bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chromatographic analysis of toxic phosphylated oximes (POX): a brief overview
Authors: Becker Christian , Worek Franz , John Harald 
Published: September 2010

AbstractPoisoning with organophosphorus compounds (OP), e.g. pesticides and nerve agents, causes inhibition of acetylcholinesterase (AChE) by phosphylation of the active site serine residue. Consequently, accumulation of stimulating acetylcholine in the synaptic cleft induces cholinergic crisis which ultimately may lead to death. For standard causal therapy, enzyme reactivators are administered representing oxime derivatives of quarternary pyridinium compounds, e.g. pralidoxime (2‐PAM), obidoxime and HI 6. The mechanism of action includes removal of the phosphyl moiety by a nucleophilic attack of the oximate molecule substituting the enzyme and forming a phosphylated oxime (POX). POX is produced in stoichiometric amounts of reactivated enzyme and exhibits a significantly enhanced toxicity (inhibition rate constant) when compared to the parent OP. However, stability of POX under physiological conditions appears to be highly limited. Nevertheless, the presence of POX reveals a potential critical issue for both therapeutic efficacyin vivoand pharmacokinetic and pharmacodynamic (PK‐PD) modelling based on cholinesterase activity data. Detailed characterization represents an important need for elaboration of the entire oxime pharmacology.Nevertheless, reports on POX toxicity and analysis are quite rare and may therefore be indicative of the challenge of POX analysis. This review provides a concise overview of chromatographic approaches applied to POX separation. Chromatography represents the key technology for POX purification and quantification in kineticin vitrostudies using buffers and biological fluids. Applications based on reversed‐phase chromatography (RPC), ion pair chromatography (IPC) and an affinity approach as well as thin layer chromatography (TLC) are discussed and novel applications and data are presented. Copyright © 2010 John Wiley & Sons, Ltd.
Spred2 expression during mouse development
Authors: Tuduce Ioana Laura , Schuh Kai , Bundschu Karin 
Published: September 2010

AbstractSPREDs (Sprouty‐related proteins with Ena/Vasodilator‐stimulated phosphoprotein homology‐1 domain) are known membrane‐associated modulators of receptor tyrosine kinases by inhibiting the mitogen‐activated protein kinase (MAPK) signaling pathway. Although Spred2−/− mice exhibit dwarfism and increase of early haematopoiesis, the precise expression and role of SPRED2 in mouse development remains unknown. Here, we demonstrate a detailed Spred2 expression pattern during mouse development using X‐Gal stainings from samples of a gene‐trapped Spred2 mouse line. In early stages, Spred2 was highly expressed in ectodermal and mesodermal tissues, and later on in developing neural tissue, heart, lung, intestine, urogenital tract, and limbs. Strikingly, we observed that Spred2 was mainly expressed at leading edges of further outgrowing structures and in folds of newly forming grooves. Therefore, SPRED2 is likely involved in the regulation of dynamic developmental processes. These new data provide valuable information for further studies regarding the still enigmatic physiological SPRED functions during mouse development. Developmental Dynamics 239:3072–3085, 2010. © 2010 Wiley‐Liss, Inc.
A new vector frequency modulation method for power conversion circuits
Authors: Takano Akio 
Published: September 2010

AbstractThis paper presents an effective PWM method for power conversion circuits. The proposed method is called Vector Frequency Modulation (VFM) in this paper. VFM is different from conventional PWM methods. Although VFM is based on the concept of the space voltage vector, all necessary calculations of the periods of the voltage vectors can be performed without using traditional equations. The voltage vectors are classified into two groups, zero vectors and nonzero vectors. Instead of the complicated equations, a very simple algorithm is employed in VFM. One vector period is fixed and the zero vectors are distributed among the nonzero vectors in the ratio determined by the command voltage or frequency. The action of VFM is performed in software, and no modulation‐wave oscillators, comparators, and up‐down counters are needed.First, a reversible chopper is modulated by VFM and a 2‐kW DC motor is driven by the chopper. The motor speed is regulated by modern control theory. Next, a three‐phase inverter is modulated by VFM and a 2.2‐kW induction motor is driven by the inverter. Experimental results are presented to demonstrate that VFM is useful for power conversion circuits. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 59–68, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.20982
A multibranch exchange method for distribution loss minimization
Authors: Murai Masahiko , Kosaka Yoko , Kobayashi Takenori , Kaneshige Yumiko 
Published: September 2010

