2(CO)2{k(P)-iPr2PCH2CO2Me}2](13). If CO is passed over 8 in the solid state, the corresponding monocarbonyl compound 14 is formed. The hydridoruthenium(II) complex 16, which is obtained from equimolar amounts of [RuHCl(CO)(PiPr3)2] (15) and 2, reacts with HC≡CMe by insertion to give the vinyl derivative [RuCl{E - CH=CHMe}(CO)(PiPr3){k2(P,O)-iPr2CH2CO2Me}] (17). Treatment of 5 with HC̊' (R' = H, Me, tBu, Ph) and of 6, 8, 9 with HC≡CPh affords upon photochemical activation the octahedral vinylidene complexes [RuX2-(=C=CHR){k(P)-iPr2PCH2CO2R}{k2(P,O)-iPr2PCH2CO2R}] (18-21 and 23-25) in good to excellent yield. At room temperature, these compounds (with the exception of 25) are highly fluxional in solution. From 31P-NMR measurements, the free energies of activation ΔG
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280108
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  • 181
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    Reaktionen von R2Al—AlR2 (R = CH(SiMe3)2) mit Trimethylsilylazid  -  Insertion in die Al—Al-Bindung und Abbau zum trimeren Dialkylaluminiumazid (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 81-85 
    Details
    ISSN: 0009-2940
    Keywords: Aluminium-aluminium bond ; Insertion of trimethylsilyl azide ; Trimeric dialkylaluminium azide ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of R2Al—AlR2 (R = CH(SiMe3)2) with Trimethylsilyl Azide  -  Insertion into the Al—Al Bond and Formation of a Trimeric Dialkylaluminium AzideTetrakis[bis(trimethylsilyl)methyl]dialuminium(4) (1) reacts with trimethylsilyl azide under insertion of one nitrogen atom into the Al—Al bond. As shown by NMR spectra and crystal structure the product contains three and four coordinated Al atoms due to the coordination of the α-nitrogen atom of the azide group to one of the Al atoms. An electronically delocalized N3-system is formed with a N—N bond length of 132.0 pm and a bond order of 1.5 for both N—N bonds. With an excess of trimethylsilyl azide further reaction is observed only under mild irradiation conditions with an exchange of the azide group between Si and Al and formation of Me6Si2 and the dialkylaluminium azide 3, which is better synthesized by the reaction of Me3Si—N3 with Cl—Al[CH(SiMe3)2]2. The sterically highly shielded aluminium azide 3 is a trimer in the solid state showing a non-planar 12-membered Al3N9 heterocycle with short N—N bonds (114 pm).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280112
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  • 182
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    Transition-Metal Complexes with the Novel Scorpionate Ligand Dihydrobis-(tetrazolyl)borate: Synthesis and Characterization of Infinite Two-Dimensional Metal-Ligand Frameworks and One-Dimensional Water SubstructuresDedicated to Professor Dr. Herbert Schumann on the occassion of his 60th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 323-328 
    Details
    ISSN: 0009-2940
    Keywords: Poly(azolyl)borates, metal complexes of ; Bis(tetrazolyl)borate, metal complexes of ; Metal-nitrogen coordination ; Coordination polymers ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dihydrobis(tetrazolyl)borate metal compounds of the composition [M(L)2{μ-H2B(CHN4)2}2]n for M = Mn, Fe, Co, Zn, Cd with L = H2O and for M = Cu with L = NH3 are obtained from metal salts and K[H2B(CHN4)2]. Single-crystal X-ray studies reveal the formation of two-dimensional rhombic grid sheets through the bridging action of the bis(tetrazolyl)borate ligands. Each metal atom is octahedrally coordinated with two trans L ligands and four H2B(CHN4)-2 nitrogen donors. Two additional, hydrogen-bonded water molecules occupy the rhombic openings in the compounds with M = Mn, Fe, Co, Zn, and Cd. The water of crystallization is held in place through hydrogen bonding from the water ligands and to the nitrogen atoms to give a substructure of parallel kinked water chains. Temperature-variable magnetic measurements show a Curie-Weiss behavior for the paramagnetic complexes with M = Mn, Fe, Co, and Cu.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280402
