bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chiral capillary electrophoresis applied to the determination of phenylglycidol enantiomers obtained from cinnamyl alcohol by asymmetric epoxidation using new titanium(IV) alkoxide compounds as catalysts
Authors: Morante‐Zarcero Sonia , Crego Antonio L. , Sierra Isabel , Fajardo Mariano , Marina M. Luisa 
Published: August 2004

AbstractA capillary electrophoresis method for the simultaneous determination of phenylglycidol enantiomers in the presence of an excess of cinnamyl alcohol was developed. The effects of the nature, pH and concentration of the buffer, the nature and concentration of chiral selector, the addition of methanol or acetonitrile, and the capillary temperature on the chiral resolution of phenylglycidol enantiomers were studied. Separations were achieved using 20 mM succinylated β‐cyclodextrin dissolved in a 10 mM borate buffer (pH 10.0). Chiral resolution for the phenylglycidol enantiomers in the optimized electrophoretic conditions was higher than 2.0 with an analysis time less than 7 min. The method developed was validated in terms of selectivity, linearity, precision (instrumental repeatability, method repeatability, intermediate precision), the limits of detection and quantitation, and accuracy. Limits of detection of 6.5 mg/L and 8.3 mg/L for (2S,3S)‐(−)‐3‐phenylglycidol ((S,S)‐PG) and (2R,3R)‐(+)‐3‐phenylglycidol ((R,R)‐PG), respectively, were obtained. The method was applied to study the asymmetric epoxidation of cinnamyl alcohol with titanium(IV) alkoxide compounds as catalysts in order to evaluate their catalytic activity and stereoselectivity of the epoxidation processes.
Evaluation of chiral purity for a substituted imidazole p38 MAP kinase inhibitor and its intermediates using a single chiral capillary electrophoresis method
Authors: Zhou Lili , Thompson Richard , Ellison Dean , Wyvratt Jean M. 
Published: August 2004

AbstractThe chiral separation of a substituted imidazole p38 MAP kinase inhibitor and its intermediates was investigated using capillary electrophoresis (CE) with various sulfated cyclodextrins. After initial screens, a single CE chiral method with a randomly sulfated β‐CD was selected for the evaluation of chiral purity for all three compounds. Operational parameters, such as the concentration of the chiral selectors, background electrolyte (or mobile phase) pH, organic modifiers, and temperature were varied in order to achieve an optimized method. The optimal method was validated in terms of linearity, sensitivity, precision, ruggedness, and specificity.
Enantiomeric separation of basic compounds using heptakis(2,3‐di‐O‐methyl‐6‐O‐sulfo)‐β‐cyclodextrin in combination with potassium camphorsulfonate in nonaqueous capillary electrophoresis: Optimization by means of an experimental design
Authors: Servais Anne‐Catherine , Fillet Marianne , Chiap Patrice , Dewé Walthère , Hubert Philippe , Crommen Jacques 
Published: August 2004

AbstractThe enantiomeric separation of a series of basic pharmaceuticals (β‐blockers, local anesthetics, sympathomimetics) has been investigated in nonaqueous capillary electrophoresis (NACE) systems using heptakis(2,3‐di‐O‐methyl‐6‐O‐sulfo)‐β‐cyclodextrin (HDMS‐β‐CD) in combination with potassium camphorsulfonate (camphorSO3−). For this purpose, a face‐centered central composite design with 11 experimental points was applied. The effect of the concentrations of HDMS‐β‐CD and camphorSO3− on enantioresolution was statistically evaluated and depended largely on the considered analyte. The presence of camphorSO3− was found to be particularly useful for the enantioseparation of compounds with high affinity for the anionic CD. CamphorSO3− seems to act as a competitor, reducing the affinity for the CD, probably by ion‐pair formation with these analytes. For compounds with lower affinity for HDMS‐β‐CD, the combination of camphorSO3− and the CD appeared to have a favorable effect on enantioresolution only if the optimal CD concentration could be reached. On the other hand, for compounds characterized by a very low affinity for the anionic CD, the association of camphorSO3− and HDMS‐β‐CD is always unfavorable. Finally, experimental conditions were selected by means of the multivariate approach in order to obtain the highest resolution (Rs) value for each studied compound.
Enantioseparation of aromatic amino acids and amino acid esters by capillary electrophoresis with crown ether and prediction of enantiomer migration orders by a three‐dimensional quantitative structure‐property relationship/comparative field analysis model
Authors: Park Hyun‐Ju , Choi Youngmie , Lee Wonjae , Kim Kyoung‐Rae 
Published: August 2004

