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  • 1990-1994  (12)
  • 1985-1989  (1)
  • 1955-1959
  • Biochemistry and Biotechnology  (7)
  • 13.10.+q  (4)
  • 25.30.−c  (4)
Material
Years
  • 1990-1994  (12)
  • 1985-1989  (1)
  • 1955-1959
  • 1995-1999  (3)
Year
  • 1
    ISSN: 1434-601X
    Keywords: 13.10.+q ; 23.20.−g ; 36.10.−k ; 36.10.Dr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The probability for non-radiative (n.r.) excitations in muonic209Bi was determined from a (μ −,γγ)-measurement by comparing the intensities of muonic X-ray transitions in single and coincidence spectra. The values of Pn.r(3p→1s)=(17.9±2.0)% and Pn.r.(3d→1s)=(3.0±2.2)% were measured for the first time. The strength of the n.r. decay of the 2p-level was found to be (4.2±2.2)%. The n.r. transition probabilities of two subcomplexes of the (2p→1s)-transition leading to different mean excitation energies are (3.2±1.8)% and (5.0±2.0)%, respectively.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Keywords: 23.40.−s ; 25.30.−c ; 25.85.−w
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Fission fragments from the reaction237Np(μ −,γ,f) have been measured in coincidence with muonic X-rays. The efficiency of the fission fragment detector is determined from (μ −,γ,f)-data of the same experiment. The total fission probability perμ-stopP t has been measured as well as the fission probabilities Pf of the non-radiative muonic (3d→1s)- and (2p→1s)-transitions; the latter has been divided into two parts leading to different mean excitation energiesE:P t =(54±17)%,P f (3d→1s)=(41±21)%,P f (2p→1s,E=6.218 MeV)=(61±19)%, andP f (2p→1s,E=6.525 MeV)=(57±18)%. The influence of the muon on the fission barrier is discussed. The fission probability after muon capture is compared with a calculated value using a distribution of nuclear excitation energies following muon capture and the fission probability as measured in a238U(3He,αf)-reaction.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-601X
    Keywords: 13.10.+q ; 14.60.Ef ; 25.85.Ge ; 27.90.+b ; 36.10.Dr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The ratios of prompt to delayed fission yields for the isotopes233U,234U,235U,236U,238U,237Np,242Pu, and244Pu and the fission probabilities relative to each other have been investigated experimentally. Using the value of the total fission probability for237Np the absolute probabilities for prompt and delayed fission have been determined. The fission probabilities per muon captureP fc have been derived for all the isotopes and compared with an evaluation based on excitation functions from theory.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-601X
    Keywords: 25.30.−c ; 25.85.−w ; 25.85.Ge ; 36.10.Dr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The mean life times of negative muons bound to actinide nuclei have been measured by detecting the time difference between a stopped muon and the arrival of fragments from delayed fission after muon capture. The deduced capture ratesΛ c are 1.392(4)·107/s for237Np, 1.290(7)·107/s for242Pu and 1.240(7)·107/s for244Pu. The results are compared with published data for the fission and the neutron decay channels and for the electron decay of the bound muon. Including a former measurement ofΛ c for239Pu, an isotopic dependence of the muon capture rates in the Pu isotopes is clearly observed.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1434-601X
    Keywords: 13.10.+q ; 14.60.Ef ; 23.20.−g ; 25.30.−c ; 25.85.−w ; 27.90.+b ; 36.10.−k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A study of muonic238U has been performed in a combined (μ −,γ f) and (μ −,γγ) coincidence experiment to investigate the role of non-radiative transitions and their fission probabilities. An augmentation of the outer fission barrier ofΔE b =(0.6±0.1) MeV due to the presence of the muon is deduced. A significant contribution to the prompt fission yield not only results from the (2p→1s) and (3d→1s) non-radiative transitions, but also from other radiationless transitions. Specifically, the measured fission probabilities of the transitions (2p→1s), (3d→1s), and (3p→1s) are (1.5±0.4)%, (5.7±1.7)%, and (5.3±1.9)%, respectively.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1434-601X
    Keywords: 23.40.Bw ; 13.10.+q ; 25.85.−w ; 25.30.−c ; 27.80.+w ; 13.60.−r
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The probability for delayed muon induced fission of209Bi has been determined from a (μ −,f 1 f 2) measurement. The measured fission probability P f =(4.2±0.7)×10−5 is compared with theoretical predictions. The high fission threshold reaction seems well suited for studying the influence of two-body meson-exchange currents in nuclear muon capture.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 7 (1990), S. 16-31 
    ISSN: 0887-3585