AbstractThis paper presents a multibranch exchange method for reconfiguration of distribution systems to reduce their line losses. In this method several switches are closed and opened simultaneously in each branch exchange operation to expand the search neighborhood. The switches to be closed are selected as the intermediate systems will be meshed configuration. Sequential branch opening method can be applied to open the switches to obtain the radial configuration efficiently. Test examples show the effectiveness of the proposed method in the case of double branch exchange. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 40–48, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21015
Selective Deposition of Gold Nanoparticles on or Inside Carbon Nanotubes and Their Catalytic Activity for Preferential Oxidation of CO
Authors: Castillejos Eva , Chico Rubén , Bacsa Revathi , Coco Silverio , Espinet Pablo , Pérez‐Cadenas María , Guerrero‐Ruiz Antonio , Rodríguez‐Ramos Inmaculada , Serp Philippe 
Published: September 2010

AbstractGold nanoparticles have been deposited on three kinds of carbon nanotubes (CNTs), including nitrogen‐doped CNTs, by three different methods, namely, impregnation, organometallic decomposition, and deposition–precipitation. The choice of the gold precursor, the support, and the preparation procedure is critical for the control of the size and location (on or inside the nanotubes) of the gold nanoparticles. These catalysts were tested for the selective oxidation of CO in a hydrogen‐rich atmosphere. We have shown that the use of nitrogen‐doped CNTs as a support permits one to reach much higher activity and selectivity at low temperaturethan with the other CNT supports. This catalyst also shows a good stability under reaction conditions without detectable sintering.
Ruthenium Complexes Bearing N–H Acidic Pyrazole Ligands
Authors: Jozak Thomas , Zabel Dirk , Schubert Anett , Sun Yu , Thiel Werner R. 
Published: September 2010

AbstractChelate ligands containing at least one pyrazole group were treated with RuCl2(PPh3)3, RuHCl(CO)(PPh3)3 and RuH2(CO)(PPh3)3 to form ruthenium complexes bearing protic N–H groups in close proximity to the catalytically active ruthenium centre. In the case of the hydridoruthenium complex RuHCl(CO)(PPh3)3 the resulting complexes also contain abasic hydrido ligand. The combination of acidic and basic hydrogen species in one molecule and the arising two‐site reactivity was thoroughly investigated spectroscopically and by DFT calculations. Catalytic tests on the hydrogenation and transfer hydrogenation of acetophenone showed a general activity of these systems.
p‐(Benzyloxy)calix[8]arene Synthesis Revisited: p‐(Benzyloxy)calix[4]‐, p‐(Benzyloxy)calix[5]‐, p‐(Benzyloxy)calix[7]‐, and p‐(Benzyloxy)bis(homooxa)calix[4]arenes
Authors: Huc Vincent , Npetgat Eloïne , Guérineau Vincent , Bourcier Sophie , Dos Santos Amandine , Guillot Régis , Baltaze Jean‐Pierre , Martini Cyril 
Published: September 2010

AbstractA detailed investigation of the 4‐(benzyloxy)phenol/formaldehyde reaction shows that along with the previously described p‐(benzyloxy)calix[8]arene and p‐(benzyloxy)calix[6]arene, others calixarenes are observed and easily recovered on a preparative scale. All these new calixarenes are opening interesting perspectives for the synthesis of new supramolecular hosts, easily functionalized at the para position under very mild conditions and/or exhibiting a deep hydrophobic pocket.
A Concise Catalytic Route to the Marine Sesquiterpenoids (–)‐Clavukerin A and (–)‐Isoclavukerin A
Authors: Knüppel Stephan , Rogachev Victor O. , Metz Peter 
Published: September 2010

AbstractUsing a combined organocatalytic/metal‐catalyzed strategy, the enantiopure title hydroazulenes were prepared in only four steps from (S)‐ and (R)‐citronellal, respectively. A catalyst‐controlled diastereoselective Michael addition of these aldehydes to methyl vinyl ketone followed by chemoselective dibromoolefination and one‐pot Wittig olefination/alkyne formation afforded the key dienynes that underwent regioselective domino metathesis to yield the target natural products.
NaDDBS as a dispersion agent for multiwalled carbon nanotubes in capillary EKC separation of nucleotides
Authors: Hsieh Yu‐Fang , Huang Bao‐Yu , Liu Ching‐Piao , Liu Chuen‐Ying 
Published: September 2010

