Borate-containing background electrolytes to improve CE separation in bare capillaries.

External electric field control of electroosmotic flow in non-coated and coated fused-silica capillaries and its application for capillary electrophoretic separations of peptides

Carbonyl-modified proteins are markers of oxidative damage. Here, we report a new method for detecting and quantifying carbonylated proteins by capillary sieving electrophoresis (CSE) with LIF detection (CSE-LIF). Alexa 488 hydrazide is used for the specific labeling of carbonyls while 3-(2-furoyl) quinoline-2-carboxaldehyde (FQ) is used for protein labeling. BSA subjected to metal-catalyzed oxidation is used to optimize the labeling reactions, confirm the separation power of CSE, and characterize the response of the LIF detector. The method is capable of detecting femtomole (fmol) amounts of carbonyls in proteins with molecular masses ranging from 26 to 30 kDa. Using this method, we determined that mitochondrial proteins isolated from skeletal muscle contains 2.1 +/- 0.1 (average +/- SD; n = 3) nmol carbonyl/mg protein. The methodology described here should be compatible with the analysis of single cells and needle biopsies taken from oxidative stress animal models.

Capillary isoelectric focusing (CIEF) separations are usually performed with neutral coated fused-silica capillaries in aqueous anticonvective media. Glycerol, a very viscous solvent (eta = 945 mPa x s at 25 degrees C), known to help stabilize any kind of proteins and solubilize hydrophobic ones, was tested as an alternative to using commercial gels. Viscosity and electroosmotic mobility were measured as a function of gel or glycerol content in water, and a 30:70 v/v glycerol-water medium appeared as a good compromise for performing CIEF in a bare fused-silica capillary without imposing too high a viscosity. To demonstrate the feasibility of this new CIEF system, a standard mixture of nine model proteins was separated according to their pI with a good agreement between experimental and literature aqueous pIs. Moreover, better resolution was achieved with this system than with the conventional aqueous CIEF system, as two of the model proteins could not be separated in the latter system. Glycerol-water CIEF in bare silica capillary was next applied to the separation of horse radish peroxidase, a complex mixture of protein isoforms. The good concordance with the separation obtained by the conventional CIEF system indicated the adequacy of this new system. Finally, as anticipated from the results obtained for the separation of bacteriorhodopsin, a membrane protein, glycerol-water CIEF performed in bare silica capillary appears to be a promising alternative to conventional aqueous CIEF for hydrophobic protein characterization, under their native form.

Analysis of benzyldimethyldodecylammonium bromide in chemical disinfectants by liquid chromatography and capillary electrophoresis

The present study is conducted to determine the potential mechanisms of Boron compounds, boric acid (BA) and borax (BX), on genotoxicity of zebrafish Danio rerio for 24, 48, 72 and 96-hours acute exposure (level:1, 4, 16, 64 mg/l BA and BX) in semi-static bioassay experiment. For that purpose, peripheral erythrocytes were drawn from caudal vein and Comet assay was applied to assess genotoxicity. Acute (96 hours) exposure and high concentrations of boric acid and borax increases % tail DNA and Olive tail moment. Genotoxicity was found for BA as concentration-dependent and BX as concentration and time dependent manner. In general, significant effects (P < 0,05) on both concentrations and exposure times were observed in experimental groups. DNA damage was highest at 96 h and 24 h for all BX and BA concentrations, respectively in peripheral blood of D. rerio. For the first time, our study demonstrates the effect of waterborne BA and BX exposure on genotoxicity at the molecular level, which may contribute to understanding the mechanism of boric acid and borax-induced genotoxicity in fish.

Depository effects in slowly metabolized proteins, typically glycation or the estimation of products arising from the reaction of unsaturated long chain fatty acid metabolites (possessing aldehydic groups) are very difficult to assess owing to their extremely low concentration in the protein matrix. Posttranslational nonenzymatic modifications of collagen with sugars and oxidation products of lipid metabolism in tail tendons of two groups of rats (controls and hypertriglyceridemics with a high fructose diet) were studied. Collagen (a mixture of type I and III) was digested by bacterial collagenase and separated by reversed‐phase HPLC; the profile obtained was divided into five fractions, which were further characterizated by capillary electrophoresis (CE) in a bare fused silica capillary (37/30 cm×75 µm I.D.). As the chromatographic and electromigration behaviour of individual peptides was considerably different, the combination of HPLC and CE appeared as a suitable approach capable of acceptable separation of complex peptide mixtures (over 150 peptide peaks were obtained on the electropherograms). This two‐stepped peptide mapping with subsequent statistical evaluation (linear regression analysis) was shown to represent a reliable approach for revealing posttranslational modifications in slowly metabolized model proteins in vivo.

Determination of homocysteine and other thiols in human plasma by capillary electrophoresis

This technical note describes a new microfluidic sensor that combines low-cost (USD $0.97) with rapid fabrication and user-friendly, fast, sensitive, and accurate quantification of a breast cancer biomarker. The electrodes consisted of cost-effective bare stainless-steel capillaries, whose mass production is already well-established. These capillaries were used as received, without any surface modification. Microfluidic chips containing electrical double-layer capillary capacitors (μEDLC) were obtained by a cleanroom-free prototyping that allows the fabrication of dozens to hundreds of chips in 1 h. This sensor provided the successful quantification of CA 15-3, a biomarker protein for breast cancer, in serum samples from cancer patients. Antibody-anchored magnetic beads were utilized for immunocapture of the marker, and then, water was added to dilute the protein. Next, the CA 15-3 detection (<2 min) was made without using redox probes, antibody on electrode (sandwich immunoassay), or signal amplification strategies. In addition, the capacitance tests eliminated external pumping systems and precise volumetric sampling steps, as well as presented low sample volume (5 μL) and high sensitivity using bare capillaries in a new design for double-layer capacitors. The achieved limit-of-detection (92.0 μU mL-1) is lower than that of most methods reported in the literature for CA 15-3, which are based on nanostructured electrodes. The data shown in this technical note support the potential of the μEDLC toward breast cancer diagnosis even at early stages. We believe that accurate analyses using a simple sample pretreatment such as magnetic field-assisted immunocapture and cost-effective bare electrodes can be extended to quantify other cancer biomarkers and even biomolecules by changing the biorecognition element.