AbstractThe complete enantioseparations of eight aromatic amino acids and four alkyl esters of 2‐phenylglycine were achieved by chiral capillary electrophoresis employing 20 mM Tris‐citric acid background electrolyte (pH 2.50) containing 5.0 mM of (+)‐18‐crown‐6‐tetracarboxylic acid. The relative migration times (RMTs) to that of 6‐aminonicotinic acid were characteristic of each enantiomer with good within‐day precisions (% relative standard deviation (RSD) ≤ 2.0). Quantitative structure‐property relationship (QSPR) modeling based on comparative molecular field analysis (CoMFA) was performed to investigate the correlation between the molecular field descriptor values of each enantiomer studied as analyte and its RMT. The resulting CoMFA model allowed reliable prediction for the RMT values (q2 = 0.406, r2 = 0.996), thus being expected to become a valuable tool to predict enantiomer migration orders (EMOs) of amino acids and amines whose pure enantiomers are unavailable. The CoMFA steric fields supported the well‐established chiral recognition mechanism based on molecular interaction between chiral selector (+)‐18‐crown‐6‐tetracarboxylic acid and amino acid enantiomers.
Evaluation of balhimycin as a chiral selector for enantioresolution by capillary electrophoresis
Authors: Jiang Zhengjin , Kang Jingwu , Bischoff Daniel , Bister Bojan , Süssmuth Roderich D. , Schurig Volker 
Published: August 2004

AbstractThe glycopeptide antibiotic balhimycin and its haloanalogue bromobalhimycin were evaluated as chiral selectors for enantioresolution by capillary electrophoresis. In order (i) to eliminate the adsorption of the glycopeptide antibiotics on the capillary wall, (ii) to shorten the separation time and (iii) to improve the detection sensitivity, a combined approach of the dynamic surface coating technique, the co‐electroosmotic flow electrophoresis technique and the partial filling technique was employed for the enantioresolution of 16 acidic racemates. The effect of experimental parameters (plug length of the partial filling solution containing the chiral selector, selector concentration and buffer pH) on enantiorecognition was investigated. Furthermore, the enantiorecognition ability imparted by balhimycin, bromobalhimycin and vancomycin were compared. For most tested compounds, the highest enantiorecognition was obtained with balhimycin as chiral selector. Only in the case of the enantioresolution of tiaprofenic acid, vancomycin showed a superior enantiorecognition.
Enantioseparations of hydrobenzoin and structurally related compounds in capillary zone electrophoresis using heptakis(2,3‐dihydroxy‐6‐O‐sulfo)‐β‐cyclodextrin as chiral selector and enantiomer migration reversal of hydrobenzoin with a dual cyclodextrin system in the presence of borate complexation
Authors: Lin Ching‐Erh , Lin Sheng‐Li , Fang I‐Ju , Liao Wei‐Ssu , Chen Chia‐Chong 
Published: August 2004

AbstractWe investigated the enantioseparations of racemic hydrobenzoin, together with benzoin and benzoin methyl ether, in capillary electrophoresis (CE) using the single‐isomer heptakis(2,3‐dihydroxy‐6‐O‐sulfo)‐β‐cyclodextrin (SI‐S‐β‐CD) as a chiral selector in the presence and absence of borate complexation and enantiomer migration reversal of hydrobenzoin with a dual CD system consisting of SI‐S‐β‐CD and β‐CD in the presence of borate complexation at pH 9.0 in a borate buffer. The enantioselectivity of hydrobenzoin increased remarkably with increasing SI‐S‐β‐CD concentration and the enantioseparation depended on CD complexation between hydrobenzoin‐borate and SI‐S‐β‐CD. The (S,S)‐enantiomer of hydrobenzoin‐borate complexes interacted more strongly than the (R,R)‐enantiomer with SI‐S‐β‐CD. The enantiomers of hydrobenzoin could be baseline‐resolved in the presence of SI‐S‐β‐CD at a concentration as low as 0.1% w/v, whereas the three test analytes were simultaneously enantioseparated with addition of 0.3% w/v SI‐S‐β‐CD or at concentrations >2.0% w/v in a borate buffer and 0.5% w/v in a phosphate background electrolyte at pH 9.0. Compared with the results obtained previously using randomly sulfated β‐CD (MI‐S‐β‐CD) in a borate buffer, enantioseparation of these three benzoin compounds is more advantageously aided by SI‐S‐β‐CD as the chiral selector. The enantioselectivity of hydrobenzoin depended greatly on the degree of substitution of sulfated β‐CD. Moreover, binding constants of the enantiomers of benzoin compounds to SI‐S‐β‐CD and those of hydrobenzoin‐borate complexes to SI‐S‐β‐CD were evaluated for a better understanding of the role of CD complexation in the enantioseparation and chiral recognition. Enantiomer migration reversal of hydrobenzoin could be observed by varying the concentration of β‐CD, while keeping SI‐S‐β‐CD at a relatively low concentration. SI‐S‐β‐CD and β‐CD showed the same chiral recognition pattern but they exhibited opposite effects on the mobility of the enantiomers.
Comparative study on the chiral separation of phenyl alcohols by capillary electrophoresis and liquid chromatography
Authors: Zhang Yu‐Ping , Lee Kwang‐Pill , Kim Sang‐Ho , Choi Seong‐Ho , Gopalan Anantha I. , Yuan Zhuo‐Bin 
Published: August 2004

