bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interaction of soybean agglutinin with leukemic T‐cells and its use for their in vitro separation from normal lymphocytes by lectin‐affinity chromatography
Authors: Bakalova R. , Ohba H. 
Published: June 2003

AbstractA procedure for separation of leukemic T‐cells from normal lymphocytes, using lectin‐affinity column chromatography, is described. CNBr‐activated Sepharose 6MB was used as a non‐mobile phase. The gel was covalently coupled with soybean agglutinin (SBA), then served as an affinity probe for fractionation of mixture of normal lymphocytes and leukemic cells. Leukemic cell lines, derived from acute lymphoblastic leukemia (Jurkat, MOLT‐4, RPMI‐8402), were tested. The elution of normal lymphocytes was carried out by PBS(−). The leukemic T‐cells, interacting with SBA, were removed by N‐acetyl‐D‐galactosamine or low‐concentration acetic acid. The type and viability of the separated cell fractions were analyzed by flow cytometry and fluorescent microscopy, using adequate fluorescent antibodies. The interaction of leukemic T‐cells with free SBA, as well as with SBA‐conjugated Sepharose beads, was examined fluorimetrically and visualized by fluorescent microscopy, using FITC‐SBA as a marker. The rate of cell elution on SBA‐affinity column decreased in order: normal > leukemic T‐cells. Both normal lymphocytes and leukemic T‐cells were removed in a mixture from SBA‐free Sepharose 6MB by PBS(−) and were not fractionated discretely. The leukemic T‐cells specifically interacted with SBA as well as with SBA‐affinity adsorbent. In contrast, the normal lymphocytes did not interact with free SBA as well as with SBA‐conjugated Sepharose beads in the concentrations applied. The method potentially combines a discrete cell fractionation with manifestation of a specific target cytotoxicity of SBA against leukemic T‐cells, without any influence on normal lymphocytes. Copyright © 2003 John Wiley & Sons, Ltd.
Plasticizers, antioxidants, and other contaminants found in air delivered by PVC tubing used in respiratory therapy
Authors: Hill Sandra S. , Shaw Brenda R. , Wu Alan H. B. 
Published: June 2003

AbstractOf the many compounds that leach from respiratory therapy tubing into air passing through it, we selected five compounds to analyze. The five compounds are known to be potentially carcinogenic, toxic or known to induce estrogenic activity. Parts‐per‐million and parts‐per‐billion concentrations of these species were found in the air passing through the tubing: the plasticizers di‐(2‐ethylhexyl) phthalate (DEHP) and di‐ethyl phthalate (DEP), the antioxidants butylated hydroxy toluene (BHT) and p‐nonylphenol (p‐NP), and the contaminant (from commercial preparation of DEHP) 2‐ethylhexanol (2‐EH). These levels are high enough to cause some concern about exposure for patients who use oxygen on a long‐term basis, those sensitive or allergic to these species, or those with asthma. A method was developed for analysis of solid tubing samples, showing great variability in concentrations of small, volatile molecules from sample to sample. A method was also developed for pre‐concentration of small molecules onto Tenax adsorbants from air passing through the tubing. Both solid samples and adsorbant loaded with analyte were analyzed by direct dynamic thermal desorption gas chromatography mass spectrometry (GCMS). This study does not imply that adverse reactions by patients to chemical compounds leaching from respiratory medical tubing will occur but that further investigation is warranted. Copyright © 2003 John Wiley & Sons, Ltd.
Simultaneous determination of 16 estrogens, dehydroepiandrosterone and their glucuronide and sulfate conjugates in serum using sodium cholate micelle capillary electrophoresis
Authors: Katayama Masatoki , Matsuda Yoshifumi , Shimokawa Ken‐ichi , Kaneko Satoru 
Published: June 2003

AbstractThe simultaneous determination of 16 estrogens, dehydroepiandrosterone (DHEA) and their glucuronide and sulfate conjugates by micellar electrokinetic chromatography (MEKC) with sodium cholate micelle is reported. Sodium cholate, sodium dodecylsulfate (SDS) and α‐, β‐, γ‐cyclodextrins were studied as micelle reagents in the pH range of 7.0–10.0. Estrogens, DHEA and their glucuronide and sulfate conjugates were separated using a 50 cm × 50 µm capillary with 10 mM borate–phosphate buffer (pH 8.0) containing 50 mM sodium cholate as carrier. The method could simultaneously determine 1.0–1000 µg/mL of steroids and metabolites in 100 µL of serum by photometric detection at 214 nm within 14 min and 80 ng/mL steroids could be determined by using 2.0 mL of serum. The relative standards deviations were 6.7–7.7% at 10 µg/mL in serum. The recoveries were 89.1–92.0% with 10 µg/mL serum samples. Copyright © 2003 John Wiley & Sons, Ltd.
Consideration of the Effect of Irregular Catalytic Active Component Distributions in Mesopores – Extension of a Model for Wall Catalyzed Reactions in Microchannel Reactors
Authors: Platzer B. , Xu Y. , Roßmann T. , Födisch R. , Hönicke D. 
Published: July 2003

