Photopolymerized lipids self-assembly for the solubilization of carbon nanotubes.

Because they have a great propensity to aggregation in water, solubilization of carbon nanotubes (CNTs) in aqueous media remains an important challenge. Our laboratory has reported the self-organization of synthetic lipids into hemi-micellar structures at the carbon nanotubes surface. Subsequent stabilization of these carbon nanotube/lipid assembly (CNT/LA) constructs is achieved through photopolymerization of the diyne motif of the pentacosa-10,12-diynoic lipids.

Isothermal microcalorimetry, a tool for probing SWNT bundles.

The bundling state of several dry single-walled carbon nanotube (SWNT) samples is compared using isothermal microcalorimetry (IMC). So as to get different dry samples with various bundling states, the pristine SWNTs were pretreated with a solution of an aromatic amphiphile with or without sonication, washed and dried before being studied by IMC. The bundling state of the different SWNT samples, which was first analyzed by TEM, was then correlated to the obtained IMC data thanks to the interpretation of the observed energy transfer phenomena.

Complexation of Cs+, K+ and Na+ by norbadione A triggered by the release of a strong hydrogen bond: nature and stability of the complexes.

Norbadione A (NBA) is a pigment present in edible mushrooms which is presumed to selectively complex Cs(+) cations. Due to a very uncommon complexation mechanism, we used a combination of several experimental techniques, including (1)H-NMR, (133)Cs-NMR, isothermal calorimetric, potentiometric titrations and molecular dynamics MD simulations to determine the nature of the complexed species, as well as their stability constants for the NBA-M(+) systems (M(+) = Cs(+), K(+), Na(+)) in methanol:water 80:20 solutions at 25.0 degrees C.

Expedient synthesis of mequitazine an antihistaminic drug by palladium catalyzed allylic alkylation of sodium phenothiazinate.

A short and straightforward synthesis of the antihistaminic drug mequitazine is reported, based on an efficient palladium catalyzed allylic alkylation of 1-aza-bicyclo[2.2.2]oct-2-en-3-ylmethyl acetate using sodium phenothiazinate in mild conditions.

Insight into the complexation mode of bis(nitrilotriacetic acid) (NTA) ligands with Ni(2+) involved in the labeling of histidine-tagged proteins.

According to literature reports and our own findings, the binding of new Ni(2+)-preloaded bis(nitrilotriacetic acid) (NTA) ligands with polyhistidine-tagged proteins has been found to be accompanied by a one- to two-order-of-magnitude increase in affinity, compared to the binding of a single Ni(2+)-preloaded NTA moiety. In spite of the introduction of a second NTA chelating group, a cooperative effect that is less than the theoretical maximum has been observed. Herein, we present a rational explanation for the observed stability of the ternary complex involving the postulated bis-NTA-(Ni(2+))(2) species and multivalent polyhistidine tags.

Axially chiral facial amphiphiles with a dihydronaphthopentaphene structure as molecular tweezers for SWNTs.

Syntheses of chiral 6,15-dihydronaphtho[2,3-c]pentaphene derivatives of opposite configurations are reported. Starting from anthracene, the strategy involves two key steps: a Diels-Alder reaction on a prochiral dianthraquinone, and an enantiomeric resolution using (-)-menthol. The final molecules exhibit very strong optical activity, as shown by their circular dichroism spectra, and are examples of chiral facial amphiphiles.

Highly stereoselective synthesis of (Z,E)-1-halo-1,3-dienol esters via rearrangement of Fischer chromium chloro-carbenes using microwave irradiation.

Functionalized (Z,E)-1-halo-1,3-dienol esters are synthesized in a highly stereoselective manner via CrCl2-mediated rearrangement of allylic trihalomethylcarbinol esters induced by microwave irradiation.

Tailoring carbon nanotube surfaces with glyconanorings: new bionanomaterials with specific lectin affinity.

Remarkably stable, water-soluble glyconanoring-coated SWCNTs were prepared by self organization and photopolymerization of neutral diacetylene-based glycolipids on the nanotube surface; the nanoconstructs are able to engage in specific ligand-lectin interactions in a similar way to glycoconjugates on cell membranes.