AbstractStructurally related phenyl alcohols were separated by capillary electrophoresis and liquid chromatography. A statistical experimental design was used in order to optimize the main electrophoretic parameters such as pH, concentration of selector and separation voltage in capillary electrophoresis (CE). Response surfaces were derived using the mathematical model and used for a selection of the optimal experimental conditions. Concentration of the chiral selector, the distance between the aromatic group and asymmetric center of the analytes, were identified as the factors influencing the complexation, selectivity and resolution. Experiments were also performed by high‐performance liquid chromatography (HPLC) and the results of CE and HPLC were compared.
Effects of partial/asymmetrical filling of micelles and chiral selectors on capillary electrophoresis enantiomeric separation: Generation of a gradient
Authors: Tesařová Eva , Ševčík Juraj , Gaš Bohuslav , Armstrong Daniel W. 
Published: August 2004

AbstractThe effect of several experimental parameters on enantiomeric separations in micellar capillary electrophoresis (MCE) was studied. A model separation system was tested. It was composed of an acidic phosphate buffer with sodium dodecyl sulfate (SDS) and hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) as the chiral selector. A substituted angelicin was used as a chiral analyte. Changes in the concentration of SDS micelles/SDS monomers in the presence of HP‐β‐CD and their impact on the enantioselective separation were investigated. Variation of the composition of electrolytes in the individual compartments of the separation system (inlet vial, capillary, and outlet vial) affected both the migration times and the resolution of the enantiomers. Current vs. time dependencies also were monitored during the separations. A mathematical model of electromigration in micellar systems with chiral selector present was proposed and a computer simulation was used to explain the observed phenomena and to confirm the generation of a CD/SDS‐micelle concentration gradient under certain experimental conditions. This is the reported first attempt of a computer simulation of the complex, dynamic chiral environment of the CD‐SDS‐MCE system.
Influence of methanol on the enantioresolution of antihistamines with carboxymethyl‐β‐cyclodextrin in capillary electrophoresis
Authors: Van Eeckhaut Ann , Detaevernier Marc Robert , Crommen Jacques , Michotte Yvette 
Published: August 2004

AbstractAccording to the model of Wren and Rowe, the separation between two enantiomers in capillary electrophoresis (CE) decreases if an organic modifier is added to the run buffer containing a neutral cyclodextrin (CD) in a concentration below its optimal value in a solvent‐free system. In previous work, however, it was observed that the addition of methanol to the background electrolyte (BGE) containing not charged carboxymethyl‐β‐CD in a concentration below its optimal value, increased the enantioresolution of dimetindene maleate. The enantioresolution decreased when other organic modifiers (ethanol, isopropanol or acetonitrile) were added and/or when other neutral (β‐CD, hydroxypropyl‐β‐CD) or chargeable (carboxyethyl‐β‐ and succinyl‐β‐CD) CDs were used. In this CE study further attempts are made to elucidate the observed phenomena through investigating other basic drugs. The effect of organic modifier and CD concentration on the enantioseparation was studied by means of central composite designs. It is shown that obtaining this increase in enantioresolution depends upon the type of CD, the type of organic modifier, and the structure of the analytes. It was also observed that small differences in the structure of the analytes or the CD could have an influence on the enantioresolution. The addition of methanol also resulted in different effects on the resolution of closely related analytes.
Development and validation of a capillary electrophoresis method for the enantiomeric purity determination of SLV307, a basic potential antipsychotic compound
Authors: Muijselaar Pim G. , Lammers Norbert G. F. M. , Gerding Thijs K. 
Published: August 2004

