27 research outputs found
The Outbreak of the Russian Banking Crisis
Owing to a combination of domestic, regional and international factors, Russian banks have been strongly influenced by the worldwide financial crisis which started in the second half of 2008. In this paper, we estimate an early warning model for the Russian banking crisis. In a first step, we identify 47 Russian banks which failed after September 2008. Using the Bankscope dataset, we then show that balance sheet indicators were informative as early as in 2006 and 2007 about possible failures of these banks. Especially equity, net interest revenues, return on average equity, net loans, and loan loss reserves are identified as the early indicators with high predictive power.Banking and financial crisis, early warning models, Russia, logit
Herstellung von Feinchemikalien mit rekombinanten Schweineleberesterasen
Unter Verwendung von rekombinanten Schweineleberesterasen wurden zwei Chemoenzymatische Prozesse sukkzessive etabliert, optmiert und im MaĂstab vergĂśĂert. Es wurden zwei chirale Synthesebausteine beispielhaft hergestellt und charakterisiert.
Die Arbeit gibt einen Einblick in die Prozessoptimierung von chemoenzymatischen Syntheserouten unter Ăśkonomischen Aspekten.In this thesis two chemoenzymatic processes using recombinant pig liver esterases were established, optimized and scaled-up. Two chiral fine chemical building blocks were synthesized exemplary and characerized. The established processes give insights to chemoenzymatic process development under economical point of view
A generalized projection-based scheme for solving convex constrained optimization problems
In this paper we present a new algorithmic realization of a projection-based
scheme for general convex constrained optimization problem. The general idea is
to transform the original optimization problem to a sequence of feasibility
problems by iteratively constraining the objective function from above until
the feasibility problem is inconsistent. For each of the feasibility problems
one may apply any of the existing projection methods for solving it. In
particular, the scheme allows the use of subgradient projections and does not
require exact projections onto the constraints sets as in existing similar
methods.
We also apply the newly introduced concept of superiorization to optimization
formulation and compare its performance to our scheme. We provide some
numerical results for convex quadratic test problems as well as for real-life
optimization problems coming from medical treatment planning.Comment: Accepted to publication in Computational Optimization and
Application
Asymmetric azidohydroxylation of styrene derivatives mediated by a biomimetic styrene monooxygenase enzymatic cascade
Enantioenriched azido alcohols are precursors for valuable chiral aziridines and 1,2-amino alcohols, however their chiral substituted analogues are difficult to access. We established a cascade for the asymmetric azidohydroxylation of styrene derivatives leading to chiral substituted 1,2-azido alcohols via enzymatic asymmetric epoxidation, followed by regioselective azidolysis, affording the azido alcohols with up to two contiguous stereogenic centers. A newly isolated two-component flavoprotein styrene monooxygenase StyA proved to be highly selective for epoxidation with a nicotinamide coenzyme biomimetic as a practical reductant. Coupled with azide as a nucleophile for regioselective ring opening, this chemo-enzymatic cascade produced highly enantioenriched aromatic ι-azido alcohols with up to >99% conversion. A bi-enzymatic counterpart with halohydrin dehalogenase-catalyzed azidolysis afforded the alternative β-azido alcohol isomers with up to 94% diastereomeric excess. We anticipate our biocatalytic cascade to be a starting point for more practical production of these chiral compounds with two-component flavoprotein monooxygenases. A one-pot enzymatic cascade for the asymmetric azidohydroxylation of styrenes leads to chiral 1,2-azido alcohols with up to two stereocenters
Selective RingâOpening of DiâSubstituted Epoxides Catalysed by Halohydrin Dehalogenases
Halohydrin dehalogenases (HHDHs) are valuable biocatalysts for the synthesis of βâsubstituted alcohols based on their epoxide ringâopening activity with a number of small anionic nucleophiles. In an attempt to further broaden the scope of substrates accepted by these enzymes, a panel of 22 HHDHs was investigated in the conversion of aliphatic and aromatic vicinally diâsubstituted transâepoxides using azide as nucleophile. The majority of these HHDHs was able to convert aliphatic methylâsubstituted epoxide substrates to the corresponding azidoalcohols, in some cases even with absolute regioselectivity. HheG from Ilumatobacter coccineus exhibited also high activity towards sterically more demanding diâsubstituted epoxides. This further expands the range of βâsubstituted alcohols that are accessible by HHDH catalysis
Oneâpot Synthesis of 4âAminocyclohexanol Isomers by Combining a Keto Reductase and an Amine Transaminase
Abstract
The efficient multifunctionalization by oneâpot or cascade catalytic systems has developed as an important research field, but is often challenging due to incompatibilities or crossâreactivities of the catalysts leading to side product formation. Herein we report the stereoselective preparation of cisâ and transâ4âaminocyclohexanol from the potentially bioâbased precursor 1,4âcyclohexanedione. We identified regioâ and stereoselective enzymes catalyzing reduction and transamination of the diketone, which can be performed in a oneâpot sequential or cascade mode. For this, we identified regioselective keto reductases for the selective mono reduction of the diketone to give 4âhydroxycyclohexanone. The system is modular and by choosing stereocomplementary amine transaminases, both cisâ and transâ4âaminocyclohexanol were synthesized with good to excellent diastereomeric ratios. Furthermore, we identified an amine transaminase that produces cisâ1,4âcyclohexanediamine with diastereomeric ratios >98â:â2. These examples highlight that the high selectivity of enzymes enable short and stereoselective cascade multifunctionalizations to generate highâvalue building blocks from renewable starting materials.
Introductio
Scoping the Enantioselective Desymmetrization of a Poorly Water-Soluble Diester by Recombinant Pig Liver Esterase
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Singlet-Oxygen Generation by Peroxidases and Peroxygenases for Chemoenzymatic Synthesis
Singlet oxygen is a reactive oxygen species undesired in living cells but a rare and valuable reagent in chemical synthesis. We present a fluorescence spectroscopic analysis of the singlet-oxygen formation activity of commercial peroxidases and novel peroxygenases. Singlet-oxygen sensor green (SOSG) is used as fluorogenic singlet oxygen trap. Establishing a kinetic model for the reaction cascade to the fluorescent SOSG endoperoxide permits a kinetic analysis of enzymatic singlet-oxygen formation. All peroxidases and peroxygenases show singlet-oxygen formation. No singlet oxygen activity could be found for any catalase under investigation. Substrate inhibition is observed for all reactive enzymes. The commercial dye-decolorizing peroxidase industrially used for dairy bleaching shows the highest singlet-oxygen activity and the lowest inhibition. This enzyme was immobilized on a textile carrier and successfully applied for a chemical synthesis. Here, ascaridole was synthesized via enzymatically produced singlet oxygen. Š 2020 Wiley-VCH Gmb
Tick-borne Encephalitis from Eating Goat Cheese in a Mountain Region of Austria
We report transmission of tick-borne encephalitis virus (TBEV) in July 2008 through nonpasteurized goat milk to 6 humans and 4 domestic pigs in an alpine pasture 1,500 m above sea level. This outbreak indicates the emergence of ticks and TBEV at increasing altitudes in central Europe and the efficiency of oral transmission of TBEV