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  • 183
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    New Organophosphorus Ligands: Cyclopropanation and Other Reactions of Cumulenes Bearing Diphenylphosphanyl Substituents (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 365-371 
    Details
    ISSN: 0009-2940
    Keywords: Cumulenes ; Butadienes ; Vinylcyclopropane ; Vinylidenecyclopropane ; Bicyclopropyl, phosphanyl-substituted ; Cyclopropanation ; Phosphane ligands ; Phosphane chalcogenides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrophosphorylation of 1,4-bis(diphenylphosphanyl)butadiyne with diphenylphosphane leads to the butadiene (Ph2P)2C=CH—CH=C(PPh2)2 (1). Treatment of 1 with dimethylsulfonium methylide gives the vinylcyclopropane (Ph2P)2C=CH—CH(CH2)C(PPh2)2 (2). Compound 2 reacts with aqueous hydrogen peroxide, elemental sulfur, or selenium to afford the tetrachalcogenides (Ph2XP)2C=CH—CH(CH2)C(PXPh2)2 with X = O (3), X = S (4), X = Se (5), respectively. While the tetraphosphane 1 and the vinyl-cyclopropane compound 2 cannot be converted into a bis-(cyclopropyl) compound with an excess of Me2S=CH2, the tetrasulfide 4 readily affords a mixture of (1R,1′R)-/(1S,1′S)-and meso-2,2,2′,2′-tetrakis(diphenylthiophosphinyl)-1,1′-bicyclopropyl (6, 7) in good yield. Treatment of 1,1,4,4-tetrakis-(diphenylphosphanyl)butatriene with dimethylsulfonium methylide leads to the vinylidenecyclopropane (Ph2P)2C=C=C(CH2)C(PPh2)2 (8). Compound 8 is converted into its tetrasulfide (Ph2SP)2C=C=C(CH2)C(PSPh2)2 (9) by treatment with elemental sulfur. The crystal structures of 1, 2, 4, 7, and 8 have been determined by single-crystal X-ray diffraction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280408
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    Mono- und Diferriophosphane und -thioxophosphoraneHerrn Professor Dr. Ekkehard Lindner zum 60. Geburtstag gewidmet. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 413-416 
    Details
    ISSN: 0009-2940
    Keywords: Ferriophosphanes ; Ferriophosphoranes ; Thioxophosphane ligand ; Decarbonylation reaction ; Sulfurization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mono- and Diferriophosphanes and -thioxophosphoranesHerrn Professor Dr. Ekkehard Lindner zum 60. Geburtstag gewidmet.The substitution of organic substituents in phosphanes or thioxophosphoranes by the 17-electron fragments CpFe-(CO)2 (—Fp) leads to isolobal ferriophosphanes or -thioxophosphoranes. The mono- and diferriophosphanes FpnPPh3-n [n = 1 (3), 2 (4)] are obtained by deprotonation of the mono- and diferriophosphonium salts [FpnPPh3-nH]X [n = 1 (1), 2 (2)] with DBU. They are oxidized by sulfur giving the mono- and diferriothioxophosphoranes FpnPPh3-n(S) [n = 1 (5), 2 (6)]. Sulfide 5 arises also from the reaction of CpFe(CO)2Cl and Ph2PH(S)/DBU. The one-sided decarbonylation reaction of 6 leads to FpFp′PPh(S) (7, Fp′ = CpFeCO). The Fp substituents (17 electrons) in 3-7 coordinate as one-electron donors to the PhnP- or PhnP(S) units (n = 1, 2). The bridging functions in 4 and 6 are hitherto unknown. The molecular structures of the complexes 5-7 were determined by X-ray structure analyses.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280413
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  • 185
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    About some Electrophilic Substitution Reactions with [(CF3S)3C+][AsF-6] (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 435-436 
    Details
    ISSN: 0009-2940
