bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbonate‐Melt Oxidized Iridium Wire for pH Sensing
Authors: Wang Min , Yao Sheng 
Published: October 2003

AbstractA new approach to the preparation of an iridium oxide film for pH sensing is demonstrated. A thick, uniform and dense ceramic oxide layer was grown on the surface of an iridium wire by oxidizing the wire in a molten alkali metal carbonate at high temperature. The alkali metal ion from the carbonate melt was incorporated into the oxide, resulting in a highly stable oxide compound. After treated in acid solution, the oxide layer became hydrated. SEM, XRD, TGA and element analysis were carried out to characterize the oxide film, and a possible formula of the oxide was computed as Li0.86IrO2.34(OH)0.76⋅0.39H2O. The electrode made with this new type of oxide film exhibited good pH sensitivity and stability, even in strong acid/base solutions, or in strong corrosive solution such as hydrofluoric acid. Furthermore, the electrode showed excellent long‐term stability over the test period of two and a half years. In addition, individual electrodes prepared from the same batch exhibited remarkable agreement with respect to potential/pH slopes and apparent standard electrode potentials. The performance of the electrodes depends on the properties of the oxide film, such as composition, hydration state and oxidation state.
Laccase Biosensor on Monolayer‐Modified Gold Electrode
Authors: Gupta Gautam , Rajendran Vijaykumar , Atanassov Plamen 
Published: October 2003

AbstractLaccase enzymes from two different sources, namely, tree laccase from Rhus vernicifera and fungal laccase from Coriolus hirsutus were used for the development of biosensor for catechol. Laccase was immobilized onto the amine terminated thiol monolayers on gold surface by glutaraldehyde coupling. From the different thiol monolayers investigated, cystamine was found to be optimal with respect to sensitivity, stability, reproducibility, and other electrochemical properties of the enzyme electrode. Linear calibration in the range between 1 and 400 μM for catechol was obtained for fungal laccase covalently coupled on the electrode surface. The kinetic parameters determined using the Lineweaver‐Burk and Eadie‐Hofstee plots were Km=0.65 mM and Vmax=24.5 μA for fungal laccase compared to Km=5.4 mM and Vmax=6.6 μA for tree laccase on cystamine monolayer. The electrode showed good stability for 1 month without loosing appreciable activity when stored dry in a refrigerator at −20 °C.
Potentiometric Determination of Non‐Ionic Surfactants by Liquid Membrane Electrodes
Authors: Giannetto Marco , Minari Claudia , Mori Giovanni 
Published: October 2003

AbstractIt is well known that non‐ionic surfactants (NIS) influence remarkably the potentiometric measurements with liquid membrane ion selective electrodes (ISEs), interfering particularly on performance of ISEs for earth‐alkali metals, for which the loss of selectivity with regard to alkali metals has been documented. These studies indicate that such interferences are due to the extraction of surfactants within the membrane, where a competition takes place between the originally present ionophore and the surfactant which also acts as a ligand for alkali metals. The interpretation of such phenomena enabled one to exploit this interference for analytical purposes by membrane/solution extraction experiment monitored by UV measurements and by impedance FRA analysis on coated wire electrodes. Using Ca/Mg ISEs based on the neutral ionophore ETH 4030, it has been established that the logarithm of the Ca/Mg over Na potentiometric selectivity constant is linearly correlated with the concentration of NIS like Tegopren 5863 and Triton X‐100. The proposed method has been applied for the development of a new potentiometric analytical procedure for the determination of Tegopren 5863 in synthetic seawater (SSW), ranging from 0.25 to 5 ppm. Our procedure consists in the exposure of the electrode to stirred SSW containing the surfactant; the progressive extraction of Tegopren 5863 causes a growth in electrode's sensitivity to Na+ and K+, losing selectivity for Ca2+ and Mg2+. In turn this induces an increase of EMF, as all these ions are present in the studied matrix. The potential drift was monitored for 15 hours, showing that the process reaches thermodynamic equilibrium after about 12 hours of exposure. This method presents a value of 210 ppb of Tegopren 5863 as detection limit.
Biosensors for the Rapid Repetitive Detection of Adrenaline Using Stabilized Bilayer Lipid Membranes (BLMs) with Incorporated Calix[4]resorcinarene Receptor
Authors: Nikolelis Dimitrios P. , Petropoulou Syrago‐Styliani E. , Theoharis George 
Published: October 2003

