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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 242 (1994), S. 169-176 
    ISSN: 1617-4623
    Keywords: Schizosaccharomyces pombe ; Histidine ; Shuttle vector ; Cloning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A DNA fragment which carries the his3 gene of Schizosaccharomyes pombe has been isolated and characterized for use as a selectable marker in transformations. The his3 gene encodes the imidazole acetol phosphate transaminase enzyme (E.C.2.6.1.9), which is responsible for converting imidazole acetol-P to histidinol-P in step 8 of histidine biosynthesis. The nucleotide sequences of a 2196 by gene fragment and a corresponding cDNA clone were determined. Three intron sequences punctuate the 1451 by coding region which generates a predicted polypeptide of 384 amino acids with a molecular mass of 42736 daltons. Northern analysis of his3 mRNAs indicates that the transcript is approximately 1.6 kb in size. Steady-state levels are down-regulated by nitrogen limitation but are unaffected by histidine starvation. The deduced amino acid sequence was compared to the Saccharomyces cerevisiae HIS5, Escherichia coli HisC, and Salmonella typhimurium HisC proteins, all of which are imidazole acetol phosphate transaminases. The S. pombe his3 protein was 49.5% identical to the S. cerevisiae HISS protein and 21.5% identity was found when all four proteins were compared. The shuttle vector pBGI was constructed by subcloning the smallest functional region of his3 and the S. pombe arsl sequence into pUC18 for use in transformation of His3 — S. pombe strains. New S. pombe strains in which the his3 gene was deleted have also been constructed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 183-187 
    ISSN: 0899-0042
    Keywords: (S)-N-(1-naphthyl)leucine ; N-(3,5-dinitrobenzoyl) ; amino acids ; derivatives ; 3,5-dinitroanilides of chiral acids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chiral stationary phase (CSP) derived from N-(1-naphthyl) leucine has been prepared. This CSP is conceptually similar to the CSP derived from N-(2-naphthyl)alanine and was expected to separate the enantiomers of the same clientele of analytes as does the latter. The magnitudes of the separation factors observed on the two CSPs may differ markedly for a given analyte, the new CSP often affording much greater enantioselectivity.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 57-62 
    ISSN: 0899-0042
    Keywords: chiral stationary phase ; α-amino phosphonate ; chromatographic separation of enantiomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chiral statonary phase (CSP) derived from an N-(3,5-dinitrobenzoyl)-α-aminobenzylphosphonate has been prepared and evaluated for its utility in the direct separation of enantiomers. This CSP, 2, is structurally related to earlier N-(3,5-dinitrobenzoyl)-α-acids acid-derived phases (e.g., CSP 1), but the mode of attachment to the support is different. In scope; CSP 2 is qualitaively similar to CSP 1. However, it differs quantitatively from CSP 1, showing either greater or lesser selectivity for different pairs of enantiomers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 199-206 
    ISSN: 1040-7685
    Keywords: micellar electrokinetic chromatography ; capillary electrophoresis ; bile salts ; metal-ligands ; chiral separations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have utilized micellar electrokinetic chromatography with sodium deoxycholate micelles to separate the enantiomers of bis(8-((pyridine-2-methylene)amino)quinoline)iron(II) hexafluorophosphate, Fe(PMAQ)2(PF6)2, bis(8-((pyridine-2-methylene)amino)lepidine iron(II) hexafluorophosphate, Fe(PMAL)2(PF6)2, and bis(1-(2-pyridinyl)ethylidine)-8-aminoquinoline iron(II) hexafluorophosphate, Fe(PEAQ)2(PF6)2. The influence of 13 water miscible organic additives on the resolution of each pair of enantiomers was investigated. Significant changes in resolution are seen depending upon the particular organic additive used in the separation buffer. In addition, the effects of acetone concentration on the resolution of these enantiomers in bile salt solution was investigated. Resolution for all three pairs of enantiomers is maximized in a buffer solution containing 15% acetone. