bluuebunny/crossref_metadata_2025_split huggingface dataset:
No evidence for a major effect of two common polymorphisms of the catalase gene in type 1 diabetes susceptibility
Authors: Pask Rebecca , Cooper Jason D. , Walker Neil M. , Nutland Sarah , Hutchings Jayne , Dunger David B. , Nejentsev Sergey , Todd John A. 
Published: February 2006

AbstractBackgroundType 1 diabetes (T1D) is a multifactorial disease, the genetic analysis of which has yielded few true positive linkage and association results. Replication of association in independent, large‐sample studies is essential to further identify the genes involved in T1D. Two single nucleotide polymorphisms (SNPs) in the catalase gene have been reported to be associated with T1D.MethodsMajor effects of two SNPs, C1167T (rs769217) and C(‐262)T (rs1001179), of the catalase gene on T1D susceptibility have been reported previously in Russians from Moscow. We genotyped C1167T and C(‐262)T in large family (1642 families) and British case–control (3530 cases and 3930 controls) collections and tested for association with T1D.ResultsWe found no evidence of an association between T1D and C1167T or C(‐262)T in either the family or case–control collections, or for the D11S2008 microsatellite polymorphism in families. However, we did find limited statistical evidence of an association at C1167T in USA families (P = 0.033; RR for 1167C = 1.23, 95% CI = 1.02–1.49) and C(‐262)T in UK families (P = 0.046; RR for (‐262)C = 0.86, 95% CI = 0.75–0.99).ConclusionWe found no evidence for a major effect of C1167T or C(‐262)T on T1D susceptibility in two large sample collections. Limited statistical evidence of an association at C1167T in USA families and C(‐262)T in UK families was found, but these results are likely to be false positives. The previously reported association of these SNPs may also have been a false positive, or a population specific association in Russians from Moscow. Copyright © 2006 John Wiley & Sons, Ltd.
Induced peripheral regulatory T cells: The family grows larger
Authors: Höglund Petter 
Published: February 2006

AbstractIn order to control immune reactions and to prevent autoimmunity, the immune system relies on a multitude of regulatory T cells (Treg). Most work in this field has focussed on Treg of the CD4+ T cell subset because of the central role CD4+ T cells play as initiators and regulators of immune responses. One discovery of particular importance was the identification of naturally occurring CD4+CD25+ Treg that arise in the thymus and express the transcription factor Foxp3; however, Treg can also be induced in the periphery after immune activation. A paper in this issue of the European Journal of Immunology identifies a novel type of induced murine CD8+ Treg that arise in TCR HY transgenic female mice after injection of MHC class I tetramers loaded with HY peptide. These Treg prevent subsequent rejection of male skin grafts suggesting that their manipulation may represent a new way of improving graft rejections against minor histocompatibility barriers. See accompanying article http://dx.doi.org/10.1002/eji.200535064
Sulfur–Sulfur‐Based Ligands Derived from D‐Sugars: Synthesis of PdII Complexes, Application in Palladium‐Catalyzed Allylic Alkylation for the Synthesis of Both Members of Enantiomer Pairs, and Structural Studies
Authors: Khiar Noureddine , Serrano Araújo Cristina , Suárez Bélen , Fernández Inmaculada 
Published: February 2006

AbstractA divergent synthetic approach for the synthesis of optically pure bis(thioglycosides) of type I is reported. A common chiral intermediate with up to eight free hydroxy groups is obtained in only two steps, and from this common intermediate a large number of ligands can be synthesized. A strategy resembling positional scanning enabled the rapid discovery of an efficient catalyst for the palladium‐catalyzed asymmetric allylation of malonate. Both enantiomers of the allylated product could be obtained in up to 90 % ee values through the use of natural D‐sugars as catalyst precursors, thanks to the structural similarity of α‐D‐arabinose and β‐L‐galactose. Treatment of several C2‐symmetric bis(thioglycosides) with [PdCl2(CH3CN)2] always resulted in single diastereomeric PdII complexes. Dynamic NMR studies of various PdII complexes have shown that there is efficient stereochemical control over the sulfur configuration upon coordination to the palladium, as a consequence of the exo‐anomeric effect. An explanatory model for the observed enantioselectivity based on NMR studies is discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Reduction of Multiple Bonds without Hydrogen or Hydride Complexes: Samarium Diiodide as a Mild Reducing Reagent
Authors: Concellón José M. , Rodríguez‐Solla Humberto 
Published: February 2006