AbstractThis work uses lipid film based biosensors with incorporated calix[4]resorcinarene receptor (lipophilic macrocyclic host molecule) for the rapid electrochemical detection of adrenaline. Freely‐suspended and metal supported BLMs (composed of egg phosphatidylcholine (PC) and 35% (w/w) dipalmitoyl phosphatidic acid) modified with the resorcin[4]arene receptor were used as one shot sensors to rapidly detect this catecholamine. The interactions of this compound with freely‐suspended BLMs were found to be electrochemically transduced in the form of a transient current signal with duration of seconds, which reproducibly appeared about 14 s after exposure of the membranes to adrenaline. The response time for these BLMs without incorporated receptor for adrenaline was about 1.5 min. The magnitude of the transient current signal was related to the concentration of adrenaline in bulk solution in the micromolar range. Differential scanning calorimetric (DSC) experiments were performed to explore the mechanism of interactions of BLMs with incorporated receptor with adrenaline. The interactions of adrenaline with surface‐stabilized bilayer lipid membranes (sBLMs) with incorporated receptor produced electrochemical ion current increases, which reproducibly appeared within a few seconds after exposure of the membranes to the stimulant. The use of the receptor in sBLMs increased the sensitivity of the method 6‐fold. The current signal increases were related to the concentration of adrenaline in bulk solution in the micromolar range. Stabilized lipid membranes formed by polymerization on glass fiber microfilters were used as practical chemical biosensors for the rapid detection of adrenaline. The interactions of polymerized lipid films with adrenaline were also found to provide transient current signals similar to those of freely‐suspended BLMs. The magnitude of the transient current signal was also related to the concentration of the stimulating agent in bulk solution in the micromolar range and these stabilized lipid films can be used again after storage in air. No interferences from ascorbic acid were noticed because of the negatively charged lipids in membranes. The effect of other compounds such as proteins and other compounds closely related to adrenaline was also investigated. Results of recovery experiments using human urine have shown recoveries ranged between 94 to 105%, which shows no interferences from matrix effects due to the presence of urine constituents. The present sensor based on stabilized lipid films can be used for the rapid repetitive detection of this pharmaceutical substance and keep prospects for the selective determination of catecholamines in biofluids.
Self‐Assembled Monolayer of L‐Cysteine on a Gold Electrode as a Support for Fatty Acid. Application to the Electroanalytical Determination of Unsaturated Fatty Acid
Authors: Hernández Pedro , Vicente José , Hernández Lucas 
Published: October 2003

AbstractThis article describes the formation of a SAM with chemisorbed cysteine to a gold surface by the thiol group to obtain a surface electrode with an amino and an acid group free for later reaction and accumulation with other molecules on the electrode surface. We explore the accumulation of unsaturated fatty acid and the electrochemical response of the electrode after modification with cysteine. The electrochemical study confirmed the accumulation of linoleic acid on the modified electrode. The optimum conditions for the determination of linoleic acid by differential pulse voltammetry of linoleic acid are studied a detection limit (3σ) of 0.03 μg mL−1 and a determination limit (10σ) of 0.10 μg mL−1 were obtained and applied to determination in olive oil and ham from Iberian breed hams.
Lead Ruthenate Pyrochlore Formed in Clay for Sensitive Determination of Dopamine
Authors: Zen Jyh‐Myng , Kumar Annamalai Senthil , Chen Huey‐Ping 
Published: October 2003

AbstractNatural iron‐intercalated clay (nontronite, SWa‐1) was converted into a more efficient catalyst by formation of lead ruthenate pyrochlore (Py, Pb2Ru2−xPbxO7−y) directly inside the matrix. The new material can take advantage of the electrocatalytic properties of both Py and nontronite and can even generate new catalytic active sites due to interaction of Py and nontronite. The combination of these two interesting catalysts results in a more reactive electrode (designated as SWa‐1/PyCME) for electroanalytical applications. The preparation and characterization of the SWa‐1/PyCME as well as its electrocatalytic behavior toward the oxidation of dopamine are described in this study. Surface saturation kinetics in terms of Michaelis‐Menten kinetics suited well the oxidation of dopamine on this modified electrode. Under optimized conditions, the detection limit (S/N= 3) was 0.54 nM by square‐wave voltammetry.
Voltammetry and EQCM Investigation of Glutathione Monolayer and Its Complexation with Cu2+
Authors: Fang Cheng , Zhou Xingyao 
Published: October 2003