    Keywords: Trifluoromethylthio group ; Carbenium ions ; Diphenylmethane ; Dyes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(trifluoromethylthio)carbenium hexafluoroarsenate (1) reacts with N,N-dimethylaniline and anisole to form the corresponding diphenylmethanes 2, 3 with the SCF3 group at the methine carbon atom. During the reaction of 1 with benzene, compounds such as C6H5C(SCF3)3 and C6H5SCF3 are formed along with benzophenone, a product of hydrolysis of the diphenylmethane compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280417
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  • 186
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    Synthesis and Structure of the First Dimetalated Diphosphane Disulfide [(η5-C5Me5)(CO)2FeP(H)(S)]2 (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 441-442 
    Details
    ISSN: 0009-2940
    Keywords: Diphosphane disulfides ; Metallophosphoranes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first transition metal derivative meso-[(η5-C5Me5)(CO)2FeP(H)(S)]2 (2) of the unknown diphosphane disulfide [PH2(S)]2 results from treatment of (η5-C5Me5)(CO)2FePH2 (1) with 1.5 equivalents of elemental sulfur. Compound 2 was characterized by means of spectroscopy (IR, 31P, 31P{1H}, 13C{1H}, 1H NMR) as well as X-ray diffraction analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280419
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  • 187
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    Preparation and Molecular Structures of Tetrahydrofuran, Diethylene Diglycol Dimethyl Ether and 18-Crown-6 Complexes of Strontium and Barium TetrahydridoborateDedicated to Prof. Dr. Nils Wiberg on the occasion of his 60th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 455-460 
    Details
    ISSN: 0009-2940
    Keywords: Strontium bis(tetrahydridoborate)-2 tetrahydrofuran, chain polymer of ; Strontium bis(tetrahydridoborate)-bis(diglyme) ; Barium bis(tetrahydridoborate)-bis(diglyme) ; Strontium bis(tetrahydridoborate)-1,4,7,13,16-hexaoxacyclooctadecane ; Metal-hydrogen-boron bridges ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The strontium and barium tetrahydridoborate complexes M(BH4)2 · 2 diglyme and M(BH4)2 · 18-crown-6 (M = Sr, Ba) have been prepared from the solvates M(BH4)2 · 2 THF by ligand displacement. 11B-NMR and IR data reveal strongly polar bonding of the BH4 groups to the metal centers, and X-ray structural analyses of the diglyme and crown ether compounds show molecular units in which the BH4 group is in contact via three H atoms with the metal center. In contrast, M(BH4)2 · 2 THF compounds are chain polymers in the solid state, and each metal center is surrounded by 2 THF molecules in trans position and four BH4- groups each of which forms bridges with two metal centers. Estimations of the effective radius for the BH4 group indicate a high polarity for the M-BH4 interaction.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280504
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  • 188
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    Photochemische Reaktionen von Übergangsmetall-Organyl-Komplexen mit Olefinen, 1312. Mitteilung: Lit.Photochemisch induzierte [5+2],homo[5+21-Cycloaddition von 3-Hexin an Tricarbonyl(η5-2,4-cycloheptadien-l-yl)mangan (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 515-518 
    Details
    ISSN: 0009-2940
    Keywords: Manganese ; Cycloheptadienyl ; Alkyne ; [5+2],homo[5+2] Cycloadditions ; Tricyclo[5.3.1.04,10]undeca-2,5-dien-11-yl ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical Reactions of Transition Metal Organyl Complexes with Olefins, 1312. Mitteilung: Lit. . - Photochemically Induced [5+2], homo[5+2] Cycloaddition of 3-Hexyne to Tricarbonyl(η 5-2,4-cycloheptadien-1-yl)manganeseTricarbonyl(η5-2,4-cycloheptadien-1-yl)manganese (1) reacts upon UV irradiation in hexane at 243 K with two equivalents of 3-hexyne (2) in successive [5+2],homo[5+2] cycloadditions to give tricarbonyl(η2:2:1-1,2,3,11-tetraethyltricyclo-[5.3.1.04,10]undeca-2,5-dien-11-yl)manganese (3). Its crystal and molecular structure was determined by an X-ray diffraction analysis, in solution it was studied also by IR and NMR spectroscopy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280513
