Search

The article discusses the concerns of environmental scientists on the awarding of a concession to infrastructure development firm Hong Kong Nicaragua Development Corp. (HKND) in June 2013 for the construction of an interoceanic canal across Nicaragua and other projects such as oil pipeline and international airports. The author finds that the government did not hold a bidding process for the construction projects and conduct assessments on their socio-economic and environmental impact.

Branchgrowth is directed along two, three, or four in-plane directionsin vertically aligned nanowire arrays using vapor–liquid–solidglancing angle deposition (VLS-GLAD) flux engineering. In this work,a dynamically controlled collimated vapor flux guides branch placementduring the self-catalyzed epitaxial growth of branched indium tinoxide nanowire arrays. The flux is positioned to grow branches onselect nanowire facets, enabling fabrication of aligned nanotree arrayswith L-, T-, or X-branching. In addition, a flux motion algorithmis designed to selectively elongate branches along one in-plane axis.Nanotrees are found to be aligned across large areas by X-ray diffractionpole figure analysis and through branch length and orientation measurementscollected over 140 μm2from scanning electron microscopyimages for each array. The pathway to guided assembly of nanowirearchitectures with controlled interconnectivity in three-dimensionsusing VLS-GLAD is discussed. [ABSTRACT FROM AUTHOR]

We tailored nanostructured morphology and crystal textureof ironnanocolumns by engineering the inclination and azimuthal directionsof the collimated flux characteristic of glancing angle deposition(GLAD). Under continuous substrate rotation, the flux is azimuthallyisotropic within one rotation. With large substrate rotation speeds,we can deposit vertical nanocolumns with a faceted, tetrahedral apex,BCC crystal structure and ⟨111⟩ fiber texture. Designingthe flux to have an azimuthal 3-fold symmetry, which reflects thesymmetry of the tetrahedral apex, allows us to induce both an in-planeand out-of-plane texture (biaxial texture) by evolutionary selection.In-plane crystal orientation is accompanied by a preferential azimuthalnanocolumn orientation, where the sides of tetrahedral apex are directedtoward the flux direction. This work demonstrates the flux engineeringtechnique, which can orient in-plane crystal texture and morphologyof crystalline nanocolumns on amorphous substrates. This control isa useful addition to vapor–solid, physical self-assembly withthe potential to improve the performance of porous thin film architecturesas biaxial buffer layers, and in a variety of device applicationssuch as photovoltaics and energy storage. [ABSTRACT FROM AUTHOR]

The E3 ubiquitin ligase MDM2 functions as a crucial negative regulator of the p53 tumor suppressor protein by antagonizing p53 transactivation activity and targeting p53 for degradation. Cellular stress activates p53 by alleviating MDM2-mediated functional inhibition, even though the molecular mechanisms of stress-induced p53 activation still remain poorly understood. Two opposing models have been proposed to describe the functional and structural role in p53 activation of Ser17 phosphorylation in the N-terminal "lid" (residues 1-24) of MDM2. Using the native chemical ligation technique, we synthesized the p53-binding domain (1-109)MDM2 and its Ser17-phosphorylated analogue (1-109)MDM2 pS17 as well as (1-109)MDM2 S17D and (25-109)MDM2, and comparatively characterized their interactions with a panel of p53-derived peptide ligands using surface plasmon resonance, fluorescence polarization, and NMR and CD spectroscopic techniques. We found that the lid is partially structured in apo-MDM2 and occludes p53 peptide binding in a ligand size-dependent manner. Binding of (1-109)MDM2 by the (15-29)p53 peptide fully displaces the lid and renders it completely disordered in the peptide-protein complex. Importantly, neither Ser17 phosphorylation nor the phospho-mimetic mutation S17D has any functional impact on p53 peptide binding to MDM2. Although Ser17 phosphorylation or its mutation to Asp contributes marginally to the stability of the lid conformation in apo-MDM2, neither modification stabilizes apo-MDM2 globally or the displaced lid locally. Our findings demonstrate that Ser17 phosphorylation is functionally neutral with respect to p53 binding, suggesting that MDM2 phosphorylation at a single site is unlikely to play a dominant role in stress-induced p53 activation. [ABSTRACT FROM AUTHOR]

