bluuebunny/crossref_metadata_2025_split huggingface dataset:
Redefining the separation factor: A potential pathway to a unified separation science
Authors: Bowser Michael T. , Bebault Gwendolyn M. , Peng Xuejun , Chen David D. Y. 
Published: May 2005

AbstractUnderstanding the separation process in capillary electrophoresis (CE) leads to the unification of the theories for separation science. While the separation of analytes is governed by equilibria in chromatography, and by (centrifugal) field in ultracentrifugation, the separation in CE is governed by both equilibria and (electric) field. Therefore, a comprehensive separation theory that describes the separation process of analytes in CE should be able to describe the separation processes in both chromatography and ultracentrifugation. In this paper, we propose that individual capacity factors for each analyte species be used to describe the migration behavior of an analyte. The effect of field on each analyte species, as well as the effect of equilibria are considered in deriving a generalized equation that is applicable for all separation techniques. The separation factor defined at present does not directly relate to the migration rates of the analytes, and therefore can not be used in a generalized theory. We propose that the ratio of the migration rates of a pair of analytes (γ) should be used as the separation factor, instead of the ratio of the two capacity factors. When γ is used to describe the separation of two closely migrating analytes, all separation techniques have the same resolution equation.
Simultaneous chiral separation of 3,4‐methylenedioxymethamphetamine (MDMA), 3‐4‐methylenedioxyamphetamine (MDA), 3,4‐methylenedioxyethylamphetamine (MDE), ephedrine, amphetamine and methamphetamine by capillary electrophoresis in uncoated and coated capillaries with native β‐cyclodextrin as the chiral selector: Preliminary application to the analysis of urine and hair
Authors: Tagliaro Franco , Manetto Giulia , Bellini Silvana , Scarcella Daniele , Smith Frederick P. , Marigo Mario 
Published: May 2005

AbstractThe importance of the chiral analysis of amphetamine‐related substances in both clandestine preparations and biological samples is widely recognized. For this purpose, capillary electrophoresis was successfully applied by several authors, but only few reports concerned ring‐substituted amphetamines, which represent the main components of “ecstasy”, a widely abused “recreational” substance. In the present work, the simultaneous chiral analysis of ephedrine, amphetamine, methamphetamine, 3,4‐methylenedioxymethamphetamine (MDMA), 3‐4‐methylenedioxyamphetamine (MDA) and 3,4‐methalenedioxyethylamphetamine (MDE) is reported, by using capillary electrophoresis with native β‐cyclodextrin (15 mM) as the chiral selector. After preliminary tests at different pH values (phosphate buffer 100 mM, pH 2.5–9.0) and with bare or coated fused‐silica capillaries, the optimized conditions were: pH 2.5 phosphate, uncoated capillary (45 cm × 50 μm inner diameter), potential 10 kV. Detection was either by fixed wavelength (200 nm) or multiwavelength (190–400 nm) UV absorbance. Under these conditions, good resolution was obtained for all the analytes, with excellent chiral selectivity and efficiency. The sensitivity for the individual enantiomers was better than 0.2 μg/mL, analytical precision was characterized by relative standard deviation values < 0.8% (⩽ 0.15% with internal standardization) for migration times intra‐day and < 2.0% (⩽ 0.54% with internal standardization) day‐to‐day; linearity, in the range 0.156–40 μg/mL, and accuracy were also satisfactory. After a simple liquid‐liquid extraction, urine samples could be analyzed with a sensitivity well below the recommended NIDA cut‐off of 500 ng/mL. For hair samples, it was necessary to increase the sensitivity by applying a field‐amplified sample stacking procedure, which allowed the chiral determination of MDA, MDMA and MDE at concentrations occurring in real samples from ecstasy users, with the possibility of recording UV spectra of the peaks.
Genotyping of forensic short tandem repeat (STR) systems based on sizing precision in a capillary electrophoresis instrument
Authors: Lazaruk Katherine , Walsh P. Sean , Oaks Frank , Gilbert Dennis , Rosenblum Barnett B. , Menchen Steve , Scheibler Don , Wenz H. Michael , Holt Cydne , Wallin Jeanette 
Published: May 2005

