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  • 1
    Keywords: screening ; COMPLEX ; COMPLEXES ; DYNAMICS ; SIMULATION ; ENERGY ; mass spectrometry ; NMR-SPECTROSCOPY ; SPECTROMETRY ; MASS-SPECTROMETRY ; MOLECULAR-DYNAMICS ; CHEMISTRY ; POLYSACCHARIDES ; HYDROLYSIS ; molecular dynamics ; OLIGOSACCHARIDE SYNTHESIS ; CRYSTALLOGRAPHY ; FLUORIDES ; GLYCOSIDE HYDROLASE ; HELICAL STRUCTURE
    Abstract: Glycosynthases are precise molecular instruments for making specifically linked oligosaccharides. X-ray crystallography screening of ligands bound to the 1,3(4)-beta-D-glucanase nucleophile mutant E115S of Phanerochaete chrysosporium Laminarinase 16A (Lam16A) showed that laminariheptaose (L7) bound in an arch with the reducing and nonreducing ends occupying either side of the catalytic cleft of the enzyme. The X-ray structure of Lam16A E115S in complex with alpha-laminariheptaosyl fluoride (alpha L7F) revealed how alpha L7F could make a nucleophilic attack upon itself. Indeed, when Lam16A E115S was allowed to react with alpha L7F the major product was a cyclic beta-1,3-heptaglucan, as shown by mass spectrometry. NMR confirmed uniquely beta-1,3-linkages and no reducing end. Molecular dynamics simulations indicate that the cyclic laminariheptaose molecule is not completely planar and that torsion angles at the glycosidic linkages fluctuate between two energy minima. This is the first report of a glycosynthase that joins the reducing and nonreducing ends of a single oligosaccharide and the first reported synthesis of cyclic beta-glucan
    Type of Publication: Journal article published
    PubMed ID: 20078120
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 10 (1996), S. 83-97 
    ISSN: 1438-2199
    Keywords: Amino acids ; Polyamines ; Putrescine ; Spermidine ; Spermine ; Uptake ; Excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The polyamine content in cells is regulated by both polyamine biosynthesis and its transport. We recently obtained and characterized three clones of polyamine transport genes (pPT104, pPT79 and pPT71) inEscherichia coli. The system encoded by pPT104 was the spermidine-preferential uptake system and that encoded by pPT79 the putrescine-specific uptake system. Furthermore, these two systems were periplasmic transport systems consisting of four kinds of proteins: pPT104 clone encoded potA, -B,-C, and -D proteins and pPT79 clone encoded potF, -G, -H, and -I proteins, judging from the deduced amino acid sequences of the nucleotide sequences of these clones. PotD and -F proteins were periplasmic substrate binding proteins and potA and -G proteins membrane associated proteins having the nucleotide binding site. PotB and -C proteins, and potH and -I proteins were transmembrane proteins probably forming channels for spermidine and putrescine, respectively. Their amino acid sequences in the corresponding proteins were similar to each other. The functions of potA and -D proteins in the spermidine-preferential uptake system encoded by pPT104 clone were studied in detail through a combined biochemical and genetic approach. In contrast, the putrescine transport system encoded by pPT71 consisted of one membrane protein (potE protein) haveing twelve transmembrane segments, and was active in both the uptake and excretion of putrescine. The uptake was dependent on membrane potential, and the excretion was due to the exchange reaction between putrescine and ornithine.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The amount of charges induced by high energy single ion irradiation at a p-n junction diode has been measured and its dependence on the ion incident position has been evaluated by using single-ion microprobe technique. By irradiating single He ions with various incident energy (1.4–4.05 MeV), dependence of the profiles of collected charges on the ion incident energy has been investigated. Origins of the different profiles among the different incident energy are discussed in terms of different contribution of two mechanisms of charge collection, namely, field funneling and diffusion of carriers. In the case of the ion incidence within the junction area, dependence of the charge collection profile on the ion incident energy comes from different contribution of the funneling in the charge collection process, while difference in the collection efficiency of the diffused charges affects the profile in the case of the ion incidence at outside of the junction. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The structure of silica acrogel, a porous low density material having small particle size prepared from TMOS has been investigated by DSC, SAXS, and Raman spectroscopy. The predominant particle size of the aerogel were determined to be near 3 nm by SAXS analysis. The Raman spectra are qualitatively similar to those from fused silica, although the sample before heat treatment had typical Raman peaks assigned to organic groups contained in TMOS. The observed relatively intense peaks at near 490 and 606 cm−1 suggest the existence of small rings, e.g., six(3-SiO) or eight(4-SiO) membered, in the aerogel. The structure change of the aerogel with temperature was also studied by Raman spectroscopy.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Singly charged cations of silver atoms and clusters (Agn+, n=1,3,5,7,9) were deposited on highly oriented pyrolytic graphite substrates at well-controlled, various collision energies. The total amount of Ag atoms remaining on the substrates after collision was quantified by measuring the Ag 3d5/2 photoelectron intensities. The collision energy dependence of the amount of deposited Ag atoms revealed that, for all the species, there are three distinct energy regions, for which soft landing, rebounding, or implantation is a dominant process, and that the energy ranges for the processes strongly depend on the cluster size. The deposition efficiency vs collision energy curve for each cluster is well fitted to that for Ag1, by considering the difference between the contact area of Ag1 with the surface and that of the cluster, reflecting the compactness of the clusters. Boundaries between the different deposition regimes for the clusters were less distinct than those for Ag1. Considering anisotropy in shape of a cluster, deposition efficiency around the implantation threshold was calculated, which well explains the indistinctness of the threshold observed in the experimental data. This supports the picture that the energy given to a unit surface area determines the collision process. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-8900
