bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies in the Cycloproparene Series: Cross‐Conjugated π‐Extended Alkylidenecycloproparenes
Authors: Dixon Gareth M. , Halton Brian 
Published: August 2004

AbstractThe first simple and stable cross‐conjugated π‐extended alkylidenecycloproparenes 5, 6 and 15−22 have been prepared as coloured crystalline derivatives from use of (E,E)‐1,5‐diphenylpenta‐2,4‐dienone, (E,E)‐1,5‐diarylpenta‐1,4‐dien‐3‐ones and (E,E)‐2,5‐(diarylmethylidene)cyclopentanones with the relevant 1,1‐bis(trimethylsilyl)cyclopropa[b]naphthalene. The permanent dipole moments of the compounds have been measured, and the conformational preference of the rotamers assessed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Cover Picture: Chemical Synthesis of GPIs and GPI‐Anchored Glycopeptides (Eur. J. Org. Chem. 17/2004)
Authors: Guo Zhongwu , Bishop Lee 
Published: August 2004

AbstractThe cover picture shows a glycosylphosphatidylinositol(GPI‐)anchored protein that is associated with the cell membrane. The insertion of the long lipid chains of GPIs into the membrane bilayers anchors numerous proteins and glycoproteins onto cell surfaces. GPI anchoring is ubiquitous and plays a critical role in the eukaryotic world. The chemical synthesis of some GPIs and GPI‐linked peptides and glycopeptides is summarized in detail in the Microreview by Z. Guo and L. Bishop on p. 3585 ff.
Application of stepwise discriminant analysis to classify commercial orange juices using chiral micellar electrokinetic chromatography‐laser induced fluorescence data of amino acids
Authors: Simó Carolina , Martín‐Alvarez Pedro J. , Barbas Coral , Cifuentes Alejandro 
Published: August 2004

AbstractThe use of chiral amino acids content and stepwise discriminant analysis to classify three types of commercial orange juices (i.e., nectars, orange juices reconstituted from concentrates, and pasteurized orange juices not from concentrates) is presented. Micellar electrokinetic chromatography with laser‐induced fluorescence (MEKC‐LIF) and β‐cyclodextrins are used to determine L‐ and D‐amino acids previously derivatized with fluorescein isothiocyanate (FITC). This chiral MEKC‐LIF procedure is easy to implement and provides information about the main amino acids content in orange juices (i.e., L‐proline; L‐aspartic acid, D‐Asp, L‐serine, L‐asparagine, L‐glutamic acid, D‐Glu, L‐alanine, L‐.arginine, D‐Arg, and the non‐chiral γ‐amino‐n‐butyric acid (GABA), i.e., γ‐aminobutyric acid). From these results, it is clearly demonstrated that some D‐amino acids occur naturally in orange juices. Application of stepwise discriminant analysis to 26 standard samples showed that the amino acids L‐Arg, L‐Asp and GABA were the most important variables to differentiate the three groups of samples. With these three selected amino acids a 100% correct classification of the samples was obtained either by standard or by leave‐one‐out cross‐validation procedures. These classification functions based on the content in L‐Arg, L‐Asp and GABA were also applied to nine test samples and provided an adequate classification and/or interesting information on these samples. It is concluded that chiral MEKC‐LIF analysis of amino acids and stepwise discriminant analysis can be used as a consistent procedure to classify commercial orange juices providing useful information about their quality and processing. To our knowledge, this is the first report about the combined use of chiral capillary electrophoresis and discriminant techniques to classify foods.
Direct enantioseparation of catechin and epicatechin in tea drinks by 6‐O‐α‐D‐glucosyl‐β‐cyclodextrin‐modified micellar electrokinetic chromatography
Authors: Kodama Shuji , Yamamoto Atsushi , Matsunaga Akinobu , Yanai Hiroko 
Published: August 2004

