pinecone/core-2020-05-10-deduplication huggingface dataset:
Theoretical Contribution Towards Understanding Specific Behaviour of “Simple” Protein‐film Reactions in Square‐wave Voltammetry

Surface reactions of uniformly adsorbed redox\ud
molecules at working electrode surface are seen as\ud
adequate models to studying chemical reactivity of many\ud
lipophilic enzymes. When considered under pulse voltammetric\ud
techniques, these systems show several uncommon\ud
features, whose origin is still not completely clear. The\ud
phenomena of “quasireverible maximum”, “splitting” of\ud
the net peak in square-wave voltammetry, and the very\ud
steep descent of Faradaic currents of simple surface redox\ud
reactions exhibiting fast electron transfer are just some of\ud
the features that make these systems quite interesting for\ud
further elaborations. In this work, we present a set of\ud
theoretical calculations under conditions of square-wave\ud
voltammetry in a way to try to explain some of aforementioned phenomena. The major goal of our work is to get insight to some voltammetric and chrono-amperometric\ud
features of two considered surface reactions, i.e. (1) the\ud
“simple” surface redox reaction, and (2) surface redox\ud
reaction coupled to follow-up irreversible chemical reaction\ud
of electrochemically generated redox species (or\ud
surface ECirr). We focus on the role of created Red(ads)\ud
(here in the reduction pulses only) to the current\ud
components of calculated square-wave voltammograms\ud
exhibiting fast electrode reaction. We show that the\ud
irreversible chemical removal of electrochemically generated\ud
Red(ads) species, created in the potential pulses\ud
where half-reaction of reduction Ox(ads)+ne- ---> Red(\ud
ads) is “defined” to take place, causes significant\ud
increase of all square-wave current components. The\ud
results presented in this work show how complex the\ud
chrono-amperometric features of surface redox reactions\ud
under pulse voltammetric conditions might be. In addition,\ud
we point out that both half reactions of a given\ud
simple surface redox process can occur, at both, “only\ud
reduction” and “only oxidation” potential pulses in\ud
square-wave voltammetry. This, in turn, contributes to the\ud
occurrence of many phenomena observed in simple\ud
protein-film voltammetry reactions. The effects of chemical\ud
reaction rate to the features of calculated squarewave\ud
voltammograms of surface ECirr systems with fast\ud
electrode reaction are reported for the first time in this\ud
work
Fast preparative isoelectric focusing of phycocyanin subunits in layers of granulated gels

A new method is presented for the fast preparative separation of the light-harvesting photosynthetic pigment C-phycocanin into its  and subunits, which is based on isoelectric focusing in layers of granutaled gels containing 7 M urea. The method has been successful in cases where other separation procedures failed. The recovery of the separated chains of the light -sensitive biliprotein amounts to 70 � 10 % when the separation is carried out under light exclusion and in an argon atmosphere. A simple and inexpensive setup for work under an atmosphere of protective gas is described.
Antigen-specific electrophoretic cell separation for immunological investigations

Preincubation of human blood lymphocytes with cell surface antigen specific antibodies under non-capping conditions reduces the electrophoretic mobility of the corresponding lymphocyte subpopulation. Antigen-positive and antigen-negative cells can be separated by free flow electrophoresis with high yield, purity and viability. The use of fluorescence-labelled second antibodies augments the induced decrease in net surface charge density, and allows rapid detection of antigen-positive cells in the fractions of electrophoresis. Carrier-free cell electrophoresis of human peripheral blood lymphocytes after reaction with anti-IgM-antibody or the monoclonal antibodies OKT4 or OKT8, and sandwich staining with tetrarhodamine isothiocyanate-labelled anti-IgG resulted in the large-scale separation of high pure human B and T lymphocyte subpopulations. Their functional integrity was shown in assays of lymphocyte transformation and of antigen-specific induction and regulation of antibody synthesis in vitro. These separate lymphocyte subpopulations are useful tools for immunological investigations. While, for instance, the effects of drugs on human lymphocytes are obscured by coincident changes in cell composition of the peripheral blood tested that do not by themselves reflect whole body immunocompetence, the cell separation and in vitro assays at a defined cell number and cell composition allow the recording of quantitative changes in the function of different cell subpopulations. We studied the influence of the anesthetic thiopental on separated human lymphocyte subsets. In both polyclonal lectin stimulation and in vitro antibody production, thiopental exhibited a noncytotoxic suppression of lymphocyte functions. B-Cells, T-helper and T-suppressor cells were equally affected and showed the same dose response.(ABSTRACT TRUNCATED AT 250 WORDS
Computer simulation of pulsed field gel runs allows the quantitation of radiation-induced double-strand breaks in yeast

