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  • 1
    ISSN: 1432-2048
    Keywords: Anthranilate synthase (isoenzymes) ; Daucus (anthranilate synthase) ; Nicotiana (anthranilate synthase) ; 5-Methyltryptophan ; Tissue culture (enzyme forms) ; Tryptophan ; Zea (anthranilate synthase)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tobacco (N. tabacum cv. Xanthi) cell lines contained two forms of anthranilate synthase (AS; EC 4.1.3.27) which could be partially separated by gel-filtration chromatography. One form was resistant to feedback inihibition by 10 μM tryptophan (trp) while the other form was almost completely inhibited by trp at the same concentration. Cell lines selected as resistant to 5-methyltryptophan (5MT) had more of the trp-resistant AS form. Only the trp-sensitive form was detected in plants regenerated from both normal and 5MT-resistant cell lines. Overexpression of the trp-resistant form in 5MT-resistant tobacco cells disappeared during plant regeneration but reappeared when callus was initiated from the leaves of these plants. The trp-sensitive form was localized in the particulate fraction and the trp-resistant form in the cytosol of tobacco cultured cell protoplasts. The trp-resistant form of AS from tobacco had an estimated MW of 200 000, determined by Sephacryl S-200 chromatography, compared to an estimated MW of 150 000 for the trp-sensitive form. The estimated molecular weights of AS from carrot and corn were 160 000 and 150 000, respectively. Analysis of AS activity from the diploid Nicotiana species Nicotiana otophora (chromosome number 2n=24) by high-performance liquid chromatography showed two activity peaks identical in elution time and trp inhibition characteristics to the activity from N. tabacum (chromosome No. 48). Thus the two enzyme forms found in tobacco did not appear to have originated individually from the progenitor species genomes which combined to make up the tobacco genome.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 42 (1998), S. 49-69 
    ISSN: 0029-5981
    Keywords: linear finite element analysis ; geometrically non-linear finite element analysis ; element technology ; shell elements ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the present contribution we propose a so-called solid-shell concept which incorporates only displacement degrees of freedom. Thus, some major disadvantages of the usually used degenerated shell concept are overcome. These disadvantages are related to boundary conditions - the handling of soft and hard support, the need for special co-ordinate systems at boundaries, the connection with continuum elements - and, in geometrically non-linear analyses, to a complicated update of the rotation vector.First, the kinematics of the so-called solid-shell concept in analogy to the degenerated shell concept are introduced. Then several modifications of the solid-shell concept are proposed to obtain locking-free solid-shell elements, leading also to formulations which allow the use of general three-dimensional material laws and which are also able to represent the normal stresses and strains in thickness direction. Numerical analyses of geometrically linear and non-linear problems are finally performed using solely assumed natural shear strain elements with a linear approximation in in-plane direction.Although some considerations are needed to get comparable boundary conditions in the examples analysed, the solid-shell elements prove to work as good as the degenerated shell elements. The numerical examples show that neither thickness nor shear locking are present even for distorted element shapes. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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