Oxidation of Protopine at a Pyrolytic Graphite Electrode Using Cyclic and Square‐Wave Voltammetry

This paper describes oxidation of the isoquinoline alkaloid, protopine (PR) at a pyrolytic graphite electrode (PGE) using cyclic and square‐wave voltammetry. In the alkaline range (pH 7.5–10.5) of a Britton–Robinson (B–R) buffer, a PR oxidation can be observed as a well‐developed voltammetric peak around +0.9 V (vs. Ag|AgCl|3 M KCl). With increasing pH of the B–R buffer, the PR peak is shifted to less positive potentials. The acquired voltammetric data suggest that PR strongly adsorbs onto the surface of the pyrolytic graphite where it is subjected to irreversible electrochemical oxidation in its uncharged free (tricyclic) base form. The results are discussed in connection with the electrochemical oxidation of other isoquinoline alkaloids and the potential applications of these data.     

Coating of zinc ferrite particles with a conducting polymer, polyaniline

Particles of zinc ferrite, ZnOFe2O3, were coated with polyaniline (PANI) phosphate during the in situ polymerization of aniline in an aqueous solution of phosphoric acid. The PANI-ferrite composites were characterized by FTIR spectroscopy. X-ray photoelectron spectroscopy was used to determine the degree of coating with a conducting polymer. Even a low content of PANI, 1.4 wt%, resulted in the 45% coating of the particles' surface. On the other hand, even at high PANI content, the coating of ferrite surface did not exceeded 90%. This is explained by the clustering of hydrophobic aniline oligomers at the hydrophilic ferrite surface and the consequent irregular PANI coating. The conductivity increased from 2 x 10(-9) to 6.5 S cm(-1) with increasing fraction of PANI phosphate in the composite. The percolation threshold was located at 3-4 vol% of the conducting component. In the absence of any acid, a conducting product, 1.4 x 10(-2) Scm(-1), was also obtained. As the concentration of phosphoric acid increased to 3 M, the conductivity of the composites reached 1.8 S cm(-1) at 10-14 wt% of PANI. The ferrite alone can act as an oxidant for aniline; a product having a conductivity 0.11 S cm(-1) was obtained after a one-month immersion of ferrite in an acidic solution of aniline.     

UVA-activated 8-methoxypsoralen (PUVA) causes G2/M cell cycle arrest in Karpas 299 T-lymphoma cells

We investigated the effect of UVA-activated 8-methoxypsoralen (PUVA) on the cell line Karpas 299 derived from anaplastic large-cell lymphoma (ALCL) expressing chimeric fusion protein nucleophosmin-anaplastic lymphoma kinase (NPM/ALK). NPM/ALK activates phosphatidylinositol 3 kinase (PI3K)/Akt pathway responsible for the cell protection from apoptosis. We found that PUVA treatment first induced G2/M cell cycle arrest resulting in a decrease in the cell proliferation rate. The mitochondrial apoptosis was triggered immediately following PUVA treatment, as we judged from the unmasking of mitochondrial membrane antigen 7A6. However, the mitochondrial membrane depolarization was not observed and caspase-3 was only slightly activated. The late apoptotic events were lacking: neither translocation of phosphatidylserine to the outer side of plasma membrane nor DNA fragmentation occurred. We revealed that PUVA enhanced the expression of peroxiredoxin, stress protein endoplasmin and galectin-3. Galectin-3 has been shown to protect mitochondrial membrane integrity and prevent cytochrome c release thereby blocking the effector stage of apoptosis. We suggest that the elevated level of this protein following PUVA treatment acts in synergy with the constitutively expressed chimeric kinase NPM/ALK to block the apoptosis.     

The Effect of Actinoquinol with Hyaluronic Acid in Eye Drops on the Optical Properties and Oxidative Damage of the Rabbit Cornea Irradiated with UVB Rays

Irradiation of the cornea with UVB rays leads to its oxidative damage, swelling and increased light absorption. We investigated changes in the corneal optics (evaluated by changes of corneal hydration and light absorption) and microscopical disturbances of corneas irradiated with UVB rays as influenced by eye drops containing actinoquinol with hyaluronic acid. Rabbit corneas were irradiated with a daily dose of 0.5 or 1.01 J cm⁻² of UVB rays (312 nm) for 4 days. During irradiation, the eye drops were applied on the right eye and buffered saline (or hyaluronic acid) on the left eye. On day 5 the rabbits were sacrificed and the corneas examined spectrophotometrically for light absorption. The corneal thickness (hydration) was measured using a pachymeter. Corneas of some other rabbits were examined immunohistochemically. After buffered saline treatment UVB rays evoked changes in the corneal optics and induced oxidative damage of the corneas. After actinoquinol-hyaluronic acid application, these changes were diminished. Hyaluronic acid alone was less effective. In conclusion, actinoquinol-hyaluronic acid eye drops decreased changes in corneal optics and suppressed oxidative damage in the UVB-irradiated cornea. However, the effective corneal protection by these eye drops was limited to the lower UVB dose.     