A procedure for the quantification of double-strand breaks in yeast is presented that utilizes pulsed field gel electrophoresis (PFGE) and a comparison of the observed DNA mass distribution in the gel lanes with calculated distributions. Calculation of profiles is performed as follows. If double-strand breaks are produced by sparsely ionizing radiation, one can assume that they are distributed randomly in the genome, and the resulting DNA mass distribution in molecular length can be predicted by means of a random breakage model. The input data for the computation of molecular length profiles are the breakage frequency per unit length, , as adjustable parameter, and the molecular lengths of the intact chromosomes. The obtained DNA mass distributions in molecular length must then be transformed into distributions of DNA mass in migration distance. This requires a calibration of molecular length vs. migration distance that is specific for the gel lane in question. The computed profiles are then folded with a Lorentz distribution with adjusted spread parameter  to account for and broadening. The DNA profiles are calculated for different breakage frequencies  and for different values of , and the parameters resulting in the best fit of the calculated to the observed profile are determined.
Improvement of the solubilization of proteins in two-dimensional electrophoresis with immobilized pH gradients.

website publisher: www.interscience.wiley.comMembrane and nuclear proteins of poor solubility have been separated by high resolution two-dimensional (2-D) gel electrophoresis. Isoelectric focusing with immobilized pH gradients leads to severe quantitative losses of proteins in the resulting 2-D map, although the resolution is usually high. Protein solubility could be improved by using denaturing solutions containing various detergents and chaotropes. Best results were obtained with a denaturing solution containing urea, thiourea, and detergents (both nonionic and zwitterionic). The usefulness of thiourea-containing denaturing mixtures is shown for microsomal and nuclear proteins as well as for tubulin, a protein highly prone to aggregation
The measurement of genetic diversity in mycobacterium tuberculosis using random amplified polymorphic DNA profiling

Mycobacterium tuberculosis has caused a resurgence in pulmonary disease in both developed and developing countries in recent times, particularly amongst people infected with the human immunodeficiency virus. The disease has assumed epidemic proportions in South Africa and in the 
Eastern Cape Province in particular. Of further concern is the isolation of increasing numbers of multiply drug resistant strains. Knowledge of the genetic capability of this organism is essential for the successful development of novel antibiotics and vaccines in an attempt to bring the global pandemic under control. Measurement of the genetic diversity of the organism may significantly 
contribute to such knowledge, and is of vital importance in monitoring epidemics and in improving treatment and control of the disease. This will entail answering a number of questions related to the degree of genetic diversity amongst strains, to the difference between urban and rural strains, and between drug resistant and drug sensitive strains, and to the geographical distribution of strains. In order to establish such baseline information, RAPD profiling of a large population of isolates from the western and central regions of the Eastern Cape Province was undertaken. A smaller number of drug resistant strains from a small area of KwaZulu-Natal were also analysed, with a view to establishing the genetic difference between strains from the two provinces. Cluster analysis, analysis of molecular variance and Geographical Information Systems technology were used to analyse the RAPD profiles generated. An unexpectedly high degree of genetic diversity was detected in strains from both provinces. While no correlation was seen between genetic diversity and either urban-rural situation or geographical location, a small degree of population structure could be correlated with drug resistance in the Eastern Cape. Furthermore, a significant degree of population structure was detected between strains from the two provinces, although this was still within the parameters for conspecific populations. Future work is necessary to further characterise strains from rural areas of both provinces, as well as from the eastern region of the Eastern Cape in an attempt to pinpoint the cause of the separation of the provincial populations.
A versatile electrophoresis system for the analysis of high- and low-molecular-weight proteins.

