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  • 1
    Electronic Resource
    Electronic Resource
    Ueber die Constitution der organischen Säuren u. s. w.Fortsetzung von Bd. XIX. 312. (1840)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 20 (1840), S. 273-318 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.18400200143
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  • 2
    Electronic Resource
    Electronic Resource
    Temperature effect on the stereoelective polymerization of methylthiirane in homogeneous phase (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 2225-2231 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chiral cadmium thiolates of cysteine with cyclohexyl or (-)menthyl ester groups were prepared and compared with similar compounds (with isopropyl or methyl ester groups) as initiators for stereospecific polymerization of methylthiirane in homogeneous phase. The resulting polymers are highly isotactic and in all cases stereoelection can be reversed with a small change in polymerization temperature. This temperature effect permitted to differentiate two stages in the polymerization corresponding to the formation of a precursor and to that of a high polymer, respectively.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820812
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  • 3
    Electronic Resource
    Electronic Resource
    Role of cocatalysts in polymerizations initiated with benzyl derivatives of transition metals, 1. Polymerization of ethylene (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 1389-1395 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymerization of ethylene initiated in naphta solution by Zr(CH2C6H5)4 at 200°C under high purity conditions showed a cocatalytic effect of water with a maximum rate for a mole ratio H2O/Zr close to 0,1. No activity was observed for the hypothetical compound (C6H5CH2)3ZrOZr(CH2C6H5)3. Ethylene polymerization was also initiated with supported catalysts obtained by reaction of Zr(CH2C6H5)4 with silicium oxide or pre-dried aluminium oxide with an increase of activity (by a factor of 5). The resulting polyethylenes were found to be virtually linear with 1,5 CH3 groups for 1000 C atoms and with melting points of 134 - 136,5°C. They have high molecular weights with very broad distribution. These results were interpreted by a mechanism involving Ziegler-like active centers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021840707
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  • 4
    Electronic Resource
    Electronic Resource
    Stereospecific polymerization of methylthiirane in homogeneous phase, 4. Solvent effect on stereospecificity and enantioasymmetry (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1015-1025 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The living stereospecific polymerization of methylthiirane initiated by a chiral cadmium compound was run in different solvents. The general features of the mechanism of stereoregulation are the same as in bulk. In heptane and in heptane/propylene carbonate mixtures, the stereospecificity of the reaction does not depend on monomer concentration and on the dielectric constant ε of the medium. This independence of stereospecificity is in agreement with the absence of a variation of the complexation constant between a model cadmium derivative and the monomer with the variation of ε in a large range. The enantioasymmetric process depends on the molecular weight of the chain bearing the active sites. A change from diastereoisomeric to enantiomeric forms of active sites occurs for molecular weights around 50000. The enantioasymmetric constant depends on the nature of the medium and we observed a Born law for the dependence of the enantioasymmetric constant versus reciprocal dielectric constant: log kR ∝ 1/ε. This effect can be explained by a variation of the reactivities of the two types of active sites and occurs without a change in their relative amounts.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940324
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  • 5
    Electronic Resource
    Electronic Resource
    Stereospecific polymerization of methylthiirane in homogeneous phase, 1. Oligomerization step and change in stereocontrol with molecular weight (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1317-1326 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerization of methylthiirane in homogeneous phase initiated by bis(isopropylcysteinato)cadmium is a living process. For low conversions, oligomers (essentially heptamers and octamers) are formed, apparently using one valency of cadmium, the main propagation taking place by using the other one. However, the size of the oligomers may still grow for higher conversions. The mechanism of the oligomer formation depends on the temperature. A “normal” insertion of the monomer is observed at -23°C, whereas at 20°C a disulfide bond is formed. The preferential choice of a different enantiomer in the main propagation reaction may depend on the presence of a particular type of oligomer, in the vicinity of cadmium, linked to the cysteine group. However, stereospecificity (stereoselection and stereoelection) appears only with molecular weights higher than 6000 and also depends on the temperature of propagation: with decreasing temperature, the stereoregularity increases and the stereoelection can be inverted (for a definite oligomer structure).
