Voltammetry of biologically active species and surfactants on new miniaturized and contractible (compressible) mercury electrodes

The adsorption of the polyether-antibiotic monensin from an aqueous solution on mercury was used to investigate the effect of the decreasing size of a stationary mercury drop electrode on the shape of the voltammetric desorption peak of the surfactant. The change of the i-E curve indicated an acceleration of the transport of the surfactant to the electrode as well as of time-dependent changes in the adsorption layer. A decrease of the radius of the hanging mercury drop electrode from 220 μm to 80 μm at a constant accumulation time of t_ac = 70 s resulted in an about 4-fold increase of the evaluated signal (i-E pre-wave) of monensin. A 7-fold increase of the voltammetric desorption peak of monensin at conc. 5 · 10^–7 mol/L was observed as result of a compressive accumulation of the surfactant due to a contraction of the mercury drop electrode. A scheme of an apparatus for voltammetric/polarographic measurements by means of the contractible (compressible) mercury drop electrode is described. The controlled contraction of the electrode surface is presented together with preliminary results covering a new way of accumulation of surfactants, new accumulation effects, effective in adsorptive voltammetry, and other electroanalytical techniques. Received: 26 March 1998 / Revised: 14 July 1998 / Accepted: 15 July 1998     

Recent advances in the synthesis and applications of azo initiators

This mini-review describes recent developments and trends in the area of syntheses and applications of azo compounds, which are planned to act as initiators of radical reactions, particularly polymerizations. The paper reports chemical modifications of well-known initiators (AIBN, etc.) or variants of syntheses of new types of these compounds. The chemical modifications of basic skeletons of azo initiators are discussed in the context with their properties and applications. Also discussed are the contemporary trends in the development of these initiators, particularly in preparation of microparticles and nanoparticles of polymers or hybrid inorganic–organic microparticles and nanoparticles prepared for intentional studies and applications.     

Protective effect of mitochondrially targeted antioxidant MitoQ on oxidatively stressed fibroblasts

3T3 and VH10 cells were subjected to oxidative damage by hydroxyl radicals generated from Cu(II) ions and ascorbate. The presence of reactive oxygen and nitrogen species in cells was determined using fluorescent dyes. MitoQ—a mitochondrially targeted antioxidant—was examined to prevent cell death and was compared with trolox as a reference standard serving as an antioxidant. MitoQ at lower concentrations (up to 500 nM) prevented damage of mitochondria and thereby increased viability of cells. However, at higher concentrations (over 500 nM) MitoQ decreased the viability of both strains of cells. The last observation indicates that the application of MitoQ should be evaluated also from the point of its cell-destructive potential.     

Stereospecific Synthesis of D-Glycero-D-ido-oct-2-ulose

Summary.  D-Glycero-D-gulo-heptose reacted with 2,2-dimethoxypropane to give its 2,3:6,7-di-O-isopropylidene derivative. Its base-catalyzed addition to formaldehyde resulted in the formation of 2,3:6,7-di-O-isopropylidene-2-C-(hydroxymethyl)-D-glycero-D-gulo-heptofuranose. After acid hydrolysis of this aldolization product, a new branched-chain aldose, 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose, was obtained, which was stereospecifically rearranged under the catalytic action of molybdic acid to D-glycero-D-ido-oct-2-ulose. Received October 17, 2000. Accepted December 4, 2000     

Voltage enhancement in dye-sensitized solar cell using (001)-oriented anatase TiO2 nanosheets

A nanocrystalline TiO₂ (anatase) nanosheet exposing mainly the (001) crystal faces was tested as photoanode material in dye-sensitized solar cells. The nanosheets were prepared by hydrothermal growth in HF medium. Good-quality thin films were deposited on F-doped SnO₂ support from the TiO₂ suspension in ethanolic or aqueous media. The anatase (001) face adsorbs a smaller amount of the used dye sensitizer (C101) per unit area than the (101) face which was tested as a reference. The corresponding solar cell with sensitized (001)-nanosheet photoanode exhibits a larger open-circuit voltage than the reference cell with (101)-terminated anatase nanocrystals. The voltage enhancement is attributed to the negative shift of flatband potential for the (001) face. This conclusion rationalizes earlier works on similar systems, and it indicates that careful control of experimental conditions is needed to extract the effect of band energetic on the current/voltage characteristics of dye-sensitized solar cell.     

Effects of anisotropic diffraction on quadratic multisoliton excitation in noncritically p hase-matched crystals

The generation of multiple quadratic spatial solitons aligned approximately along a crystal axis in a biaxial noncritically phase-matched crystal is shown theoretically and experimentally to be the consequence of anisotropic diffraction.     

FMR and FMAR measurement of saturation magnetization of the Fe-3 wt.% Si single crystals between 3.5 and 300 K

The saturation magnetization value of the alloy was established as 2.0782 and 2.0148 T (± 0.5 mT), at 4 and 300 K, respectively. Compared with the spin-wave theory the value of the stiffness constant was obtained 2.15 × 10²¹ eV m² and 1.9 × 10²¹ eV m² at the helium and room temperature, respectively. The influence of the highest-order term $\text{(～T}{}^{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ on the temperature dependence of magnetization is small and can be neglected. Its value corresponds to the neutron diffraction measurements.     

Microscopy and single molecule detection in photosynthesis

Progress in various fields of microscopy techniques brought up enormous possibilities to study the photosynthesis down to the level of individual pigment-protein complexes. The aim of this review is to present recent developments in the photosynthesis research obtained using such highly advanced techniques. Three areas of microscopy techniques covering optical microscopy, electron microscopy and scanning probe microscopy are reviewed. Whereas the electron microscopy and scanning probe microscopy are used in photosynthesis mainly for structural studies of photosynthetic pigment-protein complexes, the optical microscopy is used also for functional studies.     

Capillary gas chromatography-mass spectrometry of all 93 acyclic octenes and their identification in fluid catalytic cracked gasoline

The Kováts retention indices of all 93 acyclic octenes on polydimethylsiloxane and squalane as stationary phases as well as their mass spectra were measured. The means of gas chromatography-mass spectrometry (GC-MS) were used for confirmation of GC identification as well as for mass spectrometric deconvolution of the majority of gas chromatographic unseparated isomeric octene peaks. The distinction between corresponding E and Z acyclic octenes, that is either difficult or even impossible by means of GC-MS, was obtained on the basis of larger temperature coefficients of retention indices for Z isomeric octenes than for corresponding E isomers. The retention data expressed as homomorphy factors were correlated with the degree of branching, position of double bond, and position of alkyl group with respect to the double bond of acyclic octenes, and the structure-retention relationships were formulated. The 81 acyclic octenes were identified in FCC gasoline.