AbstractAutomated fluorescence analysis of polymerase chain reaction (PCR)‐amplified short tandem repeat (STR) systems by capillary electrophoresis (CE) is becoming an established tool both in forensic casework and in the implementation of both state and national convicted offender DNA databases. A new capillary electrophoresis instrument, the ABI Prism 310 Genetic Analyzer, along with the Performance Optimized Polymer 4 (POP‐4) provides an automated and precise method for simultaneously analyzing ten flourescently labeled STR loci from a single PCR amplification kit, which provides a power of discrimination of approximately one in five billion from a single PCR amplification. Data are presented on sizing precision, sizing accuracy, and resolution for the STR loci in the AmpFlSTR Profiler™ kit. Sizing accuracy is highly dependent on the electrophoresis system, and therefore the reporting of alleles based on the nucleotide size obtained from an electrophoresis system is not recommended for forensic work. The precision of the 310 capillary electrophoresis system, coupled with software developed for automated genotyping of alleles based on the use of an allelie ladder, allows for accurate genotyping of STR loci. Sizing precision of ⩽ 0.16 nucleotide standard deviation was obtained with this system, thus allowing for accurate genotyping of length variants that differ in length by a single nucleotide.
Amperometric pH regulation – a flexible tool for rapid and precise temporal control over the pH of an electrolyte solution
Authors: Hagedorn Rolf , Korlach Jonas , Fuhr Günter 
Published: May 2005

AbstractTemporal control over both pH and ionic strength of an electrolyte solution with high accuracy was achieved with a dynamic, computer feedback‐controlled amperometric pH‐stat device consisting of four pH‐regulating electrodes placed in electrolyte reservoirs that are separated by dialysis membranes from a central compartment. Theoretical predictions of the behavior of this arrangement, obtained by computer simulation, were validated by running temporal pH programs such as step functions, oscillations, and linear pH gradients. Deviations from nominal values given by the computer program are within the limits of accuracy of the pH‐measuring electrodes. No volume changes accompany a change of pH or conductivity since ions are forced to leave or enter the central compartment through the membranes by the electrical force applied between the pH‐regulating electrodes. The device is flexible, easy to use and easily miniaturized. We discuss a wide range of possible applications in biochemistry and cell science. These include automated pH adjustment, isoelectric protein separation, amperometric measurement of enzyme kinetics and the response of cell cultures to well‐defined pH changes.
Methods for determination of electrophoretic mobility and stability of complexes originating in solutions during the chiral discrimination process
Authors: Vespalec Radim , Boček Petr 
Published: May 2005

AbstractAn equation for the calculation of electrophoretic mobility of kinetically labile complexes originating in solutions during the chiral discrimination process is derived. The mobility of the complex is calculated from that of a fully ionized racemic compound, measured in absence of the chiral selector, and from the effective mobilities of its enantiomers, corresponding to the concentration of the chiral selector causing their maximum difference. Correct values of stoichiometric stability constants of both enantiomers may be calculated from the mobility of the complex obtained in this way. Both the mobility and the stability values hold only for the experimental conditions used and the selected background electrolyte. The proposed method is demonstrated for the separation of the fully ionized N‐t‐BOC‐DL‐tryptophan with β‐cyclodextrin in 20 mM aqueous solution of α‐hydroxyisobutyric acid, adjusted with NaOH to pH 4.5. Mobility of the complex is 8.4 × 10−9 m2V−1s−1 at 25°C. The stability constants of D‐ and L‐enantiomers of N‐t‐BOC‐DL‐tryptophan with β‐cyclodextrin, KD and KL, obtained from migration data using this mobility of the complex, are 374 ± 37 M−1 and 336 ± 31 M−1, respectively. The geometrical mean value of calculated stability constants, 355 M−1, agrees perfectly with the value of 350 M−1, calculated from the same experimental data by another procedure recently.
Separation of cis/trans conformers of human and salmon calcitonin by low temperature capillary electrophoresis
Authors: Thunecke Frank , Fischer Gunter 
Published: May 2005