    Keywords: Acrylic trimer ; polyacrylate ; β-oxidation ; exogenous degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A possible aerobic degradative pathway for polyacrylate was examined with trimer (1,3,5-pentane tricarboxylic acid; PTCA)-utilizing bacteria. A few metabolic products from PTCA accumulated in culture filtrates and reaction mixtures of washed cells. Fraction A was detected as a main metabolite by high-performance liquid chromatography. A small amount of fraction B was concomitant with fraction A. Another fraction, C, was also detected. These compounds were suggested by liquid chromatography-mass spectrometry analyses to be 1,3,5-(1- or 2-pentene)tricarboxylic acid (fraction A or B) and 1,3,5-(2-oxopentane)tricarboxylic acid (fraction C). Fraction A was quickly further metabolized by washed cells, but fraction B was only gradually degraded. From these results, the metabolic pathway for polyacrylate is suggested to be quite similar toβ-oxidation for saturated fatty acids. The degradation of PTCA by washed cells was slower than that by growing cells and was inhibited by 5 mM NaN3. This suggests that the metabolism is linked to a respiratory chain or energy-producing system of bacteria which can aerobically assimilate PTCA.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1572-8927
    Keywords: Molten nitrates ; HTS ; dispersion ; refractive index ; polarizability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Refractive indices of a certain molten nitrate mixture measured goniometrically with visible light at nine wavelengths, varied linearly with temperature at a given wavelength. Dispersion phenomenon was also observed at a fixed temperature. Electronic polarizability was determined using the refractive index extrapolated to infinite wavelength and the semiclassical Clausius-Mossotti equation.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0992-7689
    Keywords: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The climatology of mean wind, diurnal and semidiurnal tide during the first year (1996–1997) of simultaneous wind observations at Wakkanai (45.4°N, 141.7°E) and Yamagawa (31.2°N, 130.6°E) is presented. The locations of the radars allow us to describe the latitudinal dependence of the tides. Tidal amplitude and phase profiles are compared with those of the global scale wave model (GSWM). While the observed amplitude profiles of the diurnal tide agree well with the GSWM values, the observed phase profiles often indicate longer vertical wavelengths than the GSWM phase profiles. In contrast to the GSWM simulation, the observations show a strong bimodal structure of the diurnal tide, with the phase advancing about 6 hours from summer to winter.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1106
    Keywords: Fibroblast growth factor receptor ; Basic fibroblast growth factor ; Forebrain ischemia ; Astrocyte ; In situ hybridization ; Hippocampus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recently, we demonstrated that transient forebrain ischemia in rats leads to an early and strong induction of basic fibroblast growth factor (bFGF) synthesis in astrocytes in the injured brain regions. In this study, in order to clarify the targets of such raised endogenous bFGF levels, the messenger RNA (mRNA) expression of its receptors (flg and bek) at in the hippocampus following transient forebrain ischemia induced by four-vessel occlusion for 20 min was investigated using an in situ hybridization technique. Transient forebrain ischemia induced an increase in the number of flg mRNA-positive cells from an early stage (24 h after ischemia) in the hippocampal CA1 subfield where delayed neuronal death occurred later (48–72 h after ischemia). This increase became more marked with the progression of neuronal death and was still evident in the same area 30 days later. The time course of the appearance and distribution pattern of flg mRNA-positive cells in the CA1 subfield were quite similar to those of bFGF mRNA-positive cells. On the other hand, in situ hybridization for bek mRNA showed only slight and transient (observed 72 h and 5 days after ischemia) increases in the number of mRNA-positive cells in the CA1 subfield following ischemia. The use of in situ hybridization and glial fibrillary acidic protein immunohistochemistry in combination demonstrated that the cells in the CA1 subfield that exhibited ischemia-induced flg or bek mRNA expression were astrocytes. These data indicate that transient forebrain ischemia induces upregulation of fibroblast growth factor-receptor expression, accompanied by increased bFGF expression in astrocytes, and suggest that the increased astrocytic bFGF levels in injured brain regions act on the astrocytes via autocrine systems and are involved in the development and maintenance of astrocytosis.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0003-9861
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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