bluuebunny/crossref_metadata_2025_split huggingface dataset:
Micellar electrokinetic capillary chromatography of three natural vitamin A derivatives
Authors: Profumo Aldo , Profumo Vincenzo , Vidali Giorgio 
Published: May 2005

AbstractMicellar electrokinetic chromatography (MEKC) using bile salts has been employed to separate retinoids differing in structure and charge; bile salts in MEKC allows the separation of liposoluble molecules but, to the best of our knowledge, there are only few data on the above‐mentioned technique for the separation of highly hydrophobic compounds. The three natural vitamin A derivatives, retinal, retinol and retinoic acid, were successfully separated by MEKC using sodium cholate within a relatively short time (ca. 25 min), whereas the separation of these compounds was not successful using sodium dodecyl sulfate or sodium deoxycholate. Several parameters (pH and organic modifiers, in addition to bile salts concentration) have been tested to provide a system that can be extended to synthetic retinoids, which are often used in treating several diseases, including cancer prevention and therapy.
Probing the microheterogeneity of O‐specific chains from Yersinia ruckeri using capillary zone electrophoresis/electrospray mass spectrometry
Authors: Bateman Kevin P. , Banoub Joseph H. , Thibault Pierre 
Published: May 2005

AbstractThe analysis of underivatized oligosaccharides arising from mild acid hydrolysis of endotoxins from Yersinia ruckeri serotype 02 was achieved using on‐line capillary zone electrophoresis‐electrospray mass spectrometry (CZE‐ESMS). This technique provided unparalleled resolution of the differnt glycans obtained from purified fractions of the native endotoxins or from hydrolysis of lipopolysaccharides from Y. ruckeri. Electrophoretic conditions enabling the separation of anionic and cationic analytes were developed to determine possible sites of heterogeneity on either the core or the O‐chain glycans. Structural characterization of underivatized oligosaccharides identified in the ion electropherograms was achieved using tandem mass spectrometry under lowcollision energy conditionsNRCC 39726.
.
Electrospray interface for capillary electrophoresis‐mass spectrometry with fiber‐optic UV detection close to the electrospray tip
Authors: Foret František , Kirby Daniel P. , Vouros Paul , Karger Barry L. 
Published: May 2005

AbstractA miniaturized, integrated capillary electrophoresis‐ultraviolet detection‐electrospray ionization‐mass spectrometry (CE‐UV‐ESI‐MS) interface has been constructed and evaluated. The device incorporates a fiber optic detection cell close to the electrospray tip to allow UV monitoring of separated zones just prior to their admittance into the mass spectrometer. This configuration provides precise information about the time when UV‐active zones enter the electrospray and allows easy location of analyte mass information in the ion current profile. The miniaturized dimensions of the interface allow the use of short capillaries for fast separations.
Optimized continuous flow electrophoresis
Authors: Weber Gerhard , Boček Petr 
Published: May 2005

AbstractContinuous flow electrophoresis (CFE) was optimized by employing (i) electrophoretic regimes with stacking properties, to eliminate electrohydrodynamic dispersion, (ii) quasi‐mixed zones to prevent precipitation of the stacked analytes, (iii) sheath liquid streams at the electrode compartment membranes to prevent penetration of the electrode reaction products into the separation chamber, (iv) proper engineering of the separation chamber to provide efficient dissipation of Joule heat, and (v) counterflow at the collection outlets to eliminate the problems of dead volumes and uneven collection of separated species. Data on direct temperature measurements in the separation chamber at various levels of the dissipated electric power are presented. Preparative runs of amyloglucosidase in the isoelectric focusing (IEF) mode and rat liver organelles in the isotochophoresis (ITP) mode demonstrate the high performance of the optimized CFE system.
Determination of peptide dissociation constants and stokes radius at different protonation stages by capillary electrophoresis
Authors: Castagnola Massimo , Rossetti Diana V. , Cassiano Loredana , Misiti Francesco , Pennacchietti Lucia , Giardina Bruno , Messana Irene 
Published: May 2005

