bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separation of basic drug enantiomers by capillary electrophoresis using chicken α1‐acid glycoprotein: Insight into chiral recognition mechanism
Authors: Matsunaga Hisami , Sadakane Yutaka , Haginaka Jun 
Published: July 2003

AbstractRecombinant chicken α1‐acid glycoprotein (α1‐AGP) was prepared by the Escherichia coli expression system and completely deglycosylated α1‐AGP (cd‐α1‐AGP) was obtained by treatments of native α1‐AGP with a mixture of endoglycosidase and N‐glycosidase. The average molecular masses of chicken α1‐AGP, cd‐α1‐AGP and recombinant α1‐AGP were estimated to be about 29 200, 21 700 and 20 700, respectively, by matrix‐assisted laser desorption‐time of flight‐mass spectrometry. We compared the chiral recognition ability of chicken α1‐AGP, cd‐α1‐AGP and recombinant α1‐AGP using them as chiral selectors in capillary electrophoresis. The chicken α1‐AGP showed higher resolution for eperisone, pindolol and tolperisone than cd‐α1‐AGP or recombinant α1‐AGP. Recombinant α1‐AGP still showed chiral recognition for three basic drugs tested. By addition of propranolol as a competitor in the separation solution in CE, no enantioseparations of three basic drugs were observed with chicken α1‐AGP, cd‐α1‐AGP or recombinant α1‐AGP. These results reveal that the protein domain of the chicken α1‐AGP is responsible for the chiral recognition ability, and that the chiral recognition site(s) for basic drugs exists on the protein domain.
Capillary electrochromatographic separation of enantiomers on chemically bonded type of cellulose derivative chiral stationary phases with a positively charged spacer
Authors: Chen Xiaoming , Jin Wenhai , Qin Feng , Liu Yueqi , Zou Hanfa , Guo Baochuan 
Published: July 2003

AbstractPositively charged chiral stationary phases (CSPs) were prepared for capillary electrochromatography (CEC) separation of enantiomers by chemically immobilizing cellulose derivatives onto diethylenetriaminopropylated silica (DEAPS) with tolylene‐2,4‐diisocyanate (TDI) as a spacer reagent. Anodic electroosmotic mobility was observed in both nonaqueous and aqueous mobile phases due to the positively charged amines on the surface of the prepared CSPs. For comparison, the traditionally used 3‐aminopropyl silica (APS) was also adopted as the base material instead of DEAPS to prepare CSP. It was observed that the EOF on the DEAPS‐based CSP was 18%–60% higher than that on the APS‐based CSP under nonaqueous mobile phase conditions. Separation of enantiomers in CEC was performed on the positively charged CSPs with the nonaqueous mobile phases of pure ethanol or mixture of hexane‐alcohol and the aqueous phases of acetonitrile‐water or 95% ethanol. Fast separation of enantiomers was achieved on the newly prepared CSPs.
Enantioseparations of basic and bifunctional pharmaceuticals by capillary electrochromatography using polysaccharide stationary phases
Authors: Mangelings Debby , Hardies Nancy , Maftouh Mohamed , Suteu Christina , Massart D. Luc , Vander Heyden Yvan 
Published: July 2003

AbstractA fast screening strategy was developed in capillary electrochromatography (CEC) for the chiral separation of basic and bifunctional compounds. The screening conditions were determined on polysaccharide chiral stationary phases using 15 pharmaceutical compounds. The content and type of organic modifier, as well as the pH of the mobile phase appeared to have the largest influence on the chiral resolution. It was seen that for acidic compounds, our approach was not suitable. A generic mobile phase for basic and bifunctional compounds was determined. The testing on 20 additional compounds showed that the proposed mobile phase performed well since enantioselectivity was observed for 86% of the investigated compounds. A comparison of CEC and reversed‐phase liquid chromatography (RPLC) results was attempted to demonstrate the potential of the used technique for chiral method development.
Chiral separation of diastereomeric flavanone‐7‐O‐glycosides in citrus by capillary electrophoresis
Authors: Gel‐Moreto Nuria , Streich René , Galensa Rudolf 
Published: July 2003