AbstractThe use of samarium diiodide as a mild and selective reducing agent has become an important tool in organic synthesis. Many reducing agents are reported in the literature. However, due to their low chemoselectivities and various other drawbacks, samarium diiodide has become a useful and readily available reagent. This manuscript provides an update on earlier reviews describing conventional reduction processes of multiple bonds promoted by samarium diiodide. The most recent developments in the use of samarium metal in this field are also discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
4‐exo‐dig Cyclocarbopalladation: A Straightforward Synthesis of Cyclobutanediols from Acyclic γ‐Bromopropargylic Diols under Microwave Irradiation Conditions
Authors: Bour Christophe , Suffert Jean 
Published: February 2006

AbstractTreatment of acyclic γ‐bromopropargylic diols with tributylstannylated alkynes under palladium catalysis and microwave irradiation conditions gives high yields of the bis(alkylidene)cyclobutanediol derivatives and cyclobutenediols through an efficient 4‐exo‐dig cyclocarbopalladation. The cyclization is general with a wide variety of alkyne derivatives and gives access to new cyclobutane ring systems bearing one exocyclic double bond and one eneyne substituent as well as bicyclic dienes sharing a common double bond that may be of interest for further elaborations of complex molecules. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Total Synthesis of Altenuene and Isoaltenuene
Authors: Altemöller Martina , Podlech Joachim , Fenske Dieter 
Published: February 2006

AbstractTotal synthesis of altenuene and isoaltenuene, toxins produced by various alternaria fungi, were achieved for the first time in ten steps, starting with quinic acid and commercially available acetal‐protected phloroglucinic acid, with the longest linear sequence consisting of seven steps. The key reactions are palladium‐catalyzed Suzuki‐type couplings between an arene boronate and iodinated cyclohexenes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Samarium Diiodide Induced Reactions of Cyclopropyl Ketones: Reductive Ring Cleavage and Dimerization Leading to 1,8‐Diketones – Scope, Limitations, Mechanisms
Authors: Aulenta Francesca , Hölemann Alexandra , Reißig Hans‐Ulrich 
Published: February 2006

AbstractReactions of the samarium diiodide/HMPA complex with alkyl cyclopropyl ketones such as 3, 5, and 7 provided dimers incorporating a 1,8‐diketone moiety. The products 4, 6, and 8 were isolated in moderate to good yields. The aryl‐substituted cyclopropyl ketones afforded a broader product spectrum, which results from the attack of samarium intermediates to the aryl group. Cyclopropyl phenyl ketone (13) gave dimer 14, where one cyclopropane ring was reductively cleaved, whereas the second one is still present. The reductive dimerization of cyclopropyl 2‐thienyl ketone (21) furnished the product 22, which still contains two cyclopropyl groups. Further examples demonstrate the diversity of samarium diiodide induced reductions of cyclopropyl ketones. Plausible reaction mechanisms involving samarium ketyl intermediates are presented.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Sol‐Gel Entrapped Pyridinium Hydrobromide Perbromide as a Recyclable Bromination Agent: Its Application to a One‐Pot Bromination and Dehydrobromination Process
Authors: Levin Yevgenia , Hamza Khalil , Abu‐Reziq Raed , Blum Jochanan 
Published: February 2006

AbstractSilica sol‐gel encaged pyridinium hydrobromide perbromide can be used for clean, odorless bromination of a variety of substrates, including alkenes, ketones, and arenes. The used heterogenized bromination reagent can be recharged with bromine and recycled. In the presence of sol‐gel entrapped 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene, dibromides are dehydrobrominated to give vinyl monobromides and/or alkynes. Encapsulation of the pyridinium derivative and the guanidine base within separate sol‐gel matrices enables the use of both opposing reagents in one‐pot reactions without their mutual destroying each other. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Horseradish‐root‐modified carbon paste bioelectrode
Authors: Wang Joseph , Lin Meng Shan 
Published: February 2006