AbstractThe glutathione (GSH) self‐assembled monolayer and its compexlation with Cu2+ were studied by using voltammetry and EQCM. It was found that the monolayer could rearrange during the redox process of Cu2+/Cu+. The protonating, or not, of the carboxyl terminates of the adsorpted GSH molecules influence the compexlation interaction significantly for they are the key binding sites. The GSH monolayer had the capacity to accumulate Cu2+ and the monolayer modified gold electrode was employed to detect the low levels of Cu2+ with a limit of 1.0×10−10 mol L−1.
ECEC and ECE‐Type Mechanisms in Electrochemical Oxidation of 4‐Substituted Catechols in the Presence of 4‐Hydroxy‐6‐methyl‐2‐pyrone
Authors: Nematollahi Davood , Forooghi Zinat 
Published: October 2003

AbstractElectrochemical oxidation of 3,4‐dihydroxybenzoic acid (1) and 4‐tert‐butylcatechol (5) in the presence of 4‐hydroxy‐6‐methyl‐2‐pyrone (2) as nucleophile in aqueous solution has been studied using cyclic voltammetry and controlled‐potential coulometry. The results indicate that 1 via Michael reaction under electro‐decarboxylation reaction converts to heterocyclic compound 4, and the quinone derived from 4‐tert‐butylcatechol (5) participates in Michael reaction with 2 and through an ECE mechanism converts to the corresponding o‐quinone (6a). The electrochemical synthesis of 4 and 6a has been successfully performed in an undivided cell.
Capillary electrophoresis as a simple and sensitive method to study polysaccharides of Sinorhizobium sp. NGR234
Authors: Fraysse Nicolas , Verollet Christel , Couderc François , Poinsot Véréna 
Published: October 2003

AbstractWe report the minimum amounts of polysaccharides (6.5 ng) that can be studied using capillary electrophoresis‐laser‐induced flurescence (CE‐LIF) and describe the separation of the various monosaccharides susceptible to occur in Sinorhizobium cell wall. On‐gel hydrolysis of the polysaccharides is described. It allowed the easy and rapid determination of the monosaccharide composition of the excised lipopolysaccharides. The composition obtained fits with gas chromatography‐mass spectrometry (GC‐MS) results. This study underlines the simplicity of using CE‐LIF, which remains an entirely “water medium” method, unlike GC‐MS which is, in addition, less sensitive (at least 100‐fold) than CE‐LIF.
Proteome database of unsensitized CD4 positive T lymphocytes in T cell receptor transgenic mice
Authors: Kaji Tomohiro , Hachimura Satoshi , Kaminogawa Shuichi 
Published: October 2003

AbstractWe established a two‐dimensional electrophoresis (2‐DE) mapping database of splenic CD4 T cells prepared from I‐Ad‐restricted ovalbumin (OVA)323‐339 specific T cell receptor (TCR) transgenic mice (OVA23‐3). First we examined the purification of CD4 T cells and found that the high purity of cells produced more accurate protein maps. The first dimension utilized narrow‐range immobilized pH gradients (IPGs), pH 4.0–5.0, pH 4.5–5.5, pH 5.0–6.0, and pH 5.5–6.7. Approximately 1300 spots were detected by silver staining. Detection was performed by in‐gel tryptic digestion of the spots, matrix assisted laser desorption/ionization‐time of flight‐mass spectrometry (MALDI‐TOF‐MS) technology and database searches via the world wide web (WWW). We have so far identified 255 proteins on 2‐DE gels of whole cell lysates. This is the first construction of a proteome database for murine unsensitized CD4 T lymphocytes. To examine this further, 2‐DE mapping was utilized for splenic CD4 T cells from another TCR transgenic mouse strain (DO11.10 TCR transgenic mice). Mapping patterns were found to be almost identical to those from CD4 T cells from OVA23–3 mice. These results indicated that the 2‐DE maps in this study could be used for mouse CD4 T cells to examine protein changes in cells given certain stimuli.
Proteomic analysis of the tumorigenic human prostate cell line M12 after microcell‐mediated transfer of chromosome 19 demonstrates reduction of vimentin
Authors: Liu Xuhui , Wu Yongzhong , Zehner Zendra E. , Jackson‐Cook Colleen , Ware Joy L. 
Published: October 2003

