Fiber crystal growth from the melt for non-linear optical applications

During several years, we have been involved in the growth and characterization of non-linear optical crystals by the two most common techniques for growing single-crystal fibers from the melt: laser-heated pedestal growth and micro-pulling down. Their specific features are presented in this study and their versatility is demonstrated through two typical examples of incongruently melting materials: K₃Li_2?xNb_5+xO_15+2x (solid solution of the ternary system K₂O–Li₂O–Nb₂O₅) and Ca₅(BO₃)₃F which can only be grown from a flux.     

Characterization of the structure of human skin substitutes by infrared microspectroscopy

The skin acts mainly as a protective barrier from the external environment, thanks to the stratum corneum which is the outermost layer of the skin. As in vitro tests on skin are essential to elaborate new drugs, the development of skin models closer to reality becomes essential. It is now possible to produce in vitro human skin substitutes through tissue engineering by using the self-assembly method developed by the Laboratoire d’Organogénèse Expérimentale. In the present work, infrared microspectroscopy imaging analyses were performed to get in-depth morpho-spectral characterization of the three characteristic layers of human skin substitutes and normal human skin, namely the stratum corneum, living epidermis, and dermis. An infrared spectral analysis of the skin is a powerful tool to gain information on the order and conformation of the lipid chains and the secondary structure of proteins. On one hand, the symmetric stretching mode of the lipid methylene groups (2,850 cm^?1) is sensitive to the acyl chain conformational order. The evolution profile of the frequency of this vibrational mode throughout the epidermis suggests that lipids in the stratum corneum are more ordered than those in the living epidermis. On the other hand, the frequencies of the infrared components underneath the envelop of the amide I band provide information about the overall protein conformation. The analysis of this mode establishes that the proteins essentially adopt an α-helix conformation in the epidermis, probably associated with the presence of keratin, while modifications of the protein content are observed in the dermis (extracellular matrix made of collagen). Finally, the lipid organization, as well as the protein composition in the different layers, is similar for human skin substitutes and normal human skin, confirming that the substitutes reproduce essential features of real skin and are appropriate biomimetics.     

Non-phospholipid liposomes with high sterol content display a very limited permeability

We demonstrate that it is possible to form non-phospholipid fluid bilayers in aqueous milieu with a mixture of palmitic acid (PA),cholesterol (Chol),and cholesterol sulfate (Schol) in a molar proportion of 30/28/42.These self-assemblies are shown to be bilayers in the liquid ordered phase.They are stable between pH 5 and 9.Over this pH range,the protonation/deprotonation of PA carboxylic group is observed but this change does not appear to alter the stability of these bilayers,a behavior contrasting with that observed for binary mixtures of PA/Chol,and PA/Schol.The multilamellar dispersions formed spontaneously from the PA/Chol/Schol mixture could be successfully extruded to form Large Unilamellar Vesicles (LUVs).These LUVs show interesting permeability properties,linked with their high sterol content.These non-phospholipid liposomes can sustain a pH gradient (pH internal 8/pH external 6) 100 times longer than LUVs made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cholesterol,with a molar ratio of 60/40.Moreover,the non-phospholipid LUVs are shown to protect ascorbic acid from an oxidizing environment (1 mM iron(III)).Once entrapped in liposomes,ascorbic acid displays a degradation rate similar to that obtained in the absence of iron(III).These results show the possibility to form novel nanocontainers from a mixture of a monoalkylated amphiphile and sterols,with a good pH stability and showing interesting permeability properties.     

Voltammetry coupled to mass spectrometry in the presence of isotope O labeled water for the prediction of oxidative transformation pathways of activated aromatic ethers: Acebutolol

The coupling between an electrochemical cell (EC) and a mass spectrometer (MS) is a useful screening tool (EC-MS) to study the oxidative transformation pathways of various electroactive species. For that purpose, we showed that the EC-MS method, carried out in the presence and absence of isotope ¹⁸O labeled water leads not only to a fast identification of oxidation products but also leads to a fast elucidation of the mechanism pathway reaction. We examined herein the case of the electrochemical hydrolysis of activated aromatic ether. Acebutolol (β-blockers) was selected herein as model of activated aromatic ether, and its electrochemical oxidation was examined in both the presence and absence of isotope ¹⁸O labeled water. To elucidate electrochemical hydrolysis pathway reaction: O-dealkylation or O-dealkoxylation, our approach was used to prove its applicability. The electrochemical oxidation mechanism was then elucidated showing an O-dealkoxylation reaction. In addition, density functional theory (DFT) calculations fully support the experimental conclusions.     

Synthesis of Anhydronectriachrysone,an Extensively Conjugated γ-Pyrone

The synthesis of anhydronectriachrysone (2) through the DIBAH reduction of toralactone (3), followed by dehydration of the corresponding lactol (4) is reported (38% yield).     

A Convenient Laboratory Preparation of N,N-Dimethyl-dichloro-methylene-iminium Chloride (Phosgene-iminium chloride)

A method of preparation of the title compound 1a avoiding the use of gaseous chlorine is described. Tetramethylthiuram disulfide 4 is oxidized with sulfuryl chloride to dime thyl thiocarbamoyl chloride 5, which is converted to 1a by means of phosphorus pentachloride.     

Preparation of the N-(2-Bromo-2-Nitroethenyl) Benzenamine: The First One-Pot Synthesis of a β-Halo-β-Nitroenamine

Bromonitromethane, triethyl orthoformate and aniline react together, in a one-flask procedure, to afford the title compound.