Dependence of the Electroosmotic Flow in Bare Fused-Silica Capillaries from pH, Ionic Strength and Composition of Electrolyte Solutions Tailored for Protein Capillary Zone Electrophoresis

Capillary electrochromatographic study of the interactions of porphyrin derivatives with amino acids and oligopeptides

N-Methylpyrrolidine in cefepime for injection was determined by capillary electrophoresis with indirect UV detection. Best results were achieved with background electrolyte consisting of 10 mM creatinine adjusted to pH 3.8 with formic acid and an applied voltage of 30 kV in a bare fused-silica capillary. Indirect UV detection was performed at a wavelength of 225 nm. The application of a small amount of inlet pressure during the separation assisted the attainment of a stable baseline. The optimized method was validated regarding selectivity, linearity, accuracy, precision, ruggedness, repeatability and detection limits. Careful control of capillary conditioning enabled migration time precision values of <0.2% RSD. The use of an internal standard enabled precision values of <1% RSD to be obtained for peak area ratios.

Systematic screening approach for chiral separations of basic compounds by capillary electrophoresis with modified cyclodextrins

A method was developed for the determination of the stoichiometric Zn/protein ratio for the Aeromonas hydrophila metallo beta-lactamase AE036. Capillary electrophoresis (CE) was used to separate free Zn ions from the Zn bound to the metalloprotein, the only Zn-species which is biochemically relevant. An inductively coupled plasma-sector field-mass spectrometer (ICP-SF-MS), operated at a mass resolution of 3000, was used as an element-specific detector. If the primary structure of the protein and thus the number of sulfur-containing amino acids is known, as is the case for Aeromonas hydrophila Zn beta-lactamase, monitoring of both Zn and S with ICP-SF-MS permits the Zn/protein ratio to be determined. The method was optimised in order to obtain short migration times (less than 10 min) for the metallo beta-lactamase and for standards with bare fused silica capillaries. After optimisation, a 75 mmol L−1 bis-Tris background electrolyte buffered at a pH of 6.75 was used for the separation, a voltage of 30 kV was applied over a capillary with a total length of approximately 70 cm and the sample was introduced hydrodynamically at 1000 mbar s. Quantitative results (stoichiometric Zn/protein ratio of 1 and 2, before and after saturation of the enzyme with Zn, respectively) were obtained using external calibration with albumin as a S standard and ZnCl2 as a Zn standard. The method was also demonstrated to be precise with < 5% RSD on the Zn/protein ratio for n = 3. An absolute limit of detection of 8 ng of A. hydrophila Zn beta-lactamase (calculated on the basis of sulfur) was obtained under these conditions.

Transient isotachophoresis (TITP) is usually performed under low-electroosmotic flow (EOF) conditions using a coated capillary or a low pH background electrolyte. We used a bare fused-silica capillary for TITP stacking of anionic complexes of some heavy metals under high-EOF conditions (pH 9.0). The sample component chloride as a leading electrolyte induced stacking by an isotachophoretic mechanism and the complexing agent 4-(2-pyridylazo) resorcinol (PAR) acted as a terminating electrolyte. The optimized background electrolyte was composed of 150 mM N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid, 127 mM triethylamine, and 0.1 mM PAR at pH 9.0. The strong EOF at pH 9.0 pulled the analytes against their mobilities toward the outlet side, allowing a separation in the normal polarity mode. The stacking efficiency, reproducibility, analysis time, and sample loading capacity in coated and bare capillaries were compared. The stacking efficiency and reproducibility were higher and the analysis time was shorter in the coated capillary. However, a larger volume of a sample could be injected in the bare capillary to achieve detection limits comparable to those for the coated one without compromising the resolution between the analyte peaks. The limits of detection (S/N = 3) were in the sub-ppb range for the selected metals (Fe2+, 0.3 ppb; Ni2+, 0.16 ppb; and Zn2+, 0.8 ppb) in a standard saline sample with 250 mM NaCl matrix. The proposed method was successfully applied to the analysis of reference urine samples and human urine samples.

目的 建立快速检测人血清中氨甲蝶呤药物浓度的方法.方法用高效毛细管电泳技术,选用直径75 μm,总长60 cm,有效长度50.5 cm熔融石英毛细管,以75 mmol/L,pH 7.4的磷酸盐为电泳缓冲液,检测波长为306 nm,在25 kV电压下的快速分离检测氨甲蝶呤,并对此方法进行方法学评价.结果氨甲蝶呤的出峰时间在10 min内,线性范围在1.1～1 100.0 μmol/L间,最低检出浓度为0.55 μmol/L,回收率为88.2%～98.2%,批间精密度为5.4%,批内精密度为4.2%.结论高效毛细管电泳方法具有快速、准确且成本低的特点,为临床和科研中测定血清氨甲蝶呤提供了一种有效的手段。