AbstractCyclodextrin‐modified micellar electrokinetic chromatography was applied to the enantioseparation of catechin and epicatechin using 6‐O‐α‐D‐glucosyl‐β‐cyclodextrin together with sodium dodecyl sulfate and borate‐phosphate buffer. Factors affecting chiral resolution and migration time of catechin and epicatechin were studied. The optimum running conditions were found to be 200 mM borate‐20 mM phosphate buffer (pH 6.4) containing 25 mM 6‐O‐α‐D‐glucosyl‐β‐cyclodextrin and 240 mM sodium dodecyl sulfate with an effective voltage of +25 kV at 20°C using direct detection at 210 nm. Under these conditions, the resolution (Rs) of racemic catechin and epicatechin were 4.15 and 1.92, respectively. With this system, catechin and epicatechin enantiomers along with other four catechins ((−)‐catechin gallate, (−)‐epicatechin gallate, (−)‐epigallocatechin, (−)‐epigallocatechin gallate) and caffeine in tea samples were analyzed successfully. The difference of migration time between catechin and epicatechin is discussed.
Preparation of a positively charged cellulose derivative chiral stationary phase with copolymerization reaction for capillary electrochromatographic separation of enantiomers
Authors: Chen Xiaoming , Qin Feng , Liu Yueqi , Kong Liang , Zou Hanfa 
Published: August 2004

AbstractA positively charged chiral stationary phase (CSP) was prepared by chemically immobilizing cellulose 3,5‐dimethylphenylcarbamate onto methacryloyldiethylenetriaminopropylated silica (MCDEAPS) via a radical copolymerization reaction. The prepared CSP was evaluated for enantiomer separation in nonaqueous capillary electrochromatography (CEC). Electroosmotic flow (EOF) generated on the prepared CSP could be significantly improved with introduction of positive charges into the CSP, and separation of enantiomers in CEC has been achieved with mobile phases of ethanol and hexane‐ethanol, respectively. In addition, we investigated the solvent versatility of the immobilized CSP on enantioseparations in CEC and capillary liquid chromatography (CLC) due to the elimination of dissolution of chiral selector in a number of solvents. Chiral resolution of some enantiomers was improved by adopting tetrahydrofuran (THF) and chloroform as mobile‐phase modifiers, respectively.
Enantiomeric resolution of 2‐arylpropionic acid nonsteroidal anti‐inflammatory drugs by capillary electrophoresis: Methods and applications
Authors: Patel Bhavesh K. , Hanna‐Brown Melissa , Hadley Mark R. , Hutt Andrew J. 
Published: August 2004

AbstractThe 2‐arylpropionic acids (2‐APAs) are an important group of nonsteroidal anti‐inflammatory drugs. These agents, the majority of which are available as racemates, exhibit stereoselectivity in both their action and disposition. Developments in stereoselective separation science methodology, mainly chromatographic, have facilitated an evaluation of the pharmacological properties of the individual enantiomers of these drugs and contributed to our understanding of both their mode(s) of action and disposition. While a number of electrophoretic techniques, including capillary electrophoresis, capillary electrochromatography and isotachophoresis, have been applied to the stereoselective resolution and stereospecific analysis of these agents using a variety of chiral selectors, e.g., cyclodextrins, oligosaccharides, macrocyclic antibiotics, and proteins, the number of published applications in pharmaceutical and biomedical analysis remains relatively limited. However, the utility of electrophoretic techniques for stereospecific analysis may be illustrated using the 2‐APAs as typical examples of chiral acidic pharmaceuticals. Applications include: determination of enantiomeric composition following biosynthetic stereoselective hydrolysis; examination of both achiral and chiral impurity profiles in bulk drugs and formulated products; determination of enantiomeric impurities in both bulk drugs and formulated products; examination of configurational stability following stress testing of formulated products; determination of enantiomeric composition and metabolite profile in biological fluids following administration of the racemates and individual enantiomers. It may be anticipated that future exploitation of electrophoretic approaches to the stereospecific analysis of these agents will result in further contributions to our understanding of their stereoselective biological properties and therapeutic use.
Chiral capillary electrophoresis: Facts and fiction on the reproducibility of resolution with randomly substituted cyclodextrins
Authors: Schmitt Ulrich , Ertan Mevlut , Holzgrabe Ulrike 
Published: August 2004