AbstractA novel pseudostationary phase (PSP) of multiwalled carbon nanotubes (MWCNTs) dispersed with sodium dodecylbenzenesulfonate (NaDDBS) was used for the EKC separation of nucleotides. NaDDBS has a long hydrophobic chain and a benzylsulfonate group. It suspends more MWCNTs (about 100‐fold) than SDS, and the π–π interaction between the benzene ring of NaDDBS and MWCNTs prolongs the slurry suspension time. Using NaDDBS as a surfactant can reduce the required amount of MWCNTs and decrease the baseline noise. To produce a stable suspension, the optimum ratio (w/w) of MWCNTs to NaDDBS was investigated with turbidimetry. In this context, several parameters affecting EKC separation were studied, including buffer pH, composition, concentration, and the organic modifier. Use of NaDDBS (8 mg/L)/MWCNTs (0.8 mg/L) as the PSP in a phosphate buffer (30 mM, pH 8) yielded complete resolution of seven geometric isomers of a nucleoside monophosphate. In stacking mode, with 10% MeOH in the sample plug, the mixture of nucleoside mono‐, di‐, and tri‐phosphates was satisfactorily separated in phosphate buffer (50 mM, pH 9). The results indicate that nucleotides with bases containing more electron‐withdrawing groups interact more strongly with MWCNTs. The system has been used to separate oligonucleotides, and to analyze nucleotides in a complex matrix sample.
On‐line drug metabolites generation and their subsequent target analysis by capillary zone electrophoresis with UV‐absorption detection
Authors: Zeisbergerová Marta , Řemínek Roman , Mádr Aleš , Glatz Zdeněk , Hoogmartens Jos , Van Schepdael Ann 
Published: September 2010

AbstractThis study presents the in‐capillary enzymatic biotransformation of dextromethorphan, an antitusive drug and opioid receptor antagonist, and subsequent electrophoretic separation of its products. The study includes the optimization of separation parameters to fulfill the requirements of an online microreaction. The analyses were performed in a bare fused‐silica capillary using 100 mM sodium tetraborate (pH 10.0) mixed with linear polyacrylamide (20%, v/v) and 2‐propanol (10%, v/v). This BGE was suitable for monitoring both off‐line and in‐capillary incubations. The partial filling technique enabled the enzymatic reaction to be carried out in its optimal environment (20 mM sodium phosphate, pH 7.4). Finally, in‐capillary microreaction in the presence of cytochrome P450 3A4 gave satisfactory outcomes.
Assay of vitamin B in urine by capillary electrochromatography with methacrylate‐based monolithic column
Authors: Wei Xiaoyi , Qi Li , Qiao Juan , Yao Chunhe , Wang Fuyi , Chen Yi 
Published: September 2010

AbstractA novel and simple method for the separation of major vitamin B analytes, such as thiamine, riboflavin, nicotinamide, vitamin B4, pyridoxine, has been developed by CEC using the monolithic column. It has been found that the baseline separation of the five analytes could be achieved with 5.0 mM phosphate buffer at pH 4.0. Compared with the open‐tubular capillary and the bared capillary columns, the poly(butylmethacrylate‐co‐ethylene glycol dimethacrylate) monolithic capillary could exhibit the best resolution in the analysis. Then the method was validated and the linear calibration ranges were obtained with correlation coefficients more than 0.997. The precision and the recovery were also investigated and showed a good result. Furthermore, the proposed method was successfully applied to assay the concentration of vitamin B analytes and the metabolic situation in human urine samples.
Analysis of 5‐methyltetrahydrofolate in human blood, serum and urine by on‐line coupling of capillary isotachophoresis and zone electrophoresis
Authors: Pantůčková Pavla , Křivánková Ludmila 
Published: September 2010

AbstractThe predominant circulating folate coenzyme in plasma/serum, 5‐methyltetrahydrofolate (5‐MTHF) was determined in human blood, serum and urine using a method based on the hyphenation of capillary ITP and zone electrophoresis. Measurements were done with a commercially available instrument for capillary isotachophoresis equipped with a column‐switching system. The choice of electrolytes was limited by the instability of 5‐MTHF and volatility of electrolytes for the potential coupling of the instrumentation with MS detector. To get an insight into the separability of individual sample components in an isotachophoretic analysis, we constructed zone existence diagrams for isotachophoretic electrolyte systems having a leading electrolyte composed of acetate and ammonium of pH 4.5 and 7.0, hydrocarbonate and ammonium, pH 7.8, chloride and ammonium, pH 5.6, and chloride and creatinine, pH 5.0, with hydroxide ion as the terminator. For isotachophoretic preseparation, the non‐volatile leading electrolyte with good buffering capacity composed of 1×10−2 M HCl and 2.5×10−2 M creatinine, pH 5.0, and terminating electrolyte composed of 1×10−2 M MES was selected as the most suitable. The optimum BGE for CZE analysis from the standpoint of analyte stability, separability and volatility for MS coupling was 1×10−2 M acetate with 3.5×10−2 M ammonium, pH 4.5. Using this combination of electrolytes, LODs reached with optical detection at 220 nm were 1.6×10−7 M in human blood, 1.1×10−7 M in human serum and 4.7×10−6 M in human urine. Estimated content of 5‐MTHF in blood and serum samples of women following oral daily administration of 0.8 mg of folic acid was 1.2×10−5 and 5.8×10−6 M, respectively.
CE‐ESI‐MS coupled with dynamic pH junction online concentration for analysis of peptides in human urine samples
Authors: Ye Hongzhi , Xia Shifei , Lin Wei , Yu Lishuang , Xu Xueqin , Zheng Chunsong , Liu Xianxiang , Chen Guonan 
Published: September 2010

