Transmission electron microscopy of unstained hybrid Au nanoparticles capped with PPAA (plasma-poly-allylamine): structure and electron irradiation effects.

Hybrid (organic shell-inorganic core) nanoparticles have important applications in nanomedicine. Although the inorganic components of hybrid nanoparticles can be characterized readily using conventional transmission electron microscopy (TEM) techniques, the structural and chemical arrangement of the organic molecular components remains largely unknown. Here, we apply TEM to the physico-chemical characterization of Au nanoparticles that are coated with plasma-polymerized-allylamine, an organic compound with the formula C3H5NH2.

Self-assembly mechanism of thiol, dithiol, dithiocarboxylic acid, disulfide and diselenide on gold: an electrochemical impedance study.

The self-assembly mechanism of normal aliphatic thiol (RSH), disulfide (RSSR), diselenide (RSeSeR), dithiol (R(SH)2) and dithiocarboxylic acid (RS2H) onto a gold surface was studied in real time by electrochemical impedance spectroscopy (EIS). The different stages of adsorption could be clearly followed from the interfacial capacitance variation. An initial very fast adsorption, varying from a few seconds to several minutes depending on concentration, is the major adsorption step.

Electrochemical and spectroscopic study of the self-assembling mechanism of normal and chelating alkanethiols on copper.

The self-assembly of aliphatic thiol (RSH), dithiol (R(SH)(2)), and dithiocarboxylic acid (RS(2)H) onto mildly oxidized and highly oxidized copper was studied in real time by in situ electrochemical impedance spectroscopy (EIS). Ex situ characterization of the films was carried out using linear sweep voltammetry (LSV), polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). In situ EIS studies found a very fast adsorption of RSH, R(SH)(2), and RS(2)H (within 10-15 s).

Density functional theory-based simulations of sum frequency generation spectra involving methyl stretching vibrations: effect of the molecular model on the deduced molecular orientation and comparison with an analytical approach.

The knowledge of the first hyperpolarizability tensor elements of molecular groups is crucial for a quantitative interpretation of the sum frequency generation (SFG) activity of thin organic films at interfaces. Here, the SFG response of the terminal methyl group of a dodecanethiol (DDT) monolayer has been interpreted on the basis of calculations performed at the density functional theory (DFT) level of approximation. In particular, DFT calculations have been carried out on three classes of models for the aliphatic chains.

Validation of the calibrated thrombin generation test (cTGT) as the reference assay to evaluate the procoagulant activity of nanomaterials.

We validated a preclinical toxicological screening assay and provided guidelines to evaluate the potential impact of nanoparticles (NPs) on blood coagulation. Five NPs with various physicochemical properties were studied using several existing methods of clotting times and thrombin generation assays in human normal pool plasma. In both recalcification clotting time (RCT) and calibrated thrombin generation test (cTGT), the NPs exhibited procoagulant activity (SiO₂ ≥ SiC ≥ TiC > CuO > CB) but cTGT was more sensitive and relevant than RCT.

A comparative study of the electron transmission through one-dimensional barriers relevant to field-emission problems.

We study the transmission coefficient of one-dimensional barriers that are relevant to field-emission problems. We compare, in particular, the results provided by the simple Jeffreys-Wentzel-Kramers-Brillouin (JWKB) approximation, the continued-fraction technique and the transfer-matrix methodology for the electronic transmission through square, triangular and Schottky-Nordheim barriers (the Schottky-Nordheim barrier is often used in models of field emission from flat metals). For conditions that are typical of field emission (Fermi energy of 10 eV, work function of 4.

Functional analysis: evaluation of response intensities--tailoring ANOVA for lists of expression subsets.

Background: Microarray data is frequently used to characterize the expression profile of a whole genome and to compare the characteristics of that genome under several conditions. Geneset analysis methods have been described previously to analyze the expression values of several genes related by known biological criteria (metabolic pathway, pathology signature, co-regulation by a common factor, etc.) at the same time and the cost of these methods allows for the use of more values to help discover the underlying biological mechanisms.

