Rational design of lanthanide binding peptides

Lanthanide-binding peptides are very attractive for the design of bioprobes. Indeed, they combine the amazing properties of lanthanide ions, such as their time-resolved luminescence (Eu, Tb) or electronic relaxation (Gd) to the characteristics of the peptide scaffold, such as large solubility in water and ability to recognize biological substrates. Peptides derived from natural amino acids are reviewed in a first section. Some of their lanthanide complexes have already demonstrated their efficiency in determining protein structures and functions. Then, we will show how insertion of chelating unnatural amino acids modulates peptide-lanthanide complexes properties, such as luminescence and stability.     

Influence of glass transition temperature of crosslinked unsaturated polyester resin/styrene formulations on the final conversion after an isothermal curing at 100°C

SMC (sheet molding compound) is a composite based on fibers‐reinforced unsaturated polyester (UP) resin molded usually at 140°C to 170°C under a pressure of 60 to 100 bars. In order to develop new SMC formulations that can be molded at lower temperature (100°C) for economic and environmental reasons, the formulation of the composite had to be completely modified, both to allow a rapid reaction at 100°C, but also to avoid a vitrification phenomenon due to the fact that the glass transition temperature (Tg) of the SMC parts becomes, during the molding process, higher than the mold temperature. In this paper, the relation between the molding temperature, the glass transition temperature, and the final conversion of UP resin/styrene formulations has been underlined. The Tg of the cured resin was decreased by two different ways. The first way involved the reduction of the crosslinking density of the UP resin by using a blend of two resins, a pure maleic and a more flexible one. This blend allows to adjust the Tg over a temperature range from 197°C (Tg of the pure UP resin) to 75°C (Tg of the pure flexible resin). The second way consisted in the addition of butyl methacrylate (BuMA), a reactive plasticizer, to the formulation, allowing a decrease of the final material's Tg from 197°C to 130°C by replacing 35 wt% of styrene by BuMA. These two methods allow to obtain a final conversion of 99% after 8 minutes of molding at 100°C.     

Sol-Gel Coatings on Non-Oxide Planar Substrates and Fibers: A Protection Barrier Against Oxidation and Corrosion

Sol-gel coatings on non-oxide substrates can be used to prevent high temperature degradation and to improve wet corrosion resistance. Alumina coatings were investigated. The starting precursor was aluminium sec-butoxide, modified with chelating ligands such as 2,4-pentanedione or acrylic acid to prevent its precipitation in the presence of water. Stainless steel plates and Hi-Nicalon SiC fibers are often utilized in different kinds of applications and thus were selected as substrates. Thin films were deposited from the modified alkoxide solutions using dip-coating techniques. The parameters governing the process such as the aging of the sols, the viscosity, the withdrawal rate and the thermal treatment were investigated. The films were characterized (morphology, thickness) and showed an interesting behaviour as protection barrier in an aggressive medium.     

Syntheses, X-ray structures, solid state high-field electron paramagnetic resonance, and density-functional theory investigations on chloro and aqua Mn(II) mononuclear complexes with amino-pyridine pentadentate ligands

The two pentadentate amino-pyridine ligands L5(2) and L5(3) (L5(2) and L5(3) stand for the N-methyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine and the N-methyl-N,N',N'-tris(2-pyridylmethyl)propane-1,3-diamine, respectively) were used to synthesize four mononuclear Mn(II) complexes, namely [(L5(2))MnCl](PF6) (1(PF6)), [(L5(3))MnCl](PF6) (2(PF6)), [(L5(2))Mn(OH2)](BPh4)2 (3(BPh4)2), and [(L5(3))Mn(OH2)](BPh4)2 (4(BPh4)2). The X-ray diffraction studies revealed different configurations for the ligand L5(n) (n = 2, 3) depending on the sixth exogenous ligand and/or the counterion. Solid state high-field electron paramagnetic resonance spectra were recorded on complexes 1-4 as on previously described mononuclear Mn(II) systems with tetra- or hexadentate amino-pyridine ligands. Positive and negative axial zero-field splitting (ZFS) parameters D were determined whose absolute values ranged from 0.090 to 0.180 cm(-1). Density-functional theory calculations were performed unraveling that, in contrast with chloro systems, the spin-spin and spin-orbit coupling contributions to the D-parameter are comparable for mixed N,O-coordination sphere complexes.     

Comparison of liquid-liquid extraction with headspace methods for the characterization of volatile fractions of commercial hydrolats from typically Mediterranean species

Chemical composition of volatile fractions of nine commercial hydrolats and corresponding essential oils obtained using an industrial process were studied. The hydrolat volatile fractions were reported for the first time. A comparative study of those obtained, on the one hand, by liquid-liquid extraction (LLE) and, on the other hand, using five solid-phase microextraction (SPME) fibers and also purge-and-trap-automatic thermal desorption (P&T-ATD) was conducted with analysis performed by GC and GC/MS. The use of various techniques has resulted in a change of chromatographic profile of the hydrolat volatile fractions. Quantitative differences were established between chemical compositions of headspace and those obtained by a conventional method (LLE). Statistical analyses were carried out to summarize the results.     