AbstractA capillary electrophoresis method for the enantiomeric purity determination of SLV307, a basic potential antipsychotic compound, has been developed and validated. It is shown that the presence of the eutomer in the sample solution may have a significant effect on the peak shape of the distomer, due to electrodispersion. The method is shown to give good performance with respect to the validation parameters specificity, linearity, accuracy, precision, determination limits, stability of solutions, and robustness of extraction.
A screening strategy for the development of enantiomeric separation methods in capillary electrophoresis
Authors: Jimidar M. Ilias , Van Ael Willy , Van Nyen Patrick , Peeters Margot , Redlich Dirk , De Smet Maurits 
Published: August 2004

AbstractMethod development of enantiomeric separations in capillary electrophoresis (CE) is a time‐consuming task, since finding the appropriate chiral selector is usually a “trial and error” process. It is impossible to predict the selectivity of a selector towards a certain enantiomer. Therefore, the affinity of all selectors has to be examined one at a time. In order to speed up this process, a strategy is proposed based on simple experimental design methodology. The approach includes first a screening in function of the pH to determine the optimal migration conditions followed by a selection of the right chiral selector by means of Taguchi designs. In the approach several variables, such as the type and concentration of cyclodextrin, the concentration of buffer electrolyte, and the percentage of organic modifier, are varied simultaneously to find initial separation conditions rapidly. The resulting initial separation conditions can be optimized in further steps to be more reproducible. We discuss the results of the approach when applied on a number of selected compounds that are recently in development at Johnson & Johnson – Pharmaceutical Research and Development. Parameters, such as quality of the separation and analysis time, are evaluated to determine initial separation conditions for each compound.
Maximum ozone concentration forecasting by functional non‐parametric approaches
Authors: Aneiros‐Pérez Germán , Cardot Hervé , Estévez‐Pérez Graciela , Vieu Philippe 
Published: August 2004

AbstractPrediction of maximum ozone concentration is of great importance, especially to alert the population and to allow the authorities to take preventive measures soon enough. Ozone concentration and meteoro‐logical variables are now observed each hour or every 10 min so that we nearly get continuous observations along time, i.e. functions, as covariates. Much work has been done in the statistical community to propose effective models for predicting ozone concentration one day ahead, but there has been much less effort to study methods that take the functional nature of these data into account. We propose here two non‐linear models based on kernel estimators that handle the functional characteristics of the data by means of a measure of proximity between observed functions. In addition, we use additive ideas to take exogeneous variables into account without being too sensitive to dimensionality effects.Such procedures are called multivariate functional non‐parametric approaches, since our models/estimates are non‐parametric (because of the non‐linear structure linking the explanatory and the response variables), functional (because the variables are curves) and multi‐dimensional (because we can have many functional explanatory variables).These models are used to forecast maximum ozone concentration in Toulouse (France). We compare them to more classical techniques and the results are promising. Copyright © 2004 John Wiley & Sons, Ltd.
A multiblock operator‐splitting algorithm for unsteady flows at all speeds in complex geometries
Authors: Thakur Siddharth , Wright Jeffrey 
Published: August 2004

AbstractThis paper describes a non‐iterative operator‐splitting algorithm for computing all‐speed flows in complex geometries. A pressure‐based algorithm is adopted as the base, in which pressure, instead of density, is a primary variable, thus allowing for a unified formulation for all Mach numbers. The focus is on adapting the method for (a) flows at all speeds, and (b) multiblock, non‐orthogonal, body‐fitted grids for very complex geometries. Key features of the formulation include special treatment of mass fluxes at control volume interfaces to avoid pressure–velocity decoupling for incompressible (low Mach number limit) flows and to provide robust pressure–velocity–density coupling for compressible (high‐speed) flows. The method is shown to be robust for all Mach number regimes for both steady and unsteady flows; it is found to be stable for CFL numbers of order ten, allowing large time steps to be taken for steady flows. Enhancements to the method which allow for stable solutions to be obtained on non‐orthogonal grids are also discussed. The method is found to be very reliable even in complex engineering applications such as unsteady rotor–stator interactions in turbulent, all‐speed turbomachinery flows. Copyright © 2004 John Wiley & Sons, Ltd.
Spontaneous regression of lung metastasis in the absence of tumor necrosis factor receptor p55
Authors: Tomita Yoshiharu , Yang Xiaoqin , Ishida Yuko , Nemoto‐Sasaki Yoko , Kondo Toshikazu , Oda Makoto , Watanabe Go , Chaldakov George N. , Fujii Chifumi , Mukaida Naofumi 
Published: August 2004