AbstractPeptide electrophoretic mobility measured by capillary zone electrophoresis can be regarded as deriving from the mean of mobilities of different protonated forms, each one participating according to its charge, Stokes radius and relative percentage. The percentage is a function of the peptide dissociation constant and solutior pH. Therefore, mobility modifications due to pH variations can be related to peptide dissociation constant, charge, and Stokes radius throughout general binding equations. Thus, not only can peptide dissociation constants be measured, but information about Stokes radius modifications linked to proton loss can also be obtained with picomoles of peptide.
DNA mobility anomalies are determined primarily by polyacrylamide gel concentration, not gel pore size
Authors: Stellwagen Nancy C. 
Published: May 2005

AbstractThe dependence of DNA mobility anomalies on gel pore size has been studied in polyacrylamide gels with a wide variety of compositions, using molecular weight ladders containing multiple copies of normal (12B) and anomalously slowly migrating (12A) 147‐base pair restriction fragments from plasmid pBR322 as the migrating probe molecules. If the gel pore size is increased by decreasing the total acrylamide concentration (%T) at constant cross‐linker ratio (%C), the usual method of increasing gel pore size, the mobility anomalies decrease with increasing gel pore radius as though the 12A multimers were retarded by a sieving mechanism. However, the decrease in the mobility anomalies is independent of whether the apparent gel pore radius is larger or smaller than the DNA radius of gyration, suggesting that gel pore size is not the controlling variable. If the acrylamide concentration is held constant and the gel pore size is increased by decreasing %C at constant %T, the mobility anomalies of the largest 12A multimers (6 mers and higher) decrease with increasing gel pore radius, because of sieving effects, until the effective gel pore radius becomes approximately equal to the DNA radius of gyration, after which the mobility anomalies level off and become independent of gel pore size. The mobility anomalies exhibited by 5‐mers and smaller multimers of fragment 12A are independent of gel pore radius in all gels with constant %T. Similar results are observed with a molecular weight ladder containing phased A‐tracts from the kinetoplast bending locus. Since the anomalous electrophoretic mobilities depend primarily on the total acrylamide concentration in the gel, and not on the apparent gel pore radius, increases in the magnitude of the mobility anomalies with increasing gel concentration (and decreasing gel pore radius) cannot be taken as evidence for DNA curvature.
Quantitative description of migration behavior of porphyrins based on the dynamic complexation model in a nonaqueous capillary electrophoresis system
Authors: Bowser Michael T. , Sternberg Ethan D. , Chen David D. Y. 
Published: May 2005

AbstractThe effect of an additive (Brij 35) on the mobilities of a group of porphyrin acids is quantitatively characterized based on a 1:1 dynamic complexation model. Varying additive concentration shifts the equilibrium and changes the viscosity of the background electrolyte. The equilibrium constant, the electrophoretic mobility of the free analyte, and the electrophoretic mobility of the complex are identified as the parameters necessary to describe the analytes' migration behavior. Several statistical methods for obtaining these parameters are discussed. The equilibrium constants and complex mobilities are calculated using three different linear regression methods. The weighted y‐reciprocal method was preferred because it gives smaller error, and the data points are evenly distributed along the concentration axis. These values are confirmed using a nonlinear regression to ensure that the proper weighting was used in the linear regression plots. The parameters are then used to predict the apparent mobilities of the analytes over the entire additive concentration range, allowing the optimum separation conditions to be identified. For disclike molecules, such as porphyrins, the mobility is determined by the orientation of the molecule in an electric field, in addition to their size and charge. The strength of binding between the porphyrins and Brij 35 depends on the number of binding sites and the solvation shell.
Effects of catholytes on the mobilization of proteins after capillary isoelectric focusing
Authors: Manabe Takashi , Miyamoto Hiromitsu , Iwasaki Aiko 
Published: May 2005

