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  • 1
    Electronic Resource
    Electronic Resource
    A cooperative transition between two helical conformations in a linear system: poly-L-proline I ⇌ II. II. Kinetic studies (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 721-737 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational transition between the two helical forms I and II of poly-L-proline serves as an experimental model for the study of the kinetic, behavior of cooperative systems. The slow I ⇌ II conversion after a sudden perturbation of the solvent composition was followed polarimetrically. The dependence of the mean relaxation times on chain length and the degree of conversion was compared with Schwarz's theory. In addition, a description of the entire relaxation curves was possible in three special cases: all-or-nothing, small perturbations of the I ⇌ II equilibrium in long chains, and conversions which start off with molecules completely in one or the other conformational state. The mathematical model on which the theory is based contains only one more adjustable parameter than the equilibrium model, but it adapts to the experimental results surprisingly well. The present kinetic results and equilibrium measurements on this system are described by the same values of those parameters which are common to both models. The found value of the rate constant of the propagation step, i.e. the cis ⇌ trans isomerization of a peptide bond at an existing I-II junction, agrees with the rate of isomerization in N,N-dimethylacetamide reported in the literature. The rate of nucleation is up to 105 times smaller than the rate of propagation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360100410
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  • 2
    Electronic Resource
    Electronic Resource
    Isochinoline, II. 3.3-Dialkylsubstituierte 3.4-Dihydro-isochinoline aus Alkyl-aryl-cyclopropanen (1971)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 104 (1971), S. 248-258 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Isoquinolines, II. 3.3-Dialkyl-3.4-dihydroisoquinolines from Alkyl-aryl-cyclopropanesUnder the conditions of the Graf-Ritter reaction alkyl-aryl-cyclopropanes 8 react with nitriles 2 via dialkyl-benzyl-carbonium ions 1 to give 3.3-dialkyl-3.4-dihydroisoquinolines 3. The effect of the substituents R1, R2, and R3 in 8 on the reaction is discussed.
    Notes: Alkyl-aryl-cyclopropane 8 reagieren unter den Bedingungen der Graf-Ritter-Reaktion über Dialkyl-benzyl-carboniumionen 1 mit Nitrilen 2 zu 3.3-dialkylsubstituierten 3.4-Dihydroisochinolinen 3. Der Einfluß der Substituenten R1, R2 und R3 in 8 auf den Reaktionsverlauf wird besprochen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19711040129
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  • 3
    Electronic Resource
    Electronic Resource
    Isochinoline,1. Synthese 3.3-dialkylsubstituierter 3.4-Dihydro- und 1.2.3.4-Tetrahydro-isochinoline (1970)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 103 (1970), S. 1674-1691 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Isoquinolines, 1. Synthesis of 3,3-Dialkyl Substituted 3,4-Dihydro- and 1,2,3,4-TetrahydroisoquinolinesDialkyl benzyl carbonium ions 12 react with nitriles under the conditions of the Graf-Ritter reaction to give 3,3-dialkyl-3,4-dihydroisoquinolines 9. 3,3-Dialkyl-1,2,3,4-tetrahydroisoquinolines 26 are prepared by reduction of dihydroisoquinolines as well as by Pictet-Spengler ring closure.
    Notes: Dialkyl-benzyl-carbonium-Ionen 12 reagieren mit Nitrilen unter den Bedingungen der Graf-Ritter-Reaktion zu 3.3-dialkylsubstituierten 3.4-Dihydro-isochinolinen 9. 3.3-Dialkylsubstituierte 1.2.3.4-Tetrahydro-isochinoline 26 lassen sich außer durch Reduktion entsprechender Dihydro-isochinoline auch durch Pictet-Spengler-Ringschluß darstellen.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19701030604
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  • 4
    Electronic Resource
    Electronic Resource
    Zur kinetik der radikalischen fällungspolymerisation von methyacrylonitril in substanz unter anfangsbedingungen (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 166 (1973), S. 199-207 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The AIBN initiated bulk polymerization of methacrylonitrile was carried out at 50 to 75°C. With regard to the initiator concentration the reaction order is 1/2. The overall activation energy was found to be 22,9 kcal. mole-1. The parameter k2w/ka (kw = propagation constant, ka = termination constant) was calculated from the number average of the degree of polymerization (P̄n) and the overall reaction rate at the time t = 0 (vbr,o), taking into account only the low molecular weight fraction of polymers with a distribution of bimodal character. At a temperature of 60°C and with respect to initial state k2w/ka = 1,75 .10-5 dm3 mol-1.s-1 and the efficiency of initiation f = 0,58 was obtained. The kinetic constants do not differ from those of solution polymerization.
