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Various Experimental Parameters (various + experimental_parameter)
Selected AbstractsXanthine Sensors Based on Anodic and Cathodic Detection of Enzymatically Generated Hydrogen PeroxideELECTROANALYSIS, Issue 6 2007Aminur Rahman Abstract A xanthine biosensor was fabricated by the covalent immobilization of xanthine oxidase (XO) onto a functionalized conducting polymer (Poly-5, 2,: 5,, 2,-terthiophine-3-carboxylic acid), poly-TTCA through the formation of amide bond between carboxylic acid groups of poly-TTCA and amine groups of enzyme. The immobilization of XO onto the conducting polymer (XO/poly-TTCA) was characterized using cyclic voltammetry, quartz crystal microbalance (QCM), and X-ray photoelectron spectroscopy (XPS) techniques. The direct electron transfer of the immobilized XO at poly-TTCA was found to be quasireversible and the electron transfer rate constant was determined to be 0.73,s,1. The biosensor efficiently detected xanthine through oxidation at +0.35,V and reduction at ,0.25,V (versus Ag/AgCl) of enzymatically generated hydrogen peroxide. Various experimental parameters, such as pH, temperature, and applied potential were optimized. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 5.0×10,6,1.0×10,4 M and 5.0×10,7 to 1.0×10,4,M, respectively. The detection limits were determined to be of 1.0×10,6,M and 9.0×10,8,M with anodic and cathodic processes, respectively. The applicability of the biosensor was tested by detecting xanthine in blood serum and urine real samples. [source] Optimization of dispersive liquid,liquid microextraction of Co(II) and Fe(III) as their oxinate chelates and analysis by HPLC: Application for the simultaneous determination of Co(II) and Fe(III) in water samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 23-24 2009Mir Ali Farajzadeh Abstract In this study, dispersive liquid,liquid microextraction method was used for the preconcentration and simultaneous determination of Co(II) and Fe(III) in water samples as their oxinate chelates. In dispersive liquid,liquid microextraction process, methanol and chloroform were used as disperser and extracting solvents, respectively, and the ligand 8-hydroxy quinoline was used as a chelating agent for the extraction of Co(II) and Fe(III). HPLC was applied for the quantitation of the analytes after preconcentration. An experimental design, central composite design, coupled with response surface methodology was used for the optimization of the involved experimental parameters. In addition, the effect of various experimental parameters in the extraction was investigated using one variable at a time method. The calibration graphs were linear in the range of 20,4000,,g/L with the LODs of 3,,g/L for both analytes. The RSDs for six replicate measurements of 500,,g/L of Co2+ and Fe3+ were 3.3 and 4.1%, respectively. [source] Effects of electrospray capillary temperature on amide hydrogen exchangeRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2008Stephen J. Coales Amide hydrogen/deuterium (H/D) exchange coupled with proteolysis, high-perfeomance liquid chromatographic (HPLC) separation and mass spectrometry (MS) has become a powerful tool to study protein dynamics in solution. Prior to the execution of H/D exchange experiments, various experimental parameters have to be set, including proteolysis, HPLC, and MS conditions. Here we investigate the effects of electrospray capillary temperature on deuterium retention in backbone amides of various pepsin-generated cytochrome c peptides. Lower capillary temperature generally helps retain more deuterium than higher capillary temperature. When the capillary temperature was 150°C, on average 26% more deuterium was retained than when the capillary temperature was set at 250°C. The effects of capillary temperature varied depending on the ions monitored. There was little difference in deuterium retention among different charge state species of the same peptide at 150°C. However, a lower charge state ion loses more deuterium atoms going from 150°C to 250°C than the corresponding higher charge state species. These results indicate that the capillary temperature should be optimized not only to maximize the signal-to-noise of each ion followed in H/D exchange experiments, but also to minimize the deuterium loss of the ions. Also the loss of deuterium in several ions, especially lower charge state ones, should be monitored in the optimization, as the temperature effects vary among ions and are more significant for lower charge state ions. Copyright © 2008 John Wiley & Sons, Ltd. [source] Carrying out an optimal experimentACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2010Zbigniew Dauter Diffraction data collection is the last experimental stage in structural crystallography. It has several technical and theoretical aspects and a compromise usually has to be found between various parameters in order to achieve optimal data quality. The influence and importance of various experimental parameters and their consequences are discussed in the context of different data applications, such as molecular replacement, anomalous phasing, high-resolution refinement or searching for ligands. [source] | ||||||||||