bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bioelectrocatalytical studies of the effect of some pharmaceuticals on the acetylcholinesterase activity
Authors: Stoytcheva Margarita , Zlatev Roumen 
Published: May 2005

AbstractA bioelectrocatalytical method is applied to study the influence of some pharmaceuticals (atropine, caffeine, thiamine, nicotinic acid, quinine and eserine) on the acetylcholinesterase activity. The measuring principle is based on the process of acetylthiocholine hydrolysis, catalyzed by the acetylcholinesterase, immobilized on a graphite electrode surface. The product of this reaction is electroactive and its oxidation current is registered. The kinetics of the process, occurring with the participation of the above mentioned substances, is studied. It is found that competitive (eserine, nicotinic acid, atropine, caffeine) and noncompetitive (thiamine, quinine) inhibition takes place; kinetic parameters of the enzymic reaction (apparent Michaelis constants and constants of inhibition) are determined using electrochemical data, in the absence and in the presence of the inhibitors. It is observed that some of the tested substances behave as activators, under certain conditions. It was found that atropine, caffeine, thiamine, nicotinic acid and quinine do not show any electrochemical activity under the described conditions. Only eserine is oxidized; this however, does not interfere with the enzyme determination in a certain concentration range. Calibration plots, useful for the quantitative analysis, are constructed.
Anodic differential pulse voltammetric analysis of iodide with a cinchonine‐modified carbon paste electrode
Authors: Kwak Myung‐Keun , Park Deog‐Su , Won Mi‐Sook , Shim Yoon‐Bo 
Published: May 2005

AbstractThe stripping voltammetric determination of iodide ions has been completed using a cinchonine modified carbon paste electrode. Iodide ions were deposited onto a carbon paste electrode containing cinchonine via the ion pairing reaction in an acidic medium. The oxidation peak potential of the iodide ion is + 0.65 V. The analytical conditions for the determination of the iodide ion were optimized by cyclic voltammetry. The optimal composition of CMCPE and pH of the solution on the deposition of iodide are 40%(w/w) and 2.15, respectively. Differential pulse voltammetry was applied to determine the calibration plot and detection limit. The detection limit was 8.0 × 10−8M for 20 min of deposition time and relative standard deviation (5 determinations) was ±4.2% at a 7.0 × 10−7M iodide solution. The interferences of anions and cations were investigated. The thiosulfate ion interferes with the oxidation current of the iodide ion by about 12%. C1−, Br−, SCN−, C2O42−, CIO4−, NO3Co2+Fe(CN)63−, Ni2+, Cu2+, Cd2+, Pb2+, and Hg2+do not interfere with the determination for the iodide ion. The applicability of the CMCPE to the determination of iodide in a disinfectant has also been investigated.
Carbon electrodes in amine analysis: Effect of chemically modified carbon surfaces on signal quality and reproducibility
Authors: Surmann Peter , Peter Bernhard 
Published: May 2005

AbstractThe preparation of chemically modified graphite electrodes by various chemical treatments is described. These electrodes were tested with chlorpromazine, cyclopiroxolamine, sulfathiazole, bamipine, sparteine and diphenhydramine by differential pulse voltammetry. Compared with the unmodified and freshly polished carbon electrodes, the modified ones exhibit attractive properties such as enhanced stability against film formation. The initial signals at untreated electrodes are very high and decrease rapidly, but at pretreated electrodes the stability of the signals is usually improved. Adsorption and poisoning by film formation is suppressed by giving the surface of the electrode a chemical identity by chemical pretreatment. The improvements are not general but individual ones.
Electroanalytical sensors for nonconducting media based on electrodes supported on perfluorinated ion‐exchange membranes
Authors: Bontempelli Gino , Comisso Nicola , Toniolo Rosanna , Schiavon Gilberto 
Published: May 2005