website publisher www.interscience.wiley.comInternational audienceA new, versatile, multiphasic buffer system for high-resolution sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins in the relative molecular weight range of 300 000-3000 Da is described. The system, based on the theory of multiphasic zone electrophoresis, allows complete stacking and destacking of proteins in the above M(r) range. The buffer system uses taurine and chloride as trailing and leading ion, respectively, and Tris, at a pH close to its pK(a), as the buffering counterion. Coupled with limited variation in the acrylamide concentration, this electrophoresis system allows to tailor the resolution in the 6-200 kDa M(r) range, with minimal difficulties in the post electrophoretic identification processes
Comparison of charged cyclodextrin derivatives for the chiral separation of atropisomeric polychlorinated biphenyls by capillary electrophoresis

Charged cyclodextrin (CD) derivatives were used as chiral selectors in electrokinetic\ud
chromatography (EKC) for the chiral separation of highlyhydrophobic neutral racemates\ud
such as atropisomeric polychlorinated biphenyls (PCBs).  -CD-phosphated,  -CD sulfated,\ud
succinylated--CD (Succ--CD) and succinylated- -CD (Succ- -CD) were used\ud
as anionic CDs. As cationic CD, 6-monodeoxy-6-monoamino- -CD ( -CD-NH2) was\ud
tested for the first time in order to separate PCBs. From the different CD derivatives\ud
employed, the best separations were obtained with the cationic CD derivative. Thus,\ud
the use of  -CD-NH2 in phosphate buffer at pH 2.0 containing urea allowed the chiral\ud
recognition of eleven PCBs (45, 84, 88, 91, 95, 131, 136, 144, 149, 176, and 197). In this\ud
case, the addition of 2 M urea to the buffer solution was crucial to achieve the chiral\ud
separation of PCBs. The addition of acetonitrile to 10 mM phosphate buffer (pH 2.0)\ud
with 30 mM  -CD-NH2 and 2 M urea improved considerably the chiral resolution obtained\ud
for PCBs 91, 95, 136, 144, 149, and 197 although an increase in the analysis time was\ud
also observed. All the results obtained were compared with those previously obtained\ud
with the dual CD system carboxymethyl--CD/ -CD.\ud
Rapid determination of salbutamol in pharmaceutical preparations by chiral capillary electrophoresis

A fast and simple method of chiral capillary electrophoresis (CE) has been applied to the analysis of salbutamol in different pharmaceutical preparations. Using of a 25 mM acetate buffer (pH 5.0), containing 13.1 mg/mL carboxymethyl- -cyclodextrin (CM- -\ud
CD), an applied voltage of 20 kV and a temperature of 25 C, the enantiomers of salbutamol could be separated in about 2 min. Three different pharmaceutical preparations (two syrups, one oral solution, and two kind of tablets) containing a racemate of salbutamol\ud
were injected directly in the CE system, following dilution in dimethyl sulfoxide\ud
(DMSO). Appreciable differences in the retention times were observed for salbutamol enantiomers in the different formulations studied, which were attributed to the effect of the matrix components on the electrophoretic mobility. The standard addition method\ud
was used for the calibration due to the existence of matrix interferences. Finally, the stability of the enantiomers of salbutamol in the oral solution was studied calculating the enantiomeric ratio values when the solution was injected immediately after being opened in the first case and after being opened and stored in the fridge for two months in the second case
Retention modeling and resolution optimization for a group of N-phenylpyrazole derivatives in micellar electrokinetic chromatography using empirical and physicochemical models

