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  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Ring Expansion - Formation of Optically Active 3-Hydroxypiperidines from Pyrrolidinemethanol Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1693-1699 
    Details
    ISSN: 1434-193X
    Keywords: Pyrrolidines ; Piperidines ; Nitrogen heterocycles ; Rearrangements ; Aziridinium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of pyrrolidinemethanol derivatives (-)-1, (-)-6, (-)-7, 8, (-)-9, (+)-10, (-)-11, and (-)-21 with trifluoroacetic anhydride and then with Et3N afforded, after hydrolysis of the trifluoroacetyl group with NaOH, the optically active 3-hydroxypiperidines (-)-14, (+)-15, (-)-16, 17, (+)-18, (-)-19, (-)-20, and (+)-22, respectively. The yields are good and the enantiomeric excess excellent (up to 95 %).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of an amphiphilic triarm star copolymer based on polystyrene, poly(ethylene oxide) and poly(ε-caprolactone) (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 18 (1997), S. 343-351 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of an amphiphilic triarm star copolymer based on polystyrene, poly(ethylene oxide) and poly(ε-caprolactone) block has been achieved by a novel strategy which consists in the preparation of a diblock copolymer, polystyrene-block-poly(ethylene oxide), having a protected anionic initiator group at the junction of the two blocks. After deprotection, this function is activated by a coloured and weakly basic carbanion. The generated alcoholate initiates the ε-caprolactone anionic polymerization.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1997.030180411
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  • 5
    Electronic Resource
    Electronic Resource
    Stereospecific polymerization of methylthiirane in homogeneous phase, 5Part 4: cf. ref.8.. Study of the interconversion between active sites (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 196 (1995), S. 4069-4082 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The enantioasymmetry of polymerization reactions of racemic methylthiirane in bulk are studied, initiation being made using racemic or optically active seeds of molar weight equal to 40000, synthesized in bulk from bis(isopropyl-S-cysteinato)cadmium. In these conditions, active sites are enantiomers and the enantioasymmetric constant kR, measuring the preferential choice of the R antipode, is depending only on the relative number of the two types of active sites. We have observed an interconversion between the enantiomeric active sites CR* and CS*. The ratio [CR*]/[CS*] is only varying with conversion and reaches a limiting value that depends on cadmium concentration. For low cadmium concentrations, ([CR*]/[CS*])lim = 1.00, showing a complete racemization of the enantiomeric active sites, while for higher cadmium concentrations, ([CR*]/[CS*])lim = 1.07 ± 0.03. This value of 1.07 can be attributed to the presence of aggregation of dimeric species which create a chiral neighbourhood around cadmium atoms. Diastereoisomeric active sites present when active sites are born by chains of lower molar weights seem also to interconvert. The interconversion between active sites implies the presence of stereoblocks in the main chain.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1995.021961216
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  • 6
    Electronic Resource
    Electronic Resource
    Reduction of iodine by hydroxylamine within the pH range 0.7-3.5 (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 785-797 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reduction of iodine by hydroxylamine within the [H+] range 3×10-1-3×10-4 mol.L-1 was first studied until completion of the reaction. In most cases, the concentration of iodine decreased monotonically. However, within a narrow range of reagent concentrations ([NH3OH+]0/[I2]0 ratio below 15, [H+] around 0.1 mol.L-1, and ionic strength around 0.1 mol.L-1), the [I2] and [I3-] vs. time curves showed 2 and 3 extrema, respectively. This peculiar phenomenon is discussed using a 4 reaction scheme (I2+I-⇔I3-, 2 I2+NH3OH++H2O→HNO2+4 I-+5 H+, NH3OH++HNO2→N2O+2 H2O+H+, and 2 HNO2+2 I-+2 H+→2 NO+I2+2 H2O). In a flow reactor, sustained oscillations in redox potential were recorded with an extremely long period (around 24 h).The kinetics of the reaction was then investigated in the starting conditions. The proposed rate equation points out a reinforcement of the inhibition by hydrogen ions when [H+] is above 4×10-2 mol.L-1 at 25°C. A mechanism based on ion-transfer reactions is postulated. It involves both NH2OH and NH3OH+ as the reducing reactive species. The additional rate suppression by H+ at low pH would be connected to the existence of H2OI+ in the reactive medium. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 785-797, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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