Two-Photon Absorption and Cell Imaging of Fluorene-Functionalized Epicocconone Analogues

Epicocconone 1 is a natural chromophore isolated from the fungus Epicoccum nigrum that has shown applications in proteomics and fluorescent microscopy thanks to its unique pro-fluorescence properties. The modification of the skeleton of the natural product by replacing the triene side chain by a fluorenyl scaffold can noticeably increase the fluorophore's absorption coefficient. The synthesis of the analogues of the natural product has been made possible by the use of a palladium-catalyzed carbonylation reaction, allowing the construction of the β-keto-dioxinone key intermediate. Two-photon absorption cross-section measurements of the fluorenyl epicocconone analogues show a structure dependency with values ranging from 60 to 280 GM and live cell imaging show intense staining of intracellular vesicle-like structures around the nucleus.     

Decomposition of molybdate–hexamethylenetetramine complex: One single source route for different catalytic materials

Decomposition of ammonium heptamolybdate–hexamethylentetramine (HMTA) complex (HMTA)₂(NH₄)₄Mo₇O₂₄·2H₂O was studied as a function of treatment conditions in the range 300–1173 K. The evolution of solid products during decomposition was studied by thermal analysis and in situ EXAFS. Depending on the nature of the gas used for treatment, single phases of highly dispersed nitrides Mo₂N, carbide Mo₂C, or oxide MoO₂ can be obtained. The nature of the products obtained was explained by qualitative thermodynamical considerations. Morphology of the solids considerably depends on such preparation parameters as temperature and mass velocity of the gas flow. For the nitride-based materials, catalytic activity was evaluated in the model thiophene HDS reaction. It was demonstrated that NH₃-treated samples showed better catalytic activity than N₂-treated ones due to cleaner surface and better morphology. Transmission microscopy, XRD and XPS studies showed that MoS₂ is formed on the surface during HDS reaction or sulfidation with H₂S. Optimized nitride-derived catalysts showed mass activity several times higher than unsupported MoS₂ or MoS₂/Al₂O₃ reference catalyst.     

Hypervalent iodine-mediated aziridination of alkenes: mechanistic insights and requirements for catalysis

By detailed study of the possible side reactions in the previously reported aziridination of alkenes with N-aminoheterocycles mediated by hypervalent iodine reagents, the requirements to make this reaction catalytic in iodoarene have been determined. The reaction requires an oxidant that will oxidise iodoarenes but that does not oxidise alkenes, but it is possible that no such oxidant actually exists! A method in which the hypervalent iodine reagent can be recycled without the need for reisolation is possible. Further study into the mechanism of this reaction gives tentative evidence that the reaction proceeds through formation of an aminoiodane that reacts directly with the alkene, contrary to previous literature reports in which an acetoxyamine intermediate is suggested. The temperature effect of this reaction is remarkable.     

Wavefront sensing issues in MCAO

The problematic of wavefront sensing in Multiconjugate Adaptive Optics (MCAO) is addressed in this article. We first focus on the sky coverage estimation which drives, in particular, the choice between natural and laser guide stars and therefore has a major impact on wavefront sensor design. Then a comparison between star oriented and layer oriented concepts is proposed. Analytical developments and optimization of the concepts are derived in the simplest MCAO case: the ground layer AO system. From this study, advantages and drawbacks of each concept are highlighted. To cite this article: T. Fusco et al., C. R. Physique 6 (2005).     

Combined dealkoxycarbonylation and lactonisation of unsaturated malonates in ionic liquids

Heating unsaturated malonates with LiCl and water in [bmim][Br] or [bmim][BF₄]/[bmim][Br] produces unsaturated esters or lactones, respectively.     