AbstractComparative enantioseparation of the enantiomers of 1,1'‐binaphthyl‐2,2'‐diyl hydrogen phosphate was performed with cyclodextrin (CD)‐modified capillary electrophoresis (CE). Two single isomers, β‐CD, heptakis(2,3,6‐tri‐O‐methyl)‐β‐CD (TM‐β‐CD), and heptakis(2,6‐di‐O‐methyl)‐β‐CD (DM‐β‐CD) of 98% purity as well as heptakis(2,3‐di‐O‐acetyl)‐β‐CD were used and compared in terms of resolution power to randomly methylated and corresponding acetylated β‐CDs, which were synthesized in our laboratory. The methylated ones were characterized by means of matrix‐assisted laser desorption/ionization‐time of flight‐(MALDI‐TOF) mass spectrometry. By testing defined mixtures of single isomers and comparing their resolution power to randomly substituted CDs of similar degree of substitution we could show, that a simple characterization by the average molecular degree of substitution (DS) is not sufficient. In order to get reproducible results, a clearly defined substitution pattern is necessary, which is not given using randomly substituted CDs. Taken together, a validation of a chiral separation with “undefined” CD derivatives is almost impossible.
A simplified synthesis of polymeric nonparticulate stationary phases with macrocyclic antibiotic as chiral selector for capillary electrochromatography
Authors: Kornyšova Olga , Jarmalavičienė Reda , Maruška Audrius 
Published: August 2004

AbstractA simplified approach to synthesize nonparticulate (continuous or monolithic) beds with embedded vancomycin chiral selectors for capillary electrochromatography is proposed. In the present approach, N,N'‐diallyltartardiamide monomer with diol functionality is used, which can be readily converted to aldehyde groups via periodate treatment. Parallel to the activation of the polymeric matrix for covalent attachment of vancomycin, the periodate treatment has shown secondary effects on the polymeric bed morphology, namely the increase of the average pore size and porosity of the skeleton. Inversed size‐exclusion chromatography was applied to characterize porosimetric properties of the capillary columns before and after the periodate treatment. Electroosmotic and enantioselective properties of the nonparticulate beds synthesized are presented. The approach is of more general interest attaching different affinity groups to the polymeric matrix and/or enhancing the accessibility to the active sites, for instance, in the molecular imprinting technique.
Enantioselective analysis of primaquine and its metabolite carboxyprimaquine by capillary electrophoresis
Authors: Bortocan Renato , Bonato Pierina S. 
Published: August 2004

AbstractAn enantioselective capillary electrophoresis method for the simultaneous determination of primaquine (PQ) and carboxyprimaquine (CPQ) in rat liver mitochondrial fraction, suitable for in vitro metabolism studies is presented. The drug and metabolite were extracted by liquid‐liquid extraction using ethyl ether. The enantiomers were resolved in a fused‐silica capillary, 50 μm inside diameter (ID) and 24 cm of effective length, using an electrolyte solution consisting of a 20 mmol/L sodium phosphate solution, pH 3.0, and 10% w/v maltodextrin. Hydrodynamic sample injection was used with a 10 s injection time at 50 mbar pressure. The applied voltage was 22 kV and the capillary temperature was controlled at 20°C. Detection was carried out at 264 nm. Under these conditions, the enantiomeric fractions of the drug and of its metabolite were analyzed within 6 min. The extraction procedure was efficient in removing endogenous interferents and low values (<10%) for the coefficients of variation and deviation from theoretical values were demonstrated for both within‐day and between‐day assays. The method described allows the determination of PQ and CPQ enantiomers as low as 100 and 40 ng/mL, respectively. After validation, the method was used for an in vitro metabolism study of PQ. The results showed that the enantiomer (−)‐PQ was preferentially metabolized to (−)‐CPQ.
Heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin as a chiral selector for the separation of anionic analyte enantiomers by capillary electrophoresis
Authors: Budanova Natalia , Shapovalova Elena , Lopatin Sergei , Varlamov Valery , Shpigun Oleg 
Published: August 2004

AbstractA hepta‐substituted β‐cyclodextrin bearing seven amino groups, heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin (per‐6‐NH2‐β‐CD) was successfully used as a chiral selector for the enantioseparation of different anionic analytes. The running buffer pH and chiral selector concentration were the studied parameters crucial in achieving the maximum possible enantioresolution. Enantiomeric separation of a mixture of seven carboxybenzyl‐amino acids was achieved in 24 min. Excellent resolution was obtained for carboxybenzyl‐tryptophan (Rs = 11.2).
Enantioseparation using sulfated cyclosophoraoses as a novel chiral additive in capillary electrophoresis
Authors: Park Heylin , Lee Sanghoo , Kang Simook , Jung Yunjung , Jung Seunho 
Published: August 2004

