Pattern shape control for heat treatment purification of electron-beam-induced deposition of gold from the Me2Au(acac) precursor

Gold structures can be created in a scanning electron microscope (SEM) from the Me(2)Au(acac) precursor by direct writing with the electron beam. The as-deposited purity is usually poor, and a common purification approach is a post-annealing step that indeed is effective but also induces a volume reduction because of carbon loss and an undesirable reconfiguration of the gold structure, resulting in the loss of the original shape. We studied the shape change as a result of such purification, and to minimize this effect, the application of a tantalum and chromium buffer layer was investigated. These buffer materials are well-known for their good adhesion properties. We confirm by dedicated SEM, atomic force microscopy (AFM), and transmission electron microscopy (TEM) analysis that, for the creation of a uniform Au structure, tantalum is a better buffer layer material than chromium. Post-annealing of the Au electron-beam-induced deposition (EBID) patterns for 1 h at 600 °C in air resulted in a dramatic purity increase (from 8-12 atomic % Au to above 92 atomic % Au). The uncovered part of the tantalum layer can be easily etched away, resulting in a well-defined, high-purity, gold structure.     

An overview of recent advances in HPLC instrumentation

This review highlights the fundamentals and the most prominent advances in the field of HPLC instrumentation over the last decades. Fundamental aspects and practical considerations of column switching, conventional (heart-cut) and comprehensive two-dimensional LC are presented. Different aspects of microcolumn- and nanoliquid-chromatography are reviewed. Recent progress in column technology and the demands and developments in instrumentation and accessories for miniaturized LC are also discussed. In the field of miniaturization, particularly in chip-based nano-LC systems, some aspects on micro-fluidic chip fabrication, using particle-packed HPLC microchips or polymer-based monoliths, are addressed. An introduction to ultra performance LC (UPLC) is also presented.     

Formation and characterization of phosphate-modified silicate materials derived from sol–gel process

Phosphate-containing silicate materials prepared using sol–gel method from Si(OC₂H₅) were investigated at the variation of the amount of phosphate modifier from 5 to 50 wt% in term of P₂O₅. Chemical composition, textural and structural properties of these materials were characterized by FTIR-spectroscopy, TEM, X-ray diffraction and nitrogen adsorption. It was shown that the materials posse monomodal pore size distribution of 5–20 nm for the samples dried at 100 °C and 40–60 nm for the specimens calcined at 600 °C. The mean pore size and surface area depended on the amount of phosphoric acid. Before the stage of high temperature treatment phosphoric acid, introduced into the structure of the materials as a modifying agent, was uniformly distributed inside a porous space of the material and was not chemically bonded with silicate. After high temperature treatment both chemical interaction of silicate with phosphate, providing the formation of silicate-phosphate structures, as well as redistribution of free modifier from the bulk of granules to their surface took place. The polyphosphate layer is formed on the material surface closing the internal porous space. However, in this case a part of the phosphate modifier remains chemically unbound to SiO₂ structure.     

First example of the cascade acylation/IMDAV/ene reaction sequence,leading to N-arylbenzo[f]isoindole-4-carboxylic acids possessing anti-viral activity

The reaction between readily accessible N-aryl-3-phenylallylamines and maleic anhydride led to unexpected products – polysubstituted hydrogenated benzo[f]isoindole-4-carboxylic acids. This transformation proceeds through a previously unknown sequence of steps: N-acylation of the allylamine with maleic anhydride, intramolecular Diels-Alder reaction of the vinylarene in the intermediate N-maleamide, and Alder-ene reaction of the products of the previous two steps. Selected benzo[f]isoindoles displayed antiviral activity.     

Highly satisfactory procedures for the Pd-catalyzed cross coupling of aryl electrophiles with in situ generated alkynylzinc derivatives

[reaction: see text] Two new and very efficient procedures (Procedures A and B) are reported for the Pd-catalyzed cross coupling of aryl electrophiles with terminal alkynes via their in situ conversion into alkynylzinc derivatives. Procedure A is particularly valuable in cases where electron-deficient alkynes are used, while Procedure B is operationally simple and very satisfactory in less demanding cases.     

Numerical simulation of the chromatographic process for direct ligand-macromolecule binding studies

A numerical simulation of the direct zonal liquid chromatographic method is described for studying the binding of a ligand to a macromolecule by quantification of the interacting species present in a sample at equilibrium. The algorithm accounts for both the kinetic exchanges in solution and the dispersion effects depicted by the Fick law. Dimensionless variables are used for the concentrations which are expressed as a function of the equilibrium constant, KD. The free ligand concentration was varied in the injected samples from 0.1 to 20 KD, while that of the macromolecule was kept constant. An apparent binding isotherm was obtained from the total ligand chromatogram generated by the simulation run, when the amount emerging at almost column dead volume is plotted against that eluting at the free ligand retention time. As a continuous dissociation of the complex may occur during its migration, the apparent binding curve and the theoretical binding isotherm coincide at extremely low dissociating rates. At larger dissociation rates (0.001 s(-1) < kd <0.1 s(-1), for a first peak eluting in 1 min) the simulations were used to test various chromatographic conditions. The flow rate (or column volume) is the major effect which influences the on-column dissociation process as an exponential decay was found when the apparently bound fraction is plotted against the analysis time. The apparent equilibrium coefficient is close to the theoretical one for a binding curve generated with an initial solution containing a relatively low total concentration of binding sites (< or = KD). The apparent stoichiometric term is largely underestimated as its value decreases exponentially at increasing dissociation rates. An extrapolation at extremely short analysis times could be used to determine the stoichiometric coefficient characterizing the binding interaction.     