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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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: Calculations of flux rates for stable isotope tracer studies are based upon enrichment values of an infused tracer. We propose the determination of enrichment values by gas chromatography/mass spectrometry, which is based on tracer mole fraction and mass spectrometer signals, normalized over the total signal of an ion fragment isotopomer distribution. The method accounts for overlap of the signals of one or two tracers and the tracee, high tracer mole fraction and incomplete labelling of the (infused) tracer. For the single and multiple tracer case a linear relationship between tracer mole fraction (from zero to one) and all normalized mass spectrometer signals is derived. This linearity over the entire range is demonstrated with a single (1-13C)glucose tracer and for mixtures of (1-13C)- and (3,3-2H2)tyrosine tracers. The linearity allows determination of the tracer mole fraction for two tracers, using multiple linear regression. The corresponding calibration can rely on measurements of the pure tracer and tracee compound, without weighing or check for chemical purity. This is compared with a calibration based on tracer/tracee mixtures. Estimates for the tracer mole fraction are slightly better if based on a calibration, using standard mixtures. In all cases the tracer mole fraction can be determined with high precision (coefficient of variation smaller than 5%) and high accuracy. For tyrosine it is demonstrated that the measurement of seven channels rather than three, for the main isotopomers, does not reduce the precision in the prediction of the tracer mole fraction. Equations are also derived to use the tracer mole fraction to estimate the endogenous production of the tracee under study conditions, assuming a steady state of the host metabolism.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 7 (1980), S. 168-171 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The measurement of plasma free fatty acid turnover and oxidation by means of the isotopic dilution technique using a radiolabeled free fatty acid has proven useful for the in vivo study of fat metabolism in animals. However, because of the ethical considerations regarding the administration of radioisotopes to humans, there is a lack of adequate information regarding the in vivo regulation of free fatty turnover and oxidation in humans, particularly children. Consequently, we have developed a technique using the stable, nonradioactive [1-13C]palmitic acid molecule as free fatty acid tracer to measure plasma free fatty acid metabolism in vivo. We have analysed the isotopic enrichment of plasma palmitate by selected ion monitoring on a gas chromatograph mass spectrometer and we have used an isotope ratio mass spectrometer to determine the much lower isotopic enrichment of the expired CO2. We have found this technique to be safe to administer, to have a high degree of analytical reproducibility, and to yield values in dogs comparable with those obtained using [1-14C]palmitic acid as the tracer.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Individuals who suffer extensive loss of skin, commonly in fires, are acutely ill, in danger of succumbing either to massive infection or to severe fluid loss. Patients who survive these early threats must often cope with problems of rehabilitation arising from deep, disfiguring scars and crippling contractures. In this report we describe the physiocochemical, biochemical, and mechanical considerations that form the basis for two-stage design of a membrane useful as an experimental wound closure. Stage 1 of the design, applicable to short-term acute use, calls for a membrane which displaces efficiently air pockets from a carefully prepared woundbed, free of weak boundary layers, and maintains the moisture flux through the wound at an optimal level. Optimization of the surface energy modulus of elasticity, energy to fracture and moisture permeability of the membrane are among the essential attributes of Stage 1 design. Stage 2 of the design, applicable to long-term, chronic use, focuses on a nonantigenic membrane which performs as a biodegradable template for synthesis of neodermal tissue. A survey of candidate materials suggests reasons for selection of a porous, crosslinked collagen - glycosaminoglycan coprecipitate as the chemical basis of an evolving design which was initiated 10 years ago. Over the past several years a set of membranes has been iteratively designed on this basis and has been used to cover satisfactorily large experimental fullthickness skin wounds in guinea pigs. Such membranes have effectively protected these wounds from infection and fluid loss for over 25 days without rejection and without requiring change or other invasive manipulation. When appropriately designed for the purpose, the membranes have also strongly retarded wound contraction and have become replaced by newly synthesized, stable connective tissue. Several rules relating the molecular structure and morphology of these membranes to cellular response of adjacent tissue have also been derived. This report is the first in a series which details the methodology of preparation and the record of performance.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 14 (1980), S. 339-339 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
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