AbstractHighly sulfated cyclosophoraoses (HS‐Cys) were synthesized by the chemical modification of a family of neutral cyclosophoraoses isolated from Rhizobium leguminosarum bv. trifolii. The HS‐Cys were then analytically characterized using Fourier transform‐infrared spectroscopy and elemental analysis. These HS‐Cys were successfully used as a novel chiral additive, in low‐pH aqueous background electrolytes, for capillary electrophoretic separation of five basic chiral drugs such as arterenol, atenolol, isoproterenol, propranolol, and metoprolol.
Assessment of the N‐oxidation of deprenyl, methamphetamine, and amphetamine enantiomers by chiral capillary electrophoresis: An in vitro metabolism study
Authors: Szökő Éva , Tábi Tamás , Borbás Tímea , Dalmadi Balázs , Tihanyi Károly , Magyar Kálmán 
Published: August 2004

AbstractA chiral capillary electrophoresis method using hydroxypropyl‐β‐cyclodextrin as chiral selector was developed and validated for the quantification of the N‐oxygenated metabolites of deprenyl, methamphetamine, and amphetamine enantiomers, formed in vitro. The influence of various parameters (selector concentration, buffer pH, temperature, polymer additive, etc.) on the simultaneous separation of the optical isomers of the parent drugs and their metabolites has been evaluated. The buffer pH had the greatest impact on the separation selectivity of the N‐oxygenated compounds. Linear calibration curves were obtained over the concentration range of 2.5–50 μM for the enantiomers of amphetamine‐hydroxylamine, methamphetamine‐hydroxylamine, and deprenyl‐N‐oxide. The inter‐ and intra‐assay precision and accuracy varied by less than 15% for all analytes at concentrations of 5, 10, and 30 μM, and less than 20% at the lower limit of quantitation (2.5 μM). The sample extraction recovery ranged between 109 and 129% at the three concentration levels. The drug enantiomers were incubated with recombinant human flavin‐containing monooxygenase enzymes (FMO3 and FMO1), and human liver microsomes, respectively. The enantioselectivity of the substrate preference, as well as the stereoselective formation of the new chiral center upon the oxidation of the prochiral tertiary nitrogen of deprenyl were assessed. FMO1, the extrahepatic form of the enzyme in man, was shown to be more active in the N‐oxygenation of both deprenyl and methamphetamine isomers than FMO3. Deprenyl enantiomers and S‐methamphetamine were substrates of human recombinant FMO3. Conversion of amphetamine to its hydroxylamine derivative could not be observed on incubation with either FMO1 or FMO3. Formation of the new chiral center on the nitrogen, during N‐oxidation of the tertiary amine deprenyl, was found stereoselective. The two FMO isoforms have shown opposite preference in the formation of this chiral center. Methamphetamine‐hydroxylamine formed from methamphetamine was further transformed by FMO, amphetamine‐hydroxylamine was identified as the product of a demethylation reaction.
Influence of (hydroxy)alkylamino substituents on enantioseparation ability of single‐isomer amino‐β‐cyclodextrin derivatives in chiral capillary electrophoresis
Authors: Iványi Róbert , Jicsinszky László , Juvancz Zoltán , Roos Natascha , Otta Klára , Szejtli József 
Published: August 2004

AbstractA family of single‐isomer amino‐β‐cyclodextrin (amino‐β‐CD) derivatives containing an amino or (hydroxy)alkylamino group in one of the primary positions has been synthesized. The steric effect and hydrogen bond forming ability of the different substituents on enantioseparation of acidic enantiomers has been studied by capillary electrophoresis (CE). Three enantiomeric model compounds (mandelic acid, cis‐permethrinic acid, and cis‐deltamethrinic acid) having significantly different apparent complex stability constants with β‐CD were applied in the experiments. Dependence of separation selectivity, resolution as well as mobility difference on chiral selector concentration (0.1–20 mM, pH 6.0) was investigated. Each amino‐β‐CD showed higher enantioselectivity than the native β‐CD. One hydroxyalkyl group attached to the primary amino N‐atom significantly increased both the enantioselectivity and the resolution compared to the primary amino‐β‐CD, while two hydroxyalkyl moieties decreased them due to the predominance of steric hindrance. The value of the apparent complex stability constants obtained suited well the mobility difference model (by Wren). On the other hand, the optimum selector concentrations calculated according to the model were slightly lower than the experienced concentrations giving the maximum enantioresolution of enantiomers.
Optimization and validation of an enantioselective method for a chiral drug with eight stereo‐isomers in capillary electrophoresis
Authors: Jimidar M. Ilias , Vennekens Tom , Van Ael Willy , Redlich Dirk , De Smet Maurits 
Published: August 2004