AbstractPurified proteins and human plasma proteins were separated by capillary isoelectric focusing and detected by cathodic mobilization, e.g. by replacing the cathodic sodium hydroxide solution by solutions containing another anion. The effect of catholyte anions on the resolution of mobilized proteins was examined. Compared with the chloride or phosphate anion, organic anions having small dissociation constants improved protein resolution, especially in the range of acidic proteins. Among the catholytes examined, acetic acid gave the best resolution for purified proteins and human plasma proteins. Measurement of the changes of electric current during the mobilization process indicated that organic anions with low mobility move slowly towards the anode and retard changes of pH gradient in the capillary. Isoelectric focusing, cathodic mobilization, and direct pH measurement in polyacrylamide gel columns (1.3 mm internal diameter and 38 mm long) also revealed these effects of low mobility anions. In order to visualize the behavior of human plasma proteins in the mobilization step, micro two‐dimensional polyacrylamide gel electrophoresis was employed. The results indicated that the proteins migrate towards the cathode, preserving their relative positions attained during the isoelectric focusing step.
Potential of two‐dimensional electrophoresis in routine identification of closely related durum wheat lines
Authors: Picard Philippe , Bourgoin‐Grenèche Mireille , Zivy Michel 
Published: May 2005

AbstractFour closely related curum wheat varieties were compared by computer‐assisted analysis of two‐dimensional electrophoretic maps of leaf proteins. A low inter‐varietal polymorphism was revealed and seven reliable qualitatively varying proteins allowed rapid visual identification of genotypes. For numerous spots, presence/absence or quantitative variations were greatly affected by a batch effect. Several criteria that should be used to discard unreliable spots or gels a priori were reviewed. Nevertheless, it was shown that, provided that the experimental design allows the integration of the batch effect, screening for discriminant markers as well as computing distances based on protein quantity variations are possible and allow variety identification. Euclidean and Mahalanobis distances allowed variety discrimination and single gel classification with a minimum risk of error, not only by taking into account the quantitative variations in discriminant proteins selected by analysis of variance, but also by taking into account all reproducible spots. The possible applications of two‐dimensional electrophoresis in variety identification are discussed.
Analysis for the stability of platinum‐containing species in soil samples using capillary electrophoresis interfaced on‐line with inductively coupled plasma mass spectrometry
Authors: Michalke Bernhard , Lustig Sönnke , Schramel Peter 
Published: May 2005

AbstractOnline interfacing of capillary electrophoresis (CE) with inductively coupled plasma‐mass spectrometry (ICP‐MS) has been accomplished using a laboratory‐made nebulizer. The high resolution of CE is used for the separations of Pt species of standard solutions and real samples, followed by ICP‐MS for element‐specific detection within 12 min. The samples are analyzed immediately after sample preparation or after 2–4 h of aging in order to elucidate undesired species transformations which may occur before analysis. The method was proven not to impair the species during the analytical procedure while being a necessary prerequisite to judge time‐dependent species transformations. Quality control aspects concerning species stability during the analytical procedure and stability of electrical current during nebulization were studied. A possibly interfering suction flow was estimated and found to be negligible. The results will serve as a basis for quality assurance in future investigations about Pt speciation in soil.
Stereoselective analysis of herbicides by capillary electrophoresis using sulfobutyl ether β‐cyclodextrin as chiral selector
Authors: Desiderio Claudia , Polcaro Chiara M. , Fanali Salvatore 
Published: May 2005

AbstractCapillary zone electrophoresis has been used for the enantiomeric separation of several herbicides. Different β‐cyclodextrin (CD) derivatives have been investigated for chiral separations and among them the negatively charged sulfobutyl ether β‐cyclodextrin (SBE‐β‐CD) proved to be effective for the stereoselective resolutions of the investigated herbicides. The effect of CD concentration, buffer pH and organic modifier on effective mobilities, resolution and selectivity of the analytes have been studied. Addition of SBE‐β‐CD (5–50 mg/mL) to the buffer at pH 9 resulted in a general increase of migration times as well as resolution. A CD concentration as low as 5 mg/mL was effective to completely resolve napropamide and ethofumesate enantiomers. Buffer solutions containing 40 mg/mL of SBE‐β‐CD were chosen to study the effect of buffer pH (7, 8, and 9) on chiral separation of the herbicides. No great differences in resolution and effective mobilities have been found in the pH 7–9 range. The addition of different organic modifiers to the background electrolyte at pH 9, containing 20 mg/mL of SBE‐β‐CD, showed different effects. Methanol was the most effective in improving resolution but in some cases total loss in enantiomeric separation was observed. The qualitative analysis of an enantiomerically pure herbicide (flamprop isopropyl) commercial preparation is also shown.
Characterization of humic substances using capillary electrophoresis with photodiode array and laser‐induced fluorescence detection
Authors: Nordén Maria , Dabek‐Zlotorzynska Ewa 
Published: May 2005