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  • 189
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    Masthead (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280601
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  • 190
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    1,4,2-Diazaphospholothiazoles and -pyridines by a Hantzsch-Type Condensation Using Chloromethyldichlorophosphane (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 581-587 
    Details
    ISSN: 0009-2940
    Keywords: Anellated azaphospholes ; Hantzsch-type [3 + 2] cyclocondensation ; Chloromethyldichlorophosphane ; Regioselectivity ; 31P-, 1H-, 13C-NMR spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [3 + 2] cyclocondensation of 2-amino-1,3-thiazoline, 2-aminopyridines, 2- and 4-aminopyrimidines, 2-aminopyrazine, and 2-aminoquinoline with chloromethyldichlorophosphane in the presence of triethylamine yields regiospecifically 5,6-dihydrothiazolo[2,3-e][1,4,2]diazaphosphole (3), 1,4,2-diazaphospholo[4,5-α]pyridines (12), 1,4,2-diazaphospholo[4,5-α]pyrimidines (15), 1,4,2-diazaphospholo[4,5-e]pyrimidine (17), 1,4,2-diazaphospholo[4,5-α]pyrazine (19), and [1,4,2]diazaphospholo[4,5-α]quinoline (22), respectively. Using 2-amino-1,3-thiazole (4) and 2-aminobenzothiazoles 8, we obtained mixtures of the 1,5- and 4,5-anellated 1,4,2-diazaphospholes 5/6, 9a/10a and 9b/10b, while in the case of the methyl derivative 8c only the [1,4,2]diazaphospholo[5,4-b][1,3]benzothiazole 10c was formed. In the reaction of 2-aminothiazole and 2-aminopyrazine with Chloromethyldichlorophosphane the bis(diazaphospholo)-substituted chloromethylphosphanes 7 and 20 could be detected. The new anellated 1,4,2-diazaphospholes are colorless to pale yellow crystalline moisture-sensitive solids.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280610
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  • 191
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    Reactions at Silicon-Silicon Bonds, V. Selective Trichlorosilylation of Alkyl(diorganylamino)chlorophosphanes with Hexachlorodisilane or with Trichlorosilane/Triethylamine. - Two Routes to New Functional Trichlorosilylphosphanes (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 615-619 
    Details
    ISSN: 0009-2940
    Keywords: Reductive silylation ; Aminochlorophosphanes ; Silylphosphanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of alkyl(diorganylamino)chlorophosphanes R(R2′N)PCl 1 (1a: R = tBu, R′ = Et, 1b: R = iPr, R′ = iPr; 1c: R = iPr, R′ = Ph) with hexachlorodisilane, afforded alkyl(diorganylamino)trichlorosilylphosphanes R(R2′N)PSiCl3 2 (2a: R = tBu, R′ = Et; 2b: R = iPr, R′ = iPr; 2c: R = iPr, R′ = Ph) and silicon tetrachloride. An intermediate formed in the reaction of 1b with hexachlorodisilane, the adduct iPr(iPr2N)(Cl)P-Si(Cl)3-SiCl3 (3b = 1b · Si2Cl6), was detected by 31P- and 29Si-NMR spectra that indicate pentacoordinated silicon bound to tetracoordinated phosphorus and tetracoordinated silicon. Trichlorosilylphosphanes 2 are also available from 1 under very mild conditions by reductive trichlorosilylation with trichlorosilane in the presence of triethylamine. Compounds 2 were identified analytically, by mass spectroscopy, multinuclear NMR, and an X-ray structure determination of 2c.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280614
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  • 192
