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  • Wiley-Blackwell  (162)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 332-338 
    ISSN: 0006-3592
    Keywords: α-hydroxynitrile lyase ; cassava ; cyanogenesis ; cyanohydrin ; Escherichia coli expression vector ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The coding sequence of the cyanogenic α-hydroxynitrile lyase gene of Manihot esculenta Crantz (cassava) was cloned in the plasmid vector pMal-c2 and expressed in Escherichia coli strain JM105. DNA sequencing showed that the recombinant plasmid contained the same sequence as the cDNA clone pHNL10. Peptide sequencing of the recombinant protein showed that the N-terminus was heterogeneous, with either four or six additional amino acid residues compared with the native protein. Circular dichroism spectra indicated similar secondary structure contents for both proteins. Enzyme assays showed that specific activity of native and recombinant proteins were 0.24 and 0.26 mmol CN-/mg/min, respectively; that both proteins had optimal activity at 40°C and pH 5.5; and that both proteins were inhibited by the serine protease inhibitor phenyl-methane sulfonyl flouride (PMSF). Isoelectric focusing of native and recombinant protein revealed multiple isoforms for both proteins; the recombinant protein had a more basic mean isoelectric point (pl) (5.1) than the native protein (4.5). © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 332-338, 1997.
    Additional Material: 5 Ill.
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  • 2
    ISSN: 0887-624X
    Keywords: oligocyclosiloxanes ; hydrosilation ; heptamethylcyclotetrasiloxane ; siloxane redistribution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of oligocyclosiloxanes via hydrosilation reactions has been investigated. Hydrosilation reactions employing heptamethylcyclotetrasiloxane and vinyl-containing silanes and siloxanes yielded a variety of oligocyclosiloxanes with various numbers of cyclosiloxane rings connected through tri-, tetra-, penta-, hexa-, hepta-, or octafunctional junctions. The oligocyclosiloxanes were characterized by gas chromatography, IR spectroscopy, 29Si-, 1H-, and 13C-NMR spectroscopy, elemental analysis, and vapor phase osmometry. The polycyclics were redistributed with hexamethyldisiloxane and the resulting fragments analyzed by gas chromatography. All results were consistent with the formation of isomeric oligocyclosiloxanes due to a lack of absolute regioselectivity of the hydrosilation reaction. © 1993 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 3
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Nanogram quantities of glucuronic acid conjugates of GR117289 in rat and dog bile have been analysed by semi-microbore high-performance liquid chromatography (HPLC)/ionspray mass spectrometry with on-line UV diode array detection. The determination of drug metabolites in bile has often proved problematical due to the large number of endogenous components in this biological matrix, in particular the bile acids. Semi-microbore HPLC is useful for concentrating small quantities of material and, in combination with an on-line diode array detector, for distinguishing between drug related and endogenous components. A novel angiotensin II receptor antagonist, GR117289, had proved difficult to analyse by thermospray mass spectrometry because of its thermal lability. The use of the less thermally dependent technique of ionspray mass spectrometry allowed the characterization of nanogram quantities of glucuronic acid metabolites of GR117289 in bile.
    Additional Material: 6 Ill.
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  • 4
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The need for alternatives to autogenous bone grafts is widely recognized. This study compared the torsional strength of canine femora 1 year after grafting with one of three forms of a collagen/hydroxyapatite/tricalcium phosphate bone grafting material (COLLAGRAFT15), autogenous bone, or no graft. The groups were compared to each other and to the unoperated contralateral femora. Results of torsional testing were evaluated for torsional strength, torsional displacement, total energy to fracture and White fracture mode. Data analysis showed lower torsional strength of the operated vs. unoperated femora with the exception of morsellized COLLAGRAFT15 material, which had higher strength. However, the only difference in the operated groups was that the morsellized COLLAGRAFT15 had greater strength than several groups including the autogenous bone group. There was no difference found in angular displacement between any of the groups. However, there was a difference in the energy to fracture in both strip forms of the COLLAGRAFT15. The final conclusion is that in this model, grafting with COLLAGRAFT15 provided torsional properties at one year postoperatively at least equivalent to autogenous bone. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 5
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gas chromatography/electron capture negative ion mass spectrometry of eicosanoids, as pentafluorobenzyl (PFB) ester, methyl oxime (where applicable), trimethylsilyl (TMS) ether derivatives, is reported using a double-focusing instrument of trisector configuration. Sub-picogram detection limits were observed for prostaglandins E1, E2 and F2α during selected ion monitoring (SIM) of [M — PFB]- ions. Selected reaction monitoring (SRM) of [M — PFB]- → [M — PFB — TMSOH]-, occurring in the first field-free region, was of modest sensitivity, reflecting the stability of the [M - PFB]- ions. The leukotriene B4 (LTB4) derivative was successfully analyzed by SIM at the low-picogram level. In this instance, the fragmentation [M — PFB]- →[M — PFB — TMSOH] occurred in high yield in the first field-free region. The advantageous improvement in selectivity of detection that may be achieved with SRM was evident during the analysis of a serum extract for LTB4.