AbstractThe effect of organic modifiers (organic solvents and urea) on the electrophoretic buffer was investigated in an attempt to enhance resolution in the fingerprinting of two humic substances (HS): an aquatic fulvic acid (FA) and a soil humic acid (HA). Two detection modes, photodiode array and laser‐induced fluorescence, were applied. The addition of organic solvents (acetonitrile, acetone, 2‐propanol and tetrahydrofuran) in 10 mM Na2B4O7 (pH 9.0) resulted in a clear difference in electrophoretic behavior of the studied HS compared to the absence of organic solvents. There were also marked differences in the electrophoretic profiles using a 2‐propanol‐borate buffer with urea. The study of the interaction between metals and HS showed that there was a change in the migration pattern in the presence of Al(III), indicating the specific binding sites for aluminum.
Analysis of nitramine and nitroaromatic explosives in pink water by capillar electrophoresis
Authors: Oehrle Stuart A. 
Published: May 2005

AbstractAnalysis of nitramine and nitroaromatic explosives is of interest for environmental applications. Analysis of 14 nitramine and nitroaromatic explosives was accomplished by micellar electrokinetic capillary chromatography (MECC). Analysis times under 14 min were possible employing a phosphate‐sodium dodecyl sulfate (SDS) electrolyte and direct UV detection at 254 nm. Analysis of various waste water samples (called “pink water”) from ammunition plants was performed.
Improved and simplified in‐gel sample application using reswelling of dry immobilized pH gradients
Authors: Sanchez Jean‐Charles , Rouge Véronique , Pisteur Michel , Ravier Florence , Tonella Luisa , Moosmayer Marlis , Wilkins Marc R. , Hochstrasser Denis F. 
Published: May 2005

AbstractA simple and inexpensive methacrylate rehydration chamber was built to accomodate ten immobilized pH gradient (IPG) strips. In the chamber, entire IPG gels were used for sample application, with the protein entering the gels during their rehydration. For rehydration, commercially available or laboratory‐made strips were positioned in the grooves with the gel in contact with 500 μL of sample for 6 h or overnight. This avoided the use of sample cups, eliminated precipitation at the sample application site, thus improving resolution over the entire pH range of the gels. It also allowed precise control of protein amounts and sample volumes loaded into the IPG gels, and also lowered costs of reagents during rehydration and equilibration owing to the reduced volumes. Up to 5 mg of protein can be loaded on wide IPG gels and up to 15 mg of some samples on narrow pH range gels.
Detailed peptide characterization using PEPTIDEMASS – a World‐Wide‐Web‐accessible tool
Authors: Wilkins Marc R. , Lindskog Ingrid , Gasteiger Elisabeth , Bairoch Amos , Sanchez Jean‐Charles , Hochstrasser Denis F. , Appel Ron D. 
Published: May 2005