AbstractThe 2S‐ and 2R‐diastereomers of major flavanone‐7‐O‐glycosides found in sweet orange (Citrus sinensis), mandarine (Citrus deliciosa), grapefruit (Citrus paradisi), lemon (Citrus limon), and sour or bitter orange juice (Citrus aurantium) were separated for the first time by chiral capillary electrophoresis (CE) employing various buffers with combined chiral selectors. Native cyclodextrins (CDs), neutral and charged CD derivatives were examined as chiral additives to the background electrolyte (BGE). Separation efficiency has not proved satisfactory with one single CD as chiral selector in the buffer, a full and simultaneos separation could often be achieved only by using combined buffer with two different CDs. Chiral separation of major flavanones in sweet orange, mandarine and grapefruit juices raised more difficulties than in lemon and sour orange juices as narirutin will not readily build complexes with most CDs. Diastereomeric flavanones of mature and immature grapefruits were compared and some differences were found: naringin showed different diastereomeric ratio and 2S‐prunin appeared only in immature grapefruit. Marmalade was also examined by chiral CE. Its major flavanones corresponded to flavanone pattern of mixed sour and sweet oranges.
Quantitative chiral analysis in capillary electrophoresis from unresolved peaks using derivative electropherograms, experimental design, and artificial neural networks
Authors: Dohnal Vlastimil , Zhang Fang , Li Hua , Havel Josef 
Published: July 2003

AbstractQuantitative capillary electrophoretic analysis of chiral compounds might be difficult or even impossible when baseline separation is not reached. In this work, the use of n‐th derivative of the electropherogram was studied and examined on model and experimental data. The electropherograms should be first smoothed using Savitzky‐Golay method and the quantitative analysis is then possible using either a graphical method or multivariate calibration applying a combination of experimental design (ED) and artificial neural networks (ANNs). The best results were obtained for the first derivative, higher derivatives are not suitable because of noise accumulation. The method was applied to real experimental data to quantify chiral amino acids from unresolved peaks, but it is applicable for quantitative analysis of any other chiral analytes from poorly resolved peaks. Precision of analysis from partially resolved peaks reached was about ± 3.2% relative standard deviation.
Capillary electrophoresis as a probe of enantiospecific interactions between photoactive transition metal complexes and DNA
Authors: Schaeper James P. , Nelsen Lori A. , Shupe M. Alyson , Herbert Brad J. , Kane‐Maguire Noel A. P. , Wheeler John F. 
Published: July 2003

AbstractRecently, we have demonstrated the capacity to separate chiral transition metal (TM) complexes of the type [M(diimine)3]n+ using CE buffers containing chiral tartrate salts. In separate work, several chromium(III)‐tris‐diimine complexes in particular have been shown to bind enantioselectively with calf‐thymus (CT) DNA, and a qualitative assessment of the relative strength and enantiospecificity of this interaction is of significant interest in the characterization of these complexes as potential DNA photocleavage agents. Here, we describe two convenient approaches to investigate such binding behavior using chiral CE. For complexes with lower DNA affinities exhibiting primarily surface binding, DNA itself is used as the chiral resolving agent in the electrophoretic buffer. In this approach, resolution of the TM complexes into their Λ and Δ isomers is achieved with the isomer eluting later exhibiting superior binding affinity toward DNA. For more strongly bound TM complexes containing ligands known to intercalate with DNA, the [Cr(diimine)3]3+ complexes are preincubated with oligonucleotide and subsequently enantiomerically resolved in a dibenzoyl‐L‐tartrate buffer system that facilitates analysis of the unbound TM species only. Differences in isomer binding affinity are distinguished by the relative peak areas of the Λ‐ and Δ‐isomers, and relative binding strengths of different complexes can be inferred from comparison of the total amount of unbound complex at equivalent DNA/TM ratios.
Rapid determination of salbutamol in pharmaceutical preparations by chiral capillary electrophoresis
Authors: Ekiert Ela , García‐Ruiz Carmen , García Maria A. , Marina Maria L. 
Published: July 2003

AbstractA fast and simple method of chiral capillary electrophoresis (CE) has been applied to the analysis of salbutamol in different pharmaceutical preparations. Using of a 25 mM acetate buffer (pH 5.0), containing 13.1 mg/mL carboxymethyl‐β‐cyclodextrin (CM‐β‐CD), an applied voltage of 20 kV and a temperature of 25°C, the enantiomers of salbutamol could be separated in about 2 min. Three different pharmaceutical preparations (two syrups, one oral solution, and two kind of tablets) containing a racemate of salbutamol were injected directly in the CE system, following dilution in dimethyl sulfoxide (DMSO). Appreciable differences in the retention times were observed for salbutamol enantiomers in the different formulations studied, which were attributed to the effect of the matrix components on the electrophoretic mobility. The standard addition method was used for the calibration due to the existence of matrix interferences. Finally, the stability of the enantiomers of salbutamol in the oral solution was studied calculating the enantiomeric ratio values when the solution was injected immediately after being opened in the first case and after being opened and stored in the fridge for two months in the second case.
Capillary electrophoresis evidence for the stereoselective metabolism of itraconazole in man
Authors: Breadmore Michael C. , Thormann Wolfgang 
Published: July 2003

