Fabrication of layer-by-layer deposited multilayer films containing DNA and its interaction with methyl green

Multilayer films were fabricated by layer-by-layer electrostatic deposition techniques between poly(diallyIdimethylammonium chloride) (PDDA) and calf thymus DNA (CT DNA) on glassy carbon and quartz substrates. Electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy and UV-vis spectroscopy demonstrated the uniform assembly of PDDA/DNA multilayer films, and X-ray photoelectron spectroscopy confirmed the elemental composition of the films. Moreover, the interaction of DNA in PDDA/DNA films with methyl green was investigated by UV-vis spectroscopy and circular dichroism (CD). (C) 2001 Elsevier Science B.V. All rights reserved.

Oxidation of NADH by dopamine incorporated in lipid film cast onto a glassy carbon electrode

Stable lipid film was made by casting lipid in chloroform onto a glassy carbon electrode. This model of a biological membrane was used to investigate the oxidation of dihydronicotinamide adenine dinucleotide (NADH) by dopamine. After this electrode had been immersed in dopamine solution for 10 h, it was found that some dopamine had been incorporated in the film. The cyclic voltammogram was obtained for the oxidation of 2.0 X 10(-3) mol 1(-1) NADH with dopamine incorporated in the films. All electrochemical experiments were performed in 0.005 mol 1(-1) phosphate buffer (pH 7.0) containing 0.1 mol 1(-1) NaCl without oxygen. The oxidation current increased gradually with successive sweeps and reached steady state. It was a different phenomenon from previous results. The anodic overpotential was reduced by about 130 mV compared with that obtained at a bare glassy carbon electrode. The diffusion coefficient for 2.0 X 10(-3) mol 1(-1) NADH was 6.7 X 10(-6) cm(2) s(-1). (C) 1999 Elsevier Science S.A. All rights reserved.

ELECTROCATALYTIC OXIDATION OF REDUCED NICOTINAMIDE COENZYMES AT METHYLENE GREEN-MODIFIED ELECTRODES AND FABRICATION OF AMPEROMETRIC ALCOHOL BIOSENSORS

Chemically modified electrodes with Methylene Green adsorbed on the graphite surface and incorporated into carbon paste exhibit excellent electrocatalytic ability for oxidation of NADH. Alcohol dehydrogenase, nicotinamide adenine dinucleotide (NAD+) and m

A simple and accurate method for determining accurately dissolved inorganic carbon in seawaters

Dissolved inorganic carbon (DIC) account for more than 95% of total carbon in seawater, so it is necessary to make reliable and precise measurements of DIC to study marine carbon cycling. In order to establish a simple and speed method, an airproof device of gas extraction-absorption was designed. Finally a simple method was developed for the determination of DIC in seawater through a large mount of experiments. The determination procedure is as follows: 100 similar to 150 mL seawater was put into conical flask, then add 10% H3PO4, the DIC in seawater sample was dissolved to form CO2 gas and carried by pure N-2, then the CO2 gas was absorbed by two grades 0.1 mol/L NaOH solution. Finally the absorbed solution was titrated by HCl standard solution of 0.01000 mol/L with the end points detected with the indicator phenolphthalein and bromocresol green-methyl red mixture. The precision and accuracy of the method were satisfied. This method was used to analyse seawater samples from Jiaozhou bay in June, 2003. The result shows that the average DIC in surface seawater is 2066 mumol/L, DIC in bottom seawater is 2075 mumol/L inside bay, but the average DIC in surface seawater is 1949 mumol/L, DIC in bottom seawater is 2147 mumol/L outside bay.

Corrosion of carbon steel influenced by anaerobic biofilm in natural seawater

The bacteria in the anaerobic biofilm on rusted carbon steel immersed in natural seawater were characterized by culturing and molecular biology techniques. Two types of anaerobic bacterium, sulfate-reducing bacteria (SRB) Desulfovibrio caledoniensis and iron-reducing bacteria Clostridium sp. uncultured were found. The compositions of the rust layer were also analyzed and we found that iron oxide and sulfate green rust were the major components. To investigate the corrosion mechanisms, electrochemical impedance spectra was obtained based on the isolated sulfate-reducing bacteria and mixed bacteria cultured from rust layer in laboratory culture conditions. We found that single species produced iron sulfide and accelerated corrosion, but mixed species produced sulfate green rust and inhibited corrosion. The anaerobic corrosion mechanism of steel was proposed and its environmental significance was discussed. (c) 2008 Elsevier Ltd. All rights reserved.