Highly stereoselective reductions of alpha-alkyl-1,3-diketones and alpha-alkyl-beta-keto esters catalyzed by isolated NADPH-dependent ketoreductases

[reaction: see text] The biocatalytic reduction of alpha-alkyl-1,3-diketones and alpha-alkyl-beta-keto esters employing 1 of 20 different isolated NADPH-dependent ketoreductases proved to be a highly efficient method for the preparation of optically pure keto alcohols or hydroxy esters.     

On the Number of Solutions of the Equation a_{1}x_{1}^{m_{1}}+\cdots +a_{n}x_{n}^{m_{n}}=bx_{1}\cdots x_{n} in a Finite Field

We obtain an explicit formula for the number of solutions of a special equation in a finite field under a certain restriction on the exponents. Mathematics Subject Classifications (2000) primary: 11G25, secondary: 11T24.     

Reductions of threshold for a mid-infrared optical parametric oscillator by an intracavity optical amplifier

We demonstrate that the threshold for a mid-IR optical parametric oscillator based on periodically poled LiNbO3 is significantly reduced by the introduction of an optical amplifier inside the cavity. Thresholds as low as 8 mW and a tuning range of 3.0-4.2 microm were attained for stable single-mode operation.     

Immobilization of Urease and Cholinesterase on the Surface of Semiconductor Transducer for the Development of Light-Addressable Potentiometric Sensors

Various methods for the immobilization of urease and butyrylcholinesterase on the insulator surface of a laser-scanned semiconductor transducer (LSST) have been tested and compared for the development of an enzyme-based light-addressable potentiometric sensor (LAPS). The method of preparing photocurable membranes on LAPS is presented, and a new type of enzyme LAPS with photocurable polymeric enzyme membranes has been elaborated. It was found that sensors prepared by means of covalent bonding and cross-linking with inactive protein (type SIII) and with photocurable membrane matrices (type SIV) are more prospective. The enzyme LAPSensors with photocurable membranes demonstrate a degree of sensitivity close to the theoretical value and working ranges of 6.3·10^–5–1.1·10^–2 and 1·10^–4–1·10^–1molL^–1 urea for acrylamide and acrylate-based membrane matrices, respectively, and 2.5·10^–4–2·10^–1molL^–1 butyrylcholine for an acrylamide membrane matrix. It is shown that such sensors can be also used for the analysis of enzyme inhibitors.     

Recent progress on terahertz generation based on difference frequency generation:from power scaling to compact and portable sources

The progress achieved on power scaling and compact and portable THz sources is reviewed.By reversely stacking the GaP plates,the photon conversion efficiency is improved from 25% to 40% which corresponds to the maximum value.When the number of the plates is increased from four to five,the output power decreases because of back conversion.The THz generation is also investigated by mixing the two frequencies generated by a single Nd:YLF solid-state laser.The average output power reaches 1 μW.The introduction of two Nd:YLF crystals significantly improves the output power to 4.5 μW.This configuration facilitates the generation of different output frequencies.