bluuebunny/crossref_metadata_2025_split huggingface dataset:
Response patterns with indirect UV detection in capillary zone electrophoresis
Authors: Lu Bing , Westerlund Douglas 
Published: May 2005

AbstractCapillary zone electrophoresis with indirect UV‐detection was used to separate mixtures containing both positively and negatively charged species. In order to understand the dependence of detector response patterns on the changes in compositions of the background electrolytes and the charge of marker ions (UV‐absorbing ions), the separations were performed in two different systems. In a three‐ion system (analyte ion, coion and counterion) a marker ion was the major ionic component of a buffer solution and in a two‐coion or counterion system the marker ion was used as an additive. In the three‐ion system the response profile of an analyte was in good agreement with the mathematical treatment based on the Kohlrausch regulation function. In the two‐coion or counterion system the response patterns were more complicated; however, the experimental results agree well with data obtained from a computer simulation program. Peak directions of the analytes were not only determined by their relative charge to the marker ion, but were also associated with their relative mobilities to the buffer coion and the marker ion. The analytes with higher effective mobilities compared to the marker ion were detected as positive peaks and the ones with lower effectice mobilities as negative peaks. Similarly to the three‐ion system, the detector response of an analyte was stronger by applying a marker coion compared to a counterion. An interesting result was obtained in the separation of a mixture of quaternary ammonium ions and sugars by using a cationic marker ion. The highest and most symmetrical peak was not a cation, but raffinose anion, which appeared most closely to the system peak. The observation suggests that the electromigration dispersion in its zone was eliminated by migrating close to the electroosmosis. A system peak with the mobility corresponding to the electroosmotic flow was obtained in both systems, and an additional system peak with a mobility close to that the marker ion was present in the systems using marker ions as additives.
High resolution capillary electrophoretic separation of oligonucleotides in low‐viscosity, hydrophobically endcapped polyethylene oxide with cubic order
Authors: Magnusdottir Soffia , Viovy Jean‐Louis , François Jeanne 
Published: May 2005

AbstractA triblock self‐associating polymer with the structure n‐ dodecane‐poly(ethylene oxide)‐n‐dodecane and a very low polydispersity has been used as a matrix to separate a sample of single‐stranded oligonucleotides containing Pd(A)25–30 and Pd(A)40–60. Above a concentration of 4%, this associative polymer forms a micellar network with cubic order and a well‐defined micellar spacing, in which the dodecane micellar cores are bridged by polyoxyethylene segments. This medium combines a low viscosity with excellent resolution of oligonucleotides. This work confirms that associative polymers are potentially powerful media for separation in capillary electrophoresis, and argues in favor of the use of monodisperse products presenting a high‐order in the physical gel state.
Capillary zone electrophoresis of ds‐DNA in isoelectric buffers: Effect of adding of competing, nonamphoteric ions
Authors: Gelfi Cecilia , Mauri Daniela , Perduca Massimiliano , Stellwagen Nancy C. , Righettis Pier Giorgio 
Published: May 2005

AbstractWhen separating ds‐DNA in isoelectric His buffer (pHpI7.6), in the 50–250 mM concentration range, some unique phenomena were observed: improved resolution for smaller DNA fragments, up to ca. 150 bp, and a rapid deterioration of resolution above this critical length (which corresponds to the persistence length). Such phenomenon depended also on voltage and concentration of sieving liquid polymer. Direct binding of His to the DNA helix was hypothesized, with resultant stiffening and an increment of diameter of the DNA fragments, thus inducing an early onset of reptation at the applied voltage in the 100–300 V/cm range. In order to prove this hypothesis, “competing ions” (notably NaCl and KBr) were added to the His background electrolyte: a partial reversal of the His effect was already apparent at low concentrations of such ions (10 mM) and was complete at higher concentrations (30 and 50 mM). By molecular modeling, it was found that His could be docking on the negatively charged oxygen (bound to the phosphate) by offering both charged (primary and tertiary amino) groups to simultaneous binding, thus forming a salt and neutralizing the negative charge borne by the oxygen. The following characteristic bond distances were found: 0.34 nm between the N (imidazolic) and O; 0.32 nm between the primary N and O; 0.36 nm between the two nitrogens engaged in salt formation with the oxygen. In addition, for complexation to occur, the distance between the noncharged nitrogen in the imidazole ring and the nearest phosphate oxygen (engaged in the phosphodiester bridge) should be 0.44 nm. Under these conditions, the two rings present (a six‐membered, ideal one, salt‐linked with the oxygen and rather highly elongated, and the imidazole) will not be precisely coplanar, since the primary and tertiary nitrogens will be one slightly above and one slightly below the plane of the drawing. Upon extensive binding, occupying every available phosphate site, π‐π interactions could occur among the stacks of bound His residues, thus further stabilizing the complex.
On‐line partial filling micellar electrokinetic capillary chromatography‐electrospray ionization‐mass spectrometry of corticosteroids
Authors: Wiedmer Susanne K. , Jussila Matti , Riekkola Marja‐Liisa 
Published: May 2005