Novel chiral derivatizing isothiocyanate-based agent for the enantiomeric excess determination of amines.

The expedient synthesis of a novel chiral (1S,2S)-N-[(2-isothiocyanato)cyclohexyl] trifluoromethanesulfonamide and its use as a derivatizing auxiliary for the straightforward determination of optical purity of chiral amines are reported.

Semi-covalent surface molecular imprinting of polymers by one-stage mini-emulsion polymerization: glucopyranoside as a model analyte.

This paper describes a new type of surface imprinting technique that combines the advantages of both the semi-covalent approach and one-stage miniemulsion polymerization. This process has been successfully applied for the preparation of glucose surface-imprinted nanoparticles. The selective artificial receptors for glucopyranoside were fully characterized by IR, TEM and BET analyses, and their molecular recognition abilities by binding experiments carried out in batch processes.

Evaluation of antioxidant properties of monoaromatic derivatives of pulvinic acids.

The natural mushroom pigment Norbadione A and three other pulvinic acids were shown by our group to display very efficient antioxidant properties by comparison with a collection of potent molecules including catechols, flavonoids, stilbenes, or coumarins. Despite numerous publications on robust and straightforward synthetic access to pulvinic acids by us and others, no report has been made to unravel the structure-activity relationships that govern the striking antioxidant activity. Herein is presented the synthesis of 18 diverse pulvinic acid derivatives and the study of their radical scavenging capacities by four different assays.

Carbon nanotube-acridine nanohybrids: spectroscopic characterization of photoinduced electron transfer.

Single-walled carbon nanotubes (NT) were covalently functionalized with either 9-phenyl acridine (PhA) or 10-methyl-9-phenyl acridinium (PhMeA(+)). Absorption and fluorescence properties of acridine derivatives tethered to the nanotubes were studied in homogeneous dispersions. Exciplex emission was observed for NT functionalized with 9-phenylacridine.

3-Aryltetronic acids: efficient preparation and use as precursors for vulpinic acids.

3-Aryltetronic acids were prepared in one step by treatment of a mixture of methyl arylacetates and methyl hydroxyacetates with potassium tert-butoxide, via tandem transesterification/Dieckmann condensation. Several mushroom or lichen pigments, vulpinic acids, were synthesized from 3-(4-methoxyphenyl)tetronic acid in three steps involving the reaction of the corresponding dianion with an alpha-ketoester and the dehydration of the tertiary alcohols obtained into mixtures of (E)- and (Z)-alkenes, which were converted under UV irradiation at 254 nm to natural (E)-isomers. Syntheses of pinastric acid, 4,4'-dimethoxyvulpinic acid, and the first synthesis of recently isolated methyl 3',5'-dichloro-4,4'-di-O-methylatromentate were hence achieved in an efficient manner.

Carbon nanotubes as templates for polymerized lipid assemblies.

Amphiphilic molecules-molecules that have both hydrophobic and hydrophilic properties-can self-assemble in water to form diverse structures such as micelles, vesicles and tubes, and these nanostructures can be used for delivering drugs, stabilizing membrane proteins or as nanoreactors. We have previously shown that lipids can self-organize on the surface of single-walled carbon nanotubes into regular ring-shaped assemblies. Here we show that these lipid assemblies can be polymerized and isolated from the nanotube template by application of an electric field.

Synthesis of pulvinic derivatives via TBAF-mediated regioselective opening of an unsymmetrical monoaromatic pulvinic dilactone.

The synthesis of the monoaromatic pulvinic dilactone 1 from a tetronic acid derivative is reported. The reaction of 1 with various amines was found to provide the two pulvinamides regioisomers 2a and 2b. Using tetrabutylammonium fluoride (TBAF) as an activator, pulvinamides 2a could be obtained with excellent regioselectivities and good yields.

CrAsH-quantum dot nanohybrids for smart targeting of proteins.

Smart nanohybrids were prepared by conjugation of CrAsH to hydrosoluble and biocompatible quantum dots (QDs). The resulting probes were shown to bind efficiently and selectively to Cys-tagged proteins. The interaction with the protein was detected by an increase of the fluorescence emission of CrAsH.