AbstractElectroanalytical sensors, suitable for the analysis and monitoring of electroactive analytes present in gaseous phase or low‐conductive liquid media, and based on electrodes in close contact with perfluorinated ion‐exchange polymers are reviewed. The basic operative mechanism of these sensors, in which ion‐exchange polymers act as solid polymer electrolytes (SPE's), is thoroughly discussed, while stressing the fundamental reasons why their behavior differs from that of conventional membrane electrodes. The procedures for preparing composite working electrodes by coating one side of ion‐exchange membranes with stable porous films of conductive materials are described, along with the most common strategies followed to assemble this type of sensors. Useful examples of measurements in electrolyte‐free media of inorganic and organic electroactive species of interest mainly for environmental analysis are given. Future prospects for the development of these sensors are also discussed.
Analytical applications of poly(3‐methylthiophene)‐coated cylindrical carbon fiber microelectrodes
Authors: Agüí L. , Yáñez‐Sedeño P. , Pingarrón J. M. 
Published: May 2005

AbstractSome analytical applications of carbon fiber microelectrodes (CFMEs) modified with cyclic voltammetric electrogenerated poly(3‐methylthiophene) (P3MT) coatings are described. Cyclic voltammograms in aqueous solutions of the phenolic antioxidants tert‐butylhydroxyanisole (BHA), tert‐butylhydroquinone (TBHQ), propylgallate (PG), and tert‐butylhydroxytoluene (BHT) showed that electrocatalytic effects and an improved electrode kinetics occurred at the modified microelectrodes when compared with GC electrodes of conventional size. Moreover, reproducible voltammograms were obtained, obviating the need of cleaning or pretreatment of the coated microelectrode. Another important analytical advantage was the greatly improved resolution for mixtures of analytes. The behavior of P3MT‐CFMEs in organized media was tested by considering their voltammetric response towards the electrochemical oxidation of PG. The nonionic surfactant Pluronic F 68 was selected as the most suitable to form micellar solutions of PG, as well as the emulsifying agent for the preparation of oil‐in‐water emulsions. A 20:80 ethyl acetate:n‐hexane mixture was used as the organic phase and a 0.05 mol L−1 H3PO4/H2PO4− buffer solution of pH 2.0 as the aqueous continuous phase. Cyclic voltammetry demonstrated that the PG oxidation current was purely diffusion‐controlled in the organized medium. The analytical characteristics obtained by using differential pulse voltammetry were slightly better than those obtained in aqueous solution. Furthermore, the improved resolution for mixtures of analytes is retained in the oil‐in‐water emulsified medium. The proposed method was applied with good results to the determination of PG in spiked commercial dehydrated soup samples by direct emulsification of aliquots of the sample extract in the ethyl acetate:n‐hexane mixture.
A PVC‐based pentathia‐15‐crown‐5 membrane potentiometric sensor for mercury(II)
Authors: Gupta Vinod K. , Jain Suresh , Khurana Upendra 
Published: May 2005

AbstractPoly(vinyl chloride) (PVC)‐based membrane of pentathia‐15‐crown‐5 exhibits good potentiometric response for Hg2+ over a wide concentration range (2.51 × 10−5 to 1.00 × 10−1 mol dm−3) with a slope of 32.1 mV per decade of Hg2+ concentration. The response time of the sensor is as fast as 20 s. The electrode has been used for a period of six weeks and exhibits fairly good discriminating ability towards Hg2+ in comparison to alkali, alkaline and some heavy metal ions. The electrode can be used in the pH range from 2.7 to 5.0.
Continuous flow and flow injection stripping voltammetric determination of silver(I), mercury(II), and bismuth(III) at a bulk modified graphite tube electrode
Authors: Ye Ruidong , Khoo Soo Beng 
Published: May 2005

AbstractThe epoxy‐impregnated graphite tube electrode bulk modified with 2‐mercaptobenzoxazole, employed in a wall‐jet configuration, was found to be useful for the continuous flow and flow injection stripping voltammetric determinations of AgI, HgII and BiIII. For continuous flow, detection limits for AgI, HgII and BiIII were 1.8 × 10−10 M, 1.9 × 10−9 M and 9.5 × 10−9 M, respectively (10 min accumulation, S/N = 3). Precisions for 5.00 × 10−9 M AgI, 1.00 × 10−8 M HgII and 1.00 × 10−7 M BiIII were 10.5%, 5.77 % and 7.90% (relative standard deviations, n = 6), respectively. In the case of flow injection stripping, with a 500 μL injection loop, detection limits of 0.59 ng, 2.0 ng and 120 ng were obtained for AgI, HgII and BiIII, respectively (S/N = 3). Selected metal ions, inorganic and organic substances were investigated for interferences. The electrode was tested with a certified sample and then applied to the determinations of the metal ions in a urine and a sea‐water sample.
Nitrate ion‐selective sensor based on electrochemically prepared conducting polypyrrole films
Authors: Sun Bianting , Fitch Peter G. 
Published: May 2005