AbstractThe one‐line combination of micellar electrokinetic chromatography (MECC) with electrospray ionization‐mass spectrometry (ESI‐MS) was investigated using some corticosteroids as model components. The on‐line technique is difficult because the micelles in the electrolyte solution tend to soil the mass spectrometer and lower the sensitivity of the spectrometer. To prevent the micelles from reaching the mass spectrometer, several techniques have been developed among which is the partial filling (PF) technique. In this study the PF‐MECC technique was investigated in an on‐line MECC‐ESI‐MS study of mixtures of corticosteroids. Because the compounds are uncharged, partitioning or interaction with micelles is required to achieve separation. Surfactant solutions of sodium dodecyl sulfate (SDS), sodium cholate (SC), and SDS/SC mixtures were used as micellar phase. Good MECC separation was achieved after optimization of the surfactant concentrations and the length of the injected micellar plug. Both hydrodynamic and electrokinetic injections of the micellar solutions were tested. A basic ammonium acetate solution was used as the CE electrolyte solution. The ESI‐MS analysis of the compounds was performed in the positive ionization mode, using an acidic sheath liquid. Because of the low MS intensities of the corticosteroids, the peaks were isolated during the MS runs. MS‐MS and MS‐MS‐MS data on the corticosteroids were obtained by off‐line injection of the compounds.
Rapid estimation of octanol‐water partition coefficients of pesticides by micellar electrokinetic chromatography
Authors: Wu Yuan Sheng , Lee Hian Kee , Li Sam F. Y. 
Published: May 2005

AbstractMicellar electrokinetic chromatography (MEKC) was evaluated as a new technique for the rapid estimation of octanol‐water partition coefficient (logKow). Retention measurements for more than 40 reference pesticides with varied structural characteristics and hydrophobicity were carried out in two MEKC systems, based on sodium dodecyl sulfate (SDS) and sodium cholate (SC), respectively. To enable an accurate determination of capacity factors in the SC‐MEKC system, cypermethrin (a synthetic pyrethroid insecticide) was utilized instead of Sudan III as the SC micelle tracer, since a few highly hydrophobic pesticides were found to elute after Sudan III. The linear correlation between logarithmic capacity factor (logk̃′1) and logKow in the two systems was examined. It was found that, under the typical buffer condition (10 mM sodium phosphate with 60 mM surfactant, pH 7.0), the SDS‐MEKC system provided a somewhat wider dynamic range for hydrophobicity (logKow from −1.0 to 4.5). However, the correlation of logk̃′i with logKow was not very high when all the reference pesticides were included in one single calibration set. For the SC‐MEKC system, the dynamic range for logKow was in the range of 1.0–5.5, and a good linear correlation existed between logk̃′i and logKow, even when all reference pesticides were incorporated into a single calibration group. By comparing the regression line of the reference pesticides with that of a group of simple aromatic derivatives, it was discovered that molecular size and functionality posed a less significant effect on the measurement of logKow in the SC‐MEKC system than in the SDS‐MEKC system. Thus, SC‐MEKC shall be the system of choice for the estimation of logKow. The typical error on logKow determination using the current MEKC technique was within 0.5 units, suggesting that MEKC can be a valuable complement to reversed phase – high performance liquid chromatography (RP‐HPLC) for the indirect determination of logKow. Besides maintaining all the advantages of the HPLC approach, the MEKC technique showed some unique benefits, such as better inter‐column reproducibility, higher throughput, and less handling of toxic pesticides and solvents.
Multimodal application of lectin affinity electrophoresis of α‐fetoprotein
Authors: Taketa Kazuhisa 
Published: May 2005