AbstractCritical alterations in proteins that accompany or control the aggressiveness of human prostate cancers remain poorly defined. Previously we demonstrated that the highly tumorigenic, metastatic human prostate cell line M12 was converted to a slow growing, poorly tumorigenic cell line by introduction of an intact human chromosome 19, generating the M12 (F6) hybrid cells. The objective of this report was to identify changes in the protein profile of these M12(F6) microcell hybrid cells. A combination of two‐dimensional gel electrophoresis and matrix assisted laser desorption‐time of flight‐mass spectroscopy was used to compare proteins made by these two cell lines. No consistently increased proteins were identified. However, seven proteins were reproducibly reduced more than twofold: vimentin, hsp90, ATP synthase, 26S protease regulatory subunit, heterogeneous nuclear ribonucleoprotein, T‐Complex protein 1 β, and α‐1 tubulin. The striking reduction in vimentin protein was accompanied by significantly decreased vimentin mRNA, revealed by Northern blotting. Our findings implicate reduced vimentin in the conversion of these tumorigenic prostate epithelial cells into slow growing, less aggressive cells. These studies demonstrate that application of proteomic analysis to specific problems in an experimental context can yield biologically relevant information about the prostate cancer cell phenotype.
Towards the development of an integrated capillary electrophoresis optical biosensor
Authors: Bossi Alessandra , Castelletti Laura , Piletsky Sergey A. , Turner Anthony P. F. , Righetti Pier Giorgio 
Published: October 2003

AbstractExtending the previous preliminary study on the construction of a capillary electrophoresis (CE)/sensor for the detection of reducing analytes, we focus the interest on the simultaneous detection of redox active species, which are important indicators of the oxidative damage in tissues, of food preservation, and of pollution. The CE/sensor was built by modifying the detector‐portion of the capillary with the redox‐sensitive polymer polyaniline (PANI). The analyte is detected by monitoring the changes in optical absorption of the PANI film. The CE/sensor was tested, with good results, with ascorbic acid, glutathione (GSH), as well as with compounds with very close similarity (ascorbic and isoascorbic acid). The kinetics of oxidation and reduction of PANI were evaluated. Further a PANI/CE‐biological sensor was developed by coupling an enzyme, glucose oxidase (GOD), to the PANI‐modified portion of the capillary. The stability of the immobilized GOD and the sensitivity of the CE/biosensor were studied, by using glucose as test analyte in concentrations within the physiological range. The results indicate that the CE/biosensor had good stability (more than 75% of original activity retained after 30 operational days), manufacturing reproducibility and a sensing range convenient for monitoring physiological glucose (1–24 mM).
Free solution mobility of small single‐stranded oligonucleotides with variable charge densities
Authors: Dong Qian , Stellwagen Earle , Dagle John M. , Stellwagen Nancy C. 
Published: October 2003

AbstractThe free solution mobilities of six single‐stranded 16‐nucleotide DNA oligomers with the same sequence, containing up to 11 neutral phosphoramidate internucleoside linkages, have been measured by capillary electrophoresis. The mobilities of the partially charged oligomers increase linearly with the logarithm of increasing charge density, as predicted by the Manning theory of electrophoresis (G. S. Manning, J. Phys. Chem. 1981, 85, 1506–1515). For comparison, the mobilities of eight fully charged single‐stranded oligomers containing similar numbers of charged phosphate residues have also been measured. The mobilities of the variable length, fully charged oligomers increase more rapidly with the increasing number of charged phosphate residues than the mobilities of the constant size, partially charged phosphoramidate derivatives, because of the larger diffusion coefficients of the modified oligomers.
Quantitative evaluation of sample application methods for semipreparative separations of basic proteins by two‐dimensional gel electrophoresis
Authors: Barry Richard C. , Alsaker Britt L. , Robison‐Cox James F. , Dratz Edward A. 
Published: October 2003