What do we know about effects of desert dust on air quality and human health in West Africa compared to other regions?

This study aims to compare, on the one hand, the geographical distribution of the desert dust source areas, their contribution to quantities emitted into the atmosphere, the trajectories and the quantities deposited, with on the other hand the areas of research interest focused on the desert dust impacts on air quality and/or human health. Based on a systematic review of the literature using the ISI Web of Knowledge database, we found 231 articles published over the last decade on the desert dust impacts on air quality. Of these, 48% concerned Asian dust and 39% Saharan dust, with the remaining 13% divided between the other dust source areas.

Anti-apoptotic role of HIF-1 and AP-1 in paclitaxel exposed breast cancer cells under hypoxia.

Background: Hypoxia is a hallmark of solid tumors and is associated with metastases, therapeutic resistance and poor patient survival.

Results: In this study, we showed that hypoxia protected MDA-MB-231 breast cancer cells against paclitaxel- but not epirubicin-induced apoptosis. The possible implication of HIF-1 and AP-1 in the hypoxia-induced anti-apoptotic pathway was investigated by the use of specific siRNA.

Global analysis of quorum sensing targets in the intracellular pathogen Brucella melitensis 16 M.

Many pathogenic bacteria use a regulatory process termed quorum sensing (QS) to produce and detect small diffusible molecules to synchronize gene expression within a population. In Gram-negative bacteria, the detection of, and response to, these molecules depends on transcriptional regulators belonging to the LuxR family. Such a system has been discovered in the intracellular pathogen Brucella melitensis, a Gram-negative bacterium responsible for brucellosis, a worldwide zoonosis that remains a serious public health concern in countries were the disease is endemic.

Simulations of infrared and optical rectification by geometrically asymmetric metal-vacuum-metal junctions for applications in energy conversion devices.

We use a transfer-matrix methodology to simulate the rectification of infrared and optical radiation by geometrically asymmetric metal-vacuum-metal junctions in which one of the metals is flat while the other is extended by a tip. We determine in particular the power this junction could provide to an external load and the efficiency with which the energy of incident radiations is converted. We consider first situations in which the external radiation is monochromatic, with typical frequencies in the infrared and optical domains.

Ewald-type formulas for Gaussian-basis Bloch states in one-dimensionally periodic systems.

Expressions for integrals involving general Gaussian (s, p, d, [ellipsis (horizontal)]) basis Bloch functions are presented. Applying the Poisson transformation and the Ewald-type partitioning scheme, all lattice sums appearing in these expressions lead to fast convergence in both direct and Fourier spaces. Numerical results produced for selected test cases show that a limited number of terms in the lattice sums are necessary to get convergence in the two spaces.

Hypoxia-induced decrease in p53 protein level and increase in c-jun DNA binding activity results in cancer cell resistance to etoposide.

Tumor hypoxia is one of the features of tumor microenvironment that contributes to chemoresistance in particular by cellular adaptations that modulate the apoptotic process. However, the mechanisms involved in this resistance still need deeper understanding. In this study, we investigated the involvement of four transcription factors, c-Myc, nuclear factor kappaB (NF-kappaB), p53, and c-jun/activator protein 1 (AP-1) in the hypoxia-induced resistance to etoposide in HepG2 cells.

Rectification properties of geometrically asymmetric metal-vacuum-metal junctions: a comparison of tungsten and silver tips to determine the effects of polarization resonances.

We simulate with a transfer-matrix methodology the rectification properties of geometrically asymmetric metal-vacuum-metal junctions in which one of the metals is flat while the other is extended by a tip. We consider both tungsten and silver as the material for the tip and we study the influence of the dielectric function of these materials on the rectification properties of the junction. We determine in particular the power that these junctions could provide to an external load when subject to a bias whose typical frequency is in the infrared or optical domain.

