Potassium Ferricyanide Concentration Research Articles

Development of a Novel Electrochemical Surface Plasmon Resonance Instrument Based on a Mini Three Electrode Flow Cell

The construction and performance of a novel electrochemical (EC) surface plasmon resonance (SPR) instrument based on a mini three electrode flow cell that was designed and manufactured by MEMS technology is described. The working electrode is 50nm gold and counter and reference electrodes, made of Au and Ag/AgCl separately, are 0.6 mm in diameter. The flow channel is made of polydimethylsiloxane (PDMS) with 1mm in width, 200μm in depth, 5μL in volume. The process for activating and modifying the working electrode is given by the real-time SPR detection. The Cyclic voltammetry (CV) and SPR detection are conducted simultaneously in potassium ferricyanide solution system. It is proved that the signal of redox reaction and the change of refractive index have a well correlation by the potential sweep experiment. Four kinds of concentration of potassium ferricyanide are analyzed and the peak oxidizing current, obtained from the curve, is proportional to the respective concentration of the sample. The EC-SPR experiment is also carried out in CuSO4 system and the results is similar to potassium ferricyanide.

Identification and Characterization of a Novel-type Ferric Siderophore Reductase from a Gram-positive Extremophile

Iron limitation is one major constraint of microbial life, and a plethora of microbes use siderophores for high affinity iron acquisition. Because specific enzymes for reductive iron release in gram-positives are not known, we searched Firmicute genomes and found a novel association pattern of putative ferric siderophore reductases and uptake genes. The reductase from the schizokinen-producing alkaliphile Bacillus halodurans was found to cluster with a ferric citrate-hydroxamate uptake system and to catalyze iron release efficiently from Fe[III]-dicitrate, Fe[III]-schizokinen, Fe[III]-aerobactin, and ferrichrome. The gene was hence named fchR for ferric citrate and hydroxamate reductase. The tightly bound [2Fe-2S] cofactor of FchR was identified by UV-visible, EPR, CD spectroscopy, and mass spectrometry. Iron release kinetics were determined with several substrates by using ferredoxin as electron donor. Catalytic efficiencies were strongly enhanced in the presence of an iron-sulfur scaffold protein scavenging the released ferrous iron. Competitive inhibition of FchR was observed with Ga(III)-charged siderophores with K(i) values in the micromolar range. The principal catalytic mechanism was found to couple increasing K(m) and K(D) values of substrate binding with increasing k(cat) values, resulting in high catalytic efficiencies over a wide redox range. Physiologically, a chromosomal fchR deletion led to strongly impaired growth during iron limitation even in the presence of ferric siderophores. Inductively coupled plasma-MS analysis of ΔfchR revealed intracellular iron accumulation, indicating that the ferric substrates were not efficiently metabolized. We further show that FchR can be efficiently inhibited by redox-inert siderophore mimics in vivo, suggesting that substrate-specific ferric siderophore reductases may present future targets for microbial pathogen control.

A Multilayer MEMS Platform for Single-Cell Electric Impedance Spectroscopy and Electrochemical Analysis

The fabrication and characterization of a microchamber electrode array for electrical and electrochemical studies of individual biological cells are presented. The geometry was tailored specifically for measurements from sensory hair cells isolated from the cochlea of the mammalian inner ear. Conventional microelectromechanical system (MEMS) fabrication techniques were combined with a heat-sealing technique and polydimethylsiloxane micromolding to achieve a multilayered microfluidic system that facilitates cell manipulation and selection. The system allowed for electrical stimulation of individual living cells and interrogation of excitable cell membrane dielectric properties as a function of space and time. A three-electrode impedimetric system was incorporated to provide the additional ability to record the time-dependent concentrations of specific biochemicals in microdomain volumes near identified regions of the cell membrane. The design and fabrication of a robust fluidic and electrical interface are also described. The interface provided the flexibility and simplicity of a "cartridge-based" approach in connecting to the MEMS devices. Cytometric measurement capabilities were characterized by using electric impedance spectroscopy (1 kHz-10 MHz) of isolated outer hair cells. Chemical sensing capability within the microchannel recording chamber was characterized by using cyclic voltammetry with varying concentrations of potassium ferricyanide (K(3)Fe(CN)(6)). Chronoamperometric recordings of electrically stimulated PC12 cells highlight the ability of the platform to resolve exocytosis events from individual cells.