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  • 6
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The collisionally activated decomposition of [M + H]+ ions, generated by fast atom bombardment (FAB) of glutathione conjugates, has been studied by tandem mass spectrometry (MS/MS) using hybrid sector/quadrupole instruments. Abundant fragments of diagnostic utility were present in the daughter ion spectra. Common fragmentation modes were observed but their relative importance was strongly dependent on the nature of the conjugated species. As an example of a general approach to the characterization of glutathione conjugates in biological samples, the acetaminophen-glutathione conjugate was identified in rat bile, following coadministration of (2H0)- and (2H3)acetaminophen, using the experimental sequence: (i) conventional FAB mass spectrometric analysis, (ii) MS/MS using constant neutral loss (129 u) scanning to identify parent ions corresponding to glutathione conjugates, (iii) MS/MS to yield daughter ion spectra of parents so identified and corresponding to (2H0)- and (2H3)-labeled conjugates.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 7 (1994), S. 625-628 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Over the H0 acidity range from + 2 to -8, four different mechanistic variations occur in the Fischer indole reaction, leading to an unusual parabolic dependence of the rate constants on the acidity of the medium. In strongly acidic media kinetic isotope effects indicate that the rate-determining step is deprotonation to form the ene-hydrazine tautomer, whereas in weakly acidic media the tautomerization is so rapid that [3,3]-rearrangement becomes rate limiting. At an intermediate acidity, the deprotonation is rate determining, with the rate being strongly dependent on the concentration of the anionic counter ion.
    Additional Material: 2 Ill.
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  • 8
    ISSN: 0368-1467
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new vibrator, commercially available as the Sonomec Wave-Pulse Generator, is described, in which micro-organisms may be disrupted by shaking with glass beads. The amplitude and frequency of vibration of the shaker may be varied independently by suitable linkages incorporated in the mechanism. A study has been made of the effect of several variables, particularly the height of the liquid column in the vibrating container, on the rate of disruption. A relation is shown to exist between the acoustic heating produced in the container by the passage of sound waves through the liquid and the rate of disruption of baker's yeast. It is considered that at most depths of the liquid column, the action is similar to that of other shakers, but at a certain depth of liquid, additional forces arise which greatly increase the rapidity of disruption. How these forces act is not known. Factors affecting the rate of disruption of baker's yeast, Corynebacterium xerosis and Bacillus megatherium have been studied and a comparison has been made of the fractions obtained by differential centrifugation of the cell dispersion and compared with similar preparations from the Hughes press.
    Additional Material: 6 Ill.
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  • 9
    ISSN: 0368-1467
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two commercially available ultrasonic instruments are described, in which micro-organisms and other cells may be disintegrated.Sound waves (20 kc/s) are generated in the cell suspension by means of titanium velocity transformers (probes) coupled to a magnetostriction transducer. One instrument operating at 500 W will disintegrate from 2 to 500 ml, the other operating at 50 W from 1 ml to 30 ml.Yeast was used as a test organism but results on some other organisms are also given. Cell rupture is shown to be independent of sonically generated free radicals, but enzyme inactivation (alcohol dehydrogenase) is accelerated by free radicals. Increasing the viscosity, decreasing surface tension of the suspending medium, or the presence of CO2 decreases disintegration. The addition of solid nuclei such as powdered glass, as well as small air bubbles, increases disintegration.This is consistent with disintegration being due to cavitation, but does not indicate the precise mechanism of cell rupture. Some effects of sonic disruption are compared with disruption by other methods.
    Additional Material: 3 Ill.
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  • 10
    ISSN: 0749-1581
    Keywords: Two-dimensional NMR ; Artifacts ; BIRD pulses ; Coherence transfer ; Methylene groups ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When the proton-proton decoupled heteronuclear two-dimensional chemical shift correlation experiment is applied to a molecule containing methylene groups, the spectra show not only the expected signals at the two proton chemical shifts, but also a strong artifact. This artifact appears at the average of the two proton chemical shifts, and arises from coherence transfer between the two protons caused by the BIRD pulse. It is not caused by strong coupling between the protons, and so may appear in any spectrum. The dependence of this artifact on experimental conditions was analysed, and is illustrated with results obtained on the methylene groups from the cyclophane ring in N6′,N9-octamethylenepurinecyclophane.
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