An electrochemical multienzymatic biosensor for determination of cholesterol

This paper describes an electrochemical biosensor for free cholesterol monitoring. The sensor is a multienzymatic electrodic system in which horseradish peroxidase and cholesterol oxidase are simultaneously immobilized within a polymeric film, on the surface of a pyrolitic graphite electrode. From voltammetric and amperometric (flow-injection) data obtained, the efficiency, reproducibility and stability of the system are discussed. Results obtained, of interest for basic and applied biochemistry, represent a first step for construction of a mediator-free biosensor with potentialities for a successful application in the biosensor area.     

Stimulating effect of graphite admixture on hydrogen sorption-desorption properties of mechanically activated titanium powder

The effect of graphite admixture on hydrogen sorption-desorption properties of mechanically activated electron microscopy, temperature-programmed reaction, and temperature-programmed desorption techniques. The major effect of graphite addition was found to be the formation of microporous carbon matrix particles containing randomly distributed titanium particles only several nanometers in diameter. This powder architecture enhances hydrogen transport to the titanium surface without hindrances and promotes titanium-hydrogen interaction by modifying the titanium surface and subsurface layers with interstitial carbon atoms.     

OVERVIEW ON SURFACE MICROSTRUCTURING BY PHOTODESORPTION ETCHING OF CHLORINATED SILICON

Developing a mechanistic interpretation of complex dynamical chemical systems such as halogen photoetching requires correlated microscopic data on the kinetics, dynamics, surface composition and microstructure of prototypical and real surfaces. This overview is concerned especially with two important variables which significantly influence the microetching mechanisms and structures; (I) the role of electronic point defects induced by substitutional doping in producing site-specific reactions and, (II) the quantum mechanical enhancement of chemical reaction induced by uv-radiation at low fluences and temperatures.

From uv-photoetching and photodesorption studies of heavily doped Si(100) and Si(111) with chlorine beams at low laser fluences, the mechanisms of photostimulated desorption is analyzed based primarily on the kinetics of chemisorption and surface layer microanalysis obtained from core-level photoemission. These results are coupled with time-of-flight dynamical measurements on the energetics of the photodesorption process to provide a more unified understanding of anisotropic photon-stimulated microetching.

Substantial alterations of the etching mechanisms occur when selective surface molecular processes are driven quantum mechanically by low level photon radiation rather than thermally. This is clearly reflected in the dynamical mechanisms for photodesorption which become strongly site- and atomic process-selective illustrated by the energetics of the processes. Creation and transport of charged carriers, especially at high doping levels by photoionization coupled with field-induced charge transport, introduces new reaction channels into the surface chemistry leading to resultant changes in the microstructure on an atomic scale. The results from the kinetics, velocity dynamics and film composition measurements are combined in terms of the dependency of chlorine adsorption on doping at high carrier levels and low laser fluences, to provide an improved interpretation of the anisotropic microetching in terms of field-promoted electron-hole activation.     

Inhibitory effects of non-steroidal anti-inflammatory drugs on superoxide generation.

Effects of non-steroidal anti-inflammatory drugs (NSAID: amfenac sodium, diclofenac sodium, indomethacin and ketoprofen) on the generation of superoxide anion (O2-) by isolated rat polymorphonuclear leukocytes (PMN) were studied spectrophotometrically using cytochrome c. The effects of these drugs were also studied on O2- production by the xanthine-xanthine oxidase and reduced nicotinamide adenine dinucleotide phosphate (NADPH)-NADPH oxidase systems. Amfenac sodium, at 0.1 mM, inhibited significantly O2- generation in rat PMN induced by opsonized zymosan. At 0.5 mM, diclofenac sodium and indomethacin inhibited the O2- generation in rat PMN. All of the above drugs slightly inhibited O2- production by the xanthine-xanthine oxidase system. On the other hand, O2- production by the NADPH-NADPH oxidase system was significantly inhibited by the addition of amfenac sodium, ketoprofen or indomethacin. These results suggest that non-steroidal anti-inflammatory drugs do not work as an O2- scavenger and block O2- production by the NADPH-NADPH oxidase system of rat PMN. It is concluded that amfenac sodium and the other drugs are able to inhibit granulocyte O2- production by blocking the activation of NADPH-oxidase.     

Catalytic determination of selenium with a picrate-selective electrode

A method is described for the determination of selenium, based on its catalytic effect on the picrate—sulfide reaction. The determination involves a variable-time kinetic procedure using potentiometric monitoring with a picrate-selective electrode and automatic measurement of the time required for the potential to change by a preselected amount (5.0 mV). Selenium in the range 3–30 μg was determined with an average error of about 4% and relative standard deviations of about 2%. The reaction can also be followed spectrophotometrically.     

Mesoionic compounds with a bridged nitrogen atom. 4. Thiazolo[3, 2-a]quinolinium 1-oxide derivatives

It is shown that diverse 2-substituted thiazolo[3,2-a]quinolinium 1-oxides can be obtained from 2-quinolylmercaptoacetic acids. The structures of the synthesized compounds were confirmed by the PMR and mass spectra.See [1] for communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 621–626, May, 1980.