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  • 1985-1989  (2)
  • Chemistry  (2)
  • Fine structure
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 279-288 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Diffusion of gases through legume nodules is important for nitrogen fixation. A mathematical model is presented for diffusion and enzymatic reaction for legume nodules with a reactive core and an inert shell. The transient model is solved numerically for spherical geometry for acetylene reduction by nitrogenase enzyme. The results are used to estimate the diffusivities of acetylene and ethylene in the nodules by comparing predicted and experimental lag times. The experimental results are also analyzed using an effectiveness factor plot for spherical nodules with inert shells and reactive cores. The results show that the diffusivities are slightly higher than those for acetylene and ethylene in water because of some contribution of gas phase diffusion. Applications to oxygen diffusion through nodule tissue are suggested.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metabolism of dihydrotachysterol3 (DHT3), a vitamin D analogue, has been investigated in vivo in the rat after intraperitoneal injection, and the metabolism of the 25-hydroxylated metabolite of DHT3 was studied in vitro in the isolated perfused rat kidney. A large number of metabolites have been obtained and some have been identified. The rat plasma or kidney perfusate were extracted and the metabolites separated by high-performance liquid chromatography (HPLC) in straight- and reverse-phase systems and using cyano columns. Metabolites were identified, using a photodiode array assembly which monitored the HPLC eluate, by the characteristic ultraviolet spectrum of DHT compounds. Tentative structures were assigned to some of the metabolites obtained on the basis of their mobility in the various HPLC systems used in comparison to that of known metabolites of vitamin D. Gas chromatography/mass spectrometry (GC/MS) and direct probe mass spectrometry have been used to confirm the identity of seven metabolites formed in vitro, of which only two have been definitely shown also to be formed in vivo. GC/MS was carried out after derivatization forming trimethylsilyl ethers, n-butyl boronate cyclic esters, and N-O-methyl oximes before and after oxidation with sodium periodate and/or reduction with sodium borohydride. Molecular ions of these compounds are usually of low abundance and characteristic mass fragments at m/z 273, 255 and 121 are always seen with metabolites of DHT.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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