AbstractData available from the literature and experimental results have shown that the distribution of the catalytic active components can be irregular already for fresh catalysts. The determination of the local concentrations of the catalytic active components using wavelength dispersive X‐ray spectroscopy confirms this for microstructured wafers used in microchannel reactors. Considering this nonuniform distribution, the used model gives the relation between the local concentration profiles of the reactants inside the pores and the product yield in the entire pore. These results were used in an equation for the diffusion flux at the pore mouth, which is useful for a microchannel model developed in a recent paper [1]. The theoretical considerations deal with cylindrical pores with known reactant concentrations at the pore mouth and known distribution of the catalytic active component within the pore. Beside numerical results, some analytical solutions with low mathematical expense, applicable to special cases, are discussed. The nonconsideration of the irregular distribution of the catalytic active component can be the reason for difficulties during the extrapolation of experimental results to slightly different conditions and can have a great influence on the reaction results. The regarded examples are typical of wall‐catalyzed reactions in microchannel reactors with mesopores.
Volumetric Mass Transfer Coefficient in non‐Newtonian Fluids in Spout Fluid Beds
Authors: Anabtawi M.Z. , Hilal N. , Al Muftah A.E. 
Published: July 2003

AbstractThe volumetric liquid‐phase mass transfer coefficient, kLa, was determined by absorption of oxygen in air using six different carboxy‐methyl cellulose (CMC) solutions with different rheological values in three phase spout‐fluid beds operated continuously with respect to both gas and liquid. Three cylindrical columns of 7.4 cm, 11.4 cm, and 14.4 cm diameters were used. Gas velocity was varied between 0.00154–0.00563 m/s, liquid velocity between 0.0116–0.0387 m/s, surface tension between 0.00416–0.0189 N/m, static bed height between 6.0–10.8 cm, and spherical glass particles of 1.75 mm diameter were used as packing material. A single nozzle sparger of 1.0 cm diameter was used in the spouting line. The volumetric mass transfer coefficient was found to increase with gas velocity, liquid velocity, and static bed height and to decrease with the increase of the effective liquid viscosity of the CMC solution. A dimensionless correlation was developed and compared with those listed in the literature.
An Extended Planar C5 Conformation and a 310‐Helical Structure of Peptide Foldamer Composed of Diverse α‐Ethylated α,α‐Disubstituted α‐Amino Acids
Authors: Tanaka Masakazu , Nishimura Shin , Oba Makoto , Demizu Yosuke , Kurihara Masaaki , Suemune Hiroshi 
Published: June 2003

AbstractOptically active peptide foldamers Tfa‐[(S)‐(αEt)Leu]‐[(S)‐(αEt)Nva]‐Deg‐[(S)‐(αEt)Nle]‐OEt (10) and Tfa‐[(S)‐(αEt)Val]‐[(S)‐(αEt)Leu]‐[(S)‐(αEt)Nva]‐Deg‐[(S)‐(αEt)Nle]‐OEt (11) composed of diverse α‐ethylated α,α‐disubstituted α‐amino acids were synthesized. The dominant conformation of these peptides in solution was an unusual, fully extended planar conformation, and that in the crystal state was both right‐handed (P) and left‐handed (M) 310‐helical structures in 10 and a P 310‐helical structure in 11, respectively. The preferred planar C5 conformation of the peptides prepared from chiral α‐ethylated α,α‐disubstituted α‐amino acids was drastically different from the 310‐helical structure of the peptides prepared from chiral α‐methylated α,α‐disubstituted α‐amino acids.
A Combined Experimental and Theoretical Electron Density Study of Intra‐ and Intermolecular Interactions in ThioureaS,S‐Dioxide
Authors: Lee Chi‐Rung , Tang Ting‐Hua , Chen Likey , Wang Yu 
Published: June 2003