AbstractMultimodal application of lectin affinity electrophoresis of α‐fetoprotein (AFP) glycoforms is reviewed. Crossed affinity immunoelectrophoresis developed by Bøg‐Hansen and others was extended to tandem‐lectin affinity electrophoresis by tandem lining of two different lectin gels and to mixed‐lectin affinity electrophoresis. By introducing an antibody‐affinity blotting technique for detection of separated glycoforms of AFP, several two‐dimensional combinations of lectin affinity electrophoresis became possible: two different lectins for the first and second dimension electrophoresis, lectin‐gradient affinity electrophoresis, and electrophoretic separation of lectin isoforms in the first‐dimension electrophoresis, followed by affinity electrophoresis against the separated lectin isoforms. Usefulness of the different modalities of lectin affinity electrophoresis for several analytical purposes has been described.
Two‐dimensional gel electrophoretic analysis of the changes after immortalization of human cells: Decrease of intracellular α‐2‐macroglobulin fragment
Authors: Kondo Tadashi , Sakaguchi Masakiyo , Yamada Hidenori , Namba Masayoshi 
Published: May 2005

AbstractTo study the mechanisms of immortalization of human cells, an early step in cancer development, we compared the cellular proteins of normal and immortalized human fibroblasts. Two‐dimensional gel electrophoresis showed that one spot with a molecular mass 20 kDa and an isoelectric point of 6.0, became significantly smaller after immortalization of human cells. Further, the spot was rarely observed in four human liver cancer cell lines. Investigation of the N‐terminal amino acids revealed that the spot was a fragment of α‐2‐macroglobulin. Although the 20 kDa fragment contains methionine, the spot was not labeled with [35S]methionine. Thus we concluded that the spot might be derived from the culture medium. These results indicated that intracellular metabolism of α‐2‐macroglobulin, which is a multifunctional protease inhibitor, changed after the cells were transformed.
Structural determination of N‐linked carbohydrates by matrix‐assisted laser desorption/ionization‐mass spectrometry following enzymatic release within sodium dodecyl sulphate‐polyacrylamide electrophoresis gels: Application to species‐specific glycosylation of α1‐acid glycoprotein
Authors: Küster Bernhard , Hunter Ann P. , Wheeler Susan F. , Dwek Raymond A. , Harvey David J. 
Published: May 2005

AbstractThis paper describes a sensitive method for analysis of N‐linked carbohydrates released enzymatically from within the gel following separation of glycoproteins (50–100 pmols) by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE). The separated bands containing the glycoproteins were cut from the gel, destained, reduced and alkylated. N‐linked glycans were then released by in‐gel incubation with peptide N‐glycosidase‐F (PNGase‐F) and extracted with water and acetonitrile. Sialic acid‐containing glycans were converted into methyl esters by reaction with methyl iodide, salts and reagents were removed by passage through a mixed‐bed column of ion‐exchange resins and the glycans were examined by matrix‐assisted laser desorption/ionization (MALDI)‐mass spectrometry. Structural determination of the released glycans was performed by exoglycosidase digestion. Following glycan release and extraction, the protein could be digested within the gel with trypsin, and the masses of the tryptic peptides could be compared with those generated from a sequence database for protein identification. The method is applied to the analysis of N‐linked glycans from α1‐acid glycoprotein from man, cow, sheep and dog. Major species‐specific differences in glycosylation were found. Thus, although all four species used N‐acetyl‐neuraminic acid, only cow and sheep additionally used N‐glycolyl‐neuraminic acid. Biantennary glycans were the predominant carbohydrates in cow, sheep and dog but man produced more triantennary glycans and a substantial amount of tetraantennary sugars. Fucosylation was only found in glycans from man and cow and both cow and sheep glycans were found to have β1‐3‐ and well as β1‐4‐linked galactose residues in the antennae.
'98 Escherichia coli SWISS‐2DPAGE database update
Authors: Tonella Luisa , Walsh Brad J. , Sanchez Jean‐Charles , Ou Keli , Wilkins Marc R. , Tyler Margaret , Frutiger Séverine , Gooley Andrew A. , Pescaru Ioana , Appel Ron D. , Yan Jun X. , Bairoch Amos , Hoogland Christine , Morch Fabienne S. , Hughes Graham J. , Williams Keith L. , Hochstrasser Denis F. 
Published: May 2005

