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  • Springer  (157)
  • 2000-2004  (126)
  • 1960-1964  (27)
  • 1925-1929  (4)
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  • 1
    ISSN: 1432-1327
    Keywords: Metal substitution Cerium binding Lactoferrin Crystal structure Transferrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Proteins of the transferrin family play a key role in iron homeostasis through their extremely strong binding of iron, as Fe3+. They are nevertheless able to bind a surprisingly wide variety of other metal ions. To investigate how metal ions of different size, charge and coordination characteristics are accommodated, we have determined the crystal structure of human lactoferrin (Lf) complexed with Ce4+. The structure, refined at 2.2 Å resolution (R=20.2%, R free=25.7%) shows that the two Ce4+ ions occupy essentially the same positions as do Fe3+, and that the overall protein structure is unchanged; the same closed structure is formed for Ce2Lf as for Fe2Lf. The larger metal ion is accommodated by small shifts in the protein ligands, made possible by the presence of water molecules adjacent to each binding site. The two Ce4+ sites are equally occupied, indicating that the known difference in the pH-dependent release of Ce4+ arises from a specific protonation event, possibly of the His ligand in one of the binding sites. Comparing the effects of binding Ce4+ with those for the binding of other metal ions, we conclude that the ability of transferrins to accommodate metal ions other than Fe3+ depends on an interplay of charge, size, coordination and geometrical preferences of the bound metal ion. However, it is the ability to accept the six-coordinate, approximately octahedral, site provided by the protein that is of greatest importance.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9591
    Keywords: Fusion energy ; international collaboration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This report was prepared by a Working Group at the request of the U.S. Department of Energy, Office of Fusion Energy Sciences in 1997. The report addresses technical opportunities for mutually beneficial collaboration between the United States and other international fusion research programs. A number of outstanding opportunities are discussed.
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  • 3
    ISSN: 1476-5535
    Keywords: Keywords: echinocandin B deacylase; substrate specificity; evolution/technology; antifungal agent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aspergillus nidulans produces echinocandin B, a neutral lipopeptide. A deacylase from Actinoplanes utahensis catalyzes cleavage of the linoleoyl group from echinocandin B, a key step in generating a potential antifungal agent. Virtually all (99.8%) deacylase activity was cell-associated. The deacylase was salt-solubilized, heat-treated and purified to apparent homogeneity by a 3-step chromatographic procedure. The enzyme was a heterodimer consisting of 63- and 18-to-20-kDa subunit, optimally active at pH 6.0, and at 60°C with salt. The K m of the deacylase for echinocandin B was 50 μM and its V max was 14.6 μmol cyclic hexapeptide min−1 mg−1protein. The substrate specificity of the enzyme was broad with respect to both acyl and cyclic peptide analogues of echinocandin B. The two deacylase subunit genes were cloned and over-expressed in Streptomyces lividans. The recombinant deacylase was purified from the culture filtrate to apparent homogeneity by a 1-step chromatographic procedure. Using the recombinant deacylase, an enzymatic deacylation of immobilized echinocandin B resulted in the generation of cyclic hexapeptide at gram-level. Journal of Industrial Microbiology & Biotechnology (2000) 24, 173–180.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Research in engineering design 12 (2000), S. 61-72 
    ISSN: 1435-6066
    Keywords: Key words:Product families – Product platforms, Product portfolio architecture.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract: Consider a group of products sharing common parts and assemblies. The products in question we call a product family, and the common elements, the platform. In this paper, we present a method for designing product platforms and the derived family that takes into consideration both the technical performance requirements as well as the cost of the product family. The design of a platform-based product family is formulated as a general optimization problem in which the advantages of designing a common platform must be balanced against the constraints of the individual product variants and constraints of the family as a whole. This optimization approach forms the basis for a practical implementation as an interactive, team-based negotiation model for designing a family of interplanetary spacecraft based on a common platform. The approach is used to consider and specify different subsystems that could be made common to all the missions. It is also used to evaluate the impact of those platform design decisions on the performance of the product family, and thus be able to select from among feasible platform designs.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical crystallography 30 (2000), S. 181-184 
    ISSN: 1572-8854
    Keywords: tungsten(II) ; diiodo ; dicarbonyl ; triisopropylphosphite ; 3-hexyne ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [WI2(CO)2{P(OiPr)3}(η2-EtC2Et)] crystallizes in the monoclinic space group P21/n, with a = 11.101(12), b = 16.272(18), c = 14.892(17) Å, β = 93.27(1), Z = 4. The geometry can be considered to be pseudo-octahedral, with the 3-hexyne ligand occupying one site, with two iodo-groups, and the P(OiPr)3 ligand completing the equational plane of ligands, with two trans-carbonyl groups occupying the axial sites.
