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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: peptide folding ; NMR ; CD ; 310-helix ; gp120 ; CD4 binding domain ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A close association between the HIV surface protein gp120 and the CD4 T cell receptor initiates the viral multiplication cycle. A 15 amino acid peptide (LAV) within the CD4 binding domain of gp 120 has been shown to retain receptor binding ability. The structural behavior of the LAV peptide has been studied by CD and NMR methods in aqueous solution and upon addition of trifluoroethanol (TFE) to emulate the relatively apolar conditions at the membrane bound receptor. Previous work has shown that the LAV peptide folds into a β-pleated structure in more polar buffer/TFE mixtures, while a concerted structural change can be observed at a concentration of 60% TFE (v/v). This abrupt, cooperative refolding from a regular β-sheet to a helical secondary structure is known as “switch” behavior. Former CD experiments with LAV sequence variants have supported the assumption that four amino acids at the N-terminus (LPCR) are indispensable for the “switch.” The tetrad has a strong β-turn forming potential. The suggestion has been formulated that the tetrad can act as a nucleation site governing the refolding. The present NMR study of the LAV peptide in TFE gives evidence for a 310-helix suggesting that the tetrad adopts a type III β-turn and promotes the formation of a similar bend in the next overlapping tetrad until the sequence is restructured into a 310-helix at a critical polarity favoring intrachain hydrogen bonds. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 1596-1598 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 141-147 
    ISSN: 0006-3592
    Keywords: L-DOPA ; tyrosinase ; enzyme immobilization ; nylon 6,6 ; inactivation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The production of L-DOPA immobilized on chemically modified nylon 6,6 membranes was studied in a batch reactor. Tyrosinase was immobilized on nylon using glutaraldehyde as a crosslinking agent. The effects of membrane pore size and glutaraldehyde concentration upon enzyme uptake and L-DOPA production were investigated. Enzyme uptake was unaffected by glutaraldehyde concentration; approximately 70% uptake was observed when 25% w/v (group 1), 5% (group 2), and 3% (group 3) glutaraldehyde were used, indicating that glutaraldehyde was in excess. Similarly, uptake was the same for membranes with 0.20 and 10 μm pore sizes.Membranes produced using different levels of glutaraldehyde exhibited dramatically different capacities for L-DOPA production, despite the fact that enzyme uptake was equivalent. Membranes from groups 2 and 3 (5% and 3% glutaraldehyde) produced L-DOPA at a rate of 1.70 mg L-1 h-1 over 170 h in a 500-mL batch reactor. However, no free L-DOPA was detected when group 1 membranes were used. Experimental evidence suggests that L-DOPA was produced, but remained bound to these membranes via excess glutaraldehyde left over from the immobilization process. Membrane pore size also effected L-DOPA production; less production was observed when 10-μm membranes were used, despite equivalent enzyme uptake. The observed difference in production may be due to differences in the pore density on the two types of membranes which could affect the access of the substrate to the immobilized enzyme.The results of these studies indicate that tyrosinase can be effectively immobilized on nylon 6,6. L-DOPA production was optimal when 0.20-μm-pore-size membranes were activated with 3-5% glutaraldehyde. Stability studies indicated a 20% reduction in activity over 14 days when the immobilized enzyme was used under turnover conditions. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2621-2624 
    ISSN: 0173-0835
    Keywords: Acidic polysaccharides ; Exopolysaccharides ; Soil bacteria ; Polyacrylamide gel electrophoresis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The electrophoretic behavior in polyacrylamide gels of the acidic polysaccharides produced by the soil bacteria Bradyrhizobium (Chamaecytisus) strain BGA1 and Bradyrhizobium japonicum USDA110 has been studied. Both polysaccharides were polydisperse, producing a ladder-like pattern after fixation with Alcian Blue and silver staining of the gel. The polysaccharide molecules were separated according to their size, and they behaved as a collection of flexible random coils of different size and similar charge/mass ratio. The electrophoretic behavior was not affected by the presence of acetyl groups in the polysaccharide. The range of molecular weights of the exopolysaccharide produced by B. japonicum USDA110 was wider and with larger molecules than that of the polysaccharide produced by strain BGA1. The resolution was dependent on the electrophoresis buffer; the best results were achieved with Tris-borate; in Tris-glycine buffer, the resolution was worse, and it was not improved by the addition of sodium dodecyl sulfate (SDS).