Ammonium fluoride as a novel chemical modifier for the elimination of magnesium chloride interference on the determination of lead by graphite furnace atomic absorption spectrometry

Ammonium fluoride was found to be very efficient modifier for the elimination of MgCl₂ interference on Pb determination. Ammonium fluoride probably converts strongly interfering volatile MgCl₂ to less volatile MgF₂ matrix that makes possible the release of Pb analyte at lower temperature, before the matrix starts to vaporize. It was observed likewise that NH₄F removes the interferences mentioned, i.e. caused by MgCl₂ presence, much more effectively as compared with some modifiers, before now recommended for this purpose. The application of this modifier to the determination of Pb in 2% (m/v) MgCl₂ has ensured the characteristic mass and LOD value in the original sample of 12 pg and 60 ng g⁻¹, respectively (10 μl aliquots of sample). Applying the modifier to standards and samples enables the use of matrix-free standard solutions for attaining accurate analysis as verified by recovery studies.     

Assay of urinary 8‐hydroxy‐2′‐deoxyguanosine by capillary electrophoresis with spectrophotometric detection using a high‐sensitivity detection cell and solid‐phase extraction

A sensitive capillary electrophoretic method featuring spectrophotometric detection using a commercial Z‐cell was devised for the assay of 8‐hydroxy‐2′‐deoxyguanosine (8OHdG) in human urine. Solid‐phase extraction (SPE) based on hydrophilic‐lipophilic‐balanced RP sorbent was utilized for urine sample pretreatment and analyte preconcentration. The separation was carried out in conventional fused‐silica capillaries employing a Z‐cell with hydrodynamic sample injection (at 50 mbar for 12 s). The BGE (pH* 9.2, adjusted with 1 M NaOH) contained 0.15 M boric acid and 10% v/v ACN. The detection wavelength was 282 nm. The calibration curve for 8OHdG (measured in spiked urine) was linear in the range 10–1000 ng/mL; R² = 0.9993. The LOD was 3 ng/mL (11 nmol/L) of 8OHdG. Determination of the 8OHdG urinary levels was possible even in healthy individuals.     

The Reversibility of UV‐B Induced Alterations in Optical Properties of the Rabbit Cornea Depends on Dose of UV Irradiation

Solar UVB radiation evokes photokeratitis, accompanied by increased corneal hydration and changes in corneal transparency, resulting in increased light absorption. Corneal optical properties are disturbed and visual acuity decreased. The aim of this study was to investigate the reversibility of these UVB‐induced changes. Rabbit corneas were irradiated with UVB doses of 0.5 J cm^?2 or 1.01 J cm^?2 during 4 days. Some rabbits were sacrificed after the last irradiation and some 2 months later. Corneas were investigated spectrophotometrically for light absorption, and corneal hydration was evaluated by central corneal thickness with an ultrasonic pachymeter. Corneal impression cytologies were examined immunohistochemically for proinflammatory cytokines and malondialdehyde. The increased corneal light absorption, hydration and the staining of immunohistochemical markers found in corneas after irradiation returned to normal values during 2 months in corneas irradiated with the lower UVB dose. In contrast, in corneas irradiated with the higher UVB dose, a moderate but statistically significant increase in corneal light absorption, hydration and positive immunohistochemical stainings remained as residual changes. This was in contrast to normal corneas, where the staining of proinflammatory cytokines as well as malondialdehyde was negative. In conclusion, the reversibility of UVB‐induced disturbances was dependent on UVB dose.     

Influence of various starch types on PCL/starch blends anaerobic biodegradation

Research concentrated on the biodegradable capability of PCL blends with various types of starch in an anaerobic aqueous environment of mesophilic sludge from a municipal wastewater treatment plant. For blend preparation, use was made of a native starch Meritena from maize, another from Waxy – a genetically modified type of maize, as well as Gel Instant, a gelatinized starch, and an amaranth starch. Additional PCL/starch blends were prepared from the same starch types, but these were initially plasticized with glycerol. The biodegradability tests were supplemented with thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC); morphology was identified using scanning electron microscopy (SEM), plus mechanical properties were also tested. While mixtures of PCL with starches plasticized with glycerol exhibited improved mechanical properties and a higher degree of biodegradation in the anaerobic environment, mixtures of PCL with pure forms of starch were ascertained as rather resistant to the anaerobic aqueous environment. TGA and DSC analysis confirmed the removal of starch and glycerol from the PCL matrix. SEM then proved these results through the absence of starch grains in the samples following anaerobic biodegradation.     

Contemporary chiral simulators for capillary zone electrophoresis

For separation of enantiomers in presence of a chiral selector, data obtained with the 1D dynamic simulators SIMUL5complex and GENTRANS are compared to data predicted by PeakMaster 6, a recently released generalized model of the linear theory of electromigration. Four electrophoretic systems with stereoisomers of weak bases were investigated. They deal with the estimation of input data for complexation together with the elucidation of the origin of observed system peaks, the interference of analyte and system peak migration, the change of enantiomer migration order as function of the selector concentration and the inversion of analyte migration direction in presence of a multiply negatively charged selector. For all systems, data predicted with PeakMaster 6 are in agreement with those of the dynamic simulators and simulation data compare well with experimental data that were monitored with setups featuring conductivity and/or UV absorbance detection along the capillary. SIMUL5complex and GENTRANS provide the full dynamics of any buffer and sample arrangement and require very long execution time intervals. PeakMaster 6 is restricted to conventional CZE, is based on an approximate solution of the transport equations, provides data for realistic experimental conditions within seconds and represents a practical tool for an experimentalist.