Implementation of comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry for the simultaneous determination of halogenated contaminants and polycyclic aromatic hydrocarbons in fish

In the presented study, comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC?×?GC-TOFMS) was shown to be a powerful tool for the simultaneous determination of various groups of contaminants including 18 polychlorinated biphenyls (PCBs), seven polybrominated diphenyl ethers (PBDEs), and 16 polycyclic aromatic hydrocarbons (PAHs). Since different groups of analytes (traditionally analyzed separately) were included into one instrumental method, significant time savings were achieved. Following the development of an integrated sample preparation procedure for an effective and rapid isolation of several groups of contaminants from fish tissue, the GC?×?GC-TOFMS instrumental method was optimized to obtain the best chromatographic resolution and low quantification limits (LOQs) of all target analytes in a complex mixture. Using large-volume programmable temperature vaporization, the following LOQs were achieved-PCBs, 0.01-0.25 μg/kg; PBDEs, 0.025-5 μg/kg; PAHs 0.025-0.5 μg/kg. Furthermore, several capillary column combinations (BPX5, BPX50, and Rxi-17Sil-ms in the first dimension and BPX5, BPX50, Rt-LC35, and HT8 in the second dimension) were tested during the experiments, and the optimal separation of all target analytes even of critical groups of PAHs (group (a): benz[a]anthracene, cyclopenta[cd]pyrene and chrysene; group (b): benzo[b]fluoranthene, benzo[j]fluoranthene and benzo[k]fluoranthene; group (c): dibenz[ah]anthracene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene) was observed on BPX5?×?BPX50 column setup. Moreover, since the determination of target analytes was performed using TOFMS detector, further identification of other non-target compounds in real life samples was also feasible.     

New beginnings for matrix metalloproteinase inhibitors: identification of high-affinity zinc-binding groups

In an effort to identify promising non-hydroxamate inhibitors of matrix metalloproteinases (MMPs), several new zinc-binding groups (ZBGs) based on pyrone, pyrothione, hydroxypyridinone, and hydroxypyridinethione chelators have been examined. Structural studies with tris(pyrazolyl)borate model complexes show that these ligands bind to the MMP active site zinc(II) ion in a bidentate fashion, similar to that found with hydroxamate-based inhibitors. Fluorescence- and colorimetric-based enzyme assays have been used to determine the IC50 values for these ZBGs against MMP-3; mixed O,S-donor ligands were found to be remarkably potent, with IC50 values as much as 700-fold lower than that found for acetohydroxamic acid. Inhibitory activity was found to parallel metal binding affinity as determined in titrations with model complexes. These results demonstrate that MPIs based on new ZBGs are feasible and may indeed improve the overall performance of inhibitors designed against these important medicinal targets.     

Whole-cell Gluconobacter oxydans biosensor for 2-phenylethanol biooxidation monitoring

A microbial biosensor for 2-phenylethanol (2-PE) based on the bacteria Gluconobacter oxydans was developed and applied in monitoring of a biotechnological process. The cells of G. oxydans were immobilized within a disposable polyelectrolyte complex gel membrane consisting of sodium alginate, cellulose sulphate and poly(methylene-co-guanidine) attached onto a miniaturized Clark oxygen electrode, forming whole cell amperometric biosensor. Measured changes in oxygen concentration were proportional to changes in 2-PE concentration. The biosensor sensitivity was 864 nA mM⁻¹ (RSD = 6%), a detection limit of 1 μM, and the biosensor response towards 2-PE was linear in the range 0.02–0.70 mM. The biosensor preserved 93% of its initial sensitivity after 7 h of continuous operation and exhibited excellent storage stability with loss of only 6% of initial sensitivity within two months, when stored at 4 °C. The developed system was designed and successfully used for an off-line monitoring of whole course of 2-PE biooxidation process producing phenylacetic acid (PA) as industrially valuable aromatic compound. The biosensor measurement did not require the use of hazardous organic solvent. The biosensor response to 2-PE was not affected by interferences from PA and phenylacetaldehyde at concentrations present in real samples during the biotransformation and the results were in a very good agreement with those obtained via gas chromatography.     

Bulk derivatization and cation exchange restricted access media-based trap-and-elute liquid chromatography–mass spectrometry method for determination of trace estrogens in serum

Estrone (E1), estradiols (α/β-E2), and estriol (E3) are four major metabolically active estrogens exerting strong biological activities at very low circulating concentrations. This paper reports a sensitive and efficient method with automated, on-line clean-up and detection to determine trace estrogens in a small volume of serum samples using liquid chromatography–electrospray ionization–tandem mass spectrometry directly, without off-line liquid–liquid or solid-phase extraction pretreatments. Serum aliquots (charcoal stripped fetal bovine serum, 100 μL) were spiked with four estrogen standards and their corresponding isotope-labeled internal standards, then bulk derivatized with 2-fluoro-1-methyl-pyridium p-toluenesulfonate (2-FMP) to establish the calibration curves and perform method validation. Calibration was established in the concentration ranges of 5–1000 pg mL⁻¹, and demonstrated good linearity of R² from 0.9944 to 0.9997 for the four derivatized estrogens. The lower detection limits obtained were 3–7 pg mL⁻¹. Good accuracy and precision in the range of 86–112% and 2.3–11.9%, respectively, were observed for the quality control (QC) samples at low, medium, and high concentration levels. The stability tests showed that the derivatized serum samples were stable 8 h after derivatization at room temperature and at least to 48 h if stored at −20 °C. The method was applied to measure trace estrogens in real human and bovine serum samples, and three of four estrogen compounds studied were observed and quantified.     