AbstractThe incorporation of horseradish roots into the carbon paste matrix results in an effective bioelectrode for sensing hydrogen peroxide. The response is based on the hydrogen peroxidase activity in the tissue. Because of the intimate contact between the biocatalytic and sensing sites, a very fast response is observed, as desired for practical biosensing applications. The behavior of the new bioelectrode is characterized using a flow injection system. Response time (t95%) as low as 11 s has been determined. The limit of detection is 3 × 10−7 M (1 ng), the relative standard deviation is 1.4%, and the response is linear up to 1.2 × 10−4 M. Oxidizable biological compounds do not interfere in the determination of hydrogen peroxide. The response is characterized also with respect to paste composition, flow rate, applied potential, reducing‐agent concentration, injection volume, and other variables. Rapid and sensitive flow‐injection measurements of glucose are illustrated. The tissue‐modified electrode possesses many of the features desirable for use as an amperometric sensor for oxidase substrates.
Amperometric determination of free fatty acids by utilizing five sequential enzyme reactions
Authors: Sode Koji , Tamiya Eiichi , Karube Isao , Kameda Yuko 
Published: February 2006

AbstractAn enyme electrode for determination of free fatty acids was constructed. Five sequential enzyme reactions are involved in this biosensor. Acyl‐CoA synthetase (EC 6.2.1.3) was used as a specific enzyme for free fatty acids, and produced AMP. AMP was then hydrolyzed with four other sequential enzyme reactions involving oxygen consumption. The oxygen consumed was measured by an oxygen electrode. Using this sensor, a good linearity was obtained between current decrease and free fatty acid concentration below 15 mM. The minimum concentration for the determination was 1.77 mM. The assay procedure was completed within 5 min.
Ion exchange voltammetry with electroactive ionomers
Authors: Espenscheid Mark W. , Martin Charles R. 
Published: February 2006

AbstractIon exchange voltammetry is a newly proposed electroanalytical technique that uses an ionomer film coated onto an electrode surface to separate and preconcentrate an analyte ion prior to electrochemical determination at the substrate‐electrode surface. One problem with this proposed technique is that after analysis, the ionomer film is loaded with the analyte ion, and this ion must be removed prior to subsequent analyses. In this paper, we show that this film regeneration step can be accomplished electrochemically using a new type of electroreleasing polymer called an electroactive ionomer. Furthermore, we show that these electroactive ionomer film‐coated electrodes can preconcentrate an analyte cation at the substrate‐electrode surface, thus producing markedly better detection limits than analogous uncoated electrodes.
Comparison of physicochemical speciation procedures with metal toxicity to Chlorella pyrenoidosa. Copper complexation capacity
Authors: Morrison G. M. P. , Florence T. M. 
Published: February 2006

AbstractA comparison was made of methods for measuring the copper complexation capacity of natural and synthetic organic ligands in freshwaters. Complexation capacity values close to theoretical were obtained for nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid, when the following separation or analysis methods were used to detect ionic copper: algal assay (Chlorella pyrenoidosa), an aluminum hydroxide resin, ion‐selective electrode (ISE), and anodic stripping voltammetry (ASV) at the mercury film electrode (MFE) and Nafion‐coated MFEs. No complexation capacity could be measured for Cu‐NTA when the hanging mercury drop electrode (HMDE) was used.Results from the ISE and a resin with adsorbed aluminum hydroxide agreed closely with algal assay for the copper complexation capacity of solutions of fulvic acid and Fe‐humic colloids. Analysis by ASV at the HMDE, MFE, and Nafion‐coated MFE gave values‐of more than an order of magnitude lower than the other techniques because these methods failed to detect the end point for partially labile complexes with a large complexation capacity. On the other hand, the use of differential pulse polarography (DPP) detected these labile copper complexes and yielded results comparable with those for algal assay. Comparable copper complexation capacities for pristine river water samples were obtained by algal assay (2.5–4.1 × 10−6 M Cu) and DPP (2.0–3.7 × 10−6 M Cu), with lower values for the aluminum hydroxide resin (0.8–1.1 × 10−6 M Cu). Because the ASV techniques gave much lower results (0.1–0.4 × 10−6 M Cu), they are clearly unsuitable for the determination of the complexation capacity of freshwaters.
Evaluation of flow‐through photochemical reactors for liquid chromatography with electrochemical detection
Authors: Barisci Jose N. , Wallace Gordon G. 
Published: February 2006

AbstractA method which allows evaluation of the irradiation efficiency of flow‐through photoelectrochemical detector cells for liquid chromatography and flow injection analysis has been developed. The method is based on the determination of the light intensity incident inside of the irradiation cell using the potassium ferrioxalate actinometer. The concentration of the actinometer is measured electrochemically in the flowing system. Typical detector cells used for photoelectrochemical detection were evaluated to demonstrate the method.
Differential pulse adsorptive voltammetric determination of chromium in aluminum
Authors: Sarnaik K. M. , Palrecha M. M. , Dhaneshwar R. G. 
Published: February 2006