The optimization of the separation resolution for a group of N-phenylpyrazole derivatives\ud
in micellar electrokinetic chromatography (MEKC) as a function of the separation\ud
buffer composition (surfactant and organic modifier concentration) has been performed.\ud
In order to achieve our purpose, the first step has been the prediction of the\ud
migration times of the electroosmotic flow (t0) and micelles (tm), and the retention\ud
factors of solutes (k), as a function of surfactant (sodium dodecyl sulfate) and alcohol\ud
(n-propanol or n-butanol) concentrations, by means of empirical equations. Also, some\ud
physicochemical models have been applied to relate the retention factors to the surfactant\ud
and the organic modifier concentrations in order to optimize the separation\ud
resolution and to increase our knowledge of the separation process. Finally, a comparison\ud
of the resolution optimization through the use of the physicochemical and\ud
empirical models selected has been made in order to obtain the optimum separation\ud
buffer composition for the separation of a group of 17 N-phenylpyrazole derivatives\ud
as test solutes.The authors thank the Comisión Interministerial de Ciencia y Tecnología (Spain) for project PB98-0709 and\ud
Dr. O. Jiménez thanks the Universidad de Alcalá (Madrid,Spain) for project E029/98
Capillary zone electrophoresis for analysis of phytochelatins and other thiol peptides in complex biological samples derivatized with monobromobimane

A new method to improve the analysis of phytochelatins and their precursors (cysteine, γ-Glu-Cys, and glutathione) derivatized with monobromobimane (mBrB) in complex biological samples by capillary zone electrophoresis is described. The effects of the background electrolyte pH, concentration, and different organic additives (acetonitrile, methanol, and trifluoroethanol) on the separation were studied to achieve optimum resolution and number of theoretical plates of the analyzed compounds in the electropherograms. Optimum separation of the thiol peptides was obtained with
150 mM phosphate buffer at pH 1.60. Separation efficiency was improved when 2.5% v/v methanol was added to the background electrolyte. The electrophoretic conditions were 13 kV and capillary dimensions with 30 cm length from the inlet to the detector (38 cm total length) and 50 μm inner diameter. The injection was by pressure at 50 mbar for 17 s. Under these conditions, the separation between desglycyl-peptides and phytochelatins was also achieved. We also describe the optimum conditions for the derivatization of biological samples with mBrB to increase electrophoretic sensitivity and number of theoretical plates. The improved method was shown to be simple, reproducible, selective, and accurate in measuring thiol peptides in complex biological samples, the detection limit being 2.5 μM glutathione at a wavelength of 390 nm.Plan Nacional de I+D (Ref: REN 2003 – 02414
On-Line Counting of Cysteine Residues in Peptides during Electrospray Ionization by Electrogenerated Tags and Their Application to Protein Identification

The electrochemically induced mass spectrometric tagging of cysteines by substituted hydroquinones was studied for peptides in a classical electrospray solvent (i.e., MeOH/H2O/AcOH 50/49/1). The tagging efficiency was tested with different hydroquinone compounds on an undecapeptide containing one cysteine residue. 2-Carboxymethylhydroquinone was the most reactive probe and revealed to be suitable for cysteine quantification in peptides containing up to three cysteine residues, even in the case of two consecutive cysteines in the sequence. We demonstrate the compatibility of the on-line electrochemical tagging method for the cysteine content analysis of peptides coming from gel-free protein digestion procedures. The identification of bovine serum albumin and human α-lactalbumin digest samples in a peptide mapping strategy was greatly improved by the application of the electrotagging technique as post-column treatment. Indeed, the determination of cysteine content in the tryptic peptides provided powerful information in order to enhance the identification score as well as the discrimination against other protein candidates. The tagging method was then applied to the determination of four proteins in a model mixture
Separation of etodolac enantiomers by capillary electrophoresis. Validation and application of the chiral method to the analysis of commercial formulations

Separation of etodolac enantiomers, which exhibit different biological activity and pharmacokinetic profiles, has been achieved using the randomly substituted (2-hydroxy)propyl-β-cyclodextrin (HP-β-CD) as chiral selector in capillary electrophoresis. The selection of this CD was made after screening of different CD derivatives of neutral and anionic nature. The effect on the enantioresolution of the buffer concentration and of the degree of substitution (DS) and concentration of the CD as well as of instrumental parameters, such as the capillary temperature and the separation voltage, were studied. The highest resolution of etodolac enantiomers was around 2.5 using 100 mM phosphate buffer (pH 7.0) with 20 mM HP-β-CD (DS , 4.2) and UV detection at 225 (10) nm with a reference wavelength at 360 (50) nm. Validation of the chiral method in terms of selectivity, linearity, precision (instrumental repeatability, method repeatability, intermediate precision), and the limits of detection and quantitation allowed to evaluate its quality to the analysis of etodolac enantiomers in different pharmaceutical preparations containing racemic etodolac
Salt Removal During Off-GelTM Electrophoresis of Protein Samples