AbstractIn this article, an approach has been developed for the analysis of some small peptides with similar pI values by CE‐ESI‐MS based on the online concentration strategy of dynamic pH junction. The factors affected on the separation, detection and online enrichment, such as BGE, injection pressure, sheath flow liquid and separation voltage have been investigated in detail. Under the optimum conditions, i.e. using 0.5 mol/L formic acid (pH 2.15) as the BGE, preparing the sample in 50 mM ammonium acetate solution (pH 7.5), 50 mbar of injection pressure for 300 s, using 7.5 mM of acetic acid in methanol–water (80% v/v) solution as the sheath flow liquid and 20 kV as the separation voltage, four peptides with similar pI values, such as L‐Ala‐L‐Ala (pI=5.57), L‐Leu‐D‐Leu (pI=5.52), Gly‐D‐Phe (pI=5.52) and Gly‐Gly‐L‐Leu (pI=5.52) achieved baseline separation within 18.3 min with detection limits in the range of 0.2–2.0 nmol/L. RSDs of peak migration time and peak area were in the range of 1.45–3.57 and 4.93–6.32%, respectively. This method has been applied to the analysis of the four peptides in the spiked urine sample with satisfactory results.
An expanding negative detection method for the visualization of DNA in polyacrylamide gels by eosin Y
Authors: Zhu Zhong‐Xin , Cong Wei‐Tao , Zhang Peng‐Hui , Ma Wei‐De , Min Liu , He Hong‐Zhang , Choi Jung‐Kap , Jin Li‐Tai , Li Xiao‐Kun 
Published: September 2010

AbstractA sensitive and easy technique has been developed for the negative detection of DNA following PAGE using eosin Y. After electrophoresis, gels are fixed and stained within 40 min to provide a detection limit of 0.1–0.2 ng of single DNA band, which appears as transparent and colorless under the opaque gel matrix background. The sensitivity of the new stain is fourfold better than zinc‐imidazole negative and ethidium bromide stains. Furthermore, the newly developed staining method has been successfully applied to RNA visualization in polyacrylamide gels. In addition, the inclusion of inorganic salts in staining solution was also investigated, which has great effect on the staining efficiency.
An integrated on‐chip sirtuin assay
Authors: Ohla Stefan , Beyreiss Reinhild , Scriba Gerhard K. E. , Fan Yi , Belder Detlev 
Published: September 2010

AbstractA microchip‐based assay to monitor the conversion of peptide substrates by human recombinant sirtuin 1 (hSIRT1) is presented. For this purpose a fused silica microchip consisting of a microfluidic separation structure with an integrated serpentine micromixer has been used. As substrate for the assay, we used a 9‐fluorenylmethoxycarbonyl (Fmoc)‐labeled tetrapeptide derived from the amino acid sequence of p53, a known substrate of hSIRT1. The Fmoc group at the N‐terminus resulting from solid‐phase peptide synthesis enabled deep UV laser‐induced fluorescence detection with excitation at 266 nm. The enzymatic reaction of 0.1 U/μL hSIRT1 was carried out within the serpentine micromixer using a 400 μM solution of the peptide in buffer. In order to reduce protein adsorption, the reaction channel was dynamically coated with hydroxypropylmethyl cellulose. The substrate and the deacetylated product were separated by microchip electrophoresis on the same chip. The approach was successfully utilized to screen various SIRT inhibitors.
Capillary electrophoresis of the proteolytic activity of the stratum corneum obtained by tape stripping
Authors: Papoiu Alexandru D. P. , Yosipovitch Gil , Shihabi Zak 
Published: September 2010

