The micro-distribution of carbonaceous matter in the Murchison meteorite as investigated by Raman imaging

The carbonaceous Murchison chondrite is one of the most studied meteorites. It is considered to be an astrobiology standard for detection of extraterrestrial organic matter. Considerable work has been done to resolve the elemental composition of this meteorite. Raman spectroscopy is a very suitable technique for non-destructive rapid in situ analyses to establish the spatial distribution of carbonaceous matter. This report demonstrates that Raman cartography at a resolution of 1 microm2 can be performed. Two-dimensional distribution of graphitised carbon, amorphous carbonaceous matter and minerals were obtained on 100 microm2 maps. Maps of the surface of native stones and of a powdered sample are compared. Graphitic and amorphous carbonaceous domains are found to be highly overlapping in all tested areas at the surface of the meteorite and in its interior as well. Pyroxene, olivine and iron oxide grains are embedded into this mixed carbonaceous material. The results show that every mineral grain with a size of less than a few microm2 is encased in a thin carbonaceous matrix, which accounts for only 2.5 wt.%. This interstitial matter sticks together isolated mineral crystallites or concretions, including only very few individualized graphitised grains. Grinding separates the mineral particles but most of them retain their carbonaceous coating. This Raman study complements recent findings deduced from other spatial analyses performed by microprobe laser-desorption laser-ionisation mass spectrometry (microL2MS), transmission electron microscopy (TEM) and scanning transmission X-ray microscopy (STXM).     

Template assembled cyclopeptides as multimeric system for integrin targeting and endocytosis

The alpha(V)beta(3) integrin receptor plays an important role in human metastasis and tumor-induced angiogenesis. c[-RGDfV-] peptide represents a selective alpha(V)beta(3) integrin ligand that has been extensively used for research, therapy, and diagnosis of neoangiogenesis. We report here the modular synthesis and biological characterization of template assembled cyclopeptides as a multimeric system for targeting and endocytosis of cells expressing alpha(V)beta(3) integrin. c[-RGDfK-] was cleanly assembled in a multivalent mode by chemoselective oxime bond formation to a cyclodecapeptides template labeled by different reporter groups. Binding propensity to the alpha(V)beta(3) receptor and the associated good uptake property displayed by the multivalent molecules demonstrated the interest in the RAFT molecule to design new multimeric system with hitherto unreported properties. These compounds offer an interesting perspective for the reevaluation of integrins as angiogenesis regulators (Hynes, R. O. Nature Med. 2003, 9, 918-921) as well as for the design of more sophisticated systems such as molecular conjugate vectors.     

Solid-phase synthesis of 4-methylcarboxy-1,4-benzodiazepine-2,5-diones

A solid-phase synthesis of 1,4-benzodiazepinone-2,5-diones is described. This new route can afford benzodiazepinone bearing a N-urethane-protected amine and a carboxylic acid function. This kind of building block is valuable as a dipeptide mimic or beta-turn mimetic, and it can be introduced in place of any amino acid in peptide synthesis. Using an "analytical probe" strategy, we optimized the synthesis of a model compound on SynPhase Lanterns. Therefore, the efficiency of several linkers was investigated.     

Solvolysis–hydrolysis of N-bearing alkoxysilanes: Reactions studied with 29Si NMR

The hydrolysis reactions of 8 different N-bearing alkoxy-silane coupling agents, namely: 3-cyanopropyl triethoxy silane (CPES), triethoxy-3-(2-imidazolin-1-yl) propyl silane (IZPES), and amino silanes, 3-aminopropyl triethoxy silane (APES), 3-aminopropyl trimethoxy silane (APMS), 3-(2-aminoethylamino)propyl trimethoxysilane (DAMS), 3-[2-(2-aminoethylamino)ethylamino] propyl trimethoxysilane (TAMS), 4-amino-3,3-dibutyl trimethoxy silane (ADBMS) and trimethoxy [3-(phenylamino)propyl] silane (PAPMS) were carried out in ethanol/water 80/20 (w/w) solutions in acidic media and followed in situ by ¹H-, ¹³C- and ²⁹Si-NMR spectroscopy. Acidic conditions were selected in order to enhance the formation of silanol and to slow down the self condensation reactions of the hydrolyzed functions. ²⁹Si NMR spectroscopy revealed the formation of intermediate species, particularly the solvolysis of γ-amino silanes by reaction exchange with the alcoholic solvent.     

