Biosensor immunoassays for the detection of bisphenol A

Bisphenol A (BPA) is a xenoestrogen found in the environment, in consequence, for the biosensor detection of BPA we raised antibodies (polyclonal (PAbs) and monoclonal (MAbs)) against a structural analogue of BPA, 4,4 bis-(4-hydroxyphenyl) valeric acid (BVA). The kinetics of the MAb-BPA interaction were evaluated and the MAb providing the highest affinity was directly immobilized onto the sensor chip surface to evaluate a direct assay. Afterwards, the performance of the MAbs and the PAbs was compared in an inhibition assay using a BVA-coated chip.The highest sensitivity (limit of detection (LOD) of 0.4 μg L⁻¹) was obtained with MAb 12 in the direct assay. However, the inhibition assay was the most robust and the PAbs showed the highest sensitivity (LOD of 0.5-1 μg L⁻¹). The antibodies were specific for BVA and BPA as only minor cross-reactivities were found toward structurally related compounds or other endocrine disruptors. In the inhibition assay (with a run time of 6 min), water samples spiked with BPA at different levels (0.5-50 μg L⁻¹) resulted in recoveries varying between 68% and 121%. The sensitivity of the inhibition assay could be improved 40 times (LOD of 0.03 μg L⁻¹ with the Mab 12-based assay) using solid phase extraction (SPE).     

From Tethered to Freestanding Stabilizers of 14-3-3 Protein-Protein Interactions through Fragment Linking

Small-molecule stabilization of protein-protein interactions (PPIs) is a promising strategy in chemical biology and drug discovery. However, the systematic discovery of PPI stabilizers remains a largely unmet challenge. Herein we report a fragment-linking approach targeting the interface of 14-3-3 and a peptide derived from the estrogen receptor alpha (ERα) protein. Two classes of fragments—a covalent and a noncovalent fragment—were co-crystallized and subsequently linked, resulting in a noncovalent hybrid molecule in which the original fragment interactions were largely conserved. Supported by 20 crystal structures, this initial hybrid molecule was further optimized, resulting in selective, 25-fold stabilization of the 14-3-3/ERα interaction. The high-resolution structures of both the single fragments, their co-crystal structures and those of the linked fragments document a feasible strategy to develop orthosteric PPI stabilizers by linking to an initial tethered fragment.     

A state-of-the-science review of analytical methods for urinary dialkylphosphate metabolites in the assessment of exposure to organophosphate pesticides: From 2000 to 2022

The general population and workers are exposed to organophosphate insecticides, one of the leading chemical classes of pesticides used in rural and urban areas. This paper aims to conduct an integrative review of the most used analytical methods for identifying and quantifying dialkylphosphate—which are metabolites of organophosphate insecticides—in the urine of exposed workers, discussing their advantages, limitations and applicability. Searches utilized the PubMed, the Scientific Electronic Library Online and the Brazilian Digital Library of Theses and Dissertations databases between 2000 and 2021. Twenty-five studies were selected. The extraction methods most used were liquid–liquid extraction (LLE) (36%) and solid-phase extraction (SPE) (36%), with the SPE being more economical in terms of time and amount of solvents needed, and presenting the best percentage of recovery of analytes, when compared with LLE. Nineteen studies (76%) used the gas chromatography method of separation, and among these, 12 records (63%) indicated mass spectrometry used as a detection technology (analyzer). Studies demonstrate that dialkylphosphates are sensitive and representative exposure biomarkers for environmental and occupational organophosphate exposure.     

The Performance of Planar Electrochromatography in a Horizontal Chamber

JPC – Journal of Planar Chromatography – Modern TLC - Planar electrochromatography in the reversed-phase mode has been performed in a commercially available development chamber, which...     

Developing DNP/Solid-State NMR Spectroscopy of Oriented Membranes

Dynamic nuclear polarization (DNP)/solid-state nuclear magnetic resonance (NMR) spectroscopy bears great potential for the investigation of membrane-associated polypeptides which can often be produced only in small amounts and which need to be ‘diluted’ in lipid bilayer environments to adopt or maintain their functional structure. Here we present investigations using biradicals, such as TOTAPOL and bTbK, for solid-state NMR signal enhancement using DNP in the context of lipid membranes. By transferring polarization from electron to nuclear spins using microwave irradiation signal enhancement factors of up to 13 are obtained with TOTAPOL and up to 17 with bTbK. The possible reasons why these factors are below those obtained in glassy samples of bulk solvents (40–60 under similar conditions) are evaluated and discussed. In order to further ameliorate the enhancement factors the physico-chemical characteristics of TEMPOL, TOTAPOL, bTbK, and bCTbK, such as their partitioning between hydrophilic and hydrophobic solvents or their stability under different environmental conditions are presented. Finally, having provided proof-of-concept that DNP/solid-state NMR measurements can be performed with oriented membrane samples work in progress is presented on the development of a flat-coil probe for DNP/solid-state NMR experiments on oriented membranes.     

Some combinatorial and geometric characterizations of the finite dual classical generalized hexagons

We characterize the dual of the generalized hexagons naturally associated to the groupsG ₂(q) and³ D ₄(q) by looking at certain configurations, and also by considering intersections of traces. For instance, the dual of a generalized hexagon of finite order (s, t) is associated to the Chevalley groups mentioned above if and only if the intersection of any two tracesx ^y andx ^z, with some additional condition, contains at mostt/s + 1 elements.     

Insight into the Supramolecular Architecture of Intact Diatom Biosilica from DNP‐Supported Solid‐State NMR Spectroscopy

Diatom biosilica is an inorganic/organic hybrid with interesting properties. The molecular architecture of the organic material at the atomic and nanometer scale has so far remained unknown, in particular for intact biosilica. A DNP‐supported ssNMR approach assisted by microscopy, MS, and MD simulations was applied to study the structural organization of intact biosilica. For the first time, the secondary structure elements of tightly biosilica‐associated native proteins in diatom biosilica were characterized in situ. Our data suggest that these proteins are rich in a limited set of amino acids and adopt a mixture of random‐coil and β‐strand conformations. Furthermore, biosilica‐associated long‐chain polyamines and carbohydrates were characterized, thereby leading to a model for the supramolecular organization of intact biosilica.     

Das Verfahren zum Nachweis von Ziegenmilch in Kuhmilch

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