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  • Springer  (139)
  • 1995-1999  (139)
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  • 1999  (62)
  • 1998  (77)
  • 1
    Electronic Resource
    Electronic Resource
    Propionyl-CoA carboxylase of Myxococcus xanthus: catalytic properties and function in developing cells (1998)
    Springer
    Archives of microbiology 170 (1998), S. 179-184 
    Details
    ISSN: 1432-072X
    Keywords: Key wordsMyxococcus xanthus ; Propionyl-CoA ; carboxylase ; Acetyl-CoA carboxylase ; Kinetic constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An acyl-coenzyme A carboxylase that carboxylates acetyl-CoA, butyryl-CoA, propionyl-CoA, and succinyl-CoA was purified from Myxococcus xanthus. Since the enzyme showed maximal rates of carboxylation with propionyl-CoA, the enzyme is thought to be propionyl-CoA carboxylase. The apparent K m values for acetyl-CoA, butyryl-CoA, propionyl-CoA, and succinyl-CoA were found to be 0.2, 0.2, 0.03, and 1.0 mM, respectively. The native enzyme has a molecular mass of 605–615 kDa and is composed of nonidentical subunits (α and β) with molecular masses of 53 and 56 kDa, respectively. The enzyme showed maximal activity at pH 7.0–7.5 and at 25–30°C, and was affected by variation in concentrations of ATP and Mg2+. During development of M. xanthus, the propionyl-CoA carboxylase activity increased gradually, with maximum activity observed during the sporulation stage. Previous work has shown that a propionyl-CoA-carboxylase-deficient mutant of M. xanthus reduces levels of long-chain fatty acids. These results suggest that the propionyl-CoA carboxylase is also responsible for the carboxylation of acetyl-CoA to malonyl-CoA used for the synthesis of long-chain fatty acids during development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050631
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  • 2
    Electronic Resource
    Electronic Resource
    Structural study of fucoidan from Cladosiphon okamuranus tokida (1999)
    Springer
    Glycoconjugate journal 16 (1999), S. 19-26 
    Details
    ISSN: 1573-4986
    Keywords: fucoidan ; sulfated fucan ; seaweed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A structural study was carried out on a fucoidan isolated from the brown seaweed Cladosiphon okamuranus. The polysaccharide contained fucose, glucuronic acid and sulfate in a molar ratio of about 6.1 : 1.0 : 2.9. The results of Smith degradation showed that this polysaccharide has a linear backbone of 1→3-linked α-fucopyranose with a half sulfate substitution at the 4-positions, and a portion of the fucose residues was O-acetylated. The data obtained from partial acid hydrolysis, a methylation analysis and NMR spectra indicated that the α-glucuronic acid residue is linked to the 2-positions of the fucose residues, which were not substituted by a sulfate group. These results indicated that the average structure of this fucoidan is as follows: -[(→3Fuc-4(±OSO3-)α1−)5→3[GlcAα1→2]Fucα1−]n−. (Half of each fucose residue was sulfated. One O-acetyl ester was present in every 6 fucose residues.)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006945618657
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  • 3
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    Single crystals of Dy1-xGdxVO4 for magnetic applications (1998)
    Springer
    Details
    Publication Date: 1998-05-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 4
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    Propionyl-CoA carboxylase of Myxococcus xanthus : catalytic properties and function in developing cells (1998)
    Springer
    Details
    Publication Date: 1998-08-03
    Print ISSN: 0302-8933
    Electronic ISSN: 1432-072X
    Topics: Biology
    Published by Springer
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  • 5
    Electronic Resource
    Electronic Resource
    Blue Luminescence from Silicon Nanoparticles Suspended in Organic Liquids (1999)
    Springer
    Journal of cluster science 10 (1999), S. 359-380 
    Details
    ISSN: 1572-8862
    Keywords: Silicon ; nanoparticles ; luminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have prepared several nanometer-sized silicon colloids in organic liquids in the range from 3.7 to 9.8 nm with a constant weight density of 1 mg/ml by a gas evaporation technique. The blue–green luminescent energy was found to be independent of size, in contrast to its intensity and optical absorption, which showed a clear size effect. Special emphasis is placed on the advantage of using a colloidal system: controllability of mass density in a unit volume, isolation of each particle, selection of wide band-gap substances, capability of absolute quantum efficiency, and easy surface modification. As an example of the above advantages, we have determined the absolute quantum yield as a function of size. From the quantum yield thus derived and the proposed model that combines surface as well as volume effects, experimentally obtained parameters such as the diffusion velocity of an electron–hole pair and the initial flight distance of this pair are found to be consistent with those obtained from other data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021981714227
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  • 6
    Electronic Resource
    Electronic Resource
    Cellulose/poly(acryloyl morpholine) composites: synthesis by solution coagulation/bulk polymerization and analysis of phase structure (1998)
    Springer
    Cellulose 5 (1998), S. 123-134 
    Details
    ISSN: 1572-882X
    Keywords: cellulose ; poly(acryloyl morpholine) ; composite ; interpenetrating polymer network
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cellulose/poly(acryloyl morpholine) (CELL/PACMO) compo sites were synthesized by bulk polymerization in the gel state of cellulose impregnated with reactive ACMO monomer. The thermal transition behaviour and phase structure of the CELL/PACMO composites obtained in film form were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and solid-state 13C NMR spectroscopy. For compositions rich in PACMO (CELL ≤ 30 wt %), it was revealed by DSC and DMA that the synthesized samples gave a composition-dependent Tg value higher than that of PACMO homopolymer, and the magnitude of the lowering of their dynamic modulus E′ in the glass transition region became extremely small in comparison with the corresponding drop in E′ noted for plain PACMO samples. These observations were interpreted as being due to the development of an interpenetrating polymer network (IPN)-type organization, resulting from successful fixation of an original netw ork structure of cellulose gels into the polymerized bulks. From the measurements of proton spin-lattice relaxation times in the NMR study, the IPN-like composites were estimated to be substantially homogeneous on a scale of a few nanometers. 0969--0239 © 1998 Blackie Academic & Professional
