Sensitive Detection of DNA Methyltransferase Activity Based on Exonuclease-Mediated Target Recycling

Analytical ChemistryDOI: 10.1021/ac502845b

Inducing microscopic thermal lesions for the dissection of functional cell networks on a chip

Lab Chip, 2015, Advance ArticleDOI: 10.1039/C4LC00805G, PaperPhilipp Rinklin, Dzmitry Afanasenkau, Simone Wiegand, Andreas Offenhausser, Bernhard WolfrumElectrical heating of microstructured conductors is used to induce highly resolved lesions in confl…

Sheathless Capillary Electrophoresis-Tandem Mass Spectrometry for Top-Down Characterization of Pyrococcus furiosus Proteins on a Proteome Scale

Analytical ChemistryDOI: 10.1021/ac503439n

Visual and Portable Strategy for Copper(II) Detection Based on a Striplike Poly(Thymine)-Caged and Microwell-Printed Hydrogel

Analytical ChemistryDOI: 10.1021/ac502843t

Automated Dispersive Solid-Phase Extraction Using Dissolvable Fe3O4-Layered Double Hydroxide Core–Shell Microspheres as Sorbent

Analytical ChemistryDOI: 10.1021/ac503323e

Femtogram-Scale Photothermal Spectroscopy of Explosive Molecules on Nanostrings

Analytical ChemistryDOI: 10.1021/ac503318e

All-in-One Centrifugal Microfluidic Device for Size-Selective Circulating Tumor Cell Isolation with High Purity

Analytical ChemistryDOI: 10.1021/ac5035049

A droplet-to-digital (D2D) microfluidic device for single cell assays

Lab Chip, 2015, Advance ArticleDOI: 10.1039/C4LC00794H, PaperSteve C. C. Shih, Philip C. Gach, Jess Sustarich, Blake A. Simmons, Paul D. Adams, Seema Singh, Anup K. SinghWe have developed a new hybrid droplet-to-digital microfluidic platform (D2D) that…

Electrochemically controlled in-tube solid phase microextraction

Publication date: Available online 30 October 2014
Source:Analytica Chimica Acta
Author(s): Seyyed Hamid Ahmadi , Ahmad Manbohi , Kourosh Tabar Hydar
We report a new in-tube solid phase microextraction approach named electrochemically controlled in-tube solid phase microextraction (EC in-tube SPME). This approach, which combined electrochemistry and in-tube SPME, led to decrease in total analysis time and increase in sensitivity. At First, pyrrole was elctropolymerized on the inner surface of a stainless steel tube. Then, the polypyrrole (PPy)-coated in-tube SPME was coupled on-line to liquid chromatography (HPLC) to achieve automated in-tube SPME–HPLC analysis. After the completion of EC-in-tube SPME–HPLC setup, the PPy-coated tube was used as working electrode for uptake of diclofenac as target analyte. Extraction ability of the tube in presence and in absence of applied electrical field was investigated. It was found that, under the same extraction conditions, the extraction efficiency could be greatly enhanced by using the constant potential. Important factors are also optimized. The detection limit (S/N=3) and precision were 0.1μgL−1 and 4.4%, respectively.

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Modelling the electrophoretic migration behaviour of peptides and glycopeptides from glycoprotein digests in capillary electrophoresis-mass spectrometry

Publication date: Available online 29 October 2014
Source:Analytica Chimica Acta
Author(s): Albert Barroso , Estela Giménez , Fernando Benavente , José Barbosa , Victoria Sanz-Nebot
In this study, the classical semiempirical relationships between the electrophoretic mobility and the charge-to-mass ratio (me vs. q/Mα) were used to model the migration behaviour of peptides and glycopeptides originated from the digestion of recombinant human erythropoietin (rhEPO), a biologically and therapeutically relevant glycoprotein. The Stoke’s law (α=1/3), the classical polymer model (α=1/2) and the Offord’s surface law (α=2/3) were evaluated to predict migration of peptides and glycopeptides, with and without sialic acids (SiA), in rhEPO digested with trypsin and trypsin-neuraminidase. The Stoke’s law resulted in better correlations for the set of peptides used to evaluate the models, while glycopeptides fitted better with the classical polymer model. Once predicted migration times with both models, it was easy to simulate their separation electropherogram. Results were later validated predicting migration and simulating separation of a different set of rhEPO glycopeptides and also human transferrin (Tf) peptides and glycopeptides. The excellent agreement between the experimental and the simulated electropherograms with rhEPO and Tf digests confirmed the potential applicability of this simple strategy to predict, in general, the peptide-glycopeptide electrophoretic map of any digested glycoprotein.

