Physicochemical and interfacial investigation of lipid/polymer particle assemblies

A model study was investigated to develop colloidal supramolecular assemblies consisting of particles coated with lipid layers. The interactions between monodisperse sulfate-charged poly(styrene) submicrometer particles and zwitterionic/cationic lipid vesicles composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-3-trimethylammonium propane were considered. The influence of relevant experimental parameters on the final associations was examined by quasi-elastic light scattering to point out some new phenomena occurring in these colloidal systems. The major role of electrostatic interactions as driving forces to control the organization between cationic lipids and oppositely charged poly(styrene) particles was clearly evident, whereas this influence was less pronounced when considering the zwitterionic lipids. The characterization of these original complex assemblies was completed by a thorough study of the surface modification. The combination of zeta potential measurements, X-ray photoelectron spectroscopy analyses, and microscopy observations proved that the envisioned model can really correspond to polymer particles surrounded by lipids.     

Synthesis of trifluoromethyl cyclohexyl, cyclohexenyl and aryl compounds via stepwise Robinson annulation

The diketone 2-fluoro-2-(trifluoromethyl)-1-phenylhexane-1,5-dione 3 was synthesized by a Mukaiyama Michael type reaction from the corresponding tetrafluoroenol silyl ether prepared from pentafluoropropiophenone. This diketone was treated under basic conditions and was converted, depending on the stoichiometry of the base, into the surprisingly stable ketol 4-fluoro-4-(trifluoromethyl)-3-hydroxy-3-phenylcyclohexanone 4 as a single diastereomer (catalytic KOH) or to the biphenylol 6-(trifluoromethyl)biphenyl-3-ol (excess KOH, THF) 5. Solvolysis of the trifluoromethyl group (anionic activation) occurred using excess KOH in alcohol. The corresponding cyclohexenone derivative 7, the usual product of Robinson annulation, might be prepared in good yield via mesylation of the ketol. Thus various unprecedented fluorinated cyclohexane and aromatic derivatives were achieved in a few steps from the commercially available pentafluoropropiophenone.     

Determination of seven arsenic species in seafood by ion exchange chromatography coupled to inductively coupled plasma-mass spectrometry following microwave assisted extraction: method validation and occurrence data

The determination of seven arsenic species in seafood was performed using ion exchange chromatography on an IonPac AS7 column with inductively coupled plasma mass spectrometry detection after microwave assisted extraction. The effect of five parameters on arsenic extraction recoveries was evaluated in certified reference materials. The recoveries of total arsenic and of arsenic species with the two best extraction media (100% H₂O and 80% aqueous MeOH) were generally similar in the five seafood certified reference materials considered. However, because MeOH co-elutes with arsenite, which would result in a positively biased arsenite concentration, the 100% H₂O extraction conditions were selected for validation of the method. Figures of merit (linearity, LOQs (0.019-0.075 mg As kg⁻¹), specificity, trueness (with recoveries between 82% (As(III)) and 104% (As(V) based on spikes or certified concentrations), repeatability (3-14%), and intermediate precision reproducibility (9-16%) of the proposed method were satisfactory for the determination of arsenite, monomethylarsonic acid, dimethylarsinic acid, arsenate, arsenobetaine and arsenocholine in fish and shellfish. The performance criteria for trimethylarsine oxide, however, were less satisfactory. The method was then applied to 65 different seafood samples. Arsenobetaine was the main species in all samples. The percentage of inorganic arsenic varied between 0.4-15.8% in shellfish and 0.5-1.9% at the utmost in fish. The main advantage of this method that uses only H₂O as an extractant and nitric acid as gradient eluent is its great compatibility with the long-term stability of both IEC separation and ICP-MS detection.     

Visible‐Light‐Mediated Metal‐Free Synthesis of Trifluoromethylselenolated Arenes

The first visible‐light‐mediated synthesis of trifluoromethylselenolated arenes under metal‐free conditions is reported. The use of an organic photocatalyst enables the trifluoromethylselenolation of arene diazonium salts using the shelf‐stable reagent trifluoromethyl tolueneselenosulfonate at room temperature. The reaction does not require the presence of any additives and shows high functional‐group tolerance, covering a very broad range of starting materials. Mechanistic investigations, including EPR spectroscopy, luminescence investigations, and cyclic voltammetry allow rationalization of the reaction mechanism.     

Regioselective remote CH fluoroalkylselenolation of 8-aminoquinolines

Herein, the direct C-5 fluoroalkylselenolation of 8-aminoquinolines is described. The Pd-catalyzed reaction is performed with the in situ generated fluoroalkylselenyl chloride and various 8-aminoquinoline amides or sulfonamides. The desired products were formed in moderate to excellent yields.     

Physical corrosion of semi‐crystalline polymers

Polymer‐solvent compounds can be formed from homogeneous solutions obtained at high temperature but also by solvent diffusion at the solid interface of a bulk polymer at room temperature. This phenomenon we call “physical” corrosion as it modifies the surface structure without chemical change. Here we report preliminary experiments indicating that the thermodynamics seems to be little dependent upon the path used while the morphology is.     

1,4-Additions of electron-rich heterocycles onto β-perfluoroalkyl enones

β-(Trifluoromethyl) enones, easily obtained in few steps from commercially available methyl hemiketal of trifluoroacetaldehyde, react with electron-rich O- and N-containing heterocycles (furans and benzofurans, pyrroles and indoles, hydroxycoumarins), through a 1,4 addition, to give heterocycles bearing a functionalized side-chain. β-(chlorodifluoromethyl)enones and β-(pentafluoroethyl)enones behave in the same way.     

Molecular docking and 3D-quantitative structure activity relationship analyses of peptidyl vinyl sulfones: <Emphasis Type="Italic">Plasmodium Falciparum</Emphasis> cysteine proteases inhibitors

Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) based on three-dimensional quantitative structure–activity relationship (3D-QSAR) studies were conducted on a series (39 molecules) of peptidyl vinyl sulfone derivatives as potential Plasmodium Falciparum cysteine proteases inhibitors. Two different methods of alignment were employed: (i) a receptor-docked alignment derived from the structure-based docking algorithm GOLD and (ii) a ligand-based alignment using the structure of one of the ligands derived from a crystal structure from the PDB databank. The best predictions were obtained for the receptor-docked alignment with a CoMFA standard model (q ² = 0.696 and r ² = 0.980) and with CoMSIA combined electrostatic, and hydrophobic fields (q ² = 0.711 and r ² = 0.992). Both models were validated by a test set of nine compounds and gave satisfactory predictive r ² _pred values of 0.76 and 0.74, respectively. CoMFA and CoMSIA contour maps were used to identify critical regions where any change in the steric, electrostatic, and hydrophobic fields may affect the inhibitory activity, and to highlight the key structural features required for biological activity. Moreover, the results obtained from 3D-QSAR analyses were superimposed on the Plasmodium Falciparum cysteine proteases active site and the main interactions were studied. The present work provides extremely useful guidelines for future structural modifications of this class of compounds towards the development of superior antimalarials.