Simultaneous Determination of Epinephrine, Noradrenaline and Dopamine in Human Serum Samples by High Performance Liquid Chromatography with Chemiluminescence Detection

AbstractA simple, rapid and accurate high performance liquid chromatographic (HPLC) technique coupled with chemiluminescence (CL) detection was developed for the simultaneous determination of epinephrine (E), noradrenaline (NA) and dopamine (DA). It was based on the analyte enhancement effect on the CL reaction between luminol and potassium ferricyanide. The effects of various parameters, such as potassium ferricyanide concentration, luminol concentration, pH value and component of the mobile phase on chromatographic behaviors of the analytes (E, NA and DA) were investigated. The separation was carried out on C18 column using the mobile phase of 0.01 mol/L potassium hydrogen phthalate solution and methanol (92:8, V/V). Under the optimum conditions, E, NA and DA showed good linear relationships in the range of 1×10−8–5×10−6, 5.0×10−9–1.0×10−6 and 5.0×10−9–1.0×10−6 g/mL respectively. The detection limits for E, NA and DA were 4.0×10−9, 1.0×10−9 and 8.0×10−10 g/mL. The proposed method has been applied successfully to the analysis of E, NA and DA in human serum samples.

Chemically sensitized ormosil-modified electrodes—Studies on the enhancement of selectivity in electrochemical oxidation of hydrogen peroxide

The chemically sensitized ormosil-modified electrodes were made by encapsulating potassium ferricyanide together with organic-ionophore (dibenzo-18-crown-6/Nafion) within ormosil films. The modified electrodes were studied in details from following angles; (1) the effect of variation in potassium ferricyanide concentration in ormosil films; (2) the effect of variation in dibenzo-18-crown-6 concentration in ormosil films; (3) effect of pH on the electrochemistry of ormosil-modified electrodes, and (4) variation in the microstructure of ormosil's films as a function of chemical sensitizers based on atomic force microscopy. Another remarkable contribution of such films based on the bilayer configuration was investigated and the results justified further enhancement in the selectivity for electrochemical sensing of peroxide. Two approaches of bilayer configuration were adopted based on the absence and the presence of chemical sensitizers (Nafion/crown ether) in the upper layer. Excellent results of peroxide sensing were recorded with remarkable finding as given below: (1) introduction of bilayer configuration reduced the sensing of interfering analytes like ascorbic acid, (2) the presence of crown ether in the upper layer caused enhancement in peroxide sensing, (3) the presence of crown ether in the upper layer and Prussian blue in the lower layer increased the detection limit of peroxide sensing to 0.1 μM as compared to that of 0.5 μM recorded in earlier publication, (4) the presence of the bilayer resulted in an increase in the linear range of peroxide sensing, (5) the single layer Prussian blue modified electrode showed electrocatalytic oxidation of ascorbic acid whereas the same with the bilayer containing crown ether reduced the electrochemical sensing of ascorbic acid, followed by an increase in peroxide sensing, and (6) the kinetics of peroxide reduction on the bilayer ormosil-modified electrode was reduced as compared to that on the single layer modified-electrode. The results based on cyclic voltammetry showed a linear increase in cathodic and anodic peak currents with increasing the concentration of ferricyanide within the ormosil film. The results on the effect of pH suggested that lowering of pH caused faster reduction as well as oxidation of peroxide whereas the reverse was recorded with increasing the pH. An increase in dibenzo-18-crown-6 concentration resulted higher oxidation current of peroxide, followed by a decrease in reduction of the same. The results of cyclic voltammery and amperometric measurements were also reported in this communication. The calibration curve of peroxide sensing using the bilayer ormosil-modified electrodes was reported.