AbstractThe use of cup‐loading for sample application has become widely used in two‐dimensional electrophoresis (2‐DE) for resolution of basic proteins, but no side‐by‐side quantitative study has been published which compares cup‐loading with the alternative passive and active rehydration methods to fully promote one type of loading method over another. Replicate 2‐D gels from each loading method were quantitatively evaluated for gel‐to‐gel reproducibility using IPG 6–11 strips and semipreparative protein loads (300 μg). Gels were stained with SYPRO Ruby and analyzed with PDQuest. An inexpensive home‐made assembly for cup‐loading was used with the Protean IEF Cell for separation of whole cell extracts from the archaeon, Sulfolobus solfataricus. Cup‐loading was determined to be far superior for IPG 6–11 separations than active or passive rehydration methods. Cup‐loading consistently produced the greatest number of detectable spots, the best spot matching efficiency (56%), lowest spot quantity variations (28% coefficient of variation, CV), and the best‐looking gels qualitatively. The least satisfactory results were obtained with active rehydration, followed closely by passive rehydration in off‐line tubes. Passive rehydration experiments, performed using an on‐line isoelectric focusing (IEF) tray, produced comparable spot numbers to cup‐loading (84%), with 55% of the spots having higher intensity but 10% more spot quantity variance than cup‐loading.
Study of ethidium bromide effect on dsDNA separation by capillary zone electrophoresis and laser light scattering
Authors: Liang Dehai , Zhang Jun , Chu Benjamin 
Published: October 2003

AbstractThe effect of ethidium bromide (EB) on dsDNA separation was studied by using capillary zone electrophoresis (CZE) and laser light scattering (LLS). By increasing the concentration from 1 to 15 μg/mL, EB showed significant influence on the separation of pBR322 HaeIII in terms of resolution, speed, and signal‐over‐noise ratio. The physicochemical properties of DNA, such as mobility under electric field, charge‐over‐size ratio, and hydrodynamic radius, showed two declines, a sharp drop followed by a relaxed decrease, with increasing EB concentration. Such observations could be explained by using two modes of the dye binding process: intercalation and outside binding. The combination of results obtained from CZE and LLS also confirmed the existence of outside binding. Compared with intercalation, outside binding showed a weaker dye concentration dependence in neutralizing the negative charges on the DNA fragments. Static light scattering showed that <Mw> and <Rg> of DNA in 1×Tris‐borate‐EDTA (TBE) were increased with increasing EB concentration. <Rg>/<Rh> of DNA with dye had a value larger than 1.5, suggesting a random coil conformation.
Avoiding pitfalls in electrokinetic remediation: Robust design and operation criteria based on first principles for maximizing performance in a rectangular geometry
Authors: Oyanader Mario A. , Arce Pedro , Dzurik Andrew 
Published: October 2003

AbstractThe role of the symmetrical conditions on the temperature field is studied in a capillary of rectangular geometry. By using the generalized flux, i.e., Robin‐type of boundary conditions for the heat transfer in such a capillary domain, it is possible to identify clearly conditions under which the velocity field will depend crucially on the basic parameters and, therefore, what types of flow regimes may arise in the capillary channel. In addition, it is possible to conclude under what conditions the velocity field will not at all depend on some of these. The behavior is intimately tied to the symmetrical conditions associated with the temperature field in the system. A “skew” or asymmetrical parameter, W∞, has been identified in the temperature profiles; this parameter is useful for studying the role of the symmetrical conditions on the hydrodynamics field and in determining a set of a priori design criteria that limits the range of values of the parameters. Several numerical examples are presented to show the flow situations found in the system.
Comparison of automated in‐gel digest methods for femtomole level samples
Authors: Finehout Erin J. , Lee Kelvin H. 
Published: October 2003

AbstractA comparison of automated in‐gel digestion methods for low picomolar to femtomolar levels of protein is presented. Gel spots with 4 pmol to 120 fmol of protein were stained with either Coomassie colloidal blue or SYPRO Ruby and digested using an automated platform. The sequence coverages and average peak intensities obtained from a matrix‐assisted laser desorption/ionization‐mass spectrometry (MALDI‐MS) analysis are compared. Results show that methods using an acetonitrile extraction or digest times greater than the standard 4 h give no significant increase in peptide sequence coverage for automated digestion of low protein level samples. It is also shown that digests from SYPRO Ruby‐stained gels show a greater improvement upon ZipTip cleanup than digests from Coomassie colloidal blue‐stained gels. The digests from SYPRO Ruby‐stained gels are also shown to give a higher average peptide intensity if a method with minimal gel plug washing is used.