Supramolecular discrimination of carbon nanotubes according to their helicity.

Adsorption of specifically designed and geometrically constrained polyaromatic amphiphiles on single-walled carbon nanotubes (SWNTs) was found to be selective of the nanotube helicity angle. Starting from the same SWNT mixture, photoluminescence and resonant Raman spectroscopies show that a pentacenic-based amphiphile leads to the solubilization of armchair SWNTs and that a quaterrylene-based amphiphile leads to the solubilization of zigzag SWNTs. The results were predicted by the design of the two amphiphiles and are consistent with a supramolecular recognition of the nanotube graphene-type atomic structure by the aromatic part of the molecules through optimized pi-pi-stacking interactions.

Supramolecular self-assembly of amphiphiles on carbon nanotubes: a versatile strategy for the construction of CNT/metal nanohybrids, application to electrocatalysis.

Homogeneous coating of carbon nanotubes with metallic nanoparticles was achieved using supramolecular auto-organization of amphiphilic molecules as template. The resulting Pd nanoparticles/carbon nanotube nanohybrids were then evaluated in electrocatalysis experiments, showing superior activity in ethanol oxidation compared to analogous systems.

Oligomeric PEG-phospholipids for solubilization and stabilization of fluorescent nanocrystals in water.

Water soluble fluorescent nanocrystals were obtained by encapsulation of hydrophobic quantum dots (QDs) with amphiphilic phospholipids derived from the ring opening metathesis of norbornene-based monomers. The robustness of the newly coated quantum dots was assessed by comparative studies under various ionic conditions which indicated an overall enhancement of their fluorescence stability.

Total synthesis of norbadione A.

A short, convergent synthesis of the mushroom pigment norbadione A is described. The construction of an appropriately substituted naphtholactone intermediate involved a regioselective Diels-Alder reaction between a bis(triisopropylsilyloxy)diene and 2,6-dichlorobenzo-1,4-quinone. A double Suzuki-Miyaura cross-coupling between a diboronate and two identical enol triflates was another key feature of the synthesis.

Microchemical imaging of iodine distribution in the brown alga Laminaria digitata suggests a new mechanism for its accumulation.

Brown algal kelp species are the most efficient iodine accumulators among all living systems, with an average content of 1.0% of dry weight in Laminaria digitata. The iodine distributions in stipe and blade sections from L.

C-2 Epimerization of aldonolactones promoted by magnesium iodide: a new way towards non-enzymatic epimerization.

The first example of a non-enzymatic C-2 epimerization of aldonolactones is reported. The reaction of 2,3,4,6-tetra-O-benzyl-d-gluconolactone or 2,3,4,6-tetra-O-benzyl-d-mannonolactone with MgI(2) in EtOH afforded their respective C-2 epimer. Studies conducted in EtOD showing the incorporation of a deuterium atom only at the C-2 position of the epimerized product reveal an epimerization rather than a racemization reaction.

Anti-hyperglycemic activity of a TGR5 agonist isolated from Olea europaea.

Olive tree (Olea europeaea) leaves are well known for their effect on metabolism in particular as a traditional anti-diabetic and anti-hypertensive herbal drug. These properties are until now only attributed to oleuropein, the major secoiridoid of olive leaves. Here we describe the isolation and the identification of another constituent implicated in the anti-diabetic effect of this plant, i.

A one-pot synthesis of (E)-disubstituted alkenes by a bimetallic [Rh-Pd]-catalyzed hydrosilylation/hiyama cross-coupling sequence.

A bimetallic [Rh-Pd] catalyst was prepared by soaking into an iodide ionic gel an equimolar solution of [RhCl(PPh(3))(3)] and Pd(OAc)(2) in CH(2)Cl(2). Its catalytic activity was evaluated by rhodium-catalyzed hydrosilylation (H), palladium-catalyzed Hiyama coupling (C), and in the one-pot hydrosilylation/Hiyama coupling sequence (H/C). It was found that the homogeneous combination [RhCl(PPh(3))(3)]/NaI was a superior system compared to the polyionic mono- and bimetallic rhodium catalysts in the hydrosilylation of terminal alkynes.