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  • 6
    ISSN: 1572-8927
    Keywords: Thermoelectric power ; tetra-n-butylammonium hydroxide ; heat of transport ; enthalpy of transport ; entropy of transport ; transported entropy ; thermocell ; hydrogen electrode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using a hydrogen-electrode thermocell with a temperature difference of 8 K, initialthermoelectric power εin has been determined in aqueous tetra-n-butylammoniumhydroxide solutions for concentrations ranging from 0.001 to 0.2 molal at meantemperatures of 25 and 35°C. Graphs of a function of εin vs. m 1/2/(1 + m 1/2) yieldintercepts and infinite-dilution limiting slopes as m 1/2 → 0. Using the value $$\overline{\overline S} _{{\text{OH}}}^{\text{o}} $$ = 68.8±0.3 J-K−1for the standard transported entropy of the hydroxideion, values for the enthalpy of transport of tetra-n-butylammonium hydroxide atinfinite dilution were determined to be 36.5±1.5 kJ-mol−1 at25° and 37.7±2.0kJ-mol−1 at 35°C.
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  • 7
    ISSN: 1572-9028
    Keywords: nitrous oxide decomposition ; carbon‐supported copper catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Copper supported on three different allotropic forms of carbon materials have been prepared and evaluated as catalysts for the N2O decomposition and reduction reactions. It was found that all the catalysts underwent severe deactivation during the N2O decomposition reaction due to the gasification of carbon substrates. This behavior was particularly evident when activated carbon was used as the support medium. The chemical identity of the active entity involved in the carbon gasification process is believed to consist of a mixture of Cu+ and Cu2+ species and, according to the well established mechanism, the reaction proceeds in such a manner so that the surface of the catalyst undergoes a redox cycle at the gas/solid carbon interface. The introduction of CO into the system was shown to result not only in an enhancement in the activity of the desired N2O decomposition reaction, but also served to inhibit the deleterious carbon gasification process. In addition, this procedure stabilized the copper particles in the metallic state, which is the active species responsible for the dissociation of N2O. Copper dispersed on a diamond substrate appeared to attain the highest activity for the N2O reduction reaction, a feature that is associated with the ability of the metal to undergo a wetting and spreading action on the support surface, possibly resulting in an epitaxial relationship between the two components.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Acta applicandae mathematicae 61 (2000), S. 37-52 
    ISSN: 1572-9036
    Keywords: rational approximation ; Padé approximants ; convergence properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A selective survey is given of convergence results for sequences of Padé approximants. Various approaches for dealing with the convergence problems due to `defects" are discussed. Attention is drawn to the close relationship between analyticity properties of a function and the `smoothness" of its Taylor series coefficients. A new theorem on the convergence of horizontal sequences of Padé approximants to functions in the Baker–Gammel–Wills conjecture function class is presented.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of geometry 67 (2000), S. 23-34 
    ISSN: 1420-8997
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract For any odd integern ≥3 and prime powerq, it is known thatPG(n−1, q2) can be partitioned into pairwise disjoint subgeometries isomorphic toPG(n−1, q) by taking point orbits under an appropriate subgroup of a Singer cycle ofPG(n−1, q2). In this paper, we construct Baer subgeometry partitions of these spaces which do not arise in the classical manner. We further illustrate some of the connections between Baer subgeometry partitions and several other areas of combinatorial interest, most notably projective sets and flagtransitive translation planes.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 51 (2000), S. 166-172 
    ISSN: 1432-1432
    Keywords: Key words: Homoplasy — Microsatellites — Microsatellite evolution — Allele evolution — Apodemus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Microsatellite length variation was investigated at a highly variable microsatellite locus in four species of Apodemus. Information obtained from microsatellite allele sequences was contrasted with allele sizes, which included 18 electromorphs. Additional analysis of a 400-bp unique sequence in the flanking region identified 26 different haplotype sequences or ``true'' alleles in the sample. Three molecular mechanisms, namely, (1) addition/deletion of repeats, (2) substitutions and indels in the flanking region, and (3) mutations interrupting the repeat, contributed to the generation of allelic variation. Size homoplasy can be inferred for alleles within populations, from different populations of the same species, and from different species. We propose that microsatellite flanking sequences may be informative markers for investigating mutation processes in microsatellite repeats as well as phylogenetic relationships among alleles, populations, and species.
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