bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of different carbon electrodes for adsorptive stripping analysis of nucleic acids
Authors: Cai Xiaohua , Rivas Gustavo , Farias Percio A. M. , Shiraishi Haruki , Wang Joseph , Palecek Emil 
Published: May 2005

AbstractRecently we have shown (see Ref. [8]) that submicrogram amounts of nucleic acids can be measured by potentiometric stripping analysis (PSA) at carbon paste electrodes. In this article we investigate and compare various carbon electrode materials for use in stripping analysis of nucleic acids. Both the interfacial and redox properties of DNA and RNA are strongly dependent upon the nature of the carbon material and the electrode pretreatment step. In view of the high solvent decomposition background response near the guanine oxidation peak, only potentiometric stripping analysis can be used for convenient quantitation of trace levels (ng/mL) of nucleic acids. The trend in sensitivity: carbon paste > pyrolytic graphite > highly oriented pyrolytic graphite > carbon strip [with detection limits for oligo(dG)20 of 20, 30, 40 and 50 ng/mL, respectively, using 5 min accumulation]. No response was observed for trace measurements at the glassy carbon or carbon fiber electrodes. The influence of the surface pretreatment and accumulation time is described along with the analytical‐performance characteristics at each electrode. Useful information about the adsorption behavior of nucleic acids at different carbon electrodes are also obtained.
A study of the stripping voltammetric behavior of selected metal chelates and its application to automated analysis of river waters
Authors: Maxwell Tracy J. , Franklin Smyth W. 
Published: May 2005

AbstractThe ASV and AdSV behavior of Zn2+, Cd2+, Pb2+, Cu2+, Ni2+ and Sn4+in the presence of selected complexing/chelating agents has been studied. The presence of 2,5‐dimercapto‐l,3,4‐thiadiazole(I) lowers the limit of detection (LOD) for the ASV determination of Zn2+, Cd2+ and Pb2+ in 5 × 10−3 mol dm−3 LiCl supporting electrolyte with a deposition time of 120s to 0.82, 0.17 and 0.34 ppb, respectively, due to participation of the adsorbed complexing agent in the overall process. Similarly, Cd2+ can be determined in the presence of benzimidazole sulfoxides (II) and (III) by ASV in Britton‐Robinson (BR) buffer pH9 with 120s deposition with lower LODs of 0.12 and 0.06 ppb. respectively. AdSV can also be used to determine Cd2+ with (II), (III) and ammonium pyrrolidine dithiocarbamate (IV) with LODs of 0.70, 0.64 and 0.20 ppb, respectively and with Zn2+ having an AdSV LOD of 1.09 ppb using adsorption of its chelate with (IV) at −900mV for 60 s in a supporting electrolyte of 5 × 10−3moldm−3 LiCI. Participation of the adsorbed complexing agent in the ASV process is also observed for Sn4+ and Cu2+ in an oxalate/ammonium chloride/HCl buffer with lowered LODs of 0.51 ppb and 0.76 ppb in the presence of p‐methylene blue (V). The chelating agent 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol(VII) can be used to determine Cd2+,Zn2+ and Pb2+using the AdSV technique down to LODs of 9.3, 2.7 and 6.3 ppb, respectively. Several of these methods have been combined in the development of an automated method for the determination of trace Zn, Cd, Pb and Cu in an artificial river water matrix. The accuracy and precision of this procedure is discussed. Determination of Ni, Sn and As by this automated method and in such a matrix proved to be inaccurate.
Interaction of brilliant cresyl blue and methylene green with DNA studied by spectrophotometric and voltammetric methods
Authors: Liu Junli , Li Jinghong , Dong Shaojun 
Published: May 2005

AbstractThe binding behavior of two cationic dyes, brilliant cresyl blue (BCB) and methylene green (MG) to calf thymus DNA was studied by spectrophotometric and voltammetric methods. A red shift of the adsorption spectra and hypochromism accompany the binding of BCB and MG to calf thymus DNA. In 5 × 10−2 mol dm−3 NaCl, 5 × 10−3 mol dm−3 tris‐ HCl pH 6.87 buffer solution, the apparent binding constants are: KBCB+ 3.0 × 104M−1 (N= 4.13) and K= 8.8 × 104M−1 (n= 4.44). Electrochemical studies show that the formal potentials shift negatively upon addition of DNA, indicating that the oxidized forms of the dyes have stronger affinity to DNA than the reduced ones. K/KBCBH and K/KMGH are evaluated to be 10.39 and 7.04, respectively. Our investigation suggests that the two cationic dyes interact with DNA predominantly via electrostatic interaction.
Immobilization of a cerium redox mediator on a glassy carbon electrode for electroorganic reactions
Authors: Morita Masayuki , Kitamura Shingo , Ishikawa Masashi , Matsuda Yoshiharu 
Published: May 2005