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Combined derivatization and high-performance liquid chromatography with fluorescence and ultraviolet detection for simultaneous analysis of octreotide and gabexate mesylate metabolite in human pancreatic juice samples

A simple and sensitive method based on the combination of derivatization and high-performance liquid chromatography with ultraviolet and fluorimetric detection was developed for the simultaneous determination of octreotide and gabexate mesylate metabolite in human pancreatic juice samples. Parameters of the derivatization procedure affecting extraction efficiency were optimized. The developed method was validated according to the International Conference on Harmonization guidelines. The calibration curves were linear over a range of 0.1–15 µg/mL for octreotide and 0.20-15 µg/mL for gabexate mesylate metabolite. Derivatized products of octreotide and gabexate mesylate metabolite were separated on a Luna C18 column (4.6 × 250 mm; 5 µm particle size) using a gradient with a run time of 36 min, without further purification. The limits of detection were 0.025 and 0.05, respectively, for octreotide and gabexate mesylate metabolite. This paper reports the validation of a quantitative high performance liquid chromatography–photodiode array–fluorescence (HPLC-PDA-FL) method for the simultaneous analysis of octreotide and gabexate mesylate metabolite in pancreatic juice by protein precipitation using zinc sulfate–methanol–acetonitrile containing the derivatizing reagent, 4-fluoro-7-nitro-[2,1,3]-benzoxadiazole (NBD-F). Derivatized products of octreotide and gabexate mesylate metabolite were separated on a Luna C18 column (4.6 × 250 mm; 5 µm particle size) using a gradient with a run time of 36 min, without further purification. The method was validated over the concentration ranges 0.1–15 and 0.2–15 µg/mL for octreotide and gabexate mesylate metabolite, respectively, in human pancreatic juice. Biphalin and methyl-p-hydroxybenzoate were used as the internal standards. This method was successfully utilized to support clinical studies in humans. The results from assay validations show that the method is selective, sensitive and robust. The limit of quantification of the method was 0.1 µg/mL for octreotide and 0.2 µg/mL for gabexate mesylate metabolite, and matrix matched standard curves showed a good linearity up to 15 µg/mL. In the entire analytical range the intra- and inter-day precision (RSD%) values were respectively ≤5.9% and ≤3.1% for octreotide and ≤2.0% and ≤3.9% for gabexate mesylate metabolite. For both analytes the intra- and inter-day accuracy (bias) values ranged respectively from −6.8 to –2.5% and from −4.6 to −5.7%. This method utilizes derivatization with NBD-F and provides adequate sensitivity for both drugs. Copyright © 2014 John Wiley & Sons, Ltd.

Qualitative and quantitative analysis of the major constituents in Acorus tatarinowii Schott by HPLC/ESI-QTOF-MS/MS

Acorus tatarinowii Schott (ATS) is a well-known traditional Chinese medicine (TCM) for the treatment of epilepsy, amnesia and insomnia. In this study, a methodology utilizing high-performance liquid chromatography (HPLC) coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF-MS/MS) was established for the separation and structural identification of the major chemical constituents in ATS for the first time. Overall, 46 major constituents including flavonoid glycosides, phenylpropane derivatives, amides and lignans were identified or tentatively characterized. Seven major constituents, including four phenylpropane derivatives and three lignans, were further quantified as marker substances, which showed good linearity within the test ranges. These results indicated that the developed quantitative method was linear, sensitive, and precise for quality control of ATS. Copyright © 2014 John Wiley & Sons, Ltd.

Selective extraction based on poly(MAA-VB-EGMDA) monolith followed by HPLC for determination of hordenine in plasma and urine samples

Hordenine is an active compound found in several foods, herbs and beer. In this work, a novel sorbent was fabricated for selective solid-phase extraction (SPE) of hordenine in biological samples. The organic polymer sorbent was synthesized in one step in the plastic barrel of a syringe by a pre-polymerization solution consisting of methacrylic acid (MAA), 4-vinylphenylboronic acid (VB) and ethylene glycol dimethacrylate (EGDMA). The conditions for preparation were optimized to generate a poly(MAA-VB-EGMDA) monolith with good permeability. The monolith exhibited good enrichment efficiency towards hordenine. By using tyramine as the internal standard, a poly(MAA-VB-EGMDA)-based SPE-HPLC method was established for analysis of hordenine. Conditions for SPE, including volume of eluting solvent, pH of sample solution, sampling rate and sample volume, were optimized. The proposed SPE-HPLC method presented good linearity (R2 = 0.9992) within 10–2000 ng/mL and the detection limits was 3 ng/mL, which is significantly more sensitive than reported methods. The method was also applied in plasma and urine samples; good capability of removing matrices was observed, while hordenine in low content was well extracted and enriched. The recoveries were from 90.6 to 94.7% and from 89.3 to 91.5% for the spiked plasma and urine samples, respectively, with the relative standard deviations <4.7%. Copyright © 2014 John Wiley & Sons, Ltd.