Free Superoxide is an Intermediate in the Production of H2O2 by Copper(I)‐Aβ Peptide and O2

Oxidative stress is considered as an important factor and an early event in the etiology of Alzheimer's disease (AD). Cu bound to the peptide amyloid‐β (Aβ) is found in AD brains, and Cu‐Aβ could contribute to this oxidative stress, as it is able to produce in vitro H₂O₂ and HO^. in the presence of oxygen and biological reducing agents such as ascorbate. The mechanism of Cu‐Aβ‐catalyzed H₂O₂ production is however not known, although it was proposed that H₂O₂ is directly formed from O₂ via a 2‐electron process. Here, we implement an electrochemical setup and use the specificity of superoxide dismutase‐1 (SOD1) to show, for the first time, that H₂O₂ production by Cu‐Aβ in the presence of ascorbate occurs mainly via a free O₂^.? intermediate. This finding radically changes the view on the catalytic mechanism of H₂O₂ production by Cu‐Aβ, and opens the possibility that Cu‐Aβ‐catalyzed O₂^.? contributes to oxidative stress in AD, and hence may be of interest.     

Capacitive Impedance for Following In-Situ Grafting Kinetics of Diazonium Salts

A new method to follow in-situ grafting kinetics of diazonium compounds based on imposing small amplitude high frequency AC oscillations at grafting potential, is outlined. This enables the time-resolved measurements of capacitive impedance concomitantly with the growth of the organic layer at the working electrode. The impedance values were quantitatively correlated with the ex-situ (from voltammograms) and in-situ (from quartz crystal microbalance) measured surface coverages, providing a validation of the new methodology. The versatility of the developed approach was demonstrated on the grafting via reduction of 4-nitrobenzenediazonium on Au and glassy carbon (GC) substrates and via deposition of in-situ generated diazonium salts from 1-aminoanthraquinone and 4-ferrocenylaniline on GC. The capacitive impedance measurements are simple, fast, and non-destructive, making it an appealing methodology for an exploration of grafting kinetics of a wide range of diazonium salts.     

Microwave-accelerated multicomponent synthesis and X-ray characterization of novel benzothiadiazinone dioxide derivatives,analogues of Monastrol

Research on Chemical Intermediates - We demonstrate here a rapid and comfortable synthetic sequence to benzothiadiazinone dioxide (six-membered cyclic sulfamide) derivatives, analogues of...     

High repetition rate mid-infrared laser source

An efficient, high-power mid-infrared laser source based on ZnGeP₂ (ZGP) optical parametric oscillator (OPO) is presented. Using a Q-switched Ho:YAG laser as the pump source a total output power of 10.6 W was obtained in the 3–5 μm band at 10 kHz and 8.5 W at 20 kHz. The Ho:YAG laser was pumped by two diode-pumped polarization coupled Tm:YLF lasers. Optical-to-optical efficiency achieved is >8.8% (laser-diode 792 nm to mid-IR 3–5 μm). With a commercial PtSi infrared camera (256×256 pixel focal plane array, 24 μm pitch) the pointing stability of Ho pump, signal and idler beam was measured to be better than 30 μrad. Whilst propagating the OPO beams over 100 m, little absorption for the idler beam was observed, resulting in a significant higher peak-to-peak value of ±22%, whereas the peak-to-peak stability of the signal pulses remained unchanged (±13%). To cite this article: M. Schellhorn et al., C. R. Physique 8 (2007).     

Protective Effect of Dermal Brimonidine Applications Against UV Radiation‐induced Skin Tumors,Epidermal Hyperplasia and Cell Proliferation in the Skin of Hairless Mice

Brimonidine at 0.18%, 1% and 2% concentrations applied topically in hairless mice significantly decreased tumor burden and incidences of erythema, flaking, wrinkling and skin thickening induced by UVR. The unbiased median week to tumor ≥1 mm was increased by the 1% and 2% concentrations. The tumor yield was reduced by all concentrations at week 40 for all tumor sizes but the ≥4 mm tumors with the 0.18% concentration. At week 52, the tumor yield was reduced for all tumor sizes and all brimonidine concentrations. The tumor incidence was reduced by all concentrations at week 40 for all tumor sizes, but the ≥4 mm tumor with the 0.18% concentration and at week 52 for all tumor sizes with the 1% and 2% concentrations and with the 0.18% concentration only for the ≥4 mm tumors. Reductions in ≥4 mm tumor incidences compared to the vehicle control group were 54%, 91% and 86% by week 52 for the 0.18%, 1% and 2% concentrations, respectively. Brimonidine at 2% applied 1 h before or just after UVB irradiation on hairless mice decreased epidermal hyperplasia by 23% and 32% and epithelial cell proliferation by 59% and 64%, respectively, similar to an epidermal growth factor receptor (EGFR) inhibitor.