AbstractCerium(III) species have been immobilized in Nafion films coated on a glassy carbon electrode by a dipping method. The redox activity was characterized in aqueous acidic solutions by cyclic voltammetry. The redox process was diffusion‐limited, suggesting that the cerium(III) species distributed in the multilayer of Nafion and that the diffusion of the charge‐compensating anion in the film was rate‐controlling. The cerium(III)‐immobilized Nafion films showed a mediation activity for the electrochemical oxidation of substituted benzylalcohols to yield corresponding arylaldehydes and carboxylic acids. The activity and the selectivity of the process depended on the oxidation potential of the substrate compound. Macroelectrolysis of p‐nitrobenzylalcohol using cerium(III)‐immobilized electrodes gave corresponding p‐nitrobenzaldehyde with a high rate and selectivity.
Electrolyte effects on mixed valence state stability of an electropolymerized bis(fulvalene)diiron film
Authors: Nishihara Hiroshi , Nakagawa Toshie , Aramaki Kunitsugu 
Published: May 2005

AbstractCyclic voltammetry and spectroelectrochemistry of an electropolymerized film of [Fe2(C10H8)(C10H7CClCHCHO)] (1) were carried out in acetonitrile with Bu4NPF6, Bu4NBF4, Bu4NClO4 or Bu4NHSO4 to determine how the two parameters concerning the stability of the mixed valence state, comproportionation constant, Kc, and mixing coefficient, α, depend on the type of counterions. The difference in electrolyte anions causes slight changes in α exhibiting the magnitude of delocalization of charge between two metal centers. However, significant changes in Kc, suggest that the ion‐pairing and electrostatic repulsion are main factors that alter the electrochemical stability of the mixed valence state.
The determination of ethanol in wine by voltammetry with an internal standard
Authors: Yu Ji Jin , Huang Weiguang , Hibbert D. Brynn 
Published: May 2005

AbstractA rapid method for the electroanalysis of ethanol is presented that incorporates flow extraction at room temperature, with voltammetric detection and potassium ferrocyanide [K4Fe(CN)6] as internal standard. In 0.1 M NaOH electrolyte, ethanol was oxidised at a platinum comb‐shaped working electrode at −300 mV (vs. a Ag/AgCl reference electrode) and K4Fe(CN)6 was oxidized at +180 mV. The ratio of the anodic peak currents was linear with ethanol concentration in the range of 0.1 to 8.0% (v./v.), and the detection limit (calculated as 3 σ background) was 0.012 % (v./v.) for Osteryoung square wave voltammetry (OSWV) and 0.023 %(v./v.) for cyclic voltammetry (CV). The average extraction efficiency of ethanol from aqueous solutions, at 20 ± 1°C, was 8.5%. The repeatability was in the range of 2.5 to 3.3% RSD (n = 8), and accuracy was in the range of 95.2 to 104.7% for the determination of wine samples. Application to wines compared well with GC and HPLC methods and the nominal ethanol concentration determined by gravimetry. Analytical parameters in CV and OSWV are optimized, and the dependence of the extraction efficiency with temperature and nitrogen gas flow is presented.
Large‐scale fractionation of proteins by isoelectric focusing in a multi‐compartment electrolysis apparatus
Authors: Jonsson Mats , Rilbe Harry 
Published: May 2005

AbstractA preparative electrolysis apparatus for isoelectric focusing of large amounts of proteins is described. It contains 46 separation compartments, and its total volume is about 7.6 liters. The compartments are closed, and internal cooling and stirring are effected by slow rotation of the whole apparatus in a tank filled with cold water. The apparatus can be run with an electric load of up to 5 kW, and an isoelectric focusing takes 2–3 days. It has been shown that crude pepsin can be purified in this apparatus. Preparations of hemoglobin and bovine whey have also been run in the apparatus. Fourteen grams of whey protein has been completely separated into its main components, serum albumin (pI 4.60), α‐lactalbumin (pI 5.01), and β‐lactoglobulin (pI 5.13–5.23), whereas the latter component was partially separated into its subcomponents A and B.
Photometric evaluation of slab gels I. Data acquisition and image analysis
Authors: Kronberg Harald , Zimmer Hans G. , Neuhoff Volker 
Published: May 2005

