Recent advances in the MS analysis of glycoproteins: Capillary and microfluidic workflows

Recent developments in bioanalytical instrumentation, MS detection, and computational data analysis approaches have provided researchers with capabilities for interrogating the complex cellular glycoproteome, to help gain a better insight into the cellular and physiological processes that are associated with a disease and to facilitate the efforts centered on identifying disease-specific biomarkers. This review describes the progress achieved in the characterization of protein glycosylation by using advanced capillary and microfluidic MS technologies. The major steps involved in large-scale glycoproteomic analysis approaches are discussed, with special emphasis given to workflows that have evolved around complex MS detection functions. In addition, quantitative analysis strategies are assessed, and the bioinformatics aspects of glycoproteomic data processing are summarized. The developments in commercial and custom fabricated microfluidic front-end platforms to ESI- and MALDI-MS instrumentation, for addressing major challenges in carbohydrate analysis such as sensitivity, throughput, and ability to perform structural characterization, are further evaluated and illustrated with relevant examples.     

Azulen-1-yl diazenes substituted at C-3 with phenyl-chalcogene moieties: dye synthesis, product characterization and properties

Abstract  

Two synthesis strategies were used for the generation of azulene-1-yl diazenes substituted at C-3 with a phenyl-chalcogenyl moiety, the synthesis of azulenes substituted at C-3 followed by azo-coupling and azulene substitution at C-3 in azulene-azo dyes. The last synthetic route seems to give more satisfactory results for the synthesis of the desired chalcogenic derivatives. Another target of this study was to investigate the changes induced by the phenyl-chalcogenic substitution on the NMR and UV-vis spectra, and also to compare this effect with the one exerted by halogen atoms and by strongly electron donating groups such as AcNH or PhCOO. Whereas the latter groups exhibit a strong influence on the NMR and UV-vis spectra, PhS, PhSe, or PhTe groups as well as halogen atoms produce only a small effect because of the moderate change in electron distribution over the entire molecule.     

Sensitive detection of endocrine disrupters using ionic liquid--single walled carbon nanotubes modified screen-printed based biosensors

Simple and low cost biosensor based on screen-printed electrode for sensitive detection of some alkylphenols was developed, by entrapment of HRP in a nanocomposite gel based on single-walled carbon nanotubes (SWCNTs) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) ionic liquid. Raman and FTIR spectroscopy, CV and EIS studies demonstrate the interaction between SWCNTs and ionic liquid. The nanocomposite gel, SWCNT-[BMIM][PF₆] provides to the modified sensor a considerable enhanced electrocatalytic activity toward hydrogen peroxide reduction. The HRP based biosensor exhibits high sensitivity and good stability, allowing a detection of the alkylphenols at an applied potential of −0.2 V vs. Ag/AgCl, in linear range from 5.5 to 97.7 μM for 4-t-octylphenol and respectively, between 5.5 and 140 μM for 4-n-nonylphenol, with a response time of about 5 s. The detection limit was 1.1 μM for 4-t-octylphenol, and respectively 0.4 μM for 4-n-nonylphenol (S/N = 3).     

Artemisinin evaluation in Romanian Artemisia annua wild plants using a new HPLC/MS method

Artemisinin, a sesquiterpene lactone from Artemisia annua L., has received considerable attention in the last few decades as a potent antimalarial drug. Artemisinin has rather low toxicity; it is effective against drug-resistant Plasmodium species and against cerebral malaria. This study reports the development of a rapid and sensitive assay for the quantification of artemisinin in A. annua by reversed phase HPLC/MS. In the selected optimal experimental conditions, artemisinin exhibited a well-defined chromatographic peak with a retention time of 2 ± 0.2 min. The chromatographic signal shows a linear dependence with artemisinin concentration, enabling the use of this signal for artemisinin quantification according to the following regression equation: y = 2665.40x - 14697.61. The correlation coefficient (R(2)) was 0.9989. For every concentration within the range of the standard curve (0.1-2 μg mL(-1)), accuracy was between 95 and 104%. Artemisinin content in Romanian A. annua wild plants varies between 0.17 and 0.21% (dry weight basis).     

Antioxidant capacity and total phenolic contents of oregano (Origanum vulgare), lavender (Lavandula angustifolia) and lemon balm (Melissa officinalis) from Romania

The study reported here presents a comparative screening of three medicinal plants including oregano (Origanum vulgare L.), lavender (Lavandula angustifolia) and lemon balm (Melissa officinalis) having the same geographical origin, the Southeast region of Romania, and growing in the same natural conditions. The contents of total phenolics and total flavonoids for the extracts of these were determined. Furthermore, the total antioxidant capacity was also evaluated. It was found that Origanum vulgare and Melissa officinalis extracts present the most effective antioxidant capacity in scavenging DPPH radicals, while Lavandula angustifolia is less active. High performance liquid chromatography-mass spectrometry analysis was used to identify the components of extracts. Major phenolic acids identified in the analysed species were ferulic, rosmarinic, p-coumaric and caffeic, while predominant flavonoids were quercetin, apigenin kaempherol, which were present as glucosides.     