AbstractIn order to clarify the roles of tumor necrosis factor (TNF)‐α in lung metastasis, we injected Renca cells intravenously into TNF receptor p55‐deficient (TNF‐Rp55 KO) and wild‐type (WT) mice. Microscopic and macroscopic metastasis foci appeared in lungs at 7 and 14 days after the tumor injection, respectively. Moreover, metastasis foci expanded at similar rates in both WT and TNF‐Rp55 KO mice until 21 days, and lungs were occupied with metastasis foci. However, later than 21 days after the injection, metastasis foci spontaneously regressed in TNF‐Rp55 KO mice, whereas WT mice exhibited a progressive growth of metastasis foci. Moreover, metastasis foci remained reduced sizes in TNF‐Rp55 KO mice even at 26 days, when all WT mice died with lungs filled with metastasis foci. Later than 21 days after the tumor injection, the number of apoptotic tumor cells was increased in TNF‐Rp55 KO mice. In contrast, neovascularization was less evident in TNF‐Rp55 KO than WT mice, with depressed hepatocyte growth factor (HGF) gene in TNF‐Rp55 KO mice at 21 days after the tumor injection. Thus, TNF‐Rp55‐mediated signals can maintain tumor neovascularization at least partly by inducing HGF expression, and eventually support lung metastasis process. © 2004 Wiley‐Liss, Inc.
MAZ51, an indolinone that inhibits endothelial cell and tumor cell growth in vitro, suppresses tumor growth in vivo
Authors: Kirkin Vladimir , Thiele Wilko , Baumann Petra , Mazitschek Ralph , Rohde Katrin , Fellbrich Guido , Weich Herbert , Waltenberger Johannes , Giannis Athanassios , Sleeman Jonathan P. 
Published: August 2004

AbstractWe have recently described MAZ51, an indolinone that blocks the ligand‐induced autophosphorylation of VEGFR‐3, a receptor tyrosine kinase that plays a central role in the regulation of lymphangiogenesis. Here we show that MAZ51 is able to block the proliferation of VEGFR‐3‐expressing human endothelial cells and is less potently able to induce their apoptosis. MAZ51 also inhibits the proliferation and induces the apoptosis of a variety of non‐VEGFR‐3‐expressing tumor cell lines. These data suggest that MAZ51 blocks the activity of tyrosine kinases in addition to VEGFR‐3. In vivo, MAZ51 significantly inhibits the growth of rat mammary carcinomas. These data establish MAZ51 as a compound with antitumor properties that inhibits tumor growth directly and also indirectly by interfering with tumor‐host interactions. © 2004 Wiley‐Liss, Inc.
Electrolytic deposition of calcium etidronate drug coating on titanium substrate
Authors: Duan Ke , Fan Yuwei , Wang Rizhi 
Published: August 2004

AbstractWear debris‐induced osteolysis is the major cause of aseptic loosening and failure of hip implants. One of the promising therapeutic interventions to improve the longevity of hip implants is to administrate bisphosphonate drug to inhibit osteoclastic bone resorption. This study aimed at developing new techniques of directly combining bisphosphonate with implants to achieve local delivery and controlled release of the drug. Instead of using soluble sodium salt, we proposed to apply sparingly soluble calcium salt of bisphosphonate as a potential long‐term antiosteolysis coating on hip implants. Calcium salt of etidronate, a member of the bisphosphonate family of potent osteoclast inhibitors, was used in this pilot study. By adopting the electrolytic deposition (ELD) technique, which was developed for ceramic coatings including calcium phosphates, we demonstrated that a thin layer of calcium bisphosphonate could be deposited onto titanium surface. The drug coating is amorphous as characterized with X‐ray diffraction, and has globular morphology under the scanning electron microscope. Electrospray‐ionization mass‐spectrometry (ESI‐MS) and Fourier‐transformed infrared spectroscopy confirmed that the molecular structure of the etidronate (m/z 205, H3L−, the single dissociated form of parent etidronic acid, denoted as H4L) was preserved after the ELD process. In vitro release into a “physiological” buffer solution confirmed that the etidronate concentration was limited by its low solubility. The etidronate concentration was 8 × 10−5 M at day 1 and kept relatively stable at ∼6 × 10−5 M from day 2 to day 8. The deposition mechanisms of the drug coating and its potential efficacy as an antiosteolytic release source were discussed. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 72B: 43–51, 2005