NDRG1 and CRK-I/II are regulators of endothelial cell migration under Intermittent Hypoxia.

Intermittent Hypoxia (IH) that develops in neovascularized solid tumours has been described to positively influence the tumour growth by modulating the behaviour of cancer cells as well as of endothelial cells. However, the molecular mechanisms regulated by IH still remain poorly understood. In this work, the effects of IH were investigated on endothelial cells by a proteomic approach.

Enhanced polarizability of aromatic molecules placed in the vicinity of silver clusters.

We use a charge-dipole interaction model to study the polarizability of aromatic molecules that are placed between two silver clusters. In particular we examine the enhancement in polarizability induced by the clusters at plasmon-like resonant frequencies of the cluster-molecule-cluster system. The model used for these simulations relies on representation of the atoms by both a net electric charge and a dipole.

A charge-dipole interaction model for the frequency-dependent polarizability of silver clusters.

We present a charge-dipole interaction model for the calculation of the frequency-dependent polarizability of silver clusters. The model relies on the representation of silver atoms by both a net electric charge and a dipole. Time variations of the atomic charges are related to the currents that flow through the bonds of the structures considered and the atomic charges and dipoles are eventually determined from the application of a least-action principle.

Intermittent hypoxia is an angiogenic inducer for endothelial cells: role of HIF-1.

The presence of hypoxia in tumor and its role in promoting angiogenesis are well-established. Recently, in addition to chronic hypoxia, cycling or intermittent hypoxia has also been demonstrated. However, its role in inducing new blood vessel formation is less clear.

Hypoxia regulates inflammatory gene expression in endothelial cells.

Hypoxia can activate the endothelium toward a pro-inflammatory phenotype and enhance leukocyte adhesion. This process is involved in pathological conditions such as vascular remodeling or ischemia-reperfusion injury. This study was aimed to obtain a global picture of the response of the endothelial cells to hypoxia with respect to inflammatory genes.

Tumour hypoxia affects the responsiveness of cancer cells to chemotherapy and promotes cancer progression.

A solid tumour forms an organ-like structure that is comprised of cancer cells as well as stroma cells (fibroblasts, inflammatory cells) that are embedded in an extracellular matrix and are nourished by vascular network. However, tumoral microenvironment is heterogeneous due to the abnormal vasculature network and high proliferation rate of cancer cells. Because of these features, some regions are starved from oxygen, a phenomenon called hypoxia.

Structure-based drug design targeting biosynthesis of isoprenoids: a crystallographic state of the art of the involved enzymes.

Biosynthesis of the universal terpenoid precursors, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), from three acetyl CoA moieties through mevalonate was studied extensively in the 1950s. For several decades, the mevalonate paradigm reigned supreme and a mevalonate origin was attributed to a growing number of natural products, in many cases erroneously. Besides this biosynthetic pathway, the existence of a second one leading to IPP and DMAPP through 1-deoxy-D-xylulose 5-phosphate and 2C-methyl-D-erythritol 4-phosphate was discovered more recently in plants and some eubacteria.

Monoclinic form of isopentenyl diphosphate isomerase: a case of polymorphism in biomolecular crystals.

Type 1 isopentenyl diphosphate isomerase (IDI-1) has been crystallized in a new crystal form. After data collection from small thin needle-shaped crystals, a new monoclinic form of the studied protein was identified. In this article, the three crystal forms of IDI-1 (orthorhombic, monoclinic and trigonal) are compared.

Electronic structure of Pd nanoparticles on carbon nanotubes.

The effect of the oxygen plasma treatment on the electronic states of multi-wall carbon nanotubes (MWCNTs) is analyzed by X-ray photoemission measurements (XPS) and UPS, both using synchrotron radiation. It is found that the plasma treatment effectively grafts oxygen at the CNT-surface. Thereafter, the interaction between evaporated Pd and pristine or oxygen plasma-treated MWCNTs is investigated.