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850705
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  • 6
    Electronic Resource
    Electronic Resource
    Stereospecific polymerization of methylthiirane in homogeneous phase, 3.Part 2: cf. ref. 6 Study of the enantioasymmetric process (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1003-1014 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Enantioasymmetry was studied for polymerizations of methylthiirane initiated by bis(isopropyl-S-cysteinato)cadmium and run in bulk. The ratio of rates of consumption of the two antipodes is independent of their concentrations. The enantioasymmetric constant kR, measuring the preferential choice of the R-antipode, is depending on both the relative number of the two types of active sites and on their reactivities. An effect on enantioasymmetry of the molecular weight of the growing chains bearing the active sites, is occurring with two distinct stages: The first one is observed, with an enantioasymmetric constant kR = 1,5, from the appearance of stereospecificity up to molecular weights of 35000 (for the main chain) and the second one with kR = 1,07 for molecular weights higher than 35000. In the first stage, the cysteinato end group of the oligomer chain remains linked to cadmium (by cadmium-nitrogen complexation) and the two active sites are diastereoisomers having different reactivities. In the second stage, the macrocyclic oligomer becomes too large and cadmium-nitrogen interaction is suppressed. The active sites are now enantiomers having the same reactivity. In this case, enantioasymmetry depends only on the unbalance between the amounts of the two types of active sites. The maximum size the macrocyclic oligomer can reach depends on the initiator concentration.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940323
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  • 7
    Electronic Resource
    Electronic Resource
    Stereospecific polymerization of methylthiirane in homogeneous phase, 2.Part 1: cf. ref.3. Mechanism of stereoregulation (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 1709-1721 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the living polymerization of methylthiirane initiated with bis(isopropyl-(S)-cysteinato)-cadmium, stereospecificity depends on temperature of propagation, on initiator concentration and also on the length of the growing polymer chain. The kinetics of stereospecific and non-stereospecific processes are described. In both cases, the order with respect to monomer is equal to zero and that with respect to initiator is one-half. The stereospecific propagation is proposed to involve cadmium thiolates associated as “dimeric species” and coordinated by both the monomer and by an oligomeric or polymeric chain.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930714
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  • 8
    Electronic Resource
    Electronic Resource
    Role of cocatalysts in polymerizations initiated with benzyl derivatives of transition metals, 2Part 1: cf.1.. Polymerization of styrene (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 1397-1406 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymerization of styrene in toluene solution at 50°C was found not to be initiated with sufficiently pure tetrabenzylzirconium or -titanium. However, a cocatalytic effect of water was observed with a maximum rate for a mole ratio H2O/Mt (Mt = Zr or Ti) close to 0,1. No activities were observed for the hypothetical compounds (C6H5CH2)3Mt - O - Mt(CH2C6H5)3. This cocatalytic effect was also observed with tribenzylchlorozirconium (1), tribenzylzirconiooxytriphenylsilane (2), or 6,6-dibenzyl-2,2,4,4-tetramethyl-1,3,5-trioxa-2,4-disila-6-zirconacyclohexane (3). Styrene polymerizations were also initiated by supported catalysts obtained by reaction of Zr(CH2C6H5)4 with aluminium oxide or silicium oxide pre-dried at various temperatures. The activities of such systems were equal or slightly lower than those obtained with the system Zr(CH2C6H5)4/H2O (mole ratio 10 : 1). The resulting polystyrenes have very high molecular weights with very broad distribution. Copolymerization experiments with methyl methacrylate gave as main product a copolymer containing only 4% of monomeric units of styrene. A discussion of all results led to the conclusion that the main polymerization involves an anionic-type propagation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021840708
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  • 9
    Electronic Resource
    Electronic Resource
    Crystallization of the RNA-binding domain of the transcriptional antiterminator protein sacy from Bacillus subtilis (1997)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 28 (1997), S. 590-594 
    Details
    ISSN: 0887-3585
    Keywords: SacY ; antiterminator ; RNA-binding motif ; crystallization ; x-ray crystallography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: SacY is the antiterminator protein involved in the induction by sucrose of the expression of the levansucrase gene (sacB) of Bacillus subtilis. In the presence of sucrose, SacY is activated and prevents premature termination of transcription by binding to a RNA-antiterminator (RAT) sequence partially overlapping with the terminator sequence. SacY consists of a RNA-binding N-terminal domain, SacY(1-55), and a regulatory domain, SacY(56-280), sensitive to the sucrose concentration. SacY(1-55) is in itself capable of binding to the RAT sequence and preventing termination independently of the sucrose concentration. In this paper we describe the overexpression, the purification, and the crystallization of SacY(1-55). We obtained six different crystal forms, some of them diffracting to high resolution (〉1.5 Å). Self rotation function calculations indicated the presence of a dimer in the asymmetric unit, which is in agreement with a proposed oligomeric state in solution as observed by high-resolution NMR measurements. The crystallization of some site-directed cysteine mutants opens the way of solving the structure by multiple isomorphous replacement. Proteins 28:590-594, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Purification, crystallization, and preliminary X-ray analysis of PepX, an X-prolyl dipeptidyl aminopeptidase from Lactococcus lactis (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 278-281 
    Details
    ISSN: 0887-3585
    Keywords: overproduction ; crystallography ; X-prolyl dipeptidyl aminopeptidase ; PepX ; Lactococcus lactis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The X-prolyl dipeptidyl aminopeptidase PepX, a serine peptidase isolated originally from Lactococcus lactis subsp lactis NCDO 763, was cloned and overproduced in Escherichia coli. The enzyme was isolated in its active form in two purification steps. Crystals of PepX were grown by the hanging drop vapor diffusion method using polyethyleneglycol 4000 as precipitant at pH 5.0. The crystals are orthorhombic with cell dimensions a = 92.8 Å, b = 102.6 Å, and c = 101.6 Å, space group P21212, and probably contain one monomer of 87.5 kDa in the asymmetric unit. The crystals, very stable under X-rays, diffract to at least 2.2 Å and are suitable for high-resolution structural analysis. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340230216
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