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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The endpoint accuracy of a reaching movement strongly affects kinematics, particularly during the final phases of movement. However, where and how accuracy is represented in the central nervous system remains unknown. In this study, the discharge of 150 neurons located primarily in the dorsal premotor cortex (PMd), were recorded from monkeys performing an instructed delay, centre-out reaching task in which movement direction and target size were systematically varied. Linear regression analyses were used to assess the dependence of movement kinematics and cell discharge on target direction, size and tangential velocity (i.e. speed). The speed and timing of the movement were dependent on both direction and target size. Initially direction was the dominant predictor whilst target size became more important as the hand reached the target. A temporal multiple linear regression analysis found significant correlations with target size in 99 of 150 cells. The discharge of 134 cells was directionally tuned and 83 cells modulated with mean speed. Significant correlations of discharge with target size occurred throughout the task as did correlations with direction. However, correlations with direction preferentially occurred early in the task, prior to movement onset, whilst correlations with target size tended to occur late, well after movement onset. This temporal dependency of the firing in relationship to target direction and size mirrored that observed for the kinematics. We conclude that the discharge of PMd cells is highly correlated with the accuracy requirement of the movement. The timing of the correlations suggest that accuracy information is available for the planning and for the on-line control of endpoint accuracy.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: We report the molecular characterization and the detailed study of the recombinant maltooligosyl trehalose synthase mechanism from the thermoacidophilic archaeon Sulfolobus acidocaldarius. The mts gene encoding a maltooligosyl trehalose synthase was overexpressed in Escherichia coli using the T7-expression system. The purified recombinant enzyme exhibited optimum activity at 75°C and pH 5 with citrate–phosphate buffer and retained 60% of residual activity after 72 h of incubation at 80°C. The recombinant enzyme was active on maltooligosaccharides such as maltotriose, maltotetraose, maltopentaose and maltoheptaose. Investigation of the enzyme action on maltooligosaccharides has brought much insight into the reaction mechanism. Results obtained from thin-layer chromatography suggested a possible mechanism of action for maltooligosyl trehalose synthase: the enzyme, after converting the α-1,4-glucosidic linkage to an α-1,1-glucosidic linkage at the reducing end of maltooligosaccharide glc(n) is able to release glucose and maltooligosaccharide glc(n−1) residues. And then, the intramolecular transglycosylation and the hydrolytic reaction continue, with the maltooligosaccharide glc(n−1) until the initial maltooligosaccharide is reduced to maltose. An hypothetical mechanism of maltooligosyl trehalose synthase acting on maltooligosaccharide is proposed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1365-2958
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Medizin
    Notizen: The hyperthermophilic euryarchaeon Pyrococcus abyssi and the related species Pyrococcus furiosus and Pyrococcus horikoshii, whose genomes have been completely sequenced, are presently used as model organisms in different laboratories to study archaeal DNA replication and gene expression and to develop genetic tools for hyperthermophiles. We have performed an extensive re-annotation of the genome of P. abyssi to obtain an integrated view of its phylogeny, molecular biology and physiology. Many new functions are predicted for both informational and operational proteins. Moreover, several candidate genes have been identified that might encode missing links in key metabolic pathways, some of which have unique biochemical features. The great majority of Pyrococcus proteins are typical archaeal proteins and their phylogenetic pattern agrees with its position near the root of the archaeal tree. However, proteins probably from bacterial origin, including some from mesophilic bacteria, are also present in the P. abyssi genome.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 766-768 
    ISSN: 1399-0047
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: This is the first crystallization report of a glycoside hydrolase which belongs to family 82. A recombinant form of His-tagged ι-carrageenase from Alteromonas fortis was expressed, purified and crystallized. Crystals were obtained by the vapour-diffusion method using polyethylene glycol (MW = 6000) as a precipitant. They belong to space group P21, with unit-cell parameters a = 56.75, b = 91.04, c = 125.01 Å, β = 93.41°. The unit cell contains two molecules in the asymmetric unit related by a non-crystallographic twofold axis. Crystals diffracted to 2.0 Å resolution on a synchrotron beamline.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 918-920 
    ISSN: 1399-0047
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: A recombinant form of His-tagged κ-carrageenase from Pseudoalteromonas carrageenovora has been expressed, purified and crystallized. Crystals have been obtained by the vapour-diffusion method using polyethylene glycol (Mr = 4000) as a precipitant. These crystals belong to the space group P212121, with unit-cell parameters a  =  58.2, b  =  62.8, c  =  77.9 Å, and diffract to 2.2 Å resolution on a rotating-anode X-ray source.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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