    Notes: Die durch AIBN initiierte Polymerisation von Methacrylonitril wurde bei 50-75°C in Substanz untersucht. Die Reaktionsordnung ist in bezug auf die Initiatorkonzentration 1/2. Die Bruttoaktivierungsenergie beträgt 22,9 kcal . mol-1. Wird K2w/ka (Kw = Wachstumskonstante, ka = Abbruchskonstante) aus dem Zahlenmittel des Polymerisationsgradaes (P̄n) und der Bruttogeschwindigkeit zur Zeit t = 0 (vbr,0) bestimmt, darf bei Polymeren mit bimodaler Molekulargewichtsverteilung nur der kurzkettige Anteil berücksichtigt werden. Für 60°C wird unter Anfangsbedingungen k2w/ka = 1,75.10-5 dm3.mol-1. s-1 und der Radikalausbeutefaktor f = 0,58 gefunden. Die kinetischen Konstanten unterscheiden sich nicht von denen der Lösungspolymerisation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021660117
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  • 5
    Electronic Resource
    Electronic Resource
    Steady state multiplicity and stability in an adiabatic controlled cycled stirred tank reactor (1974)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 20 (1974), S. 256-263 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Steady state multiplicity in exothermic adiabatic reaction systems has previously been demonstrated by a number of authors. Specifically, the work of Root and Schmitz proved the existence of multiple steady states in a loop reactor, but difficulty was encountered in controlling such a reaction system at the intermediate steady states.Since a close analogy can be demonstrated between loop reactors and controlled cycled reactors (CCTR), it appeared reasonable to attempt to achieve steady state multiplicity in a CCTR. When the chemical reaction of Root and Schmitz was carried out in a CCTR, it proved relatively easy to obtain experimental values of intermediate steady statesf and to control the reactor at these conditions by means of a simple on-off temperature controller.This work suggests that chemical systems displaying steady state multiplicity can be experimentally investigated in a CCTR and that cyclic operation may be the best way for controlling such reactions systems.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690200208
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  • 6
    Electronic Resource
    Electronic Resource
    A theoretical study of a controlled-cycled stirred-tank reactor (1971)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 17 (1971), S. 220-225 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical study was carried out for a stirred reactor in which the feed and product streams were periodically interrupted. The cycled reactor proved superior to a continuous stirred-tank reactor for first- and second-order reactions, and surpassed a plug-flow reactor for those cases in which the reaction rate passes through a maximum, such as autocatalytic and exothermic adiabatic reactions. Temperature-programmed cycled reactors were also studied, but appeared to have little advantage over conventional reactors.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690170143
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  • 7
    Electronic Resource
    Electronic Resource
    Kooperative Konformationsumwandlungen von linearen Biopolymeren (1970)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 82 (1970), S. 468-479 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Konformationsumwandlungen in Proteinen, Nucleinsäuren und anderen Biopolymeren spielen offenbar bei vielen biologischen Prozessen, insbesondere bei Regelungsvorgängen, eine entscheidende Rolle. Sie verlaufen häufig kooperativ, d.h. der Elementarprozeß der Umwandlung eines individuellen Segments dieser Makromoleküle wird über intramolekulare Wechselwirkungen vom Zustand anderer Segmente beeinflußt. Im allgemeinen bevorzugen die Segmente den gleichen Zustand wie ihre Nachbarn. Die daraus folgenden Gleichgewichtseigenschaften kooperativer Systeme  -  z. B. die große Schärfe und die Kettenlängenabhängigkeit der Umwandlungen  -  lassen sich für lineare Systeme quantitativ mit dem linearen Ising-Modell erklären. Die molekularen Ursachen der Kooperativität können für einfache Modellpolymere gedeutet werden.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19700821203
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  • 8
    Electronic Resource
    Electronic Resource
    Cooperative transition between two helical conformations in a linear system: Poly-L-proline I ⇌ II. I. Equilibrium studies (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 329-352 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solvent-induced conformational transition between the two helical forms of poly-L-proline is studied as a model for cooperative order ⇌ order transitions. The chain length dependent equilibrium data in two solvent systems are described by Schwarz's theory, which is based upon the most general formulation of the linear Ising model with nearest neighbor interactions. The parameter σ which describes the difficulty of nucleation of a I (II) residue in an uninterrupted II (I)-helix is 10-5 in both solvent systems. The ratios of the nucleation difficulties of states I and II at the ends of the chains β′ and β″ are very different in the two systems. Nucleation difficulty within the chain is interpreted as being due to unfavorable excess interaction energies at the I-II and II-I junctions, which add up to 7 kcal/mole of nuclei as calculated from the σ value. A similar value is computed from the atomic interactions at the junctions. In contrast to this intrinsic properly of poly-L-proline, the energies of I and II residues at the ends are heavily influenced by interactions of the endgroups with the solvent. The above values of the nucleation parameters are determined by a new least-square fitting procedure which does not necessitate the assumption of the dependence of the equilibrium constant s for propagation upon the external parameters, but yields this function from the experimental transition data. A quantitative explanation of this experimental s function through the binding of solvent is attempted. In the transition region a very small free energy change (about 0.1 kcal/mole), arising from a preferential binding of solvent molecules to one of the conformational states, is sufficient for a complete conversion from one helical form to the other.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1970.360090308
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  • 9
    Electronic Resource
    Electronic Resource
    Binding of alcohols to the peptide CO group of poly-L-proline in the I and II conformation. II. Binding constants from infrared measurements in solution (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1759-1776 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trifluoroethanol, benzyl alcohol, and n-butanol bind to the peptide and acelyl CO groups of poly-O-acetyl-L-hydroxyproline in dichloromethane via hydrogen bonds. The binding aflinity decreases from trifhioroelhanol to n-buitanol. For the acelyl CO groups the binding does not depend on the conformation of the polymer but for the peptide CO groups the binding constants are larger by a factor of two to five time when it is in the helix II conformation (all peptide bonds trans) than when it assumes the helix I conformation (all peptide bonds cis). This preference is explained by the higher accessibility of the peptide CO groups in the II helix. The small additional energy which results from the preferential binding is sufficient, to induce a complete I → II transition because of the very high cooperativily of the system. The quantitative dependence of the equilibrium constant s for the propagation step of the transition on solvent composition (ratio of trifluoroethanol or benzyl alcohol to n-butanol) is derived from the binding data. It agrees satisfactorily with the empirical relation obtained from a best fit to transition curves of Ganseret al. The I ⇌ II conversion of poly-L-proline is therefore an example of a conformational transition whose solvent dependence can be explained by a binding mechanism.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360101003
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  • 10
    Electronic Resource
    Electronic Resource
    Binding of benzyl alcohol to the peptide CO group of cyclotri-L-prolyl studied by infrared spectroscopy (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 731-733 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110318
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