Enzymatic Conversion of Flavonoids using Bacterial Chalcone Isomerase and Enoate Reductase

Flavonoids are a large group of plant secondary metabolites with a variety of biological properties and are therefore of interest to many scientists, as they can lead to industrially interesting intermediates. The anaerobic gut bacterium Eubacterium ramulus can catabolize flavonoids, but until now, the pathway has not been experimentally confirmed. In the present work, a chalcone isomerase (CHI) and an enoate reductase (ERED) could be identified through whole genome sequencing and gene motif search. These two enzymes were successfully cloned and expressed in Escherichia coli in their active form, even under aerobic conditions. The catabolic pathway of E. ramulus was confirmed by biotransformations of flavanones into dihydrochalcones. The engineered E. coli strain that expresses both enzymes was used for the conversion of several flavanones, underlining the applicability of this biocatalytic cascade reaction.     

Stress-induced chemical detection using flexible metal-organic frameworks

In this work we demonstrate the concept of stress-induced chemical detection using metal-organic frameworks (MOFs) by integrating a thin film of the MOF HKUST-1 with a microcantilever surface. The results show that the energy of molecular adsorption, which causes slight distortions in the MOF crystal structure, can be converted to mechanical energy to create a highly responsive, reversible, and selective sensor. This sensor responds to water, methanol, and ethanol vapors, but yields no response to either N2 or O2. The magnitude of the signal, which is measured by a built-in piezoresistor, is correlated with the concentration and can be fitted to a Langmuir isotherm. Furthermore, we show that the hydration state of the MOF layer can be used to impart selectivity to CO2. Finally, we report the first use of surface-enhanced Raman spectroscopy to characterize the structure of a MOF film. We conclude that the synthetic versatility of these nanoporous materials holds great promise for creating recognition chemistries to enable selective detection of a wide range of analytes.     

High magnetic field properties of mixed terbium-yttrium ferrite garnets

Magnetization measurements in d.c. magnetic fields up to 180 kOe have been performed on polycrystalline specimens and on single crystals of mixed terbium-yttrium iron garnets: Tb _x Y_3–x Fe₅O₁₂ in the 4.2–300 K temperature range. On polycrystals (x=2.5; 2; 1; 0.37) the concentration dependence of both compensation point and spontaneous magnetization has been determined. In the single crystals (x=2; 1; 0.37) a strong magnetic anisotropy has been observed with a change of the easy direction of magnetization from [111] to [100] whenx decreases; abrupt field-induced transitions have been observed at low temperatures when the external field is applied along the [100] direction.     

Étude asymptotique de certains mouvements browniens complexes avec drift

Sans résuméLa recherche de cet auteur a été réalisée en partie avec l'aide de NSF Grant MCS 82-02552     

Synthesis of vulpinic acids from dimethyl tartrate

A series of vulpinic acids differing by the aryl or heteroaryl groups placed in the ester α-position were prepared by Suzuki-Miyaura cross-coupling involving a common iodide and the corresponding aryl boronates. The preparation of the iodide precursor from (+)-dimethyl l-tartrate required four steps: the esterification of one hydroxyl group, a Dieckmann cyclization allowing the construction of the tetronic acid moiety, a dehydration leading to the installation of the exocyclic double bond and lastly, an N-iodosuccinimide-mediated iodation of the alkene obtained.     

Studies on measuring software

A quality control workshop prototype based on a quantitative approach which is operational from the validation phase was developed. Several telecommunications software systems were analyzed, particularly those areas pertaining to complexity and reliability. The workshop, the methods use to collect, handle, and analyze data, and the tools employed are described. The results allow evaluation of tool usefulness, pertinence of metrics, and validation of the reliability model. It is noted that the research carried out will lead to the application and evaluation of software quality assurance plans and to the evaluation of current beliefs concerning validity, efficiency, and costs     

Efficiency of the intercalation of aluminum atoms under a monolayer and submonolayer two-dimensional graphite film on a metal

Intercalation of aluminum atoms under a two-dimensional graphite film on a metal was studied by high-resolution Auger spectroscopy. The spectra were recorded directly from the highly heated (up to 2100 K) sample. It is shown that the efficiency of this process increases significantly if the film is of the island type, rather than continuous, and if part of the metal surface is not covered with graphite. It is concluded that the graphite-island boundaries are the defects via which the intercalating atoms penetrate under the graphite film.     

Embedding of Biological Regulatory Networks and Property Preservation

In the course of understanding biological regulatory networks (BRN), scientists usually start by studying small BRNs that they believe to be of particular importance to represent a biological function, and then, embed them in a larger network. Such a reduction can lead to neglect relevant regulations and to study a network whose properties can be very different from the properties of this network viewed as a part of the whole. In this paper we study, from a logical point of view, on which conditions concerning both networks, properties can be inherited by BRNs from sub-BRNs. We give some conditions on the nature of the network embeddings ensuring that dynamic properties on the embedded sub-BRNs are preserved at the level of the whole BRN.     

Decarboxylative Amination of SMAHOs by Dialkyl Azodicarboxylates

The decarboxylative addition of substituted malonic acid half oxyesters (SMAHOs) to dialkyl azodicarboxylates is described. The reaction was promoted by 1,4-diazabicyclo[2.2.2]octane (DABCO) as an organocatalyst in heated toluene. High yields of the coupling products were generally obtained, and the scope of the reaction proved rather important with the potential presence of functionalized side chains at the α-position, affording an original access to α-aminoester derivatives.     

Die Syzyganten zweier simultanen binären biquadratischen Formen

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