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    Reactions of Complex Ligands, LXIVPart LXIII: Ref.. Synthesis of 5,5′-Diphenyl-2,2′-bifuran, a Biaryl Compound with Remarkable Fluorescence Properties (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 641-643 
    Details
    ISSN: 0009-2940
    Keywords: Carbene ligands ; Tungsten complexes ; 2,2′-Bifuran ; Copper coupling reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2-oxacyclic α,β-unsaturated carbene complex 1 reacts with an excess of dimethylamine to give the diphenylbifuran 2. The structure of 2 was established by independent synthesis from 2-phenylfuran (4) via regioselective lithiation and transmetalation to zinc and tin organometallics 6a-c and final oxidative copper coupling reactions.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280618
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  • 193
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    Synthesis of 2- and 3-Stannolenes via Addition of Trimethyltin Alkoxides to 3-Diethylboryl-4-ethyl-1,1-dimethylstannole (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 679-687 
    Details
    ISSN: 0009-2940
    Keywords: Stannole, diethylboryl-substituted ; Trimethyltin alkoxides ; 2-, 3-Stannolenes, organometallic-substituted ; NMR, coupling constants, 2J(Sn,Sn), sign determination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trimethyltin alkoxides (2) react stereoselectively with 3-diethylboryl-4-ethyl-1,1-dimethylstannole (1) via addition of the Me3Sn group to C(2) to the C(2) = C(3) bond and a 1,2 shift of an ethyl group from boron to C(3) to give the 2-stannolenes 3. The molecular structure of 3f' [R = (S)-2-Bu] was determined by single-crystal X-ray analysis, confirming the cis positions of the Et(RO)B and the Me3Sn group. These 2-stannolenes 3 undergo, upon heating to ca. 80°C, facile rearrangement by irreversible allylic migration of the Et(RO)B group to the 3-stannolenes 4 in which the cis positions of the boryl and the stannyl group are retained. All 2-stannolenes (in contrast to the 3-stannolenes) are readily deprotoborylated to give the 3-stannolene 5. The structures of 3, 4, and 5 follow conclusively from 1H-, 11B-, 13C-, and 119Sn-NMR spectra. The negative sign of the geminal coupling constants 2J(SnSn) was determined in the case of 3, 4, and 5 by 2D 119Sn/1H heteronuclear shift correlations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280705
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  • 194
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    Synthesis of Structures of (Acyloxy)boranesDedicated to Prof. Dr. A. Schmidpeter on the occasion of his 65th birthday.Synthesis of Structures of (Acyloxy)boranes (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 751-762 
    Details
    ISSN: 0009-2940
    Keywords: Trifluoroacyloxy-9-borabicyclo[3.3.1]nonane ; Pivaloyloxy-9-borabicyclo[3.3.1]nonane dimer ; Bis(9-borabicyclo[3.3.1]nonyl]oxalate ; Tetrakis(9-borabicyclo[3.3.1]nonyl)-dihydroxyoxalate ; Bis(9-borabicyclo[3.3.1]nonyl)-2,2-dimethylmalonate tetramer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 9-Borabicyclo[3.3.1]nonane (9-BBNH) reacts with monocarboxylic acids to afford 9-(acyloxy)-9-borabicyclo[3.3.1]nonanes which are dimers in the solid state as shown by X-ray crystal structures of the benzoate and pivalate. More complex reactions were observed by allowing 9-BBNH to react with dicarboxylic acids in THF or monoglyme. Thus, (9-BBN)2 oxalate 3 contains a fully delocalized oxalate unit with equal C-O and B-O bond lengths. Traces of water convert it into the tetrakis(9-BBN) oxalate 5. A rather unusual structure is veryfied by 9-BBN 2,2-dimethylmalonate 7 which according to its molecular structure is a tetramer featuring a 32-membered ring system. In contrast, reactions of oxalic acid with thexylborane leads to reduction of the acid and formation of a bicyclic dioxaborolo-dioxaborolane 10. Several intermediates were detected by 11B-NMR spectroscopy as well as in reactions of BH3 · THF or BH3 · SMe2 with oxalic acid.  -  It follows from the present study that (acyloxy)boranes derived from dicarboxylic acids are strong Lewis acids with an unexpected variety of structural features.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280803
