Phosphites as ligands in ruthenium-benzylidene catalysts for olefin metathesis

The use of phosphites in second generation, ruthenium-based olefin metathesis pre-catalysts leads to an improvement in catalyst stability and activity at low catalyst loadings.     

First substoichiometric version of the catalytic enantioselective addition of an alkyllithium to an aldehyde

A substoichiometric enantioselective version of the extremely fast nucleophilic addition of Alk-Li to RCHO is made possible thanks to a thorough analysis of the aggregation phenomena involved in the reaction: calculated quantities of LiCl must be added to the medium at the right time to keep the catalytic cycle running.     

Use of alkyl 2,4,6-triisopropylbenzoates in the asymmetric homologation of challenging boronic esters

(-)-Sparteine induced lithiation of primary 2,4,6-triisopropylbenzoates and subsequent homologation of boronic esters is reported. A comparative study with lithiated N,N-diisopropylcarbamates has demonstrated the superiority of the hindered benzoate.     

Light-emitting electrochemical cells based on a supramolecularly-caged phenanthroline-based iridium complex

The complex [Ir(ppy)(2)(pphen)][PF(6)] (Hppy = 2-phenylpyridine, pphen = 2-phenyl-1,10-phenanthroline) has been prepared and evaluated as an electroluminescent component for light-emitting electrochemical cells (LECs). Like in analogous LECs using bpy-based iridium(III) complexes a significant enhancement of the device stability is observed.     

Decarboxylation of aromatic carboxylic acids by gold(I)-N-heterocyclic carbene (NHC) complexes

A recently isolated gold(I) complex, [Au(IPr)(OH)], permits the transformation of carboxylic acids to the corresponding decarboxylated gold(I)-aryl complex without the use of silver co-catalyst under mild reaction conditions.     

Top-Down Analysis of Small Plasma Proteins Using an LTQ-Orbitrap. Potential for Mass Spectrometry-Based Clinical Assays for Transthyretin and Hemoglobin

Transthyretin (TTR) amyloidosis and hemoglobinopathies are the archetypes of molecular diseases where point mutation characterization is diagnostically critical. We have developed a Top-down analytical platform for variant and/or modified protein sequencing and are examining the feasibility of using this platform for the analysis of hemoglobin/TTR patient samples and evaluating the potential clinical applications. The platform is based on a commercial high resolution hybrid orbitrap mass spectrometer (LTQ-Orbitrap(?)) with automated sample introduction; automated data analysis is performed by our own software algorithm (BUPID topdown).The analytical strategy consists of iterative data capture, first recording a mass profile of the protein(s). The presence of a variant is revealed by a mass shift consistent with the amino acid substitution. Nozzle-skimmer dissociation (NSD) of the protein(s) yields a wide variety of sequence-defining fragment ions. The fragment ion containing the amino acid substitution or modification can be identified by searching for a peak exhibiting the mass shift observed in the protein mass profile. This fragment ion can then be selected for MS/MS analysis in the ion trap to yield sequence information permitting the identification of the variant. Substantial sequence coverage has been obtained in this manner. This strategy allows for a stepwise MS/MS analysis of the protein structure. The sequence information obtained can be supplemented with whole protein NSD fragmentation and MS/MS analysis of specific protein charge states. The analyses of variant forms of TTR and hemoglobin are presented to illustrate the potential of the method.     

Microwave assisted acid cleavage for denaturation and proteolysis of intact human adenovirus

Microwave assisted acid cleavage was applied directly to intact adenovirus type 5 to achieve denaturation and proteolysis in a single reaction. The speed of the digestion, coupled with the simplicity of MALDI analysis, allowed peptide products to be profiled in less than 5 min. Identification of peptides from a range of proteins by MALDI-TOF confirms that both denaturation and proteolysis were achieved using low concentrations of acetic acid (12.5%) and short incubations (1.5 to 2 min) at high temperatures (140° C). These conditions favor production of peptides that carry Asp on their C-termini. When this cleavage reaction is carried out in highly enriched H(2) (18)O, a single atom of (18)O is introduced site-specifically into the carboxyl terminal. The labeling reaction is applied to label reporter peptides from human adenovirus type 5 harvested from HeLa cells. Small peptide products of endogenous processing were also observed.     

Generation of a library of particles having controlled sizes and shapes via the mechanical elongation of master templates

Herein we describe a versatile and readily scalable approach for the fabrication of particles with a variety of shapes and sizes from a single master template by augmenting the particle replication in nonwetting templates (PRINT) method with mechanical elongation. Repetition of the elongation steps in one direction leads to the fabrication of linear particles with high aspect ratio (AR), over 40 times greater than in the original master, while a range of particle shapes can be obtained by repeating the elongation procedure while changing the stretching direction, generating diamond, rectangular, curved parallelogram particles from a single cubic master.     

Immobilization of Magnetic Nanoparticles onto Conductive Surfaces Modified by Diazonium Chemistry

Core-shell γ-Fe(2)O(3)@SiO(2) nanoparticles (NPs) substituted by PEG and NH(2) groups may be immobilized on metal surfaces (glassy carbon or gold) substituted by 4-carboxyphenyl groups through electrostatic interactions. Such immobilization is evidenced by (i) IRRAS owing to the Si-O band, (ii) SEM images, which show that the surface coverage by the NPs is nearly 100%, and (iii) the NPs film thickness measured by ellipsometry or AFM, which corresponds to about one NPs monolayer. Such NPs film is permeable to redox probes, which allows us to propose electrochemical methods based on direct or local measurements as a way to inspect the NPs assembly steps through their ability to alter mass and charge transfer. This process also applies to patterned polystyrene surfaces, and selective immobilization of NPs substituted by amino groups was carried out onto submillimeter patterns obtained by local oxidation. Biological applications are then expected for hyperthermia activation of the NPs to trigger cellular death. Finally, some tests were performed to further derivatize the immobilized NPs onto surfaces through either a covalent bond or electrostatic interactions. Future work will be dedicated to the recovery of such Janus NPs from the substrate surface.     

“One‐step” Preparation of Thiol‐Ene Clickable PEG‐Based Thermoresponsive Hyperbranched Copolymer for In Situ Crosslinking Hybrid Hydrogel

A well‐defined poly(ethylene glycol) based hyperbranched thermoresponsive copolymer with high content of acrylate vinyl groups was synthesized via a “one‐pot and one‐step” deactivation enhanced atom transfer radical polymerization approach, which provided an injectable and in situ crosslinkable system via Michael‐type thiol‐ene reaction with a thiol‐modified hyaluronan biopolymer. The hyperbranched structure, molecular weight, and percentage of vinyl content of the copolymer were characterized by gel permeation chromatography and ¹H NMR. The lower critical solution temperature of this copolymer is close to body temperature, which can result in a rapid thermal gelation at 37 °C. The scanning electron microscopy analysis of crosslinked hydrogel showed the network formation with porous structure, and 3D cell culture study demonstrated the good cell viability after the cells were embedded inside the hydrogel. This injectable and in situ crosslinking hybrid hydrogel system offers great promise as a new class of hybrid biomaterials for tissue engineering.