AbstractThe photometry of two‐dimensional electrophoretograms is described in some detail. This method has a high sensitivity of 5·10−4 O.D., because it takes advantage of the noise characteristics of photometric signals. Digital image analysis is used to locate and evaluate the individual spots on the electrophoretogram. The presented procedure of segmentation detects the faintest protein spots visible by eye and separates even confluent spots reliably and automatically. The combination of scanning photometry and image analysis is a sensitive, versatile, and accurate method for the evaluation of slab gels.
Fingerprinting of casein digests by isoelectric focusing and SDS electrophoresis
Authors: Righetti Pier Giorgio , Muneroni Paola , Todesco Rosanna , Carini Sandra 
Published: May 2005

AbstractWe have demonstrated the possibility of performing fingerprints in the single isoelectric focusing dimension, able to resolve at least 50 peptide zones, down to a minimum critical length of 12 amino acids. Isoelectric focusing can be coupled to SDS‐gel gradient electrophoresis, provided the fragments have a minimum molecular mass of 3500 daltons. We have applied this system to the analysis of digests of casein micelles. Upon digestion with extracts of lactobacilli, α and β caseins are broken preferentially into two major fragments, a pI 7.1 chain of 10 000 daltons, and a pI 6.4 chain of 14 000 daltons. Upon digestion with an extract of L. jugurti, only two fragments remain undigested, a pI ∼︁ 3 chain of 5500 daltons (probably the 43 to 90 amino acid fragment of α casein) and a pI ∼︁ 9 chain of 4200 daltons (probably the 1 to 36 amino acid sequence of casein).
A device for measuring the segmental voltages along electrofocusing gels
Authors: Jackiw B. Andrew , Chidakel Burt E. , Chrambach Andreas , Brown Ray K. 
Published: May 2005

AbstractA device for the measurement of segmental voltages along electrofocusing gels made of polyacrylamide has been designed and tested successfully. It allows for continuous monitoring of the changing voltage gradients which occur during electrofocusing. By means of 11 equidistant embedded platinum probes, the voltage drop at any one segment or sequential array of segments can be determined at any time without disturbing the ongoing electrofcusing. The wires are sealed into the wall of a 6 mm diameter (ID) Pyrex gel tube at 1.0 cm intervals. Measurements on a gel containing 2% Ampholine (pH‐range 3.5–10) showed that the voltage gradient changes during electrofocusing. Starting with a uniform voltage drop of 10 ± 2%cm across a 10 cm gel, two transient peaks of high potential (comprising at 15 min 17% and 25% of the applied voltage) move progressively from the gel periphery toward its center. They coalesce into a broad single peak centered at 0.4 of the distance from the anodic gel terminus within 1.5 h. This major single peak remained stationary, changing slightly in magnitude during the next 18 h of electrofocusing. At this final stage, the voltage peak occurred at pH 6.3 and approximately 25% of the applied voltage was across this segment of gel.
A density‐gradient column for rapid preparative isoelectric focusing
Authors: Jonsson Mats , Ståhlberg Jan , Fredriksson Stig 
Published: May 2005

AbstractIn this paper a 112‐ml density‐gradient column is described, which allows a rapid, low‐resolving pre‐focusing over its shorter dimension (20 mm), followed by a high‐resolving fine‐focusing over the longer dimension (112 mm) when the column is turned through 90°. This is possible due to the rectangular cross‐sectional shape of the column and to a special design of the electrode vessels. Test runs made with sperm whale myoglobin have shown that very good separations can be obtained in as little as four hours.
Visualization of proteins with a silver “stain”: A critical analysis
Authors: Poehling Hans‐Michael , Neuhoff Volker 
Published: May 2005