AbstractNitrate‐doped polypyrrole (PPy) films on a glassy carbon substrate have been prepared electrochemically in aqueous, acetonitrile, and propylene carbonate solutions for use as nitrate sensors. Lithium nitrate, sodium nitrate, nitric acid, tetraethylammonium p‐toluene sulfonate (TS), and tetradodecylammonium nitrate (TDN) were employed as electrolytes. The effect of dibutylphthalate (DBP) as a plasticizer on the sensitivity and lifetime of PPy film sensors was also investigated. A Nernstian behavior with a slope of 56.9 m V/decade over 0.1–7.4 × 10−5 M NO and a detection limit of 4.7 × 10−5 M were observed for the polymer sensor prepared in acetonitrile solution containing lithium nitrate and 15% plasticizer (DBP). A lifetime of more than 6 months for this PPy film electrode was obtained.
Catalytic polarographic prewave of cobalt(II) induced by carbendazim. Application to the voltammetric determination of benomyl
Authors: Alvarez Jesús L. Muñíz , Calzón Josefa A. García , Fonseca Juan M. López 
Published: May 2005

AbstractMethyl 1H‐benzimidazol‐2‐ylcarbamate (carbendazim or MBC) catalyzes the reduction of CoII at mercury electrodes in sodium barbital/nitric acid/sodium chloride media. On the basis of a detailed study of the CoII prewave induced by carbendazim, a mechanism for the electrode reaction is proposed and adequate conditions for the analytical determination of carbendazim by differential pulse voltammetry are established. Based on this finding, a voltammetric method for the indirect determination of methyl[1‐(butylcarbamoyl)‐1H‐benzimidazol‐2yl]carbamate (benomyl) is described, following the conversion of benomyl to carbendazim.
Calibration of denaturing agarose gels for molecular weight estimation of DNA: Size determination of the single‐stranded genomes of parvoviruses
Authors: Snyder Cathrine E. , Schmoyer Richard L. , Bates Robert C. , Mitra Sankar 
Published: May 2005

AbstractVertical slab gel electrophoresis of DNA with CH3HgOH‐containing agarose produces sharp bands whose mobilities are suitable for size estimation of single‐stranded DNA containing 600–20 000 bases. The relationship of electrophoretic mobility to size of DNA over this range is a smooth, S‐shaped function, and an empirical model was developed to express the relationship. The model involves terms in squared and reciprocal mobilities, and produced excellent fit of known standard markers to measured mobilities. It was used to estimate the sizes of six parvovirus DNAs: Kilham rat virus (KRV), H‐1, LuIII, and minute virus of mice (MVM) DNAs had molecular weights of 1.66 – 1.70 × 106, while the molecular weight of bovine parvovirus (BPV) DNA was 1.84 × 106 and that of adenoassociated virus (AAV) DNA was 1.52 × 106.
Tritium/PPO gel fluorographic efficiency is reduced by Coomassie Blue staining
Authors: Higgins Ratchford C. , Dahmus Michael E. 
Published: May 2005

AbstractWhen [3H]‐labeled proteins are analyzed by polyacrylamide gel electrophoresis, the sensitivity of fluorograhic detection following gel impregnation with PPO (2,5‐diphenyloxazole) in DMSO (dimethylsulfoxide) is significantly reduced if the gel has been stained with Coomassie Brilliant Blue R‐250. Since the reduction in fluorographic efficiency depends on the concentration of stain, which in turn depends upon protein concentration, substantial errors may enter into quantitative measurements of fluorograms depending on sample composition. Another reduction in fluorographic efficiency results from reduced penetrability of the gels to PPO when a build‐up of methanol in DMSO and DMSO/PPO solutions is allowed. This loss of fluorographic sensitivity should be sample independent, however.
High resolution preparative isoelectric focusing in layers of granulated gels
Authors: Frey Manuela D. , Radola Bertold J. 
Published: May 2005