The Off-Gel™ technology was recently described for protein fractionation in a solution placed on top of an immobilized pH gradient gel. In addition, this process was found to remove salts from the biological samples to analyze. This desalting effect is studied experimentally in a conductometric prototype cell. A simplified analytical model is developed to understand this process and a good agreement is found with the conductivity measurements. To illustrate the desalting of a biological sample, a 1 mg·mL−1 solution of β-lactoglobulin A in 0.1 M NaCl is subjected to electrophoresis in a single compartment Off-Gel™ cell. The analysis of the resulting sample by ESI-MS demonstrates the effective removal of salt. A finite element diffusion-migration model is also used to illustrate how the nonuniformity of the electric field in the cell, associated with the salt migration, can slow down the desalting process
Enantioselective separation of the sunscreen agent 3-(4-methylbenzylidene)-camphor by electrokinetic chromatography: Quantitative analysis in cosmetic formulations

3-(4-Methylbenzylidene)-camphor (MBC) is a chiral sunscreen agent used in cosmetic products. In this work, the enantioseparation of MBC has been performed by EKC and applied to the analysis of the MBC enantiomers in cosmetic creams. Different experimental conditions (type and concentration of the chiral selector, temperature, and sample solvent) have been optimized. Due to the neutral nature of this compound, anionic CD derivatives were investigated as chiral selectors. Carboxymethylated-β-CD (CM-β-CD) showed the highest chiral separation power, observing that a 15 mM concentration of this CD at a working temperature of 15°C enabled to obtain the highest enantioresolution. However, under these conditions, tailing of peaks obtained for the enantiomers was observed. The addition of increasing concentrations of the neutral α-CD to CM-β-CD at a 15 mM concentration in a 100 mM borate buffer at pH 9.0 improved the enantiomeric separation and decreased peak tailing. The use of DMF for the total dissolution of the cosmetic creams, and methanol:water (1:1 v/v) for appropriate dilution enabled to observe good shape and size for the peaks of the MBC enantiomers. After optimizing a method for the preconditioning of the capillary, the analytical characteristics of the chiral separation method for the analysis of MBC were investigated. Linearity, LODs and LOQs, precision (instrumental repeatability, method repeatability, intermediate precision), accuracy, and selectivity were evaluated. The method was applied to analyze MBC enantiomers contained in two commercial cosmetic creams containing racemic MBC and to study the skin absorption of this compound with time.Authors thank the Ministry of Science and Technology (Spain) for the research project BQU2003-03638. C.G.-R. thanks the Ministry of Science and Technology for the Ramón y Cajal program (RYC-2003-001). B.G. thanks CSIC and the RYC-2003-001 project for the grants.\ud
Authors also thank Cyclolab (Budapest, Hungary) for the kind gift of CE-b-CD used in this wor
Chiral analysis of pollutants and their metabolites by capillary electromigration methods

Chiral separation of enantiomers is one of the most challenging tasks for any analytical technique including capillary electrophoresis (CE). Since the first report in 1985 showing the great possibilities of CE for the separation of chiral compounds, the amount of publications concerning this topic has quickly increased. Although chiral electromigration methods have mainly been used for enantioseparation of drugs and pharmaceuticals, they have also been applied to analyze chiral pollutants. This article intends to provide an updated overview, including works published till January 2005, on the principal applications of CE to the chiral analysis of pollutants and their metabolites, with especial emphasis on articles published in the last ten years. The main advantages and drawbacks regarding the use of CE for chiral separation of pollutants are addressed including some discussion on the foreseen trends of electromigration procedures applied to chiral analysis of contaminants.J. Hernández-Borges wishes to thank the Ministerio de Educación y Ciencia de España for the FPU grant.Peer reviewe