AbstractOptimal silver staining of proteins in polyacrylamide gels is a fine balance between silver deposition on the proteins and the level of background staining. Reproduciable staining requires empirical standardization of many steps in the procedure. Silver staining in the present form does not stoichiometrically stain proteins, unlike Coomassie Blue. Staining intensity does not bear a linear relationship to protein mass. This is demonstrated by densitometric evaluation of both silver and Coomassie‐stained marker proteins fractioned by sodium dodecly1 sulfate polyacrylamide gel electrophoresis (SDS‐PAGE). Although silver staining is more sensitive than Coomassie Blue, the increment in sensitivity is both different for individual proteins and dependent on protein concentration. Nevertheless it is an excellent method for one‐ and two‐dimensional (2‐D) electrophoresis if only minimal amounts of protein are available and only a qualitative or semi‐quantitative evaluation is required.
A sensitive method for determining the nephrotoxic effects of the analgesic acetaminophen upon esterases using isoelectric focusing
Authors: Hennis Hugh L. , Allen Robert C. , Hennigar Gordon R. , Simmons Margaret A. 
Published: May 2005

AbstractIn a study of the biochemical mechanisms of renal toxicity of acetaminophen, quantitative studies of the nonspecific kidney esterases were carried out in New Zealand white female rabbits. After the administration of a sublethal dose of 2.5 g/kg acetaminophen, four animals each plus four controls were sacrificed at 24 and 48 h. subsequent isoelectric focusing of kidney homogenate supernatants over a pH range of 3.5–8.0 showed marked changes in each of the groups. Zymograms of the nonspecific esterases in each group showed a characteristic pattern which deviated greatly from control animals. A morphological and histochemical examination of kidney sections from all animals showed no pathological changes in any of the kidneys. This would indicate that abnormal biochemical changes are being manifested in the kidney long before any morphological deviations. It would seem that this group of enzymes could provide a valuable market for early toxicological changes.
Steady‐state rheoelectrolysis — a method for isoelectric focusing without carrier ampholytes. I. The pH course to be excepted on rheoelectrolysis of a buffer solution composed of a weak acid and its salt with a strong base
Authors: Rilbe Harry 
Published: May 2005

AbstractRheoelectrolysis is defined as convection‐free electrolysis of an electrolytic solution under simultaneous liquid transport from anolyte to catholyte and vice versa. Equal rate of transfer in both directions is assumed in this paper, and hence there is no liquid flow within the electrolyser. If this process is conducted long enough, a steady state can be expected, characterised by mutually balancing flows of ion constituents within the electrolyser (by electric migration) and in external ducts (by pumps). The differential equation of the steady state is deduced, and it is shown that it is easily solvable if transport numbers and diffusion coefficients are constant throughout the electrolyser. In this case the concentration courses become linear. The conditions for the presence of both buffer components in all parts of the electrolyser. are given. These conditions being satisfied, it is possible to calculate the pH course to be expected throug the eleltolyer. It is found that a pH span of about 2.6 unite can be covered by the rheoelectolysis of an odinary buffer solution. The pH gradient is at a minimum at the centre of the apparatus and increases towards both electrodes. The pH courses is sigmoid in shape and appears to be very useful for isoelectric focusing of proteins and other ampholytes. The method may become important in preparative work on a large scale in order to save the cost of carrier ampholytes in quantities.
Sex differences in blood protein patterns: Two dimensional electrophoretic analysis of the acidic proteins of rat plasma
Authors: Khirabadi Bijan S. , Gersten Douglas M. , Park Chan M. , Ramey Estelle R. , Ramwell Peter W. , Ledley Robert S. 
Published: May 2005

AbstractPlasma from normal male and female rats was analyzed, after removal of albumin by affinity chromatography, by two‐dimensional electrophoresis. The results demonstrated gender differences in two plasma proteins with apparent molecular weights of 70 000 and 84 000 and isoelectric points ranging from 6.2 to 6.4, and 5.1 to 5.5, respectively. Both proteins were found to be more concentrated in the plasma minus albumin (P‐alb) fraction of females than males in both Wistar and Sprague‐Dawley rats. The 70 000 protein is serum albumin which was more completely removed from male plasma than female plasma. A possible mechanism responsible for this difference is discussed. The results support the existence of “maleness” and “femaleness” in blood protein patterns of rats.
Application of direct tissue rocket‐line immuno‐electrophoresis to the study of α‐amylase production and its localization in wheat seeds during the early stages of germination
Authors: Daussant Jean , Renard Henii A. , Skakoun Anna 
Published: May 2005