AbstractItraconazole (ITC) is a hydrophobic antimycotic drug with three chiral centers that is used clinically as a stereoisomeric mixture. A chiral capillary electrophoretic method for the separation of ITC stereoisomers and those of its main metabolite hydroxyitraconazole (HITC) was developed to determine the stereoselective nature of the ITC to HITC biotransformation. The method is based on the formation of inclusion complexes of the target analytes with the negatively charged sulfated β‐cyclodextrin in the presence of moderate concentrations of methanol in a low‐pH phosphate buffer. The addition of polyethylene glycol 4000 was found to be critical in obtaining baseline resolution of eight peaks, two from ITC, four from HITC, and two from R051012 (internal standard), in under 20 min. Application of the developed procedure to serum samples from patients being treated with ITC showed clearly the presence of a stereoselective component in the metabolism of this antimycotic drug. This could be shown from in vitro incubations with single enzyme Supersomes™ to be in part due to the stereoselective formation of HITC by the human CYP3A4 enzyme. For one patient, monitoring of the ITC and HITC concentrations and peak ratios over a 103 day period of treatment with ITC showed a strong dependency of the chiral ITC ratio to the concentration of ITC, while the dominant enantiomeric ratio of HITC was largely independent of the total HITC concentration.
Coated microfluidic devices for improved chiral separations in microchip electrophoresis
Authors: Ludwig Martin , Belder Detlev 
Published: July 2003

AbstractChiral separations of fluorescein isothiocyanate‐labeled amines have been performed in poly(vinyl alcohol) (PVA)‐coated microfluidic glass chips. Baseline separation of enantiomers could be realized in coated devices while they could not be resolved in uncoated chips. The electroosmotic flow (EOF) in PVA‐coated channels is suppressed over a wide pH range which leads to a considerable improved reproducibility of migration times in repetitive analysis. Due to the high resolution obtained in such devices, it was possible to reliable determine the enantiomeric purity with high accuracy. One percent of the minor enantiomer could be determined in the presence of large excess of the other enantiomer. As the EOF was suppressed, the anionic compounds were detected at the anode whereas the dominant EOF in uncoated devices resulted in an effective mobility to the cathode. Applying PVA‐coated channels considerable improved precision of migration times was found. The relative standard deviation of migration times was below 1% in PVA‐coated devices. Accordingly, excessive rinsing or etching steps in order to stabilize the EOF could be omitted while this was necessary for a reliable operation of uncoated devices.
Enantioselectivity of alcohol‐modified polymeric surfactants in micellar electrokinetic chromatography
Authors: Tarus Jepkoech , Agbaria Rezik A. , Morris Kevin , Billiot Fereshteh H. , Williams Alicia A. , Chatman Trenderlyn , Warner Isiah M. 
Published: July 2003

AbstractA novel method of modifying sodium undecanoyl‐L‐leucinate (SUL) micelles employed in chiral separation of analytes in micellar electrokinetic chromatography (MEKC) to enhance selectivity toward specific analytes is discussed. The current study aimed at modifying the SUL micelles by introducing different alcohols into the mono‐SUL micelles. The micellar solutions were then polymerized in the presence of alcohols followed by postpolymerization extraction of the alcohols to yield alcohol‐free polymeric surfactants (poly‐L‐SUL). The effects of hexanol (C6OH) and undecylenyl alcohol (C11OH) on micellar properties of this surfactant were investigated by use of surface tensiometry, fluorescence spectroscopy, pulsed field gradient‐nuclear magnetic resonance (PFG‐NMR), and MEKC. The surface tension and PFG‐NMR studies indicated an increase in the critical micelle concentration (cmc) and micellar size upon increasing the alcohol concentration. Fluorescence measurements suggested that alcohols induce closely packed micellar structures. Coumarinic and benzoin derivatives, as well as (±)‐1, 1'‐binaphthyl‐2,2'‐dihydrogen phosphate (BNP) were used as test analytes for MEKC experiments. Examination of MEKC data showed remarkable resolutions and capacity factors of coumarinic derivatives obtained with modified poly‐L‐SUL as compared to the unmodified poly‐L‐SUL. Evaluation of fluorescence, PFG‐NMR, and MEKC data suggest a strong correlation between the polarity and hydrodynamic radii of alcohol‐modified micelles and the resolution of the test analytes.
Synthesis, analytical characterization and initial capillary electrophoretic use in acidic background electrolytes of a new, single‐isomer chiral resolving agent: Hexakis(2,3‐di‐O‐acetyl‐6‐O‐sulfo)‐ α‐cyclodextrin
Authors: Li Shulan , Vigh Gyula 
Published: July 2003