Development and validation of an HPLC-MS/MS method to quantify clopidogrel acyl glucuronide, clopidogrel acid metabolite, and clopidogrel in plasma samples avoiding analyte back-conversion

A new sensitive and fast quantitative analytical method for the simultaneous determination of clopidogrel, its main metabolite clopidogrel carboxylic acid, and the newly described acyl glucuronide metabolite, in human plasma samples, is presented. The analytical procedures (plasma storage, handling, and extract storage in the autosampler) were optimized in order to avoid back-conversion; a known drawback in measurements of clopidogrel. Clopidogrel acyl glucuronide was confirmed as a major source of back-conversion to the parent drug in the presence of methanol, and thorough stability experiments were carried out to find the most appropriate conditions for an accurate analysis of clopidogrel and the two metabolites. The method was validated by assessing selectivity, sensitivity, linearity, accuracy, and precision for all three analytes, in accordance to Food and Drug Administration guidelines. Spiked quality controls in plasma as well as incurred samples were used to verify back-conversion in the selected conditions, with results meeting European Medicines Agency acceptance criteria (concentrations within 80–120% of the first reading). The method was then applied to a pharmacokinetic study, and for the first time, a pharmacokinetic curve of clopidogrel acyl glucuronide in human plasma is presented. The concentrations ranged up to 1,048.684 ng/mL, with a mean of 470.268 ng/mL, while clopidogrel had a mean C _max of 1.348 ng/mL; these orders of magnitude show how much the back-conversion of this metabolite may influence clopidogrel quantification if it is not properly controlled.     

Thermal behaviour of some new complexes with bismacrocyclic ligands as potential biological active species

Novel complexes of type [M₂LCl₄]·nH₂O ((1) M:Ni, n = 5; (2) M:Cu, n = 0 and (3) M:Zn, n = 2; L: ligand resulted from 1,2-phenylenediamine, 3,6-diazaoctane-1,8-diamine and formaldehyde template condensation) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR and UV–Vis data. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. Processes as water or hydrochloric acid elimination as well as oxidative degradation of the organic ligand were observed. Complexes display a different thermal behaviour as result of dissimilar chemical interaction of metal ions with chloride anions. The final product of decomposition was metal(II) oxide as powder X-ray diffraction indicated.     

Thermal behavior of some vanadyl complexes with flavone derivatives as potential insulin-mimetic agents

Two new complexes having general formula VOL₂·nH₂O [(1) L: 5-hydroxyflavone, n = 1; (2) L: chrysin, n = 4] were synthesized and characterized. Based on IR and electronic data we concluded that studied flavones act as bidentate ligands in complexes with metallic ion coordinated in a square-pyramidal stereochemistry. The thermal analysis (TG, DTA) elucidated the composition and also the number and nature of the water molecules. The thermal behavior also indicated strong interactions between oxovanadium (IV) and these oxygen donor ligands.     

SL2-modules of small homological dimension

Let V _n be the SL₂-module of binary forms of degree n and let V = V_n1 ???V_np V = {V_{{n_1}}} \oplus \cdots \oplus {V_{{n_p}}} . We consider the algebra R = O(V)^{\textS\textL₂} R = \mathcal{O}{(V)^{{\text{S}}{{\text{L}}_2}}} of polynomial functions on V invariant under the action of SL₂. The measure of the intricacy of these algebras is the length of their chains of syzygies, called homological dimension hd R. Popov gave in 1983 a classification of the cases in which hd R ≤ 10 for a single binary form (p = 1) or hd R ≤ 3 for a system of two or more binary forms (p > 1). We extend Popov’s result and determine for p = 1 the cases with hd R ≤ 100, and for p > 1 those with hd R ≤ 15. In these cases we give a set of homogeneous parameters and a set of generators for the algebra R.     

Irreducibility Results for Compositions of Polynomials with Integer Coefficients

We obtain explicit upper bounds for the number of irreducible factors for a class of polynomials of the form f ○ g, where f,g are polynomials with integer coefficients, in terms of the prime factorization of the leading coefficients of f and g, the degrees of f and g, and the size of coefficients of f. In particular, some irreducibility results are given for this class of compositions of polynomials.