AbstractLine immunoelectrophoresis was adapted to the quantitative analysis of antigens directly from tissues without any previous extraction. The technique was used in a study on the production and the distribution of two α‐amylase isozymes (I and II) in tissues of wheat seeds that sprouted (radicle emergence) after different periods of germination. The α‐amylase content was examined in the scutellum and in three tissue fractions dissected from a 0.5 mm slice parallel and next to the scutellum (aleurone layer, outer and inner part of starchy endosperm). At the stages of germination investigated, α‐amylase I was not detected in these tissues. The results indicate that α‐amylase II accumulated in the scutellum and also in the aleurone layer after one day's germination; after about two day's germination, the α‐amylase II content in the aleurone layer was similar to or higher than that in the scutellum. Moreover, the production and distribution of α‐amylase II do not seem to be correlated with the radicle emergence.
The agar contact replica technique after isoelectric focusing as a screening method for the detection of enzyme variants
Authors: Pretsch Walter , Charles Daniel J. , Narayanan Komaratchi R. 
Published: May 2005

AbstractElectrofocusing has been adapted in order to make screening experiments for the detection of enzyme variants more efficient. The principle of the new technique consists in making agar copies of the polyacrylamide gel by contact; the original gel and the agar copies are then developed for different enzyme systems. By doing so, the number of enzymes,i.e.loci, per test animal screened after a single electrofocusing run is increased. This method has proved to be feasible for the detection of mouse variants with altered enzyme banding patterns due to parental treatment with chemical mutagens.
Routine phenotyping of phosphoglucomutase (PGM1) by thin‐layer focusing: Isoelectric points of 14 different variants
Authors: Dykes Dale D. , Copouls Barbara A. , Polesky Herbert F. 
Published: May 2005

AbstractA routine technique for phenotyping the PGM1 marker system was developed using thin‐layer isoelectric focusing on agarose. Resolution of PGM1 variants by thin‐layer isoelectric focusing on 0.5 mm gels was found to be superior to isoelectric focusing on ⩾ 1 mm gels. Isoelectric points were determined for 14 different PGM1 variants and should serve as a useful tool for comparing variants between laboratories.
Sensitive fluorescence staining for RNA and DNA species separated in polyacrylamide gels
Authors: Neuhoff Volker , Huether Gerald , Engelhardt Uta 
Published: May 2005

AbstractThe fluorescent dye, Hoechst Dye No. 33258, was found to be of excellent quality for staining of not only DNA, as reported in the literature, but also of RNA species after separation in polyacrylamide micro gels. The staining procedure is simple and very sensitive. There are no problems with background staining and under certain conditions the nucleotide‐dye complex is stable for a long time. The fluorescence intensity is linear to the amount of nucleic acid bound by the dye within certain limits.
Electrophoretic separation of human lymphocytes by means of immunomicrospheres
Authors: Smolka Adam , Kempner David , Rembaum Alan 
Published: May 2005

AbstractImmuno‐labeling of human peripheral blood lymphocytes with either polyglutaraldehyde or polyacrolein microspheres was shown by analytical electrophoresis to generate two electrokinetically distinct sub‐populations of lymphocytes. By means of free‐flow electrophoresis, the high mobility fraction was found to consist predominantly of T lymphocytes using an anti‐T cell antibody, while the low mobility fraction consisted of lymphocytes labeled with immunomicrospheres, identifying these cells as B lymphocytes. The immunomicrosphere‐induced reduction of B‐cell mobility below that of the T cells thus allowed the enrichment and recovery of viable T cells in preparative quantities by free‐flow electrophoresis.
Detection of specific bovine serum albumin‐sodium n‐dodecyl sulphate complexes by polyacrylamide gel electrophoresis
Authors: Dominguez‐Reboiras M. , Jones M. N. 
Published: May 2005

AbstractPolyacrylamide gel electrophoresis has been adapted to investigate bovine serum albumin (BSA) at sub‐saturation concentration levels of sodium n‐dodecyl sulphate (SDS). Two specific complexes were detected which coexisted between SDS concentrations of 0.4 and 5 mM. The binding isotherm for SDS on BSA was determined under comparable conditions by equilibrium dialysis and used in conjunction with the electrophoretic data to determine the composition of the complexes. The complexes had the following stoichiometry, BSA (SDS)5 and BSA (SDS)36, and closely resembled two of the three complexes that have been observed by moving boundary electrophoresis. The experiments indicate that the polyacrylamide gel electrophoresis (PAGE) technique when applied below surfactant saturation could be a useful tool in the study of protein‐surfactant interactions.