AbstractThe thioureaS,S‐dioxide molecule is recognized as a zwitterion with a high dipole moment and an unusually long CS bond. The molecule has a most interesting set of intermolecular interactions in the crystalline state—a relatively strong O⋅⋅⋅HN hydrogen bond and very weak intermolecular C⋅⋅⋅S and N⋅⋅⋅O interactions. The molecule hasCssymmetry, and each oxygen atom is hydrogen‐bonded to two hydrogen atoms with O⋅⋅⋅HN distances of 2.837 and 2.826 Å and angles of 176.61 and 158.38°. The electron density distribution is obtained both from Xray diffraction data at 110 K and from a periodic density functional theory (DFT) calculation. Bond characterization is made in terms of the analysis of topological properties. The covalent characters of the CN, NH, CS, and SO bonds are apparent, and the agreement on the topological properties between experiment and theory is adequate. The features of the Laplacian distributions, bond paths, and atomic domains are comparable. In a systematic approach, DFT calculations are performed based on a monomer, a dimer, a heptamer, and a crystal to see the effect on the electron density distribution due to the intermolecular interactions. The dipole moment of the molecule is enhanced in the solid state. The typical values ofρbandHbof the hydrogen bonds and weak intermolecular C⋅⋅⋅S and N⋅⋅⋅O interactions are given. All the interactions are verified by the location of the bond critical point and its associated topological properties. The isovalue surface of Laplacian charge density and the detailed atomic graph around each atomic site reveal the shape of the valence‐shell charge concentration and provide a reasonable interpretation of the bonding of each atom.
Efficient Domino Process Based on the Catalytic Generation of Non‐Metalated, Conjugated Acetylides in the Presence of Aldehydes or Activated Ketones
Authors: Tejedor David , García‐Tellado Fernando , Marrero‐Tellado José Juan , de Armas Pedro 
Published: June 2003

AbstractThe extremely mild and highly efficient catalytic generation of non‐metalated, conjugated acetylides is reported. These acetylides are used to generate enol‐protected functionalized propargylic alcohols 1, 1,3‐dioxolane compounds 2, or 3,4,5‐trisubstituted 4,5‐dihydrofurans 4 through serial multibond‐forming processes. The method calls for a nucleophile (a tertiary amine or phosphine) as a chemical activator, a conjugated terminal acetylene as the acetylide source, and an aldehyde or activated ketone as the electrophilic partner. The chemical outcome of this process depends on the nature of the nucleophile, the temperature, stoichiometry and solvent, and it can be tailored selectively by the appropriate choice of the experimental conditions.
Photoelectron Spectra and Electronic Structures of Some Acceptor‐Substituted Cyclopropanes: Linear Correlation of Substituent Effects on MO Energies with Molecular Structures
Authors: Rademacher Paul , Coskun Timur , Kowski Klaus , Larionov Oleg , de Meijere Armin 
Published: June 2003

AbstractThe relationship between electronic and geometrical structures in acceptor‐substituted cyclopropanes has been investigated by B3LYP DFT calculations and photoelectron (PE) spectroscopy. The spectra of cyclopropanecarbaldehyde (2), cyclopropanecarboxylic acid (3), cyclopropanecarboxylic acid methyl ester (4), nitrocyclopropane (5), isothiocyanatocyclopropane (6), cyanocyclopropane (7), and 1,1‐dicyanocyclopropane (8) have been analyzed. The first ionization potential (IP1) of compounds 2–5 was found to be 0.1–0.4 eV higher than that of the analogous isopropyl derivatives indicating—contrary to expectation—that in these compounds the cyclopropyl group acts as a weaker electron donor than an isopropyl group. In the other compounds, IP1 values are 0.4–1.1 eV lower than in the open‐chain congeners. The Walsh orbitals ωS and ωA of the three‐membered ring are substantially stabilized to different extents by interactions with substituent orbitals, and this is reflected in shortened distal and elongated vicinal CC bonds. Although the nitro group in compound 5 causes large stabilizations of both ωS and ωA, their energy difference Δω remains rather small; this is in agreement with a relatively small difference Δr of the CC bond lengths. For the investigated monosubstituted cyclopropanes 2–7, the largest effects with respect to Δω and Δr are caused by the formyl group in carboxaldehyde 2. Comparison of the results for nitriles 7 and 8 indicates that the effects of the cyano groups are additive. A linear relationship between Δω and Δr was established by B3LYP DFT calculations on geometrically distorted cyclopropane (1) and from the PE data of 2–8.
Synthesis and Microstructural Characterisation of Two New One‐Dimensional Members of the (A3NiMnO6)α(A3Mn3O9)β Homologous Series (A = Ba, Sr)
Authors: Hernando María , Boulahya Khalid , Parras Marina , González‐Calbet Jose M. , Amador Ulises 
Published: June 2003