Potassium Ferricyanide Mediated Disposable Biosensor for Determination of Maltose and Glucose

A disposable sensor system for determination of glucose and maltose in the same sample was demonstrated by using potassium ferricyanide mediated enzyme electrode and screen-printing technology. The sensor consisted of a glucose oxidase (GOD) electrode and an amyloglucosidase(AG)/glucose oxidase electrode (AG electrode). The faradaic current of the electrode is dependent on the concentration of potassium ferricyanide(III), 100 mmol/L being optimum for the sensor response. The linear range of the system was up to 35 mmol/L glucose or 25 mmol/L maltose with coefficients of variation (CVs) ranging from 4.6% to 6.9%. The results obtained by using the enzyme electrode system agreed well with those obtained by the Fehling titration method.

Guard cell responses to potassium ferricyanide

Micromolar concentrations of potassium ferricyanide inhibit light‐induced stomatal opening. The extent of the inhibition is dependent on the presence of carbon dioxide and the concentration of potassium ferricyanide needed to obtain 50% inhibition of stomatal opening is 40‐fold higher in CO2‐free air than in normal air. The fungal toxin, fusicoccin (1 μM), overcame the ferricyanide inhibition of stomatal opening indicating that the electron acceptor may interact more or less directly with the activity of the plasma membrane H+‐ATPase. Although potassium ferricyanide strongly inhibited stomatal opening, it had only minor effects on stomatal maintaining or stomatal closure due to darkness or ABA.

Comparison of techniques for minimizing interference of bilirubin on serum creatinine determined by the kinetic Jaffé reaction

This study compared the effect of sodium dodecyl-sulfate, potassium ferricyanide, and preincubation technique to continuous-flow analysis and prior deproteinization to correct the negative interference of bilirubin on serum creatinine found by the kinetic Jaffé reaction. Bilirubin increased to 684 mumol/L did not interfere with serum creatinine measured by the methods incorporated with dialysis or deproteinization. Trichloroacetic acid was the best protein precipitant. The reagent incorporated with sodium dodecyl sulfate was more appropriate to minimize bilirubin interference than reagent containing potassium ferricyanide. An increase in potassium ferricyanide concentration resulted in false positive creatinine values. Incorporation of both SDS and potassium ferricyanide in the reagent did not help in minimizing the bilirubin interference over use of each chemical alone. The 10 minutes of preincubation of the sample with alkaline buffer incorporating with either SDS or potassium ferricyanide before starting the Jaffé reaction was the appropriate way to overcome unconjugated bilirubin interference at a level of 342.0 mumol/L. However, the technique did not work uniformly with icteric patient sera containing conjugated, unconjugated, and delta bilirubin. This is a challenging problem that remains to be solved by the clinical chemist.

Kinetic properties of purified sheep lung microsomal nadh-cytochrome b5 reductase

1. 1. Lung NADH-cytochrome b5 reductase was saturated with its artificial substrate, potassium ferricyanide at approximately 0.1 mM ferricyanide concentration, and the activity of the lung enzyme was inhibited by the higher concentrations of potassium ferricyanide. Ferricyanide at 0.5 and 1.0 mM inhibited the activity of the enzyme by about 20 and 61% respectively. The apparentK K m value was calculated as 13.7/gmM potassium ferricyanide and 4.3 μM NADH. 2. 2. The Michaelis constants for cytochrome b5 and NADH were determined to be 1.67 and 7.7μM from the Lineweaver-Burk plots. These results demonstrate that affinity of the lung reductase for its natural substrate is almost 10 times higher than that for potassium ferricyanide. 3. 3. Addition of non-ionic detergent stimulated the rate of reductase-catalyzed reduction of lung cytochrome b5 up to 8.2-fold. 4. 4. Kinetic studies performed with lung reductase by varying NADH and cytochrome b5 concentrations at different fixed concentrations at cytochrome b5 or NADH showed a series of parallel lines indicating a “ping-pong” type of kinetic mechanism for interaction of NADH and cytochrome b5 with lung cytochrome b5 reduetase.

