Modified screen-printed electrodes for the investigation of the interaction of non-electroactive quinazoline derivatives with DNA

Five morpholino-quinazoline derivatives have been investigated voltammetrically using a competition with the tris(o-phenanthroline) cobalt(III) redox marker for the accumulation at dsDNA modified screen-printed electrodes. An association of quinazolines with DNA was observed at the modified electrodes polarized by the negative potential of –0.4 V vs. Ag/AgCl. This was confirmed by a potentiometric stripping analysis based on the DNA guanine signal. Calibration curves for quinazolines within a concentration range of μmol/L were obtained with DP voltammetry using 5 × 10^–7 mol/L Co(phen)₃ ³⁺ marker. The quinazolines exhibit no effect on the DNA complex with the fluorescent thiazole orange derivative TO-PRO-3. The role of the accumulation potential in the association interaction with DNA is discussed.     

Urine profiling using capillary electrophoresis-mass spectrometry and multivariate data analysis

This work presents the development of a general and fast method for metabolic profiling of urine, using capillary electrophoresis-electrospray ionisation mass spectrometry (CE-ESIMS) and multivariate data analysis (DA). Human urine samples collected before and after ingestion of paracetamol were analysed at acidic and basic CE conditions, using both positive and negative ESI-MS detection. Analysis of the entire resulting data set, with no prior knowledge of the target compounds, using pair-wise 'fuzzy' correlation and eigenvalue analysis enabled the samples to be discriminated between on the basis of blank urine and urine collected after drug intake. By generating two-dimensional loadings plots, it was also possible to identify the m/z values of the substances responsible for the differentiation between control and dosed samples.     

Eye models for the prediction of contrast vision in patients with new intraocular lens designs

Theoretical calculations of the polychromatic modulation transfer function (MTF) and wave-front aberration were performed with physiological eye models. These eye models have an amount of spherical aberration that is representative of a normal population of pseudophakic eyes implanted with two different types of intraocular lens (IOL) made from high-refractive-index silicone. These theoretical calculations were compared with the measured contrast sensitivity function (CSF) under mesopic lighting conditions and with wave-front aberration (obtained with a Hartmann-Shack wave-front sensor) collected from 37 patients bilaterally implanted with the same types of lens. The relationships between the ocular wave-front aberration and the MTF predicted by the eye models and the CSF and the ocular wave-front aberration measured in eyes implanted with IOLs were investigated. The predicted improvements in MTF and wave-front aberration correlated well with the improvements measured in practice. Physiological eye models are therefore useful tools for IOL design.     

Converting a curve to right-angled increments

Servo systems used in numerical control are to be fed by incremental commands. For the two-dimensional case the Taylor expansion off(x,y) is a useful way to compute these increments. The proper increment in each moment can simply be deduced from the sign of the terms involved in the Taylor expansion. Three special curves are analyzed: the straight line, the circle or the circular arc and the general curve of second order. The computation and the execution of the commands can be more or less synchronous. Simplified flow diagrams for the computer program under two different assumptions are shown.     

Selective reagents for solvent extraction of metals—I. Quinaldic acids

Alkyl- and alkoxy-substituted quinoline-2-carboxylic acids were synthesized and tested for metal extraction. Zn²⁺ and Cu²⁺ were extracted from aqueous sulphate solutions by reagents containing 8-alkoxy substituents at lower pH values than were Fe²⁺ or Fe³⁺. Reagents without this substituent were unselective in this respect. A possible explanation for the selectivity may be that the 8-substituent influences the coordination geometry of the metal chelates in favour of tetrahedral complexes.     

Eine Untersuchung der Mizellenbildung von kurzkettigen Carboxylaten mit Hilfe der Laser-Raman-Spektroskopie

Ohne Zusammenfassung     

The applicability of the superposition principle in differential pulse polarography

It is shown theoretically that the superposition principle is applicable to pulse voltammetry if the electrochemical system can be separated into a potential-dependent nonlinear part and a linear part. For systems not complicated by adsorption or electrode kinetics, the applicability of the principle depends on diffusion coefficients, electrode and cell geometry. For plane semi-infinite diffusion, applicability is expected; this is generally not the case for spherical electrodes or bounded regions (film electrode or thinlayer cell). The implications of the theory on differential pulse polarography are discussed and an experimental study on the applicability for iron(III), cadmium(II) and lead(II) is presented.     

Use of hydrogen-sensitive Pd-MOS materials in biochemical analysis

A metal oxide semiconductor sensitive to hydrogen was used to monitor H₂ production from immobilizedClostridium acetobutylicum cells and from immobilized hydrogenase on a continuous basis.