AbstractThe sodium salt of hexakis(2,3‐di‐O‐acetyl‐6‐O‐sulfo)‐α‐CD (HxDAS), the first member of the family of single‐isomer, fully sulfated α‐CDs, has been synthesized and used for the initial capillary electrophoretic separation of the enantiomers of nonionic, weak acid, weak base, and ampholytic analytes. HxDAS complexes less strongly with many of the analytes tested than the analogous β‐ and γ‐cyclodextrin derivatives, namely, heptakis(2,3‐di‐O‐acetyl‐6‐O‐sulfo)‐β‐cyclodextrin (HDAS) and octakis(2,3‐di‐O‐acetyl‐6‐O‐sulfo)‐γ‐cyclodextrin (ODAS). Nevertheless, it facilitated the separation of the enantiomers of a large number of weak electrolyte and nonelectrolyte analytes in acidic aqueous background electrolytes. For all analytes, the effective mobilities and separation selectivities as a function of the background electrolyte concentration of HxDAS followed the trends that were found for HDAS and ODAS.
Mechanistic study of the enantiomeric recognition of a basic compound with negatively charged single‐isomer γ‐cyclodextrin derivatives using capillary electrophoresis, nuclear magnetic resonance spectroscopy, and infrared spectroscopy
Authors: Zhou Lili , Thompson Richard , Reamer Robert A. , Lin Zhihao , French Mike , Ellison Dean , Wyvratt Jean 
Published: July 2003

AbstractThe possible mechanisms for the chiral recognition of 2‐(R)‐N‐[1‐(6‐aminopyridin‐2‐ylmethyl)piperidin‐4‐yl]‐2‐[(1R)‐3,3‐difluorocyclopentyl]‐2‐hydroxy‐2‐phenylacetamide (RR‐M3), and its enantiomer (SS‐M3) with octakis(2,3‐di‐O‐acetyl‐6‐sulfo)‐γ‐cyclodextrin (ODAS‐γ‐CD) and octakis(6‐sulfo)‐γ‐cycöpdextrom enantiomer; (OS‐γ‐CD), were investigated using capillary electrophoresis (CE), proton (1H), fluorine (19F) and carbon (13C) nuclear magnetic resonance spectroscopy (NMR), and infrared (IR) spectroscopy. Clear evidence for the formation of diastereomeric complexes between the enantiomers and the two CDs was observed. NMR spectra suggest that the phenyl and difluorocyclopentyl rings are involved in the complexation. The phenyl ring on the guest molecule is deeply penetrated into the cavity of OS‐γ‐CD, but it is not included into the cavity of ODAS‐γ‐CD. The continuous variation plots built based on the 1H NMR and IR spectra indicate a 1:1 complex stoichiometric ratio of the M3 enantiomers for both CDs. The affinity of the enantiomers for the two CDs is opposite.
Assessment of the stereoselective metabolism of methaqualone in man by capillary electrophoresis
Authors: Prost Francine , Thormann Wolfgang 
Published: July 2003

AbstractMethaqualone (MQ) and its hydroxylated metabolites are quinazoline derivatives that exhibit atropisomerism. As a continuation of our previous work with these compounds (Electrophoresis 2001, 22, 3270–3280), chiral capillary zone electrophoresis with hydroxypropyl‐β‐cyclodextrin as buffer additive and multiwavelength absorbance detection is shown to be an effective tool to provide insight into the stereoselectivity of the MQ metabolism. The five major monohydroxy MQ metabolites formed during biotransformation do not show enantiomerization at temperatures up to 85°C. Enzymatic and acidic hydrolysis of urines that were collected after concomitant administration of 250 mg of MQ and 25 mg diphenhydramine (DH) chloride are both shown to provide stereoselective metabolic patterns with 4’‐hydroxymethaqualone, the major urinary metabolite, being excreted almost exclusively as a single enantiomer. A stereoselectivity in the formation of 2’‐hydroxymethaqualone and 2‐hydroxymethaqualone was also observed in vitro using human liver microsomes and preparations containing the cytochrome P450 enzyme (CYP) CYP3A4 only. The presence of DH during incubation with human liver microsomes did not reveal a difference in the metabolic pattern obtained. Furthermore, CYP2D6 and CYP2C19 do not significantly contribute to the metabolism of MQ. This was independently observed in vitro and via analysis of urines of individuals that are either efficient metabolizer phenotypes or poor metabolizer phenotypes for the two polymorphic enzymes. Although interindividual differences in the monitored metabolic patterns were noted, no marked difference could be related to a CYP2D6 or CYP2C19 polymorphism.
pH‐dependent cyclodextrin capillary electrophoresis resolution of atropisomers
Authors: Zerbinati Orfeo , Trotta Francesco 
Published: July 2003