    Keywords: BPTI ; dithiothreitol ; DTT-sensitive mutants ; protein folding ; random mutagenesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A genetic screening procedure has been developed to identify mutant forms of bovine pancreatic trypsin inhibitor (BPTI) that can fold to an active conformation but are inactivated more rapidly than the wild type protein. Small cultures of Escherichia coli containing plasmids with mutagenized BPTI genes were grown in microtiter plates, lysed, and treated with dithiothreitol (DTT). Under these conditions, unfolding and inactivation of wild-type protein has a half-time of about 10 hours. Variants of BPTI that are inactivated within 1 hour were identified by adding trypsin and a chromogenic substrate. Approximately 11,000 mutagenized clones were screened in this way and 75 clones that produce proteins that can fold but are inactivated by DTT were isolated. The genes coding for 68 “DTT-sensitive” mutant proteins were sequenced, and 25 different single amino acid substitutions at 15 of the 58 residues of the protein were identified. Most of the altered residues are largely buried in the core of the naive wild-type structure and are highly conserved among proteins homologous to BPTI. These results indicate that a large fraction of the sequence of the protein contributes to the kinetic stability of the active conformation, but it also appears that substitutions can be tolerated a most sites without completely preventing folding Because this genetics, further studies of the isolated mutants are expected to provide information about the roles of the altered residues in folding and unfolding.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 15 (1993), S. 322-329 
    ISSN: 0887-3585
    Keywords: unfolded proteins ; mutations ; BPTI ; gel electrophoresis ; disulfide-formation kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The effects of amino acid replacements on the hydrodynamic volume of reduced and unfolded bovine pancreatic trypsin inhibitor (BPTI) have been examined by gel electrophoresis. The electrophoretic mobilities of the reduced forms of 46 BPTI variants were compared at room temperature in the absence of denaturants. The single substitutions examined include many different types of replacements at sites throughout the polypeptide, and, collectively, alter 22 of the 58 residues of the wild-type protein. The only substitutions found to alter the electrophoretic mobility of the reduced protein by more than ∼3% are those that change the net charge of the protein. For nine mutants, the rates of disulfide formation in the reduced protein were also examined and found to be very similar to that of the wild-type protein. These results suggest that any structure that may be present in the reduced protein is either relatively insensitive to amino acid replacements or does not greatly influence the averaged properties of the polypeptide chain. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 1151-1160 
    ISSN: 0006-3592
    Keywords: fluorescence ; monitoring ; methane ; fermentation ; NAD(P)H ; F420 ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On-line in situ fluorescence measurements of the methanogenic fermentation were conducted with reactors receiving either glucose or a mixture of volatile fatty acids as the substrate. The reactors were perturbed from steady-state conditions in order to assess the response of fluorescencemonitoring probes. Two fluorescence-monitoring probes were evaluated over a period of 8 months; they performed in a consistent manner, and their response was not significantly affected by the changes in pH and redox potential encountered during routine reactor operation. A commercially available probe, designed to measure NAD(P)H, demonstrated particular promise for detecting imbalance caused by the entry of air, inhibitor addition and was capable of distinguishing between different substrates. This fluorescence-monitoring probe detected imbalance more rapidly than other on-line measurements such as pH, Eh, or gas production, or off-line measurements such as volatile fatty acid concentration or gas composition. An experimental fluorescence-monitoring probe, designed to measure coenzyme F420, also showed some promise in this regard. The response of the fluorescence-monitoring probes also revealed details of the metabolic routes in the reactors and the probes represent a useful research tool. For example, a failure to observe the characteristic response of the NAD(P)H-monitoring probe to formate addition during the metabolism of acetate, propionate, or glucose strongly suggests that any formate liberated during their catabolism is degraded via a different route to exogenously added formate.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 11 (1993), S. 35-44 
    ISSN: 0263-6484
    Keywords: Tunicamycin ; acetylated low density lipoprotein ; macrophages ; endocytosis ; proteolysis and chloroquine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of tunicamycin (TM) on the metabolism of acetylated low-density lipoprotein (AcLDL) was examined to determine whether N-linked glycosylation is required for the proper function of the AcLDL pathway. Proteolytic degradation of [125I]-AcLDL was increased twofold in the presence of TM. This did not occur via an increase in total lysosomal enzyme activity or extracellular proteolysis; rather, the rate of uptake of [125I]-AcLDL was increased. The enhanced degradation of AcLDL did not lead to a commensurate increase in the rate of synthesis of cholesteryl oleate. Conversely, the rate of cholesterol esterification was reduced in the presence of TM. The uptake of [125I]-AcLDL was more sensitive to inhibition by chloroquine in TM-treated cells. However, the presence of TM did not affect the ability of chloroquine to inhibit constitutive recycling of AcLDL binding sites. These results suggest that N-linked glycosylation may be involved in the regulation of AcLDL metabolism in J774 cells.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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