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  • 195
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    A T-Shaped Selenenyl Halide: Synthesis and Characterisation of a Proposed Reaction Intermediate (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 741-742 
    Details
    ISSN: 0009-2940
    Keywords: Selenenyl halides ; Nucleophilic substitution ; Complex intermediate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The T-shaped selenenyl halide (1), which may be regarded as a model substance for the transition state in nucleophilic displacement at divalent chalcogen atoms, has been isolated and subjected to X-ray structure determination.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280715
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  • 196
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    Zinc Complexes of Drugs Containing Nitrogen Heterocycles (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 779-785 
    Details
    ISSN: 0009-2940
    Keywords: Zinc complexes ; Drug ligands ; Captopril ; Isoniazid ; Nalidixic acid ; Mercaptopurine ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four drugs whose actions have a relation to the status of zinccontaining species in the human body were used as ligands in zinc complexes. Captopril (H2Cap) forms the compound [ZnCap] (1) presumed to be a coordination polymer with O and S coordination. Isoniazid, in the presence of zinc salts, is converted to 1,2-diisonicotinoyl hydrazide (H2Nih) which forms polymeric [Zn(Nih)NH3] (2) with trigonal-bipyramidal ZnO2N3 coordination. Nalidixic acid (HNal) and zinc perchlorate yield [Zn(HNal)2(H2O)2](ClO4)2 · 2 H2O (3) containing zinc in an octahedral ZnO6 environment. Mercaptopurine (H2Mer), in the presence of ammonia, forms [Zn(Mer)(NH3)2] . H2O (4) which is a coordination polymer containing tetrahedral ZnN4 units. The structures of [Zn(Nih)NH3], [Zn(HNal)2(H2O)2](ClO4)2 . 2 H2O, and [Zn(Mer)(NH3)2] . 2 H2O were determined diffractometrically.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280807
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  • 197
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    Enantioselective Deprotonation of Benzyl Phosphates by Homochiral Lithium Amide Bases  -  Configurational Stability of Benzyl Carbanions with a Dialkoxyphosphoryloxy Substituent and Their Rearrangement to Optically Active α-Hydroxy Phosphonates (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 823-830 
    Details
    ISSN: 0009-2940
    Keywords: Phosphate-phosphonate rearrangement ; Carbanions, benzylic, configurational stability of ; Phosphonaes Lithium amides, homochiral ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Benzyl dialkyl phosphates are deprotonated enantioselectively by homochiral lithium amides of isopropyl(1-phenylethyl)amine or bis(1-phenylethyl)amine. The short-lived benzylic carbanions formed are virtually configurationally stable relative to the rearrangement to optically active phenyl-hydroxymethylphosphonates. The enantiomeric excesses are up to 50%. The pro-(S) hydrogen is removed by amides having (S) configuration. Homochiral diethyl (S)-phenyl[D1]-methyl phosphate [(S)-16c] is deprotonated by both LDA and n-BuLi with a high primary kinetic isotope effect (kH/D ≍ 50) and isomerizes to the corresponding α-hydroxy phosphonate with an enantiomeric excess of up to 85%.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280814
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  • 198