Nanoporous films of indium tin oxide (ITO), with thicknesses ranging from 250 nm to 2 μm, were prepared by Glancing Angle Deposition (GLAD) and used as highly sensitive transparent 3D-electrodes for quantitatively interrogating, by time-resolved spectroelectrochemistry, the reactivity of microperoxidase-11 (MP-11) adsorbed within such films. The capacitive current densities of these 3D-electrodes as well as the amount of adsorbed MP-11 were shown to be linearly correlated to the GLAD ITO film thickness, indicating a homogeneous distribution of MP-11 across the film as well as homogeneous film porosity. Under saturating adsorption conditions, MP-11 film concentration as high as 60 mM was reached. This is equivalent to a stack of 110 monolayers of MP-11 per micrometer film thickness. This high MP-11 film loading combined with the excellent ITO film conductivity has allowed the simultaneous characterization of the heterogeneous one-electron transfer dynamics of the MP-11 FeIII/FeII redox couple by cyclic voltammetry and cyclic voltabsorptometry, up to a scan rate of few volts per second with a satisfactory single-scan signal-to-noise ratio. The potency of the method to unravel complex redox coupled chemical reactions was also demonstrated with the catalytic reduction of oxygen by MP-11. In the presence of O2, cross-correlation of electrochemical and spectroscopic data has allowed us to determine the key kinetics and thermodynamics parameters of the redox catalysis that otherwise could not be easily extracted using conventional protein film voltammetry. On the basis of numerical simulations of cyclic voltammograms and voltabsorptograms and within the framework of different plausible catalytic reaction schemes including appropriate approximations, it was shown possible to discriminate between different possible catalytic pathways and to identify the relevant catalytic cycle. In addition, from the best fits of simulations to the experimental voltammograms and voltabsorptograms, the partition coefficient of O2 for the ITO film as well as the values of two kinetic rate constants could be extracted. It was finally concluded that the catalytic reduction of O2 by MP-11 adsorbed within nanoporous ITO films occurs via a 2-electron mechanism with the formation of an intermediate FeIII-OOH adduct characterized by a decay rate of 11 s-1. The spectroelectroanalytical strategy presented here opens new opportunities for characterizing complex redox-coupled chemical reactions not only with redox proteins, but also with redox biomimetic systems and catalysts. It might also be of great interest for the development and optimization of new spectroelectrochemical sensors and biosensors, or eventually new photoelectrocatalytic systems or biofuel cells. [ABSTRACT FROM AUTHOR]

High-performance thin-layer chromatography is a separate ion technique commonly used to identify and quantify components in chemical mixtures. Sophisticated analytical tools are required to extract the full analytical power from this technique and especially for miniaturized planar chromatography its utility has not been harnessed. A new approach uses an elegant, simplified system assembled from ordinary consumer printers and scanners to perform separations on monolithic and nanostructured ultrathinlayer phases. This system is shown to outperform existing planar chromatographic tools for analysis on miniaturized plates. Analysis can be completed in a manner of minutes, running numerous samples in parallel at a reduced cost, with very low sample and reagent volumes, all using a familiar computer interface with common office peripherals. [ABSTRACT FROM AUTHOR]

Glancing angle deposition was used to produce ∼150-nm-thick silver nanoparticle films, which were evaluated as localized surface plasmon resonance (LSPR) biosensors. The films have a strong extinction peak around 368 nm in air due to LSPR. As the refractive index of the surrounding environment is increased, the extinction peak red-shifts with a linear dependence. The films were functionalized with 11-amino-1-undecanethiol and rabbit immunoglobulin G (rIgG) to allow for the detection of anti-rIgG binding. Binding of biomolecules to the nanoparticle surface increases the local refractive index and results in a red-shifting of the extinction peak. The wavelength shift at varying concentrations of anti-rIgG was measured and fit to the Langmuir isotherm. This yielded approximate values for the saturation response, Δλmax = 29.4 ± 0.7 nm, and the surface confined binding constant, Ka = (2.7 ± 0.3) × 106 M-1. The response to nonspecific binding was also investigated. [ABSTRACT FROM AUTHOR]