Kui Jiao

Voltammetric studies on the interaction of orange G with proteins: analytical applications

The interaction of orange G with protein was investigated by voltammetric method in this paper. In pH 2.0 Britton-Robinson (B-R) buffer solution orange G displayed an irreversible voltammetric reduction peak at -0.17 V (vs. SCE) on mercury working electrode. The addition of human serum albumin (HSA) into the orange G solution resulted in the decrease of the reduction current peak apparently without the changes of peak potentials and no new peaks appeared. The electrochemical parameters of orange G solution in the absence and presence of HSA were calculated and compared. The results showed that there were no significant changes, which indicated that the electrochemical behaviors of reaction solution on the mercury working electrode showed no changes and a supramolecular electrochemical inactive biocomplex was formed. The interaction mechanism was due to the formation of the microelectrostatic field in albumin structure in aqueous solution and caused the interaction with orange G, which induced the decrease of the equilibrium concentration of orange G in the reaction solution, and the decrease of the reductive peak current. The interaction conditions were discussed carefully. Under the optimal conditions the decrease of peak current was proportional to the concentration of protein and further used to the determination of different kinds of proteins. The calibration curves for the determination of HSA, bovine serum albumin (BSA), ovalbumin (OVA), bovine hemoglobin (BHb), lipase were linear over the ranges of 4.0~28.0 mg L-1, 4.0~30.0 mg L-1, 2.0~20.0 mg L-1, 2.0~25.0 mg L-1, 2.0~30.0 mg L-1, respectively. The detection limit was 3.0 mg L-1 for HSA, 3.5 mg L-1 for BSA, 1.0 mg L-1 for OVA, BHb and lipase. The new established electrochemical method was applied to determine the content of albumin in healthy human serum samples and the results were in good agreement with the traditional Coomassie Brilliant Blue (GBB G-250) spectrophotometric method.

DIRECT ELECTROCHEMISTRY OF HEMOGLOBIN IMMOBILIZED IN THE SODIUM ALGINATE AND SIO2 NANOPARTICLES BIONANOCOMPOSITE FILM ON A CARBON IONIC LIQUID ELECTRODE

In this paper a carbon ionic liquid electrode (CILE) was fabricated by using a room temperature ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) as binder. By using the CILE as basal electrode, the hemoglobin (Hb) molecule was immobilized on the surface of CILE with a sodium alginate (SA) hydrogel and SiO2 nanoparticles organic-inorganic composite material. The direct electrochemical behaviors of Hb in the bionanocomposite film were further studied in a pH 7.0 Britton-Robinson (B-R) buffer solution. A pair of well-defined quasi-reversible cyclic voltammetric peaks of Hb was obtained on SA/nano-SiO2/Hb/CILE with the formal potential (E0’) at -0.355 V (vs. SCE), which was the characteristic of heme Fe(III)/Fe(II) redox couples. The formal potential of Hb Fe(III)/Fe(II) couple shifted negatively with increasing pH of solution with a slope of -45.2 mV/pH, which indicated that a one electron transfer accompanied with one proton transportation. The immobilized Hb showed good electrocatalytic manner to the reduction of trichloroacetic acid (TCA).

Structure of the adduct of bis(O,O′-diisopropyldithiophosphato) metal with pyridine: Ni[(iPrO)2PS2]2(py)2 and Cd[(iPrO)2PS2]2 (py)2(py = pyridine)

The crystal and molecular structures of the complex of [Ni{(iPrO)2dtp}2(py)2] and [Cd{(iPrO)2dtp}2(py)2] (dtp = dithiophosphate, py = pyridine) have been determined by X-ray crystallography. They are isomorphous. The crystal structures are very similar and consist of discrete molecules of [Ni{(iPrO)2dtp}2(py)2] and [Cd{(iPrO)2dtp}2(py)2], respectively. They both crystallize in the monoclinic system, space group P21/c, the former with lattice parameters a = 6.489(1) Å, b = 14.830(3) Å, c = 16.386(3) Å, β = 99.74(3), and Z = 2; the latter with a = 6.461(3) Å, b = 14.583(4) Å, c = 17.433(4) Å, β = 99.55(3)°, and Z = 2. They all display distorted octahedral geometry around the central metal atom. In the complexes, two O,O′-diisopropyl dithiophosphate ions act as bidentate ligands with their S atoms coordinated to metal. Each forms a four-membered chelate ring in the equatorial plane. The N atoms from two pyridine ligands are axially coordinated to the metal atom. The Ni–S bond distances are 2.5137(10) and 2.5386(9) Å, and the Ni–N bond distances are 2.127(3) Å. The Cd–S(1) and Cd–S(2) bond distance are 2.694(1) and 2.704(1) Å, respectively, and the Cd–N bond distances are 2.399(3) Å. The IR spectra data is in agreement with the structural data.

