Μm Of Oxide Research Articles

Determination of 2,4-dinitrophenylhydrazine using carbon paste modified with nanoparticles by cyclic voltammetry, high-performance liquid chromatography and spectrophotometry methods

The research deals with the manufacture of an electrode using modified carbon paste to determine 2,4-dinitrophenylhydrazine (2,4-DNPHZ), The modified carbon paste electrode (NiO-NCQD/g-C3N4/MCPE). The results show the presence of oxidation and reduction peaks, and it is subject to a quasi-reversible system; the best value ​​of pH is (1) using sulfuric acid with a concentration of (0.1M), and scan rate is 100 mv sec-1, it was linearity range of (1-1000) µM for oxidation, and (100-1000) µM for reduction, with correlation coefficient (R2=0.9717) and (R2=0.9914) for each of them, respectively. The proposed electrochemical method was compared with two methods they are spectrophotometry at a wavelength 360) nm( and high-performance liquid chromatography (HPLC) at wavelengths (340 and 250) nm. It turned out that the electrochemical method (NiO-NCQD/g-C3N4/MCPE) was superior to the spectrophotometry method in terms of the detection limit. It turns out that there is no significant difference between (HPLC) and (NiO-NCQD/g-C3N4/MCPE) in terms of accuracy. The proposed electrochemical method is a new analytical method characterized by accuracy, repeatability, and reliability.

Determination of paracetamol using screen-printed carbon electrode

A sensitive and selective electrochemical sensor based on screen-printed carbon electrode (SPCE) for detecting paracetamol has been studied. The SPCE performance was observed using cyclic voltammetry (CV) in 0.1 M phosphate buffer solution at various pH. The measurement was done at a potential range from -0.75 V to +1 V at room temperature. The response of SPCE shows that paracetamol can be detected clearly from its oxidation (0.63 V) and reduction (-0.36 V) peaks in 0.1 M phosphate buffer solution at pH 9. The obtained calibration curve followed a linear equation ipa = 3.159 + 0.134x, with R2 = 0.975 for anodic current peak and ipc = -3.373 – 0.102x, with R2 = 0.990 for cathodic current peak. The limit of detection (LOD) of the SPCE to detect paracetamol was 0.70 µM and 0.51 µM for oxidation and reduction peaks, respectively. The sensitivity of SPCE was 2.628 μA.mm-2.μM-1 for oxidation peak and 1.996 μA.mm-2.μM-1 for reduction peak. The reaction between the SPCE and paracetamol demonstrated diffusion-controlled behavior. The selectivity study indicates no interference signal from ascorbic acid, urea, uric acid, and glucose during paracetamol measurement.

An roGFP2-Based Bacterial Bioreporter for Redox Sensing of Plant Surfaces

The reduction-oxidation (redox) environment of the phytobiome (i.e., the plant-microbe interface) can strongly influence the outcome of the interaction between microbial pathogens, commensals, and their host. We describe a noninvasive method using a bacterial bioreporter that responds to reactive oxygen species and redox-active chemicals to compare microenvironments perceived by microbes during their initial encounter of the plant surface. A redox-sensitive variant of green fluorescent protein (roGFP2), responsive to changes in intracellular levels of reduced and oxidized glutathione, was expressed under the constitutive SP6 and fruR promoters in the epiphytic bacterium Pantoea eucalypti 299R (Pe299R/roGFP2). Analyses of Pe299R/roGFP2 cells by ratiometric fluorometry showed concentration-dependent responses to several redox active chemicals, including hydrogen peroxide (H2O2), dithiothreitol (DTT), and menadione. Changes in intracellular redox were detected within 5 min of addition of the chemical to Pe299R/roGFP2 cells, with approximate detection limits of 25 and 6 μM for oxidation by H2O2 and menadione, respectively, and 10 μM for reduction by DTT. Caffeic acid, chlorogenic acid, and ascorbic acid mitigated the H2O2-induced oxidation of the roGFP2 bioreporter. Aqueous washes of peach and rose flower petals from young blossoms created a lower redox state in the roGFP2 bioreporter than washes from fully mature blossoms. The bioreporter also detected differences in surface washes from peach fruit at different stages of maturity and between wounded and nonwounded sites. The Pe299R/roGFP2 reporter rapidly assesses differences in redox microenvironments and provides a noninvasive tool that may complement traditional redox-sensitive chromophores and chemical analyses of cell extracts.

A rapid screening assay for inhibitors of 11β-hydroxysteroid dehydrogenases (11β-HSD): flavanone selectively inhibits 11β-HSD1 reductase activity

A rapid screening assay for chemicals inhibiting 11β-hydroxysteroid dehydrogenase (11β-HSD) type 1 or type 2 using lysates from stably transfected cells was developed. Here, we tested a series of environmental chemicals for anti-11β-HSD activities. Inhibition of 11β-HSD2, which may cause cortisol-dependent activation of the mineralocorticoid receptor with sodium retention and hypertension, was observed for several compounds, with diethylcarbamate being the most potent inhibitor (IC 50 6.3 μM). Abietic acid inhibited both 11β-HSD1 (IC 50 27 μM for reduction and 2.8 μM for oxidation) and 11β-HSD2 (IC 50 12 μM). Our results demonstrate for the first time that flavanone selectively inhibits 11β-HSD1 reductase activity: this enzyme being considered as essential for the local activation of glucocorticoids and representing a potential target for the therapeutic treatment of diabetes type 2. Flavanone and 2′-hydroxyflavanone efficiently inhibited reductive (IC 50 18 and 10 μM) but not oxidative activity. We observed a reduced inhibitory effect of hydroxylated flavanone derivatives and of flavones containing a double-bond between atom C2 and C3. Flavanone was specific for 11β-HSD1 and did not inhibit 11β-HSD2. Our results reveal that a variety of environmental compounds exert distinct inhibitory effects on 11β-HSD1 and 11β-HSD2, opening the possibility for selectively modulating local cortisone/cortisol availability in vivo.