AbstractDiscontinuous isoelectric focusing in layers of granulated gels is used to separate up to 1000 mg protein with a resolution of 0.01‐0.015 pI. High resolution is achieved with (i) gel layers of reduced thickness (1 mm), (ii) high field strength in the final stage of focusing (100‐200 V/cm), (iii) long separation distances, and (iv) high Volthour (Vh) products ensuring steady state conditions. We describe approaches to rapid focusing based on either short separation distances or extensive prefocusing with resultant short residence times of the separated substances in the gel. The optimum load capacity is 3‐5 mg protein/ml gel‐bed volume while 10 mg protein/ml gle‐bed volume are still well tolerated. At high loading, major components are seen in the gel as transulcent zones which can be easily identified and harvested. Best results are obtained with Sephadex G‐200 (Superfine) or Bio‐Gel P‐60 (minus 400 mesh). Protein visualization with a new printing technique empolying cellulose acetate membranes requires only 2‐3 min and is insensitive to protein overloading and adhering gel particles. A simple and efficient method is described for the electrophoretic removal of carrier ampholytes from the focused proteins. High resolution preparative isoelectric focusing should prove attractive for many applications due to its great flexibility with respect to sample size, gel volume, separation time, protein recovery, ease of operation and reasonable price.
Isolation and partial characterization of rat α1‐antitrypsin
Authors: Thisner Danuta , Rosengren Åke 
Published: May 2005

Abstractα1‐Antitrypsin was isolated from rat serum by salting out with ammonium sulfate in three steps, followed by repeated ion exchange on DEAE‐Sephadex A 50 and affinity chromatography on Affi‐Gel Blue. The fractionation was paced with isoelectric focusing in polyacrylamide gels with pH range 3.5‐9.5. The resultant protein was homogeneous in crossed immunoelectrophoresis using rabbit antiserum against whole rat serum. Isoelectric focusing in α1‐antitrypsin phenotyping plates with pH range 4–5 showed a clear five‐band pattern of isolated protein (isoelectric points 4.41, 4.48, 4.50, 4.58 and 4.61, respectively). Immunofixation and zymogram techniques were used to identify the α1‐antitrypsin bands. In sodium dodecyl sulfate/polyacrylamide gel electrophoresis two bands appeared. They had relative mobilities corresponding to apparent molecular weights of 50 000 and 56 000.
Evaluation of the capacity of gel electrophoresis, steadystate and transient state electrofocusing to resolve native human des‐angiotensin‐I‐angiotensinogen from angiotensinogen
Authors: Auzan Colette , Genain Claude , Corvol Pierre , Menard Joël , Chrambach Andreas 
Published: May 2005

AbstractThe resolution of angiotensinogen (Mr56 800) linked to a decapeptide, angiotensin I (Mr 1295), from the same protein without the decapeptide presents a challenging separation problem. Polyacrylamide gel electrophoresis at an optimized pH of 6.88 is unable to distinguish between the two proteins with statistical significance on the basis of size, but is able to discriminate between them with significance on the basis of their net charge difference. Correspondingly, the proteins are separated in gel electrofocusing with a pI difference of about 0.1 pH unit. For practical purposes, neither the charge separation by gel electrophoresis nor that by steady‐state electrofocusing seems sufficiently convenient. By contrast, transient state electrofocusing provides a ready means for their separation.
A measuring grid for the analysis of isoelectrically focused proteins in polyacrylamide gel slabs
Authors: Gassner George , Sears Sheila , Graham Charles , Janardan Konanur G. 
Published: May 2005

AbstractAn overlay grid was constructed to facilitate the measurement of densiometric scans of proteins in pH gradients formed by electrofocusing. The overlay procedure provides a rapid way for data collection. The relationship between pH and gel distance closely fit a straight line, (R>0.99). The reliability of the system was shown by the close agreement of the linear regressions from six different sets of data. Also, the feasibility of using a similar grid for a nonlinear system was established.
Two‐Dimensional gel electrophoresis of dexamethasoneinduced organ‐specific developmental proteins (fsa,fsb) in rat lung fibroblasts
Authors: Floros Joanna , Phelps David S. , Smith Barry T. 
Published: May 2005

