Interaction of tin(II) and arsenic(III) with DNA at the nanostructure film modified electrodes

Biosensors based on DNA and DNA-carbon nanotubes film immobilized at the surface of a screen-printed carbon electrode were used for simple in vitro tests of chemical toxicity. The damage to DNA caused by tin(II) and arsenic(III) compounds as components of specific reaction media was evaluated by means of an electrochemical DNA marker, [Co(phen)3](3+), as the portion of original dsDNA which survives an incubation of the biosensor in the cleavage medium. The results were confirmed by the electrically heated electrode and by the measurement of the DNA guanine moiety signal.     

Anodic stripping voltammetry with mercury electrodes in extracts of cadmium,lead, thallium and indium diethyldithiocarbamate complexes and analysis of mixtures

The selectivity of the determination of traces of cadmium, lead, thallium and indium is improved by direct coupling of liquid/liquid extraction and anodic stripping voltammetry. Metals are extracted from aqueous solution to benzene or chloroform after the addition of sodium or zinc diethyldithiocarbamate. Stripping voltammetry of Cd, Tl and Pb at a hanging mercury drop electrode or mercury film electrode is done in benzene/methanol medium (1:1) with 0.1 M NaClO₄ as supporting electrolyte. For indium, the medium is chloroform/ethanol/water (1:4:1) with 0.005 M sodium acetate/0.06 M KBr/0.06 M HCl as supporting electrolyte. The complexes in acidic solution can be decomposed by mercury (II) ions, which provides useful shifts of deposition potentials. Calibration graphs are linear at concentrations of about 10^?7 M with a detection limit of 1×10^?8 M. The method is applied to determine a single metal in the presence of a large amount (1000-fold) of interfering metal.     

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 micromol/L were obtained with DP voltammetry using 5 x 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.     

Ligand-structure effect on electrochemical reduction of copper(II) complexes

Summary Half-wave potentials for a one-electron reduction of copper(II) complexes containing polydentate ligands can be calculated using the equationE _1/2=E ⁰(Cu^2+/+)+ _{i j} E _i where E _i are contributions related to the electronic and steric properties of the ligands. The values of 18 E _i contributions are presented and explained, and the effect of the solvents on the half-wave potentials is exemplified.Dedicated to Prof. Dr. Viktor Gutmann to his 70th birthday     

Anodic stripping voltammetric determination of heavy metals in solutions containing humic acids

Summary Various simultaneous effects of humic acids on the current and potential of differential pulse anodic stripping peaks of copper, lead, cadmium and zinc in weakly alkaline and acidic (pH 2) solutions have been investigated and interpreted with regard to metal complexation and the adsorption of humic acid on the mercury electrode. The applicability of the standard additions method for metal quantitation and the experimental conditions for UV-photolysis with a high-pressure mercury lamp have been examined in model as well as real water samples.     

Uncertainty relations for information entropy in wave mechanics

New uncertainty relations in quantum mechanics are derived. They express restrictions imposed by quantum theory on probability distributions of canonically conjugate variables in terms of corresponding information entropies. The Heisenberg uncertainty relation follows from those inequalities and so does the Gross-Nelson inequality.     

DNA-based biosensors with external Nafion and chitosan membranes for the evaluation of the antioxidant activity of beer,coffee, and tea

Novel electrochemical DNA-based biosensors with outer-sphere Nafion and chitosan protective membranes were prepared for the evaluation of antioxidant properties of beverages (beer, coffee, and black tea) against prooxidant hydroxyl radicals. A carbon working electrode of a screen-printed three-electrode assembly was modified using a layer-by-layer deposition technique with low molecular weight double-stranded DNA and a Nafion or chitosan film. The membrane-covered DNA biosensors were initially tested with respect to their voltammetric and impedimetric response after the incubation of the beverage and the medium exchange for the solution of the redox indicator [Fe(CN)₆]^3?/4?. While the Nafion-protected biosensor proved to be suitable for beer and black tea extracts, the chitosan-protected biosensor was successfully used in a coffee extract. Afterwards, the applicability was successfully verified for these biosensors for the detection of a deep degradation of the surface-attached DNA at the incubation in the cleavage agent (hydroxyl radicals generated via Fenton reaction) and for the evaluation of antioxidant properties of coffee and black tea extracts against prooxidant hydroxyl radicals. The investigation of the novel biosensors with a protective membrane represents a significant contribution to the field of electrochemical DNA biosensors utilization.      

Reliability-Based Optimization of structural systems

A method to carry out a Reliability-Based Optimization (RBO) of especially nonlinear structural systems is introduced. Statistical uncertainties involving both structural and loading properties are considered. The concept is based on the separation of structural reliability analyses and the optimization procedures. Two approaches are discussed, depending on the interaction of reliability analysis and mathematical programming and the way of representation of the limit state functions (LSF) of the structure. As, for cases of practical significance, the LSF is known only pointwise it is approximated by Response Surfaces (RS). For the response calculations Finite Element (FE) procedures are utilized. Failure probabilities are determined by applying variance reducing Monte Carlo simulation (MCS) techniques such as Importance Sampling (IS). Following the reliability analysis, the optimization procedure is controlled by the NLPQL algorithm. A numerical example in terms of a template ocean platform exemplifies the procedures.Formerly Institute of Engineering Mechanics, Leopold-Franzens-University, Innsbruck, Austria