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009224931504
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  • 7
    Electronic Resource
    Electronic Resource
    Interstellar Dust in the Solar System (1998)
    Springer
    Astrophysics and space science 264 (1998), S. 213-218 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We deduce the mass distribution and total mass density of interstellar dust streaming into the solar system and compare the results to the conditions of the very local interstellar medium (VLISM). The mass distribution derived from in situ measurements shows a gentler slope and includes larger grains, compared to a model distribution proposed for the wavelength dependence of the interstellar extinction. The mass density of grains in the solar system is consistent with that expected from measurements of the visible interstellar extinction and the abundance constraints of elements in the diffuse interstellar medium (ISM), instead of those in the VLISM. This may imply that interstellar dust grains are not associated with the VLISM and that the conditions of the grains are better represented by the ones expected in the diffuse ISM. If this is the case, then the flatter slope in the mass distribution and the detection of larger interstellar grains in the solar system may even indicate that coagulation growth of dust in the diffuse ISM is more effective than previously inferred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002402322533
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  • 8
    Electronic Resource
    Electronic Resource
    Vector model analysis in nondestructive imaging by using the photothermal deflection methods (1999)
    Springer
    Applied physics 69 (1999), S. 343-346 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 78.20.Hp; 42.30.Va; 65.90.+i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The noncontact imaging of the buried structures is carried out in the open-air atmosphere by using the photothermal deflection (PTD) method. We applied these techniques to the layered samples. Besides the PTD images for the optically opaque buried structures, the parameters of the materials such as thermal diffusivity can also be calculated from the PTD amplitude and phase signal in the PTD scanning images. When the PTD signals at two different modulation frequencies are used, the thermal diffusivity of the buried structure can be obtained from the PTD signal outside of the sample nondestructively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390051011
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  • 9
    Electronic Resource
    Electronic Resource
    Tissue Distribution of Methylsulfonyl Metabolites Derived from 2,2′,4,5,5′-Penta- and 2,2′,3,4′,5′,6-Hexachlorobiphenyls in Rats (1999)
    Springer
    Archives of environmental contamination and toxicology 37 (1999), S. 135-142 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The time courses of fecal excretion and tissue distribution of metabolites derived from 2,2′,4,5,5′-pentachlorobiphenyl (CB101) and 2,2′,3,4′,5′,6-hexachlorobiphenyl (CB149) were investigated in male Wistar rats. The metabolism of both congeners involved primarily hydroxylation at the 3-position, and methylthiolation at the 4-position. Metabolites distributed in tissue were dominated by different ratios of 3- and 4-methylsulfonyl (MeSO2) metabolites. The 3-/4-MeSO2 metabolite ratios in liver and adipose tissue for both congeners were 0.41–0.61 at day 4, and then increased to 0.85–1.00 for up to day 42. In contrast, the ratios in lung were 0.03–0.04, and then decreased to 0.01. Compared to the unchanged PCBs at day 42, the distribution ratios of 3-MeSO2 metabolites were greater in the order of liver (0.46 for CB101 and 0.21 for CB149) 〉 kidney 〉 blood 〉 lung 〉 adipose tissue, whereas those of 4-MeSO2 metabolites were in the order of lung (9.50 for CB101 and 4.00 for CB149) 〉 kidney 〉 blood 〉 liver 〉 adipose tissue, indicating the different binding affinity of 3-MeSO2 metabolites in liver from that of 4-MeSO2 metabolites in lungs of rats. Furthermore, the structure-tissue affinity relationship for 3-MeSO2 metabolites was investigated, following the administration of 11 3-MeSO2-PCB congeners to rats. The results indicated that the retention potential of 3-MeSO2 metabolites in the liver largely depends on the ortho-chlorine substitution in the biphenyl ring rather than the degree of chlorination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449900498
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  • 10
    Electronic Resource
    Electronic Resource
    Sequencing, expression, and transcription analysis of the Clostridium paraputrificum chiA gene encoding chitinase ChiA (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 340-347 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Immediately (17 bp) upstream of the Clostridium paraputrificum chiB gene [J. Bacteriol. 179: 7306–7314 (1997)], we found another chitinase gene chiA encoding chitinase A (ChiA). The chiA gene consists of an open reading frame of 2496 nucleotides and encodes 832 amino acids with a deduced molecular mass of 92 585 Da. The mature ChiA is a modular enzyme composed of a family-18 catalytic domain responsible for chitinase activity, two cadherin-like domains, and a chitin-binding domain. The domain organization of ChiA is fundamentally identical to that of ChiB and the overall sequence identity between them is 35.4%. ChiA was purified from the periplasm fraction of Escherichia coli harboring the chiA gene. The molecular mass of purified ChiA (89 000 Da), determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis analysis, was in good agreement with the value (89 119 Da) calculated from the deduced amino acid sequence, excluding the signal peptide. Immunological and N-terminal amino acid sequence analyses revealed that ChiA and ChiB are major chitinases of C. paraputrificum and their production is inducible by ball-milled chitin. Northern blot analysis indicated that the chiA and chiB genes constitute a polycistronic operon. Primer-extension analysis confirmed that the transcription of this operon starts upstream of chiA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051400
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