On the scent of Spherical Dendrimers: Cyclophosphazenic Dandelion Dendrimers Up to the Eighth Generation

Abstract

Preparation of spherical dendrimers up to the eighth generation from D_3h cyclophosphazenic hexadangling cores (coded as sexapus) involves two repetitive steps: aminolysis of hexachlorocyclotriphosphazene, N₃P₃Cl₆ 0, by long-chain aliphatic diamines (such as 1,6-Diaminohexane and higher cousins) leading to sexapus cores with dangling diamino groups followed by a grafting of N₃P₃Cl₅ flagstones as 5-fold growing multipliers on these amino endings. Dendrimers of the first (compounds 1a, b) to the eighth (compounds 8a, b) are described. Dendrimer of the eighth generation, 8b, possesses 2,343,750 terminal (P-Cl) functions (molecular weight 228,977,179).     

Re-investigation of the La–Mg phase diagram

Literature results on the La–Mg binary system are critically reviewed. It is shown that most recent experimental results are not in agreement with the previously published assessments of the system. Thus, an experimental re-investigation of this phase diagram is required. Several alloys are synthesized from pure constitutive elements and characterized using X-ray diffraction, scanning electron microscopy, and differential thermal analysis. This study clarifies the phase equilibria in the La–Mg system. These results combined with the recent study of the enthalpies of formation of the intermediate compounds of this system provide a sound basis for the Calphad optimization of the system.     

Characterization of Commercial Polyvinylbutyrals

Several analyses have been carried out to thoroughly characterize five commercial polyvinyl butyral films supplied by various manufacturers. Model compounds (PVB and plasticizers) having the highest purity available were also used as reference. FT-IR and ¹H- and ¹³C-NMR spectroscopy were used to ascertain the structure of the investigated ter-polymer, as well that of the incorporated additives (mainly the plasticizer). The ratio between these components was also determined. The chemical compositions of these PVBs were similar, and two different plasticizers were identified. The glass transition temperature (T _g ) was deduced from dynamic mechanical analyses (DMA) and found to be very similar for all the investigated films. Size exclusion chromatography (SEC) was also used to study the molecular weight distribution. The analyses were performed using several detectors, and they revealed that PVBs presented similar distributions with molecular weights ranging from 250,000 to 300,000 g/mol.     

Coordination-driven self-assembly of polyoxometalates into discrete supramolecular triangles

Pd(II)-directed self-assembly of a 3-pyridyl grafted Lindqvist hexavanadate led to the formation of a unique trimeric species, as confirmed by a variety of techniques, including pulsed-field gradient NMR spectroscopy and high-resolution ESI mass spectrometry.     

Al–Cu intermetallic coatings processed by sequential metalorganic chemical vapour deposition and post-deposition annealing

Sequential processing of aluminum and copper followed by reactive diffusion annealing is used as a paradigm for the metalorganic chemical vapour deposition (MOCVD) of coatings containing intermetallic alloys. Dimethylethylamine alane and copper N,N′-di-isopropylacetamidinate are used as aluminum and copper precursors, respectively. Deposition is performed on steel and silica substrates at 1.33 kPa and 493–513 K. Different overall compositions in the entire range of the Al–Cu phase diagram are obtained by varying the relative thickness of the two elemental layers while maintaining the overall thickness of the coating close to 1 μm. As-deposited films present a rough morphology attributed to the difficulty of copper to nucleate on aluminum. Post-deposition annealing is monitored by in situ X-ray diffraction, and allows smoothening the microstructure and identifying conditions leading to several Al–Cu phases. Our results establish a proof of principle following which MOCVD of metallic alloys is feasible, and are expected to extend the materials pool for numerous applications, with innovative thin film processing on, and surface properties of complex in shape parts.