Binding of two spin-labelled derivatives of chlorpromazine to human erythrocytes

The binding to human intact erythrocytes of two different spin-labelled derivatives of chlorpromazine has been studied. The influence of the positively charged side chain of the drug has been the focus of our attention. The positively charged amphiphilic compound (spin derivative I) is water-soluble up to 80 microM at pH values below 5.9. The apolar analogue (spin derivative II) aggregates in aqueous buffer from the lowest concentration tested. Both spin derivatives undergo a slow reduction inside the erythrocyte. The reduced nitroxides are readily reoxidized by adding a low, non-quenching, concentration of potassium ferricyanide to the intact erythrocytes. The fractions of spin label I and II bound to the erythrocyte membrane or to the erythrocyte-extracted lipids remain constant as a function of the temperature (3-42 degrees C) and as a function of the concentration of the spin label up to 150 microM. E.s.r. spectra of both spin labels show a two-component lineshape when they are bound to intact erythrocytes. Below 35 degrees C for the positively charged spin probe, and below 32 degrees C for the apolar spin probe, the simulation of the lineshape shows that more than 50% of the spectrum originates from a slow-motion component. This slow-motion component is also found in erythrocyte-extracted lipids probed by the positively charged spin label below 25 degrees C. In contrast, no slow-motion component is detected in the range 4-40 degrees C for the apolar spin label in erythrocyte-extracted lipids. In this environment the apolar probe experiences a single fast anisotropic motion with an exponential dependence on 1/temperature. Detailed lineshape simulations take into account the exchange frequency between binding sites where the probe experiences a fast motion and binding sites where it experiences a slow motion. The exchange frequency is strongly temperature-dependent. Characterization of the different motions experienced inside the different locations has been achieved and compared for whole erythrocytes and for the extracted lipids. The biochemical nature of the binding sites (membrane protein/acidic phospholipid) giving rise to the slow-motion component is discussed as a function of the polarity of the spin-labelled drug and as a function of the temperature controlling the fluidity of the lipid bulk and influencing the distribution of the drug inside the membrane.

Identification of four major classes of sulfhydryl groups in human blood platelets. Ferricyanide titration of spin-labeled platelets.

Human blood platelets have been labeled with the sulfhydryl-specific spin labels, 4-iodoacetamido-2,2,6,6-tetramethylpiperidine-1-oxyl and 3-maleimido-2,2,5,5-tetramethylpyrrolidine-1-oxyl. First, the ESR spectra of platelets labeled with either reagent revealed two classes of sulfhydryl groups, a mobile class and an immobile class. Second, when spin-labeled platelets were titrated with high concentrations of potassium ferricyanide (greater than 10(-3) M), there was a decrease in the peak heights of the mobile class of sulfhydryl groups due to dipole-dipole exchange. Third, plots of peak heights of the mobile class versus ferricyanide concentration revealed three classes of mobile sulfhydryl groups compared to a single immobile class. This technique may be used to show the relative locations of spin-labeled groups on cell surfaces.

AN EFFECT OF POTASSIUM CYANIDE ON THE OXIDATION-REDUCTION POTENTIAL

Abstract (1) The effect of the existence of potassium cyanide upon the oxidation-reduction potential of potassium ferricyanide and ferrocyanide was investigated. (2) The investigation was performed in the hydrogen atmosphere in the dark room to avoid the atmospheric oxidation and the photochemical decomposition. (3) The result can be expressed approximately by the following empirical formula at 30°C. E=0.4660+0.0601logK^0.59where K is the concentration of potassium cyanide, and each concentration of potassium ferricyanide and potassium ferrocyanide is 0.01 mol. respectively.