Microfluidic flow focusing: drop size and scaling in pressure versus flow-rate-driven pumping

We experimentally study the production of micrometer-sized droplets using microfluidic technology and a flow-focusing geometry. Two distinct methods of flow control are compared: (i) control of the flow rates of the two phases and (ii) control of the inlet pressures of the two phases. In each type of experiment, the drop size l, velocity U and production frequency f are measured and compared as either functions of the flow-rate ratio or the inlet pressure ratio. The minimum drop size in each experiment is on the order of the flow focusing contraction width a. The variation in drop size as the flow control parameters are varied is significantly different between the flow-rate and inlet pressure controlled experiments.     

Molecular modeling studies focused on 5-HT7 versus 5-HT1A selectivity. Discovery of novel phenylpyrrole derivatives with high affinity for 5-HT7 receptors

The present study discusses the well-known 5-HT7/5-HT1A selectivity issue through a new series of phenylpyrrole derivatives. The first hits emerged from a virtual screening performed on a chemolibrary. Further study led to an optimization of a preliminary 5-HT7 pharmacophore model. The importance of each pharmacophoric feature is confirmed, but these characteristics have to be coupled to geometric constraints in order to achieve a 5-HT7 selectivity. Indeed, 5-HT1A affinity probably arises from extended conformations, whereas a bent one appears to be best suited for 5-HT7 selectivity.     

Photochromism of photoenolizable ketones in quinoline and 1,8-naphthyridine series studied by time-resolved absorption spectroscopy

For the two photochromic molecules, 3-benzoyl-2-benzyl-1-methyl-1H-quinolin-4-one (QC1) and 3-benzoyl-1,2-dibenzyl-1H-1,8-naphthyridin-4-one (QC18a) as well as the nonphotochromic 3-benzoyl-1-benzyl-2-methyl-1H-1,8-naphthyridin-4-one (QC18b), the full photochemical mechanism, which is based on the photoenolization process, has been elucidated using stationary and time-resolved spectroscopy techniques. After photoexcitation, the S1(n,pi*)-T1(n,pi*) ISC process involving the exocyclic carbonyl chromophore is demonstrated to occur. Subsequently, gamma-hydrogen transfer proceeds very rapidly to give rise to the triplet photoenol with a probable 1,4-biradical structure. For all three molecules, the biradical is clearly detected and proved quantitatively to be the direct precursor of the colored form (photochromic compounds) or ground state starting material (nonphotochromic compound). Solvent effects for the three molecules studied may suggest the existence of intramolecular hydrogen bonding in both biradical and colored form species. Structural effects on the gamma-hydrogen transfer rate and biradical decay are related to the photochromic performances.     

Usefulness of autoantigens depletion to detect autoantibody signatures by multiple affinity protein profiling

Patients with cancer produce specific autoantibodies against protein antigens present in limited amount among a large background of immunoglobulins (Igs), nonrelevant as biomarkers, including natural antibodies. Multiple affinity protein profiling (MAPPing) that combines 2-D immunoaffinity chromatography, enzymatic digestion of the isolated proteins, and identification by MS/MS, may facilitate the identification of these so far unknown patient antibodies. The first immunoaffinity chromatography is crucial, as it is used for selectively removing proteins (autoantigens) recognized by natural antibodies. Application of this depletion step to colon cancer cell proteins is specifically described along with the identification of the natural autoantigens, as well as the coupling of this depletion step with the next steps. By enabling to separate antibody-binding proteins recognized by either natural autoantibodies or patient-specific antibodies this approach may contribute significantly towards the definition of autoantibody signatures.     

Addition of lithium ethyl fluoroacetate to cis and trans α,β-epoxyaldehydes. Access to C2 fluorinated butyrolactones

The aldolisation reaction of lithium ethyl fluoroacetate with cis and trans α,β-epoxyaldehydes in their racemic forms proceeds with good C₃-OH diastereoselectivity and much less at the C₂-F carbon atom. A two-step reaction on the major aldol compounds (iodination, lactonisation) led to racemic functionalised C₂ fluorinated lactones, possessing a C₂/C₃cis relationship between the fluorine and hydroxyl groups.