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    Tris(1,10-phenanthroline)iron(II) Complexes  -  Broad Variation of the Redox Potential by 4,7-Substitution at the Phenanthroline Ligands[1] (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 845-850 
    Details
    ISSN: 0009-2940
    Keywords: Phenanthroline synthesis ; Tris(phenanthroline)iron(II) complexes ; Redox potential ; Cyclic voltammetry ; Electron transfer, outer-sphere ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new 4,7-donor-substituted phenanthrolines 2a-h were synthesized and the corresponding tris(1,10-phenanthroline)iron(II) complexes 3a-h studied by cyclic voltammetry. In more detail three novel aza-crown ether-linked (phenanthroline)iron complexes were investigated, the redox potentials of which could be fine-tuned by the addition of group-Ia,IIa metal cations. All iron(II) complexes showed reversible waves at scan rates between 50 and 500 mV · s-1 and could be reversibly oxidized and reduced by chemical means.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280816
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    Bis(cyclopentadienyl)methane-Bridged Dinuclear Complexes, 10Part 9: B. Stempfle, H. Werner, Gazz. Chim. Ital., 1995, 125, in press. The Bis(cyclopentadienyl)methane Link between Lewis Basic and Lewis Acidic Metal CentersDedicated to Prof. Dr. Herbert Schumann on the occasion of his 60th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 877-881 
    Details
    ISSN: 0009-2940
    Keywords: Bis(cyclopentadienyl)methane ; Heterobimetallic complexes ; Imido complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mononuclear rhodium complexes [(C5H5CH2C5H4)-Rh(CO)2] (1) and [(C5H5CH2C5H4)Rh(PhC≡CPh)(PiPr3)] (2) readily react with nBuLi or TlOEt to yield the corresponding lithium salts 3 and 4 or thallium salts 5 and 6. The reaction of these salts with [(C5H5)Nb(NtBu)Cl2] (7) leads to the formation of the heterodinuclear compounds [{CH2(C5H4)2}-{Rh(CO)2}{(C5H5)Nb(NtBu)Cl}] (8) and [{CH2(C5H4)2}-{Rh(PhC≡CPh)(PiPr3)}{(C5H5)Nb(NtBu)Cl}] (9), respectively. Treatment of 3-6 with [Mo(NtBu)2Cl2] (10) gives the heterodinuclear Rh/Mo complexes [{CH2(C5H4)2}{Rh(CO)2}-{Mo(NtBu)2Cl}] (11) and [{CH2(C5H4)2}{Rh(PhC≡CPh)-(PiPr3)}{Mo(NtBu)2Cl}] (12). The analogous reaction of [Mo(NMes)2Cl2(DME)] (13) with 3-6 yields the corresponding complexes [{CH2(C5H4)2}{Rh(CO)2}{Mo(NMes)2Cl}] (14) and [{CH2(C5H4)2}{Rh(PhC≡CPh)(PiPr3)}{Mo(NMes)2Cl}] (15). From the monometallated ligand [(C5H5CH2C5H4)M] (M = Li: 16; M = Tl: 17) and the imidometal compounds 7, 10 and 13, the mononuclear complexes [(C5H5CH2C5H4)(C5H5)Nb-(NtBu)Cl] (18) and [(C5H5CH2C5H4)Mo(NR)2Cl] (R = tBu: 19; R = Mes: 20) have been obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280905
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    Addition von Hydrofullerid [C60H]- an koordinierte, ungesättigte Kohlenwasserstoffe: Bindung von Fulleren an Metallkomplexe über KohlenwasserstoffbrückenHerrn Professor Herbert Walter Roesky zum 60. Geburtstag gewidmet (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1059-1060 
    Details
    ISSN: 0009-2940
    Keywords: Fullerene ; Hydrofulleride ; Manganese complex ; Rhenium complex ; Iron complexes ; Ruthenium complex ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition of Hydrofulleride [C60H]- to Coordinated, Unsaturated Hydrocarbons: Binding of Fullerene to Metal Complexes through Hydrocarbon BridgesHerrn Professor Herbert Walter Roesky zum 60. Geburtstag gewidmet.Hydrofulleride [C60H]- is added to the hydrocarbon ligands of the cationic complexes [(OC)5Re(η2-C2H4)]+, [(OC)3Mn-(η6-C6H6)]+, [(OC)3M(η5-C6H7)]+ (M = Fe, Ru), [(OC)3Fe(η5-C7H9)]+, and [(η5-C5H5)Fe(η6-C5H4CH2)]+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281017
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