AbstractTwo new members of the one‐dimensional (A3NiMnO6)α(A3Mn3O9)β homologous series, with the compositions (Sr0.75Ba0.25)5NiMn3O12 and Sr9Ni2Mn5O21, have been synthesised. Their structures can each be described as a hexagonal array of infinite one‐dimensional chains of face‐sharing polyhedra, running parallel to the c axis and separated by the Sr/Ba cations. The structure of (Sr0.75Ba0.25)5NiMn3O12, which constitutes the (α = 3, β = 2) member of the series, is made up of three face‐sharing octahedra linked by one trigonal prism. For Sr9Ni2Mn5O21 (α = 2, β = 1) the sequence of polyhedra along the chains corresponds to a motif consisting of two octahedra−one trigonal prism−three octahedra−one trigonal prism. The manganese atoms occupy the octahedral sites in both phases, while the Ni2+ cations are distributed in the trigonal‐prismatic sites in a disordered way. Only a small fraction of these (close to 20%) is located at the centres of the trigonal prisms, 80% being displaced towards the rectangular faces of the polyhedra and giving rise to a square‐planar‐like coordination. Both oxides present twinned microstructures, as evidenced by SAED and HREM. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Discrete Supramolecular Assemblies of Porphyrins Mediated by Coordination Compounds
Authors: Iengo Elisabetta , Zangrando Ennio , Alessio Enzo 
Published: June 2003

AbstractMetal‐driven self‐assembly has emerged as a viable alternative to covalent synthesis in the construction of large and sophisticated multi‐porphyrin architectures, whose complexity and function begin to approach the properties of naturally occurring systems. The design and preparation of robust and shape‐persistent discrete assemblies, obtained by coordination of meso‐pyridylporphyrins to ruthenium, palladium and zinc centers, is comprehensively discussed in this microreview, that covers research in this field carried out by the authors at the University of Trieste in the last few years. NMR spectroscopy and X‐ray crystallography were used jointly for the unambiguous characterization of the new species in solution and solid state, respectively. Very often the adducts of nanoscopic dimensions, in which the number, position, relative distance and orientation of the chromophores is well defined, were obtained through hierarchical supramolecular self‐assembly: multi‐porphyrin components were used as building blocks for the metal‐mediated assembly of more elaborate architectures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Fatty acid esters with short‐chain alcohols in two‐phase olive pomace oils
Authors: Ruiz‐Méndez M. Victoria , Ramos‐Hinojosa Álvaro E. 
Published: June 2003

AbstractTwo‐phase decanter olive pomace (TPOP) is the by‐product of a centrifugation system, used to produce olive oil, that separates olive oil and moist pomace. The water content in these olive pomaces is about 70%, while it was 45‐50% in the olive pomace stemming from three‐phase systems (oil, water, and pomace) and 30% in the old press system. The aim of this work is focused on quantification and changes undergone during olive pomace storage in ponds of esters of fatty acids with short‐chain linear alcohols, which can be considered as a refining loss. The results indicate that oil deterioration increases very rapidly, in particular when oil is extracted from the TPOP surface. Special attention should be paid to the storage of TPOP, establishing a maximum of 2 months in all cases.
Electrochemical Oxidation of Hyperforin on Glassy Carbon Electrode and Determination in Herbal Medicinal Products
Authors: Michelitsch Astrid , Wurglics Mario 
Published: June 2003

AbstractHyperforin, one of the active components of St. John's Wort and St. John's Wort extracts is oxidized on the glassy carbon electrode. Electrode process, type and reversibility were examined by means of cyclic voltammetry in various buffer systems (NaAc/HAc, Sörensen‐phosphate buffer, borate buffer). A differential pulse voltammetric method was developed for the determination of hyperforin. In the concentration range from 1.0 μg/mL to 40.0 μg/mL there is a strong linearity between the concentration of hyperforin and peak height. The detection limit is 200 ng /mL. The differential pulse voltammetric method developed is used to determine hyperforin in herbal medicinal products.
Using Ferrocenes to Assist in Voltammetric Characterization of Carbon Fiber Microelectrodes after Electrochemical and Laser Activation
Authors: Farrell Patrick C. , Kinley Patrick R. , Weiss David J. , Strein Timothy G. 
Published: June 2003