AbstractA method is presented for determining the trace amount of chromium in aluminum. Aluminum is dissolved in sodium hydroxide containing hydrogen peroxide. The method is based on the catalytic activity of nitrate ions on the reduction of Cr(III)—triethylenetetraminehexaacetic acid (—TTHA) complex. The sensitivity of this method is further improved by adsorptive preconcentration of Cr(III)—TTHA complex at a hanging mercury drop electrode (HMDE). The adsorbed complex is then reduced at a peak potential of −1.28 V, and the peak height of Cr(III) reduction is measured. The Cr(III) formed at the electrode surface by the reduction of Cr(VI), which is present in the bulk solution, is immediately complexed by TTHA. This method is suitable for the determination of chromium at levels as low as 0.5 μg g−1 (with about 25 mg of sample) and a relative standard deviation of 15%.
The determination of organochlorine compounds by adsorptive stripping voltammetry, part II: 2,4‐dichlorophenoxyacetic acid and 2,4,5‐trichlorophenoxyacetic acid
Authors: Li Chiang , James Bruce D. , Magee Robert J. 
Published: February 2006

AbstractAn indirect procedure for the determination of 2,4‐dichlorophenoxyacetic acid (2,4‐D) and 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T) in mixtures via adsorptive stripping voltammetry is reported. This method takes advantage of the formation of a new pH‐dependent peak, which is obtained when these acids interact with Fe(II). The limits of detection are 1.7 ppb for 2,4‐D and 1.5 ppb for 2,4,5‐T. The relative standard deviations (for 10 determinations) are 6.2 and 5.7%, respectively.
Flow‐reversal injection analysis for improved stripping voltammetry
Authors: Wang Joseph , Huiliang Huang , Kubiak Wladyslaw 
Published: February 2006

AbstractThe use of repeated reversals of the flow direction offers significant improvements in the sensitivity of flow‐injection stripping voltammetric measurements. The multiple passage of the same sample plug over the working electrode addresses the time restriction of conventional flow‐injection stripping measurements. The plating efficiency and the resulting stripping peak currents are greatly enhanced. The flow‐reversal stripping response of a mercury‐coated carbon fiber electrode is evaluated with respect to delay time, number of flow reversals, sample volume, and other variables. The prolonged deposition period obtained with 10 flow oscillations gives a 13‐fold enhancement of the response and a detection limit of 7 × 10−9 M (compared with 9 × 10−8 M for conventional flow‐injection operation). The stripping measurements are supported by amperometric monitoring of the current during the passage of the sample plug.
Thermal stability and regeneration of plastic membrane ion‐selective electrodes
Authors: Shoukry A. F. , Badawy S. S. , Farghali R. 
Published: February 2006

AbstractThe effect of temperature changes on the potential response of hexadecylpyridinium (HDP) and cetyltri‐methylammonium (CTA) plastic‐membrane, cation‐selective electrodes was studied. These electrodes were found to be thermally stable up to 60 and 70°C, respectively. The isothermal temperature coefficients of the electrodes calculated from the standard electrode potentials at different temperatures were 0.00222 and 0.00097 V/°C. A method for regenerating such electrodes was applied successfully in case of the HDP electrodes.
Nafion‐coated carbon fiber electrodes for neurochemical studies in brain tissue
Authors: Capella Peter , Ghasemzadeh Behnam , Mitchell Kim , Adams Ralph N. 
Published: February 2006

AbstractExtensive studies of the characteristics of electrochemically pretreated, Nafion‐coated carbon fibers used for in vivo electrochemistry are summarized. While electrochemical pretreatment provides high sensitivity for the monitoring of catecholamine neurotransmitters, it causes fibers to respond slowly. The ionomer film, which confers selectivity, adds relatively little to the electrode time constant. In terms of sensitivity and time constant changes, serious interactions occur during the course of the in vivo experiments while the electrodes are exposed to brain tissue. Fortunately, selectivity characteristics do not change during in vivo experiments. Postcalibration procedures and other measurement techniques that provide reliable experimental measurements are discussed.
Determination of microscopic electrode kinetics with electrogenerated chemiluminescence imaging
Authors: Pharr Christine M. , Engstrom Royce C. , Klancke James , Unzelman Patty L. 
Published: February 2006