AbstractConformer‐specific recognition of peptides and proteins has often been proved with the aid of indirect methods. Here we provide an analytical approach for a direct investigation of separated isomers. Cis/trans conformers of the peptide hormones human (hCT) and salmon (sCT) calcitonin exhibit different migration properties in capillary zone electrophoresis at subambient temperatures. Calcitonin consists of 32 amino acids with two proline residues incorporated. It is the longest unstructured peptide for which a conformer separation by capillary electrophoresis has yet been achieved. Lowering the temperature yielded a splitting into two and three peaks for sCT and hCT, respectively, in acidic buffer. The peak ratios of 66:34 for sCT and 71:23 for hCT are in good agreement with the conformer distribution previously reported from nuclear magnetic resonance (NMR) studies. The addition of different organic modifiers (5–20% v/v) to the running buffer does not improve the separation. The observed merging of conformer peaks in buffer containing 20% v/v 2,2,2‐trifluoroethanol (TFE) is attributed to structure formation.
Sodium alkyl ether sulfate preparative electrophoresis for the preparation of reaction centers without H‐subunit from Rhodopseudomonas viridis
Authors: Miyake Jun , Hara Masayuki , Asada Yasuo , Morimoto Yasuhiro , Shirai Makoto 
Published: May 2005

AbstractSodium alkyl ether sulfate (AES), an analog of sodium dodecyl sulfate (SDS) was used in polyacrylamide gel electrophoresis (PAGE) for the partial decomposition of the photosynthetic reaction center (RC) of Rhodopseudomonas viridis. Unlike SDS, AES did not completely dissociate RC into its subunits but selectively detached H‐subunit from RC to give RC(‐H) without losing the spectroscopic nature of RC. For the denaturation of RC(‐H), AES was found to be as mild as 3‐[3‐cholamidopropyl dimethylammonio]‐1‐propanesulfonate (CHAPS).
A heparin‐binding peptide from human serum amyloid P component characterized by affinity capillary electrophoresis
Authors: Heegaard Niels H. H. 
Published: May 2005

AbstractAffinity capillary electrophoresis (CE) was used for a detailed characterization of the binding between heparin and a peptide isolated from the heparin‐binding serum protein amyloid P component (SAP). The peptide corresponds to a tryptic fragment (T3) comprising amino acids 14–38 of SAP. By including ligands in the electrophoresis buffer various glycosaminoglycans could be screened for binding of T3 using one sample aliquot. The binding was found to be highly specific for heparin and heparin fragments down to tetramers and appeared strongest at a slightly alkaline pH while no binding could be demonstrated with heparan sulfate, chondroitin sulfate, desulfated heparin, mannose 6‐phosphate and phosphotyrosine. The T3‐heparin complexes were sufficiently stable to perform quantitative measurements of the binding using preequilibration of samples prior to a CE‐mediated separation of bound and free T3‐peptide. Plots based on quantitation of analyte peaks corresponding to free and complexed T3 yielded a dissociation constant of 1.5 μm for the interaction with heparin. The results indicate that a specific subfraction of the heparin molecules is active in binding interactions with the peptide. The affinity CE approach proved to be useful for these studies because of its sensitivity to complex formation involving charged ligands and the possibility of achieving separations under native conditions. Also advantageous is the low sample consumption and the ability to analyze unlabeled reactants in solution.
Using capillary electrophoresis/frontal analysis to screen drugs interacting with human serum proteins
Authors: McDonnell Patricia A. , Caldwell Gary W. , Masucci John A. 
Published: May 2005

AbstractWe have used capillary electrophoresis in the frontal analysis mode (CE/FA) to determine the binding capacity of β‐adrenoceptor blocking drugs to individual serum proteins, serum protein mixtures and human serum. The free drug concentration was directly measured from the height of the frontal peak and used to calculate the bound drug concentration. From the bound drug concentration, the percentage of drug bound to the serum proteins α1‐acid glycoprotein (AGP) and human serum albumin (HSA) was then determined. In addition to determining the percent of a drug bound to a protein, the drug‐protein association constant (Ka) was determined for AGP binding to β‐blockers. The data‐estimated association constants were consistent with literature values. The CE/FA studies on the β‐adrenoceptor blocking drugs and the serum proteins indicated that HSA, AGP, high density lipoprotein (HDL), and low density lipoprotein (LDL) were the main contributors to serum binding for this series of compounds. The serum‐drug binding data sorted the β‐adrenoceptor blocking drugs into high and low binding categories. The protein mixture (AGP + HSA + HDL + LDL) resulted in dividing the β‐blockers into the same high/low rankings. The protein mixture (AGP + HSA + HDL + LDL) was amenable to automation, did not autoaggregate, and had constant concentrations for the proteins.
Smith/Birnstiel mapping of genome rearrangements in Pseudomonas aeruginosa
Authors: Heuer Thomas , Bürger Christiane , Tümmler Burkhard 
Published: May 2005