AbstractThe combination of two‐dimensional polyacrylamide gel electrophoresis (2‐DPAGE), computer image analysis and several protein identification techniques allowed the Escherichia coli SWISS‐2DPAGE database to be established. This is part of the ExPASy molecular biology server accessible through the WWW at the URL address http://www.expasy.ch/ch2d/ch2d‐top.html. Here we report recent progress in the development of the E. coli SWISS‐2DPAGE database. Proteins were separated with immobilized pH gradients in the first dimension and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis in the second dimension. To increase the resolution of the separation and thus the number of identified proteins, a variety of wide and narrow range immobilized pH gradients were used in the first dimension. Micropreparative gels were electroblotted onto polyvinylidene difluoride membranes and spots were visualized by amido black staining. Protein identification techniques such as amino acid composition analysis, gel comparison and microsequencing were used, as well as a recently described Edman “sequence tag” approach. Some of the above identification techniques were coupled with database searching tools. Currently 231 polypeptides are identified on the E. coli SWISS‐2DPAGE map: 64 have been identified by N‐terminal microsequencing, 39 by amino acid composition, and 82 by sequence tag. Of 153 proteins putatively identified by gel comparison, 65 have been confirmed. Many proteins have been identified using more than one technique. Faster progress in the E. coli proteome project will now be possible with advances in biochemical methodology and with the completion of the entire E. coli genome.
Mining the human proteome: Experience with the human lymphoid protein database
Authors: Hanash Samir M. , Teichroew Daniel 
Published: May 2005

AbstractWe have undertaken an effort in the past five years aimed at developing a database of lymphoid proteins detectable by two‐dimensional (2‐D) polyacrylamide gel electrophoresis. The database contains 2‐D patterns and derived information pertaining to: (i) polypeptide constituents of unstimulated and stimulated mature T cells and immature thymocytes; (ii) cultured T cells and cell lines that have been manipulated by transfection with a variety of constructs or by treatment with specific agents; (iii) single cell‐derived T and B cell clones; (iv) cells obtained from patients with lymphoproliferative disorders and leukemia; and (v) a variety of other relevant cell populations. The database has experienced a substantial expansion in 2‐D patterns it contains, numbering currently 9167 individual 2‐D patterns. This number represents a fraction of the 30682 2‐D patterns maintained in our databases. The capacity to design and undertake experiments, produce high‐quality 2‐D patterns, and to undertake simple or rudimentary analyses of 2‐D patterns to meet the basic needs of the experiments for which the 2‐D gels were produced has exceeded the capacity to fully and uniformly integrate information generated from any gel image or experiment, across all images and experiments. While only a fraction of the information in the 2‐D patterns contained in the lymphoid database has been mined, novel findings derived from querying the database point to the merits of this protein based approach. Additional resources have recently been put into place to mine more effectively data pertaining to protein expression in lymphoid cells.
Proteomic changes associated with degeneration of myelin‐forming cells in the central nervous system of c‐myc transgenic mice
Authors: Jensen Niels A. , Celis Julio E. 
Published: May 2005