Total synthesis of (3S,4S,2′S)- and (3R,4R,2′S)-viridiofungin A triester

The total synthesis of an alkylcitrate secondary metabolite from the fungi Trichoderma viride is described. An ester dienolate [2,3]-Wittig rearrangement and a S. Julia-Kocienski olefination served as key C/C-connecting transformations. The highly convergent synthesis consists of a longest linear sequence of 17 steps.     

Stable cellulose nanospheres for cellular uptake

Pure, perfectly spherical cellulose nanoparticles with sizes of ≈80-260 nm can be prepared by dialysis starting from trimethylsilylcellulose (TMSC). The aqueous suspensions obtained are storable for several months. Subsequent covalent labeling of the cellulose nanoparticles with FITC has no influence on particle size, shape, and stability. The particles can be sterilized and suspended in biological media without structural changes. Incorporation of FITC-labeled cellulose nanoparticles into living human fibroblasts is studied using confocal LSM. In contrast to cellulose nanocrystals, fast cellular uptake is found for the nanospheres without transfection reagents or attachment of a receptor molecule. This suggests an influence of the geometry of biocompatible nanomaterials on endocytosis.     

Native polyacrylamide electrophoresis in the presence of Ponceau Red to study oligomeric states of protein complexes

Native polyacrylamide electrophoresis in the presence of two reversible protein anionic stains (Ponceau S and Ponceau 2R) was used to study the oligomeric states of soluble proteins. A mild binding of the used protein stains to nondissociated protein oligomers imposed a charge shift on the proteins resulting into separation of protein species according to their size under physiological conditions. Adsorbed stains could be easily removed after electrophoresis by washing of polyacrylamide gel with buffer and protein complexes could be visualized either by the detection of their enzyme activity or by using a nonspecific protein stain. The specific detection of enzyme activity of glycosidases, lactate dehydrogenase, or phosphatases was shown as an example.     

Synthesis and characterization of corn starch based green composites reinforced with Saccharum spontaneum L graft copolymers prepared under micro-wave and their effect on thermal, physio-chemical and mechanical properties

In this paper, green composites of the corn starch were developed by using resorcinol-formaldehyde (Rf) as the cross-linking agent and reinforced with graft copolymers Saccharaum spontaneum L(Ss) and methyl methacrylates (MMA) as principal monomer and its binary mixture with acrylamide (AAm), acrylonitrile(AN), acrylic acid (AA) prepared under micro-wave. The matrix and composites were found to be thermally more stable than the natural corn starch backbone. There was improvement in physico-chemical and mechanical properties of composite were found to exhibit better than matrix. Ss-g-poly(MMA)-MW reinforced composites were found to exhibit better tensile strength, on the other hand Ss-g-poly(MMA + AA)-MW reinforced composites showed maximum compressive strength and wear resistance than other graft copolymers reinforced composite and the basic matrix. Further the matrix and composites were subjected for biodegradation studies through soil composting method. Different stages of biodegradation were evaluated through FT-IR studies and scanning electron microscopic (SEM) techniques.     

A General Method for Preparing Bridged Organosilanes with Pendant Functional Groups and Functional Mesoporous Organosilicas

New organosilica precursors containing two triethoxysilyl groups suitable for the organosilica material formation through the sol‐gel process were designed and synthesised. These precursors display alkyne or azide groups for attaching targeted functional groups by copper‐catalysed azide–alkyne cycloaddition (CuAAC) and can be used for the preparation of functional organosilicas following two strategies: 1) the functional group is first appended by CuAAC under anhydrous conditions, then the functional material is prepared by the sol‐gel process; 2) the precursor is first subjected to the sol‐gel process, producing porous, clickable bridged silsesquioxanes or periodic mesoporous organosilicas (PMOs), then the desired functional groups are attached by means of CuAAC. Herein, we show the feasibility of both approaches. A series of bridged bis(triethoxysilane)s with different pending organic moieties was prepared, demonstrating the compatibility of the first approach with many functional groups. In particular, we demonstrate that organic functional molecules bearing only one derivatisation site can be used to produce bridged organosilanes and bridged silsesquioxanes. In the second approach, clickable PMOs and porous bridged silsesquioxanes were prepared from the alkyne‐ or azide‐containing precursors, and thereafter, functionalised with complementary model azide‐ or alkyne‐containing molecules. These results confirmed the potential of this approach as a general methodology for preparing functional organosilicas with high loadings of functional groups. Both approaches give rise to a wide range of new functional organosilica materials.     

Site‐Selective Oxidation of Monolayered Liquid‐Exfoliated WS2 by Shielding the Basal Plane through Adsorption of a Facial Amphiphile

In recent years, various functionalization strategies for transition‐metal dichalcogenides have been explored to tailor the properties of materials and to provide anchor points for the fabrication of hybrid structures. Herein, new insights into the role of the surfactant in functionalization reactions are described. Using the spontaneous reaction of WS₂ with chloroauric acid as a model reaction, the regioselective formation of gold nanoparticles on WS₂ is shown to be heavily dependent on the surfactant employed. A simple model is developed to explain the role of the chosen surfactant in this heterogeneous functionalization reaction. The surfactant coverage is identified as the crucial element that governs the dominant reaction pathway and therefore can severely alter the reaction outcome. This study shows the general importance of the surfactant choice and how detrimental or beneficial a certain surfactant can be to the desired functionalization.