AbstractA novel application of the Smith/Birnstiel technique is presented for the analysis of intraspecies genomic diversity in small genomes. Rare‐cutter total/N frequent‐cutter partial restriction digestions are separated in N separate lanes by pulsed‐field gel electrophoresis, blotted and hybridized with rare‐cutter fragment ends as probes. The evaluation of the autoradiogram results in high‐resolution restriction maps of 10–200 kbp regions. The technique was applied to the analysis of genome rearrangements in Pseudomonas aeruginosa strains. Comparison of the region encoding the tryptophan biosynthesis genes in the PAO and the IATS serotype 5 strains revealed that shared sequence characterized by almost identical restriction fingerprints was interrupted in the serotype 5 strain by small islands displaying strain‐specific restriction site signatures. A multistep rearrangement in a hypervariable chromosome region downstream of the phn locus was detected in serial airway isolates from a patient with cystic fibrosis.
Bacterial phylogeny based on comparative sequence analysis (review)
Authors: Ludwig Wolfgang , Strunk Oliver , Klugbauer Sabine , Klugbauer Norbert , Weizenegger Michael , Neumaier Judith , Bachleitner Marianne , Schleifer Karl Heinz 
Published: May 2005

AbstractComparative sequence analysis of small subunit rRNA is currently one of the most important methods for the elucidation of bacterial phylogeny as well as bacterial identification. Phylogenetic investigations targeting alternative phylogenetic markers such as large subunit rRNA, elongation factors, and ATPases have shown that 16S rRNA‐based trees reflect the history of the corresponding organisms globally. However, in comparison with three to four billion years of evolution the phylogenetic information content of these markers is limited. Consequently, the limited resolution power of the marker molecules allows only a spot check of the evolutionary history of microorganisms. This is often indicated by locally different topologies of trees based on different markers, data sets or the application of different treeing approaches. Sequence peculiarities as well as methods and parameters for data analysis were studied with respect to their effects on the results of phylogenetic investigations. It is shown that only careful data analysis starting with a proper alignment, followed by the analysis of positional variability, rates and character of change, testing various data selections, applying alternative treeing methods and, finally, performing confidence tests, allows reasonable utilization of the limited phylogenetic information.
Mycobacterial genome structure (minireview)
Authors: Philipp Wolfgang J. , Schwartz David C. , Telenti Amalio , Cole Stewart T. 
Published: May 2005

AbstractGenome maps have been constructed for the mycobacterial pathogens Mycobacterium leprae and Mycobacterium tuberculosis, as well as for the attenuated vaccine strain Mycobacterium bovis BCG Pasteur. While the chromosomes of M. tuberculosis and M. bovis BCG Pasteur show extensive conservation at the grosslevel, comparison with M. leprae revealed a high degree of diversification, with a mosaic‐like pattern apparent. The ordered libraries of M. tuberculosis and M. leprae produced during the course of these studies played a central role in the genome sequencing projects of these two bacilli, showing the utility of this approach for systematic sequencing of bacterial genomes.
Chromosome geometry and intraspecific genetic polymorphism in Gram‐positive bacteria revealed by pulsed‐field gel electrophoresis (minireview)
Authors: Leblond Pierre , Decaris Bernard 
Published: May 2005