AbstractGlucocorticoids are known to enhance fetal lung maturation. Previous studies with whole lung have shown that specific proteins are enhanced by these hormones. At least two effects of glucocorticoids on fetal lung epithelia require the presence of mesenchymal elements. Since the lung consists of several different cell types, further understanding of glucocorticoid effects on fetal lung protein synthesis requires that such studies be carried out with specific cell types. Using two‐dimensional gel electrophoresis, we have examined the synthesis and secretion of proteins by fetal rat lung fibroblasts in the presence and absence of glucocorticoid. Two proteins, fsa and fsb, are enhanced by dexamethasone, appear to be organ specific, and are enhanced only during prenatal and early postnatal life. They are not enhanced by a variety of other hormones.
Mathematical simulation of steady state isoelectric focusing of proteins using carrier ampholytes
Authors: Shimao Kazuo 
Published: May 2005

AbstractSteady state isoelectric focusing was treated as zero velocity isotachophoresis. From this standpoint, the author's theory of isotachophoresis was modified to deal with isoelectric focusing of protein molecules using carrier ampholytes, and mathematic simulations according to the modified theory were performed to calculate pH, voltag and concentration profiles in steady state isoelectric focusing. The results were in agreement with experiments with regard to resolving power for protein separation.
A new method for sex determination of the donor of forensic samples using a recombinant DNA probe
Authors: Gill Peter 
Published: May 2005

AbstractMicroscopical methods for sex determination of denatured samples in forensic laboratories are frequently unreliable. This paper describes the use of a recombinant DNA probe which hybridises specifically to a 2.47 kb repeat sequence of which 2000 copies are present on the Y chromosome. The technique enables rapid and reliable sex determinations of degraded DNA samples and produces results from blood stains greater than 4 years old in which only low molecular weight (< 10 kb) DNA is present. Stains from less than 1 μL of blood or a single hair root is required for the test using dot blot hybridisations. Electrophoretic analyses revealed that Hae III restriction of DNA samples produced somatically stable patterns.
Horizontal two‐dimensional electrophoresis with immobilized pH gradients in the first dimension in the presence of nonionic detergent
Authors: Görg Angelika , Postel Wilhelm , Weser Johann , Günther Siegfried , Strahler John R. , Hanash Samir M. , Somerlot Luke 
Published: May 2005

AbstractHorizontal two‐dimensional (2‐D) electrophoresis with immobilized pH gradients (IPG) in the first dimension, described for soluble proteins in Electrophoresis 1985, 6, 599–604, has been extended to an analysis of complex protein mixtures, such as leukemia cell proteins or bean proteins, in the presence of nonionic detergents. By optimizing the ratio of gel volumes for the first and second dimensional separation, and by decreasing the concentration of Nonidet P‐40 in the IPG gel, undistorted protein patterns in the 2‐D gel are obtained. Horizontal and vertical streaking are considerably diminished by optimized reswelling conditions of the dry IPG strips in presence of both urea and detergent. Resolution is improved and a reduced background is obtained when overcrowded gel areas are spread by flattening the pH gradient (in the first dimension) and the polyacrylamide gradient (in the second dimension).
Hybrid isoelectric focusing: Adsorption of proteins onto immobilized pH gradient matrices and desorption by carrier ampholytes
Authors: Altland Klaus , von Eckardstein Arnold , Banzhoff Angelika , Wagner Michael , Rossmann Ute , Hackler Rolf , Becher Pia 
Published: May 2005

AbstractComparing the separation patterns achieved by hybrid isoelectric focusing in immobilized pH gradients of 1 and 3 meqv/pH/L buffering power, it is demonstrated that a significant proportion of sample protein is lost in gels with the higher buffering power. A buffering power of 1 meqv/pH/L was found to be the lowest acceptable limit for flat bed gel hybrid isoelectric focusing still ensuring adequate control of the immobilized pH gradient. Protein losses were manifested as diminished overall staining intensity, disappearance of individual zones in dilution series, tailing effects and residual material at the application site, all of the above effects being more pronounced for larger than smaller proteins. Adsorption of proteins to charged binding sites of the immobilized pH gradient offers a plausible explanation for the observed phenomena. The visible effects of adsorption could be reduced by the addition of carrier ampholytes, but not by urea or detergents like Triton X‐100, 3‐(3‐chol‐amidopropyl)‐dimethylammonio‐l‐propanesulfonate (CHAPS) or octyl β‐thio‐glucoside, indicating ionic interactions between the immobilized charged groups, carrier ampholytes and proteins. The adsorption phenomena may strongly affect the quantification of proteins in immobilized pH gradients.