Detection of phenolic compounds by thick film sensors based on Pseudomonas putida

Amperometric biosensors using bacterial cells were developed for the determination of phenolic compounds and the measurement was based on the respiratory activity of the cells. For this purpose, Pseudomonas putida DSM 50026 which is one of the well-known phenol degrading organisms, was used as a biological component. The cells were grown in the presence of phenol as the sole source of organic carbon. As well as phenol adapted cells, the bacterium which used the glucose as the major carbon source, was also used to obtain another type of biosensor for the comparison of the responses and specificities towards different xenobiotics. The commercial oxygen electrode was used as a transducer to test the sensor responses for both induced and non-induced cells. Our results showed that the adaptation step enable us to obtain biosensor devices with different substrate specificity. Moreover, P. putida was immobilized on the surface of thick film working electrodes made of gold by using gelatin membrane cross-linked with glutaraldehyde. The biosensors were calibrated for different phenolic substances. Furthermore, phenol detection was performed in synthetic wastewater samples.     

Light diffraction effects from Kevlar aramid fibers

The light diffraction phenomenon from Kevlar 49 fibers exhibits unusual polarization effects and its angular and wavelength dependence cannot be described by the grating equation. This unexpected behavior is analyzed by modeling the fiber as an anisotropic grating of finite thickness in which the diffraction arises from a periodic change in the orientation of the molecular dipoles. Theoretical predictions on this basis explain all available experimental observations. These findings are discussed in regard to currently proposed structural models for the fiber.     

Quantitative analysis of phenibut in rat brain tissue extracts by liquid chromatography–tandem mass spectrometry

Phenibut (3-phenyl-4-aminobutyric acid) is a γ-aminobutyric acid mimetic drug, which is used clinically as a mood elevator and tranquilizer. In the present work, a rapid, selective and sensitive liquid chromatography–tandem mass spectrometry method for quantification of phenibut in biological matrices has been developed. The method is based on protein precipitation with acidic acetonitrile followed by isocratic chromatographic separation using acetonitrile–formic acid (0.1% in water; 8:92, v/v) mobile phase on a reversed-phase column. Detection of the analyte was performed by electrospray ionization mass spectrometry in multiple reaction monitoring mode with the precursor-to-product ion transition m/z 180.3 → m/z 117.2. The calibration curve was linear over the concentration range 50–2000 ng/mL. The lower limit of quantification for phenibut in rat brain extracts was 50 ng/mL. Acceptable precision and accuracy were obtained over the whole concentration range. The validated method was successfully applied in a pharmacological study to analyze phenibut concentration in rat brain tissue extract samples. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis of racemic 1,2,3,4-tetrahydroisoquinolines and their resolution

1-Aniline-substituted 3,4-dihydroisoquinolines were obtained in various ways using the Bischler-Napieralski reaction. The effect of the protecting group at the aniline nitrogen atom on the course of the reaction has been studied and it was found that the N-phthalyl group was stable under the cyclization conditions. The dihydroisoquinolines were reduced to the racemic 1,2,3,4-tetrahydroisoquinolines which were resolved by crystallization of the diastereomeric tartrates. Two examples of 1,2,3,4-tetrahydroisoquinolines were obtained in optically pure form (>99%ee).Dedicated to Professor M. A. Yurovskaya on her jubilee.Latvian Institute of Organic Synthesis, Riga LV-1006, Latvia. email: peteris@osi.lv. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 348–361, March, 2000.