Single-run HPLC/ESI-LITMS profiling of ginsenosides in plant extracts and ginseng based products

A rapid single-run analytical approach suitable to achieve a comprehensive characterization of ginsenosides – the main bioactive compounds present in plant materials from Panax species and ginseng-based products – was developed. The method is based on high-performance liquid chromatography coupled with electrospray positive ionization linear ion trap mass spectrometry (HPLC/ESI-LITMS). The main ions in the ESI-LITMS spectra were attributed to molecular adducts with sodium and potassium and fragments corresponding to cleavage of the glycosidic bonds. The simplicity of the approach allows laborious sample preparation and sophisticated spectral information-dependent acquisition to be avoided, and provides an opportunity for rapid screening. The method may replace existing HPLC-DAD profiling approaches. The results of this study indicate that HPLC/ESI-LITMS is applicable for quality control purposes on processed products and allows the rapid and direct identification of ginsenosides in crude plant extracts. Copyright © 2014 John Wiley & Sons, Ltd.

Quantification of malondialdehyde by HPLC-FL – application to various biological samples

Malondialdehyde (MDA) is stabile product of lipid peroxidation (LPO), and therefore MDA is frequently used as a biomarker of LPO. To determine MDA level in various biological samples (human plasma, fish liver tissue and cells in culture), we used an HPLC method with fluorescent detection based on 2-thiobarbituric acid (TBA) assay. The method was validated by the use of spiked pooled plasma samples. In tested concentration range (0.15–3.0 µmol/L) the method was linear (R2 = 0.9963), the between-day variability (coefficient of variations, CVs) was between 4.7 and 7.6%, the within-day variability CVs was between 2.6 and 6.4% and recovery was between 91.2 and 107.6%. The level of MDA in human plasma (healthy male, non-smokers, 46.3 ± 4.7 years; N = 38) was 2.2 ± 1.4 µmol/L; that in liver tissue of common carp (Cyprinus carpio; N = 12) was 0.02 ± 0.004 µmol/g tissue, and in cultured cells (human laryngeal carcinoma cells; N = 10) it was 0.18 ± 0.02 nmol/mg proteins. The HPLC-FL method is rapid, accurate and reliable to follow the extent of LPO in various biological samples, particularly in samples in which a low level of MDA is expected, such as cells in culture. Owing to the rapid analytical process and run time, it can be used for routine analysis of MDA in clinical laboratory. Copyright © 2014 John Wiley & Sons, Ltd.

Stereo-specific LC and LC-MS bioassays of antidepressants and psychotics

Stereochemistry in drug action is gaining importance because the enantiomers often differ in their biological activity and pharmacokinetic profiles. The use of racemic drugs may contribute to adverse effects owing to the presence of either inactive or toxic enantiomers. Most of the drugs currently used to treat psychiatric disorders, including depression, contain one or more chiral centers and are mostly sold as racemates. Single-enantiomer drugs provide greater selectivity for their biological targets, improved therapeutic indices and better pharmacokinetics compared with racemates. Therefore it is of great importance to monitor body fluid/tissue levels of drugs used to treat depression and psychiatric disorders. The present manuscript gives an overview of liquid chromatographic and mass spectrometric techniques reported during 2000–2013 for enantiomeric separation of various classes of antidepressants, viz. selective serotonin reuptake inhibitors, serotonin and norepinephrine reuptake inhibitors, noradrenergic and specific serotonergic antidepressants, norepinephrine reuptake inhibitors, norepinephrine–dopamine reuptake inhibitors, nonamphetamine central nervous system stimulants, serotonin and dopamine inhibitors and γ-aminobutyric acid receptor agonists in biological matrices. Techniques used for extraction, separation and quantification are discussed. Copyright © 2014 John Wiley & Sons, Ltd.

Improving the Quantification of Secondary Organic Aerosol Using a Microflow Reactor Coupled to HPLC-MS and NMR to Manufacture Ad Hoc Calibration Standards

Analytical ChemistryDOI: 10.1021/ac5028512

Determination of Multivalent Protein–Ligand Binding Kinetics by Second-Harmonic Correlation Spectroscopy

Analytical ChemistryDOI: 10.1021/ac500094v

A Mass-Spectrometry-Based Framework To Define the Extent of Disorder in Proteins

Analytical ChemistryDOI: 10.1021/ac5027435

Kinetics of Precursor Labeling in Stable Isotope Labeling in Cell Cultures (SILAC) Experiments

Analytical ChemistryDOI: 10.1021/ac503067a