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 7 (1989), S. 7-10 
    ISSN: 0263-6484
    Keywords: Glycolysis ; glutaminolysis ; tumour ; perifused cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A perifusion system was designed in order to study glucose and glutamine metabolism by freshly harvested Ehrlich ascites tumour cells in steady state conditions. Cells were perifused in the presence of 5 mM glucose, 0·5 mM glutamine or 5mM glucose and 0·5 mM glutamine. The results in steady state reveal that both substrates glucose and glutamine are continuously wasted by tumour cells, excreting two moles of lactate per mol of glucose and one mol of glutamate and ammonia per mol of glutamine consumed into the medium. Glutamine consumption in the presence of glucose was higher than with glutamine alone.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    ISSN: 0268-2575
    Keywords: kinetic model ; anaerobic digestion ; best molasses ; aerobic pretreatment ; Penicillium decumbens ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: --A comparative study was carried out on the anaerobic digestion of untreated and previously-fermented (with Penicillium decumbens) beet molasses. Four continuous stirred tank reactors were used for the study, two with freely suspended biomass, and the other with biomass supported on saponite. The reactors operated satisfactorily between hydraulic retention times (HRT) of 53·3-10·6 days and 15·4-3·1 days for untreated and previously-fermented molasses respectively. The anaerobic digestion processes of untreated and pretreated molasses were found to follow first-order kinetics for biomass loading rates in the range of 0-0·55 and 0-0·75 g chemical oxygen demand (COD) g-1 volatile suspended solids (VSS) day-1 respectively. The experimental data [namely unitary conversion or efficiency (X), HRT, biomass concentration (M) and incoming substrate concentration (S0)] conformed to an equation of the form: X/HRT = KM(1-X)-(KMSR/S0), from which the kinetic constant, K, was calculated. The kinetic constants were influenced by the pretreatment carried out and were 1·7 and 2·5 times higher for pretreated molasses than for untreated molasses in the reactors with suspended and immobilized biomass respectively. This was significant at a 95% confidence level. The specific rate of substrate uptake for cell maintenance (m) decreased by a factor of approximately 2 for the previously fermented molasses in relation to the observed values for the untreated molasses. This may be attributable to the fact that higher phenolic compound concentrations inhibit and interfere with the activity of anaerobic bacteria. © 1997 SCI.
    Additional Material: 5 Ill.
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  • 7
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    Bonn: Institute of Labor Economics (IZA)
    Publication Date: 2019-09-04
    Description: The effectiveness of social interaction depends strongly on an ability to coordinate actions efficiently. In large networks, such coordination may be very difficult to achieve and may depend on the communication technology and the network structure. We examine how pre-play communication and clustering within networks affect coordination in a challenging experimental game on eight-person networks. Free-form chat is enormously effective in achieving the nonequilibrium efficient outcome in our game, but restricted communication (where subjects can only indicate their intended action) is almost entirely ineffective. We can rationalize this result with a novel model about the credibility of cheap-talk messages. This credibility is much larger with freeform message communication than with restricted communication. We are the first to model this credibility and show, both theoretically and experimentally, an interaction effect of network structure and communication technologies. We also provide a model of message diffusion, which indeed predicts that diffusion will be more rapid without clustering and is consistent with our data.