Synthesis,Bioactivity, Pharmacokinetic and Biomimetic Properties of Multi-Substituted Coumarin Derivatives

A series of novel multi-substituted coumarin derivatives were synthesized, spectroscopically characterized, and evaluated for their antioxidant activity, soybean lipoxygenase (LOX) inhibitory ability, their influence on cell viability in immortalized human keratinocytes (HaCaT), and cytotoxicity in adenocarcinomic human alveolar basal epithelial cells (A549) and human melanoma (A375) cells, in vitro. Coumarin analogues 4a–4f, bearing a hydroxyl group at position 5 of the coumarin scaffold and halogen substituents at the 3-phenyl ring, were the most promising ABTS^•+ scavengers. 6,8-Dibromo-3-(4-hydroxyphenyl)-4-methyl-chromen-2-one (4k) and 6-bromo-3-(4,5-diacetyloxyphenyl)-4-methyl-chromen-2-one (3m) exhibited significant lipid peroxidation inhibitory activity (IC₅₀ 36.9 and 37.1 μM). In the DCF-DA assay, the 4′-fluoro-substituted compound 3f (100%), and the 6-bromo substituted compounds 3i (80.9%) and 4i (100%) presented the highest activity. The 3′-fluoro-substituted coumarins 3e and 4e, along with 3-(4-acetyloxyphenyl)-6,8-dibromo-4-methyl-chromen-2-one (3k), were the most potent lipoxygenase (LOX) inhibitors (IC₅₀ 11.4, 4.1, and 8.7 μM, respectively) while displaying remarkable hydroxyl radical scavenging ability, 85.2%, 100%, and 92.9%, respectively. In silico docking studies of compounds 4e and 3k, revealed that they present allosteric interactions with the enzyme. The majority of the analogues (100 μΜ) did not affect the cell viability of HaCaT cells, though several compounds presented over 60% cytotoxicity in A549 or A375 cells. Finally, the human oral absorption (%HOA) and plasma protein binding (%PPB) properties of the synthesized coumarins were also estimated using biomimetic chromatography, and all compounds presented high %HOA (>99%) and %PPB (60–97%) values.     

Amyloid binding and beyond: a new approach for Alzheimer's disease drug discovery targeting Aβo–PrPC binding and downstream pathways

Amyloid β oligomers (Aβo) are the main toxic species in Alzheimer''s disease, which have been targeted for single drug treatment with very little success. In this work we report a new approach for identifying functional Aβo binding compounds. A tailored library of 971 fluorine containing compounds was selected by a computational method, developed to generate molecular diversity. These compounds were screened for Aβo binding by a combined ¹⁹F and STD NMR technique. Six hits were evaluated in three parallel biochemical and functional assays. Two compounds disrupted Aβo binding to its receptor PrP^C in HEK293 cells. They reduced the pFyn levels triggered by Aβo treatment in neuroprogenitor cells derived from human induced pluripotent stem cells (hiPSC). Inhibitory effects on pTau production in cortical neurons derived from hiPSC were also observed. These drug-like compounds connect three of the pillars in Alzheimer''s disease pathology, i.e. prion, Aβ and Tau, affecting three different pathways through specific binding to Aβo and are, indeed, promising candidates for further development.

A new approach combining virtual screening, ¹⁹F and STD NMR, and biochemical assays using hiPSC and targetting multiple pathways involving Aβ, PrP^C and Tau provides a more effective strategy for Alzheimer''s disease drug discovery than Aβ only approach.     

Spectral Signatures of Oxidation States in a Manganese-Oxo Cubane Water Oxidation Catalyst

We report IR and UV/Vis spectroscopic signatures that allow discriminating between the oxidation states of the manganese-based water oxidation catalyst [(Mn₄O₄)(V₄O₁₃)(OAc)₃]³⁻. Simulated IR spectra show that V=O stretching vibrations in the 900–1000 cm⁻¹ region shift consistently by about 20 cm⁻¹ per oxidation equivalent. Multiple bands in the 1450–1550 cm⁻¹ region also change systematically upon oxidation/reduction. The computed UV/Vis spectra predict that the spectral range above 350 nm is characteristic of the managanese-oxo cubane oxidation state, whereas transitions at higher energy are due to the vanadate ligand. The presence of absorption signals above 680 nm is indicative of the presence of Mn^III atoms. Spectroelectrochemical measurements of the oxidation from [Mn Mn ] to [Mn ] showed that the change in oxidation state can indeed be tracked by both IR and UV/Vis spectroscopy.     

A Fixable Fluorescence-Quenched Substrate for Quantitation of Lysosomal Glucocerebrosidase Activity in Both Live and Fixed Cells

Fluorogenic substrates are emerging tools that enable studying enzymatic processes within their native cellular environments. However, fluorogenic substrates that function within live cells are generally incompatible with cellular fixation, preventing their tandem application with fundamental cell biology methods such as immunocytochemistry. Here we report a simple approach to enable the chemical fixation of a dark-to-light substrate, LysoFix-GBA, which enables quantification of glucocerebrosidase (GCase) activity in both live and fixed cells. LysoFix-GBA enables measuring responses to both chemical and genetic perturbations to lysosomal GCase activity. Further, LysoFix-GBA permits simple multiplexed co-localization studies of GCase activity with subcellular protein markers. This tool will aid studying the role of GCase activity in Parkinson's Disease, creating new therapeutic approaches targeting the GCase pathway. This approach also lays the foundation for an approach to create fixable substrates for other lysosomal enzymes.