AbstractHighly selective capillary electrophoresis (CE) screening methods were applied to find a satisfactory separation of a chiral drug with eight stereoisomeric compounds. The initial separation conditions were further optimized using response surface modelling by applying a Box‐Behnken experimental design. This approach resulted in a rapid and efficient optimization of the buffer concentration, the concentration of two cyclodextrins, and the run voltage, in order to obtain final separation conditions of the method. Further optimization and validation of the system in terms of sensitivity and robustness resulted in a method that is suitable for quality control release purposes.
Ultrashort partial‐filling technique in capillary electrophoresis for infinite resolution of tramadol enantiomers and its metabolites with highly sulfated cyclodextrins
Authors: Rudaz Serge , Le Saux Thomas , Prat Josiane , Gareil Pierre , Veuthey Jean‐Luc 
Published: August 2004

AbstractThe possibility to enhance resolution to infinite value in chiral capillary electrophoresis is attained as soon as the apparent mobility of one enantiomer becomes opposite to the other. This could be achieved on the basis of the carrier ability of multiple charged chiral selectors such as highly sulfated cyclodextrin (HS‐CD). With tramadol and its phase I metabolites selected as model compounds, the HS‐γ‐CD was found to be the most appropriate chiral selector. The CD concentration was determined where one enantiomer still migrated as a cation while the other migrated in the opposite side. Besides the chiral selector concentration, secondary parameters such as buffer concentration appeared to be critical to reach infinite resolution. The latter was achieved with partial filling technique using ultrashort separation zones (a few mm). In order to better understand the interaction mechanism between the selected CD and the analytes, the classical affinity capillary electrophoresis method, although not fully satisfactory because of ionic strength variations within a series of mobility shift measurements, was applied to estimate complexation constants and complex mobilities. The results obtained point to the prevailing role of complex mobility differences in the enantioselectivity mechanism.
QALY maximisation and people's preferences: a methodological review of the literature
Authors: Dolan Paul , Shaw Rebecca , Tsuchiya Aki , Williams Alan 
Published: August 2004

AbstractIn cost‐utility analysis, the numbers of quality‐adjusted life years (QALYs) gained are aggregated according to the sum‐ranking (or QALY maximisation) rule. This requires that the social value from health improvements is a simple product of gains in quality of life, length of life and the number of persons treated. The results from a systematic review of the literature suggest that QALY maximisation is descriptively flawed. Rather than being linear in quality and length of life, it would seem that social value diminishes in marginal increments of both. And rather than being neutral to the characteristics of people other than their propensity to generate QALYs, the social value of a health improvement seems to be higher if the person has worse lifetime health prospects and higher if that person has dependents. In addition, there is a desire to reduce inequalities in health. However, there are some uncertainties surrounding the results, particularly in relation to what might be affecting the responses, and there is the need for more studies of the general public that attempt to highlight the relative importance of various key factors. Copyright © 2004 John Wiley & Sons, Ltd.
In vitro study of human vascular endothelial cell function on materials with various surface roughness
Authors: Xu Chengyu , Yang Fang , Wang Shu , Ramakrishna Seeram 
Published: August 2004

AbstractIn recent years, creating a biodegradable polymer scaffold with an endothelialized surface has become an attractive concept for replacement of small‐diameter blood vessels. Toward this end, a better understanding of the interaction between endothelial cells and biodegradable polymer substrates is particularly important. Surface roughness of biomaterials is one of the important parameters that affect cell behavior. In this study, human vascular endothelial cells were cultured on electrospun and solvent‐cast poly(L‐lactic acid) substrates with different surface roughness. Cell responses were evaluated via both qualitative examinations of cell morphology changes as well as quantitative assessment of cell adhesion and proliferation rate on the different substrates. The results proved that endothelial cell function was enhanced on the smooth solvent‐cast surface rather than on the rough electrospun surface of poly(L‐lactic acid). Together with our previous findings that electrospun substrates favor vascular smooth muscle cell behavior, it is possible to design a unique three‐dimensional scaffold for application of tissue‐engineered small‐diameter vessel replacement by combining the fabrication technique of solvent casting and electrospinning. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 154–161, 2004