Direct electrochemistry of hemoglobin immobilized in polyvinylalcohol and clay composite film modified carbon ionic liquid electrode

In this paper room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluoro-phosphate (BMIMPF6) was used as binder to fabricate a carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on the surface of CILE with clay and polyvinyl alcohol (PVA) composite film by layer to layer method. UV-Vis and FT-IR spectra showed that Hb in the film retained the essential features of its native structure. Electrochemical experiments indicated that a pair of well-defined quasi-reversible redox peak was obtained in pH 7.0 Britton-Robinson (B-R) buffer solution. The reduction and oxidation peak potentials were located at -0.405 V and -0.274 V (vs. SCE) with the formal potential as -0.340 V, which was contributed to the electrochemical reaction of heme Fe(III)/Fe(II) redox couples. The results suggested that the direct electron transfer of Hb in the PVA/Clay film with the CILE was accomplished. The direct electrochemical behaviors of Hb were carefully studied with the electrochemical parameters calculated. The PVA/Clay/Hb modified CILE gave excellent electrocatalytic ability to the reduction of H2O2 and the apparent Michaelis-Menten constant (KMapp) value of Hb in the PVA/Clay film was calculated as 56.26 µmol L-1.

DIRECT ELECTROCHEMISTRY OF HEMOGLOBIN IN A NAFION AND CUS MICROSPHERE MODIFIED CARBON IONIC LIQUID ELECTRODE AND ITS ELECTROCATALYTIC BEHAVIOR

Direct electrochemistry of hemoglobin (Hb) was realized on a Nafion and CuS microsphere composite film modified carbon ionic liquid electrode (CILE) with N-butylpyridinium hexafluorophosphate (BPPF6) as binder. Scanning electron microscopy (SEM), UV-Vis absorption spectroscopy and cyclic voltammetry were used to characterize the fabricated Nafion/CuS/Hb/CILE. Experimental results showed that a pair of well-defined quasi-reversible redox peaks appeared with the formal potential as −0.386 V (vs. SCE) in pH 7.0 Britton-Robinson (B-R) buffer solution, which was attributed to the Hb heme Fe(III)/Fe(II) redox couples. The electrochemical parameters of Hb in the composite film were carefully investigated with the charge transfer coefficient (α), the electron transfer number (n) and the electron transfer rate constant (ks) as 0.505, 1.196 and 0.610 s−1, respectively. The composite film provided a favorable microenvironment for retaining the native structure of Hb. The presence of CuS microspheres showed great improvement on the electron transfer rate of Hb with the CILE, which maybe due to the contribution of specific characteristics of CuS microspheres and the inherent advantages of ionic liquid on the modified electrode. The fabricated Hb modified electrode showed good electrocatalytic ability in the reduction of H2O2. The proposed bioelectrode can be used as a new third generation H2O2 biosensor.

Voltammetric Determination of Heparin Based on Its Interaction with Brilliant Cresyl Blue

IntroductionHeparin is a polysaccharide of glycosaminoglycanclass, which consists of repeating disaccharide units ofiduronic/glucuronic acid and glucosamine residues withmany biological functions[1,2]. Many methods havebeen proposed for the detection of heparin, includingUV-Vis spectrophotometry[3—7], the light scatteringtechnique[8], HPLC and electrophoresis[9,10]and flowinjection analysis[11],etc.. But there are few reportsabout the detection of heparin by means of an electro-chemical method[12].

Application of Arsenazo III for the Polarographic Detection of Proteins

In this paper, a diazo dye of arsenazo III (AAIII) was selected as a new electrochemical probe for the determination of proteins. In Britton-Robinson (B-R) buffer solution of pH 2.4, AAIII had a sensitive second order derivative linear sweep voltammetric reductive peak at −0.39 V (vs. SCE). After the addition of human serum albumin (HSA) into AAIII solution, an interaction was taken place in the mixed solution and a biosupramolecular complex was formed, which resulted in the decreased reductive peak currents of AAIII. Based on the observed decrease in peak current, a sensitive electrochemical method was proposed for the determination of different proteins such as HSA, bovine serum albumin (BSA) and bovine hemoglobin (BHb). The optimal conditions for the interaction and the interfering effects of coexisting substances on the detection were investigated. The proposed method was successfully applied to the determination of HSA in synthetic samples with the recoveries in the range of 99.13–100.50%. The stoichiometry of HSA-AAIII biocomplex was calculated by voltammetric data with a binding number of 2 and a binding constant of 7.53 × 109.

Electrochemical Study on the Interaction of Protein with Bromothymol Blue and Its Analytical Application

Abstract The interaction of bromothymol blue(BB) with human serum albumin(HSA) was studied by electrochemical techniques and a sensitive method for proteins assay was developed. When BB interacted with HSA, the voltammetric peak current value of BB decreased linearly with the concentration of HSA in a range of 1.0—40.0 mg/L, and the peak potential shifted negatively. Based on the results, a sensitive assay method for proteins, such as HSA, bovine serum albumin(BSA), and egg albumin etc. was established. This method was further applied to determining the HSA in healthy human blood samples, and the results are not significantly different from those obtained by the classic Coomassie Brilliant Blue G-250 spectrophotometic method. The detecting conditions of this method were optimized and the interaction mechanism was discussed. The results show that the electrochemical parameters(formal potential E 0 , standard rate constant of the electrode reaction k s , parameter of kinetic nα ) of BB have no obvious changes before and after the interaction, which indicate that BB can interact with HSA, forming an electrochemical non-active complex. The equilibrium constant(β s ) and the binding ratio( m ) for this complex were calculated. The m is 4 and β s is 1.41×10 19 . This method is fast, simple, highly sensitive, and has good selectivity, which can be used in clinical measurements.