AbstractSerine proteases and some cathepsins are present in the stratum corneum. They are known to play a significant role in the pathophysiological mechanism of several dermatological conditions (e.g.atopic dermatitis) and in the induction of itch. Tape stripping of skin is a simple technique used in the investigation of skin barrier function and in the penetration of topically applied drugs. Herein, we show that CE, under stacking conditions, is a well‐suited technique to measure the proteolytic activity of enzymes in the stratum corneum. Disks of about 6 mm (id) were cut from adhered tapes and submerged directly in a buffer containing the appropriate peptide substrate. After incubation, the split peptides were separated and detected directly by CE at 214 nm in a borate buffer. The esterase activity onN‐benzoyl‐tyrosine ethyl ester and the amidase activity on succinyl‐Ala‐Ala‐Pro‐Phe‐p‐nitroanilide and the splitting of hemoglobin were detected by CE. The esterase activity was the highest when compared to the proteolytic activities. Skin scratching increased the enzymatic activity adhered to the tapes. The CE offered over the traditional end‐point colorimetric methods the ability to measure the low enzymatic activity and the ability to detect the released peptides directly. This technique is simple, non‐invasive, easy to perform and uses non‐expensive substrates. It can be useful in quantifying cathepsins and serine proteases in the skin.
Multi‐walled carbon nanotube composites with polyacrylate prepared for open‐tubular capillary electrochromatography
Authors: Chen Jian‐Lian , Lu Te‐Ling , Lin Yi‐Chen 
Published: September 2010

AbstractA new phase containing immobilized carbon nanotubes (CNTs) was synthesized by in situ polymerization of acid‐treated multi‐walled CNTs using butylmethacrylate (BMA) as the monomer and ethylene dimethacrylate as the crosslinker on a silanized capillary, forming a porous‐layered open‐tubular column for CEC. Incorporation of CNT nanomaterials into a polymer matrix could increase the phase ratio and take advantage of the easy preparation of an OT‐CEC column. The completed BMA‐CNT column was characterized by SEM, ATR‐IR, and EOF measurements, varying the pH and the added volume organic modifier. In the multi‐walled CNTs structure, carboxylate groups were the major ionizable ligands on the phase surface exerting the EOF having electroosmotic mobility, 4.0×104 cm2 V−1 S−1, in the phosphate buffer at pH 2.8 and RSD values (n=5), 3.2, 4.1, and 4.3%, for three replicate capillaries at pH 7.6. Application of the BMA‐CNT column in CEC separations of various samples, including nucleobases, nucleosides, flavonoids, and phenolic acids, proved satisfactory upon optimization of the running buffers. Their optima were found in the borate buffers at pH 9.0/50 mM, pH 9.5/10 mM/50% v/v ACN, and pH 9.5/30 mM/10% v/v methanol, respectively. The separations could also be used to assess the relative contributions of electrophoresis and chromatography to the CEC mechanism by calculating the corresponding velocity and retention factors. Discussions about interactions between the probe solutes and the bonded phase included the π–π interactions, electrostatic repulsion, and hydrogen bonding. Furthermore, a reversed‐phase mode was discovered to be involved in the chromatographic retention.
Statistical evaluation of CZE‐UV and CZE‐ESI‐MS data of intact α‐1‐acid glycoprotein isoforms for their use as potential biomarkers in bladder cancer
Authors: Ongay Sara , Martín‐Álvarez Pedro J. , Neusüß Christian , de Frutos Mercedes 
Published: September 2010

Abstractα‐1‐acid glycoprotein (AGP) is a highly heterogeneous protein that presents a vast number of isoforms (molecules of the protein differing in its peptidic and/or glycosidic moieties). In the last years, several authors have studied the potential use of AGP as a cancer biomarker. These studies focus on the correlation of different features of AGP structure (i.e. fucosylation, antennarity) with cancer or on the total protein blood concentration. In this study, the potential of CZE‐UV and CZE‐ESI‐MS analysis of intact AGP isoforms to study the correlation of this protein with bladder cancer is shown. Samples from 16 individuals (eight healthy, eight bladder cancer) were analyzed and characterized in great detail including data on intact protein isoforms and on released glycans. The analytical data were evaluated employing different statistical techniques (ANOVA; principal component analysis, PCA; linear discriminant analysis; and partial least squares‐discriminant analysis). Statistical differences between the two groups of study were observed. The best results were obtained by linear discriminant analysis of the CZE‐ESI‐MS data for intact AGP isoforms (93.75% of correct classification). Due to MS characterization, it can be observed that differences between the samples are mainly due to higher abundance of AGP isoforms containing tri‐ and tetra‐antennary fucosylated oligosaccharides in cancer patients. The results show the great potential of CE‐MS in combination with advanced data processing for the use of intact protein isoforms as disease biomarkers.