AbstractIn peptide mass fingerprinting, there are frequently peptides whose masses cannot be explained. These are usually attributed to either a missed cleavage site during the chemical or enzymatic cutting process, the lack of reduction and alkylation of a protein, protein modifications like the oxidation of methionine, or the presence of protein post‐translational modifications. However, they could equally be due to database errors, unusual splicing events, variants of a protein in a population, or artifactual protein modifications. Unfortunately the verification of each of these possibilities can be tedious and time‐consuming. To better utilize annotated protein databases for the understanding of peptide mass fingerprinting data, we have written the program “PEPTIDE‐MASS”. This program generates the theoretical peptide masses of any protein in the SWISS‐PROT database, or of any sequence specified by the user. If the sequence is derived from the SWISS‐PROT database, the program takes into account any annotations for that protein in order to generate the peptide masses. In this manner, the user can obtain the predicted masses of peptides from proteins which are known to have signal sequences, propeptides, transit peptides, simple post‐translational modifications, and disulfide bonds. Users are also warned if any peptide masses are subject to change from protein iso‐forms, database conflicts, or an mRNA splicing variation. The program is freely accessible to the scientific community via the ExPASy World Wide Web server, at the URL address: www.expasy.ch/www/tools.html.
Identification of two‐dimensional gel electrophoresis resolved yeast proteins by matrix‐assisted laser desorption ionization mass spectrometry
Authors: Larsson Thomas , Norbeck Joakim , Karlsson Hasse , Karlsson Karl‐Anders , Blomberg Anders 
Published: May 2005

AbstractProtein extract from yeast cells growing exponentially in saline medium was separated by two‐dimensional polyacrylamide gel electrophoresis (2‐D PAGE), with the separation in the first dimension on a wide range immobilized pH (3–10) gradient. From one preparative 2‐D gel a number of previously identified proteins were used as test material for our initial matrix‐assisted laser desorption ionization mass spectrometry (MALDI‐MS) efforts on large scale rapid protein spot identification. Sample preparation via in‐gel trypsin digestion was slightly modified to be compatible to MS analysis, and via this modified procedure MS generated peptide mass profiles could, in most cases with good precision, identify the protein in question. Preferential ionization was tested on a yeast aldehyde dehydrogenase (ALD7), and it was shown that the ionization of some peptides was clearly suppressed by the presence of others. Roughly 50% of the observed peptide masses was found by the search routines in the database, and the mass measurement accuracy of the peptides was within 0.5 Da. Silver‐stained gels could be used with good results for the generation of peptides to be analyzed by MALDI‐MS. For one of the 2‐D resolved proteins, glycerol 3‐phosphatase (GPP1), the post‐source decay (PSD) spectrum proved crucial in identification.
The analysis of myocardial proteins by infrared and ultraviolet laser desorption mass spectrometry
Authors: Sutton Chris W. , Wheeler Colin H. , U Sally , Corbett Joseph M. , Cottrell John S. , Dunn Michael J. 
Published: May 2005

AbstractThe use of infrared (IR) and ultraviolet (UV) matrix‐assisted laser desorption (MALDI) mass spectrometry to analyse myocardial proteins separated by two‐dimensional (2‐D) polyacrylamide gel electrophoresis (PAGE) is discussed. Proteins were electroblotted onto a FluoroTrans polyvinylidene difluoride (PVDF) membrane in order to facilitate analysis by MALDI, which represented the most efficient means of extracting large numbers of proteins simultaneously. Once on a FluoroTrans membrane, IR‐MALDI was used to obtain spectra from selected protein spots, but no useful signals were obtained with UV MALDI. Spectra were generated from 46 of 50 spots analysed with protein masses from 13 to 82 kDa and isoelectric points (pI) 4.7–7.8. For those protein spots that had previously been characterised, and for which both sequence and post‐translational modification data were known, IR‐MALDI data was within plus or minus 0.5% of the expected mass. Some spots contained more than one protein signal, illustrating the increased information obtainable from MALDI, but also suggesting the limit of resolution of 2‐D gels for separating large numbers of proteins. Attempts to digest proteins with specific proteases and generate peptide mass fingerprints by MALDI analysis on the membrane were unsuccessful with either IR or UV lasers. The peptides were extracted from the membrane and readily analysed by UV MALDI for peptide spectra. Poor data was obtained for peptide digests with IR‐MALDI, probably because of matrix suppression by digest buffer. In order to obtain the maximum amount of information from blotted proteins, both IR and UV MALDI were required.