AbstractLight produced by the electrogenerated chemiluminescence reaction of luminol in alkaline peroxide was monitored with a sensitive imaging system. The light images were taken to represent the level of microscopically local activity on the electrode surface with a spatial resolution in the submicrometer domain. The temporal resolving capabilities of the imaging system permitted the construction of time‐sequenced images and intensity‐potential profiles, the latter being equivalent to a microscopically local voltammogram. Spatial variation in luminol oxidation kinetics were observed at porphyrin‐coated glassy carbon, carbon paste, and anodized glassy carbon electrodes. Implications for other composites and microelectrodes are discussed.
State‐of‐the‐art microelectrodes for in vivo voltammetry
Authors: Broderick Patricia A. 
Published: February 2006

AbstractA comprehensive view of in vivo electrochemistry (voltammetry) is presented with a detailed evaluation of electrodes and waveforms. Special attention is given to specific kinds of electrode fabrication. The article is presented in an historical format to emphasize both the progression of the electrochemical technology and the inherent stability of the technique. Future prospects relevant to voltammetry are discussed, and 189 references are included.
Analytical and mechanistic aspects of the polarographic reduction of the herbicide pyrazon
Authors: Méndez J. Hernández , Martínez R. Carabias , Gonzalo E. Rodríguez 
Published: February 2006

AbstractThis article describes a study of the polarographic reduction of the herbicide pyrazon, which yields two polarographic reduction waves: one in acidic media and the other in alkaline media. Coulometric data indicate the exchange of two electrons per molecule, while infrared spectroscopic data reveal that the reduction process involves the azomethine (>CN) rather than the carbonyl group or the NN bond. A mechanism for the electrode reaction is postulated, and a pulse polarographic method for the quantitative determination of pyrazon is proposed. The detection limit achieved by differential pulse polarography in a 1.0 M sulfuric medium is 7 × 10−8 M (0.015 ppm).
A split‐disk, dual‐electrode amperometric cell and its application to the detection of biogenic amines with galvanostatic activation of the glassy carbon working electrodes
Authors: Mattusch Jürgen , Werner Gerhard , Štulík Karel , Pacáková Věra 
Published: February 2006

AbstractA split‐disk, dual‐electrode amperometric cell was constructed and tested using biogenic amines as the model analytes. Advantages of the cell include a small working volume (less than 1.8 μL), favorable hydrodynamic conditions, and the fact that the system can be used in parallel‐adjacent and series arrangements with the same geometry. The collection efficiency on the downstream electrode in the series arrangement is high (around 38% for reversible electrode reactions) and is very close to the theoretical value. The differences in the collection efficiencies for electrode reactions with different degrees of reversibility can improve the selectivity of measurement and assist identification of the substances. Selectivity is greatly improved in the parallel‐adjacent arrangement where one electrode is activated by galvanostatic pretreatment while the other is only mechanically polished.
Electrochemical Detection of Abasic Site‐Containing DNA
Authors: Dolinnaya Nina G. , Jan Mohammad Rasul , Kawde Abdel‐Nasser , Oretskaya Tatiana S. , Tashlitsky Vadim N. , Wang Joseph 
Published: February 2006

AbstractA simple and rapid approach for detecting apurinic (AP) sites in DNA, based on direct stripping chronopotentiometric measurements of the adenine and guanine nucleobases at a graphite electrode is described. Tetrahydrofuranyl residues, lacking a nucleobase moiety, were utilized for designing the AP sites and were incorporated in 19‐mer oligonucleotides. The change of adenine‐to‐guanine response ratio (A/G) in one‐, two‐ or three‐substituted adenosine residues for stable analogs of AP sites was exploited for electrochemical measurements of the adenine loss. The resulting A/G response ratio decreases linearly upon increasing the number of AP sites in the oligonucleotides; the values of A/G electrochemical signals were slightly enhanced when compared to the actual purine content. HPLC analysis of the released nucleobases confirmed that the sulfuric acid‐induced oligonucleotide cleavage provides complete apurination and dissolution of the released nucleobases in aqueous solution. Additional experiments with mixtures of free nucleobases and purine nucleosides reveal that the larger A/G ratio observed in the electrochemical analysis of AP‐site‐containing oligomers is attributed to the influence of the acid and/or thermal decomposition products (particularly the sugar fragments). This study represents the first step in developing a simple and direct electrochemical assay of AP sites in single‐stranded DNA.