AbstractMyelin is necessary for the conduction of high frequency and high velocity nerve impulses in the central nervous system of mammals, and severe neurological disturbances develop as a result of myelin loss. In this report, we have characterized changes in the brain proteomic profile of transgenic mice that develop a c‐myc‐induced degenerative disorder of myelin. Marked differences were seen in the accumulation of cytoskeletal proteins associated with the pathological condition fibrous gliosis in the optic nerves of affected animals, including upregulation of glial fibrillary acid protein and vimentin. In addition, the expression of several major myelin proteins, including five isoforms of myelin basic protein, four isoforms of cyclic nucleotide 3′‐phosphodiesterase, and myelin‐associated glycoprotein, was markedly reduced in the brains of c‐myc transgenic mice as revealed by immunocytochemistry and by two‐dimensional immunoblots. A number of novel proteomic disease marker candidates were revealed, which displayed pronounced changes in their expression profile. Sequence determination of these proteins and molecular cloning of their mRNAs will provide an opportunity to further evaluate their roles in the disease process.
Protein changes observed in pacing‐induced heart failure using two‐dimensional electrophoresis
Authors: Heinke Monique Y. , Wheeler Colin H. , Chang Dennis , Einstein Rosemarie , Drake‐Holland Angela , Dunn Michael J. , Remedios Cristobal G. Dos 
Published: May 2005

AbstractRapid ventricular pacing in dogs results in a low output cardiomyopathic state which is similar to idiopathic dilated cardiomyopathy in man. However, the pathophysiological mechanisms which cause this failure following pacing are unknown. Five dogs underwent rapid ventricular pacing. Hearts were stimulated at 245 beats per min (bpm) for four weeks and then reduced to 190 bpm to stabilize the failure. Six unoperated dogs were used as controls. This paper compares the two‐dimensional gel electrophoresis (2‐DE) protein patterns of left ventricular samples from the paced myocardium with the control dogs. Changes in protein expression were analyzed qualitatively and semi‐quantitatively. In the paced dog samples 69 protein spots were significantly altered of which 42 were decreased and 27 were elevated. One qualitative change was observed: elongation factor Tu was present only the control hearts. Of these proteins, 20 have been identified by a combination ofN‐terminal protein microsequencing, peptide mass profiling by mass spectrometry, amino acid compositional analysis, and by comparison with databases of canine and human ventricular proteins. Ten of these are associated with mitochondria and energy production, including: pyruvate dehydrogenase E1 component, isocitrate dehydrogenase subunit α, HSP60 and HSP70, creatine kinase M and fatty acid binding protein. The cytoskeletal protein desmin was detected in reduced quantities and a spot corresponding to a fragment of desmin was increased. These results indicate that the development of heart failure in the paced dog involves alterations in mitochondrial energy production, the cytoskeleton and calcium activation.
Method development in pharmaceutical analysis employing capillary electrochromatography
Authors: Angus Peter D. A. , Stobaugh John F. , Victorino Estelita , Payne Kent M. , Demarest Charles W. , Catalano Tom 
Published: May 2005

AbstractCapillary electrochromatography (CEC) has been employed to explore method development for a series of structurally related polar neutral compounds of pharmaceutical relevance. Capillaries with dimensions of 75 μm ID × 25 cm length (34.5 cm total) were packed with Spherisorb ODS‐1, Hypersil phenyl, and Hypersil MOS (all 3 μm particles) and were compared in the reversed‐phase mode in order to determine which phase provided the best initial performance and thus serve as the phase of choice for additional method development experiments. The various separation parameters examined for their effect on efficiency, k, resolution, and linear velocity included percent and type of organic modifier, buffer concentration, voltage, and temperature. All separations were conducted with an acidic mobile phase (aqueous mobile phase component, pH 3.0). The separation efficiencies obtained were on the order of 200000–260000 plates/m, which equates to reduced plate heights of 1.22 for columns packed with Spherisorb ODS‐1. Repeatable column‐to‐column separation performance was demonstrated.
Application of heparin to chiral separations of antihistamines by capillary electrophoresis
Authors: Jin Yingkun , Stalcup Apryll M. 
Published: May 2005

AbstractA study of the chiral separations of antihistamines, including pheniramine, chlorpheniramine, brompheniramine, carbinoxamine and doxylamine in capillary electrophoresis (CE) was accomplished using heparin as a chiral additive (CA) and phosphate buffer as the background electrolyte. Several factors were shown to affect both the selectivity and the migration time, including concentration of heparin, concentration of buffer, and the pH. A dual mechanism involving both inclusion complexation and ionic interactions with heparin is thought to be responsible for the chiral recognition. In the pH range of 2.6–3.5 and reversed polarity, baseline resolutions were obtained using a wide range of buffer and heparin concentrations. Typically, chiral resolution was obtained within 50 min.