    Keywords: C71 ; C91 ; D03 ; D85 ; ddc:330 ; networks ; clustering ; communication ; credibility ; cheap talk ; experiment
    Language: English
    Type: doc-type:workingPaper
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  • 8
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    Munich: Center for Economic Studies and Ifo Institute (CESifo)
    Publication Date: 2018-11-19
    Description: This paper investigates the impact of international shocks - interest rate, commodity price and industrial production shocks - on key macroeconomic variables in ten Central and Eastern European (CEE) countries by using near-VAR models and monthly data from the early 1990s to 2009. In contrast to previous work, the empirical analysis takes explicit account of the possibility of (multiple) structural breaks in the underlying time series. We establish strong evidence of structural breaks, particularly along the years 2007 and 2008, suggesting the very relevant impact of the recent global crisis on CEE economies. Moreover, our results suggest that the way how countries react to world commodity price shocks is related to the underlying economic structure and the credibility of the monetary policy. We also find that some countries like Slovakia and Slovenia - already euro area members - react stronger to foreign industrial production shocks than other countries and that the responses to such shocks are strongly correlated for selected CEE countries. Nevertheless, our results also shed light on substantial differences in responses to foreign interest rate shocks that originate from the US or the euro area.
    Keywords: E43 ; E50 ; E52 ; C22 ; O52 ; ddc:330 ; monetary policy ; foreign shocks ; multiple structural breaks ; near-VAR model ; CEE economies ; Schock ; Zins ; International ; Weltkonjunktur ; Makroökonomischer Einfluss ; VAR-Modell ; Schätzung ; Ostmitteleuropa
    Language: English
    Type: doc-type:workingPaper
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  • 9
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    Amsterdam and Rotterdam: Tinbergen Institute
    Publication Date: 2013-11-13
    Description: The Basel II Accord requires that banks and other Authorized Deposit-taking Institutions (ADIs) communicate their daily risk forecasts to the appropriate monetary authorities at the beginning of each trading day, using one or more risk models to measure Value-at-Risk (VaR). The risk estimates of these models are used to determine capital requirements and associated capital costs of ADIs, depending in part on the number of previous violations, whereby realised losses exceed the estimated VaR. In this paper we define risk management in terms of choosing from a variety of risk models, and discuss the selection of optimal risk models. A new approach to model selection for predicting VaR is proposed, consisting of combining alternative risk models, and we compare conservative and aggressive strategies for choosing between VaR models. We then examine how different risk management strategies performed during the 2008-09 global financial crisis. These issues are illustrated using Standard and Poor’s 500 Composite Index.
    Keywords: G32 ; G11 ; G17 ; C53 ; C22 ; ddc:330 ; Value-at-Risk (VaR) ; daily capital charges ; violation penalties ; optimizing strategy ; risk forecasts ; aggressive or conservative risk management strategies ; Basel Accord ; global financial crisis ; Basler Akkord ; Einlagengeschäft ; Risikomaß ; Unternehmenspublizität ; Finanzkrise ; Welt
    Language: English
    Type: doc-type:workingPaper
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  • 10
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    Amsterdam and Rotterdam: Tinbergen Institute
    Publication Date: 2013-11-13
    Description: In this paper we provide further evidence on the suitability of the median of the point VaR forecasts of a set of models as a GFC-robust strategy by using an additional set of new extreme value forecasting models and by extending the sample period for comparison. These extreme value models include DPOT and Conditional EVT. Such models might be expected to be useful in explaining financial data, especially in the presence of extreme shocks that arise during a GFC. Our empirical results confirm that the median remains GFC-robust even in the presence of these new extreme value models. This is illustrated by using the S&P500 index before, during and after the 2008-09 GFC. We investigate the performance of a variety of single and combined VaR forecasts in terms of daily capital requirements and violation penalties under the Basel II Accord, as well as other criteria, including several tests for independence of the violations. The strategy based on the median, or more generally, on combined forecasts of single models, is straightforward to incorporate into existing computer software packages that are used by banks and other financial institutions.
    Keywords: G32 ; G11 ; G17 ; C53 ; C22 ; ddc:330 ; Value-at-Risk (VaR) ; DPOT ; daily capital charges ; robust forecasts ; violation penalties ; optimizing strategy ; aggressive risk management ; conservative risk management ; Basel ; global financial crisis ; Finanzkrise ; Basler Akkord ; Portfolio-Management ; Risikomaß ; Prognoseverfahren ; Extremwerttheorie ; Welt
    Language: English
    Type: doc-type:workingPaper
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