AbstractFive noncommercial and four commercially available cyclodextrin (CD) derivatives were tested as chiral auxiliaries for the capillary electrophoretic (CE) resolution of racemic 1,1’‐bi‐(2‐naphthol) (BN), 1,1’‐binaphthyl‐2,2’‐diyl hydrogenphosphate (BNHP), and 1,1’‐binaphthyl‐2,2’‐diamine (BNA) at pH 4.0, 6.5, and 8.6. The noncommercial CDs were ethyloxycarbonyl‐γ‐CD (ethylcarbonate‐γ‐CD), dimethylamino ethyloxycarbonyl‐β‐CD, a mercaptosuccinic acid derivative of β‐CD, a maleic acid derivative of β‐CD and heptakis(6‐deoxy‐6‐amino)‐β‐CD derivative with one amino group on the C‐6 carbon of each glucose unit. Except for the latter, the remaining derivatives were synthesized for this work. Also commercially available methyl‐β‐CD, hydroxypropyl‐β‐CD and the native β‐ and γ‐CDs were examined. Among the nine CDs tested, the maleic acid derivative of β‐CD gave the most interesting performances, since it resolved the atropisomers of BNA and BNHP in the same electrophoretic run at pH 4.0. It resolved the BNA racemate also at pH 6.5. Both the negatively charged CD tested were found to resolve anionic BNHP enantiomers, while positively charged CDs did not with cationic BNA. Several of the CDs investigated in this work were found to resolve the BNHP racemate, although at nonoptimal concentration. None of the experimented CDs was found to resolve the electrically neutral BN atropisomers pair at the three pHs considered, while some among these nine, experimented in a previous work, did so at higher pH.
A three‐dimensional contact algorithm for sliding surfaces
Authors: Dawes A. S. 
Published: July 2003

AbstractThis paper describes a model for sliding contact between materials. This has been embodied in a contact algorithm which has been incorporated into a three‐dimensional, time‐dependent, staggered mesh, finite element Lagrangian code. We first present an overview of the code and then describe the model underpinning the contact algorithm. The stages of the algorithm are then described and finally, results are presented for a number of different problems. Copyright © 2003 John Wiley & Sons, Ltd.
Modified method of characteristics for solving population balance equations
Authors: Pilon Laurent , Viskanta Raymond 
Published: July 2003

AbstractThis paper presents a new numerical method for solving the population balance equation using the modified method of characteristics. Aggregation and break‐up are neglected but the density function variations in the three‐dimensional space and its dependence on the external fields are accounted for. The method is an interpretation of the Lagrangian approach. Based on a pre‐specified grid, it follows the particles backward in time as opposed to forward in the case of traditional method of characteristics. Unlike the direct marching method, the inverse marching method uses a fixed grid thus, making it compatible with other numerical schemes (e.g. finite‐volume, finite elements) that may be used to solve other coupled equations such as the mass, momentum, and energy conservation equations. The numerical solutions are compared with the exact analytical solutions for simple one‐dimensional flow cases. Very good agreement between the numerical and the theoretical solutions has been obtained confirming the validity of the numerical procedure and the associated computer program. Copyright © 2003 John Wiley & Sons, Ltd.
Discontinuous Galerkin spectral element lattice Boltzmann method on triangular element
Authors: Shi Xing , Lin Jianzhong , Yu Zhaosheng 
Published: July 2003

AbstractDiscontinuous Galerkin spectral element method is used to solve the lattice Boltzmann equation (LBE) in the discrete velocity space. The triangular elements are adopted because of their flexibility to deal with complex geometries. The flow past a circular cylinder is simulated by the proposed scheme. The results are consistent with those obtained from the previous numerical methods and experiments. Copyright © 2003 John Wiley & Sons, Ltd.