AbstractIn this report the voltammetry of water‐soluble ferrocene derivatives is used to characterize the surface of carbon fiber microelectrodes before and after both electrochemical and laser activation procedures. Activation of carbon electrodes is necessary to produce a reproducible surface that will allow fast electron transfer. However, the activation method that is best suited for a given analysis can differ with analyte. In order to directly compare activation methods and characterize the resulting electrode performance, the voltammetry of a set of ferrocenes which have fast and well‐known electrochemistry has been used. As expected, electrochemical activation (0.000 to 2.000 V (vs. SSCE) at 500 V/s for 15 seconds) resulted in a hydrophilic surface with increased surface area. Laser pretreatment (20 Hz pulsed nitrogen laser irradiation for 15 seconds) appeared to remove surface oxides thereby producing a more hydrophobic surface that facilitates the adsorption of neutral analytes. In general, anionic ferrocene derivatives exhibited more quasi‐reversible voltammetry and were not as strongly adsorbed as the neutral analyte, particularly with electrochemically activated probes. In addition, neutral analytes show considerable adsorption, particularly at laser‐activated electrodes, while the cationic analyte shows significant adsorption at only the electrochemically‐pretreated electrodes, indicating surface‐specific interactions.
Renewable Drops Electrochemical Sensor for Sulfide Ions Detection
Authors: Milani M. R. , Stradiotto N. R. , Cardoso A. A. 
Published: June 2003

AbstractThe design and characteristics of a novel electrochemical system, which uses a drop as a renewable electroanalytical sensor, are described. This article describes the performance of the electrochemical system, the coupling of the experimental arrangement with flow injection technique and a demonstration of its applicability for the measurement of sulfide. The method is based on renewable drops of ferricyanide ions, buffered by borate. The ferrocyanide ions, product of the reaction between ferricyanide and sulfide ions, are oxidized on a platinum microelectrode and the current measured is related to sulfide concentration. The measurements can be done in continuous or static flow mode. In continuous mode, the detection limit is 5.0×10−5 mol L−1.
Disposable Glucose Sensors for Flow Injection Analysis Using Substituted 1,4‐Benzoquinone Mediators
Authors: Lau King‐Tong , de Fortescu Stephane A. L. , Murphy Lindy J. , Slater Jonathan M. 
Published: July 2003

AbstractThe redox chemistry of several substituted benzoquinones was investigated by cyclic voltammetry at a glassy carbon electrode and candidates for inclusion in a mediated biosensor for use in flow analysis were selected on the basis of oxidation potential, electrochemical reversibility and solubility. Glucose sensors constructed by sequential deposition onto a carbon pellet of 2,6‐dimethyl‐1,4‐benzoquinone, 2,3,5,6‐tetramethyl‐1,4‐benzoquinone or phenyl‐1,4‐benzoquinone mediator solution, followed by glucose oxidase in polyvinylalcohol‐Nafion solution, were tested for response to glucose using flow injection analysis. Sensors prepared from 2,6‐dimethyl‐1,4‐benzoquinone gave highest sensitivity, with a linear range of response to glucose of 2.5–40 mM. The use of an enzyme‐free comparative electrode to eliminate the response from interferents was investigated.
Chiral separation of methadone, 2‐ethylidene‐ 1,5‐dimethyl‐3,3‐diphenylpyrrolidine (EDDP) and 2‐ethyl‐5‐methyl‐3,3‐diphenyl‐1‐pyrroline (EMDP) by capillary electrophoresis using cyclodextrin derivatives
Authors: Kelly Tamsin , Doble Philip , Dawson Michael 
Published: July 2003

AbstractA stereoselective method was developed for the simultaneous determination of methadone and its two major metabolites, 2‐ethylidene‐1,5‐dimethyl‐3,3‐diphenylpyrrolidine (EDDP) and 2‐ethyl‐5‐methyl‐3,3‐diphenyl‐1‐pyrroline (EMDP) by capillary electrophoresis. Five β‐cyclodextrin (βCD) background electrolyte (BGE) additives were evaluated for resolution efficiency. The conditions for baseline resolution of each of the three enantiomer pairs was determined to be 1 mM heptakis‐(2,6‐di‐O‐methyl)‐β‐cyclodextrin (DMβCD) in 100 mM phosphate at pH 2.6. This method represents the first successful method for the resolution of the six enantiomers associated with the metabolism of methadone. The utilisation of doubly coated capillaries in conjunction with βCD derivatives for a faster separation of the methadone‐related enantiomers is also reported. The coated capillaries were prepared using a polycation of poly(diallyldimethylammonium chloride) (PDDAC) and a polyanion of dextran sulfate. Baseline resolution of the methadone enantiomers was achieved with a BGE of 8 mM (2‐hydroxy)propyl‐β‐cyclodextrin (HPβCD) in 100 mM phosphate at pH 2.6. The migration times for the stereoselective methadone separation were approximately 4 min, which represented a reduction by a factor of approximately three, compared to that attained using analogous conditions with the uncoated capillary.