AbstractPulsed‐field gel electrophoresis (PFGE) proved to be a powerful approach to study bacterial genomics. The genome structure and genetic polymorphism of Gram‐positive bacteria from the high G+C (Streptomyces) and low G+C (Streptococcus) groups have been studied. PFGE allowed the estimation of the size of their genome at about 8 Mbp and 1.8 Mbp, respectively, and to get an insight into their chromosome geometry. Thus, physical mapping of the genome of wild‐type Streptomyces ambofaciens strains revealed the linearity of the 8 Mbp chromosomal DNA and its typical invertron structure, while the 1.8 Mbp chromosome of Streptococcus thermophilus was shown to be circular. These findings disproved the long‐standing idea of universality of bacterial chromosome circularity. In addition, strains belonging to the species S. ambofaciens and S. thermophilus allowed us to characterize the genetic polymorphism at the intraspecific level. Within the S. thermophilus species, comparison of the physical maps showed a relative conservation of gene order as well as restriction sites along the chromosome. In contrast, variable loci were characterized that revealed localized genome rearrangements. The most spectacular of these corresponded to horizontal gene transfer events of sequences. In S. ambofaciens, the physical maps of three isolates pointed to the conservation of the genetic organization. However, a strong polymorphism was observed in the terminal regions of the linear chromosomal DNA. Previous PFGE studies in S. ambofaciens gave proof of a high structural instability of a limited region of the chromosome called unstable region (i.e., DNA rearrangements such as deletions and amplifications). These intraclonal rearrangements create an impressive intraspecific polymorphism of genome size and shape (linear or circular). In both organisms, the DNA rearrangements are restricted to particular regions of the chromosome.
Polymerase chain reaction‐mediated typing of microorganisms: Tracking dissemination of genes and genomes (minireview)
Authors: van Belkum Alex , Hermans Peter W. M. , Licciardello Lidia , Stefani Stefania , Grubb Warren , van Leeuwen Willem , Goessens Wil H. F. 
Published: May 2005

AbstractThe polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for the identification of species and strains of diverse microorganisms. By aimed amplification of characteristic genes (i.e., genes encoding ribosomal RNA molecules) and subsequent genetic analysis of amplified fragments, information on microbiological systematics and phylogeny can be obtained in a fast and efficient manner. Similar types of gene identification can be used to verify or detect genes responsible for phenotypic characteristics, whereas modified forms of the PCR enable whole genome searches for genetic polymorphisms among strains of a given species. In medical sciences, both strategies, gene and genome variability analysis by PCR, have an increasing impact on the study of the spread of especially those microbes that are multiply resistant to clinically used antibiotics. In this communication we will exemplify the usefulness of PCR‐mediated typing of microorganisms from a clinical perspective while focusing on gene‐ versus genome‐scanning. Special emphasis will be placed on analysis of the dissemination and characteristics of methicillin‐resistant Staphylococcus aureus (MRSA) strains and bacterial factors providing resistance to penicillin and other β‐lactam antibiotics. Technical limitations and possibilities for improvement will be discussed.
Enantioseparation of anaestethic drugs by capillary zone electrophoresis using cyclodextrin‐containing background electrolytes
Authors: Amini Ahmad , Sörman Ulla Paulsen , Lindgren Björn H. , Westerlund Douglas 
Published: May 2005

AbstractThe enantiomers of five racemic anaestethic drugs were resolved with cyclodextrins using capillary zone electrophoresis. Parameters which affected the chiral resolution, such as type and concentration of cyclodextrin, temperature, and addition of organic modifier were investigated. The results show that the enantiomeric discrimination of the solutes is influenced by the structural shape of the solute molecules, separation temperature, and type of cyclodextrin. It was found that α‐cyclodextrin was the best enantioselector for resolution of prilocaine and ketamine, while the enantiomers of mepivacaine, ropivacaine, and bupivacaine were resolved with β‐cyclodextrin and/or modified β‐cyclodextrins, i.e., methyl‐ and 2‐hydroxypropyl‐β‐cyclodextrin, as chiral selectors. The length of the alkyl chain on the amino group of the drug molecule had a strong effect on the enantioresolution of mepivacaine, ropivacaine, and bupivacaine. Baseline separation of racemic ketamine was achieved with α‐and methyl‐β‐cyclodextrin at 15°C. Addition of 5 M urea to the running buffer containing β‐cyclodextrin at high concentrations resulted in the enantioseparation of prilocaine, mepivacaine, and ketamine. Enantioresolution was improved upon the addition of 10% methanol to the buffer containing urea and β‐cyclodextrin. Generally, the complex formed between the S‐enantiomers and modified β‐cyclodextrins was stronger than the corresponding R‐forms. An exception was prilocaine where the R‐form gave a more stable complex both with α‐ and β‐cyclodextrin.