Interaction Mechanisms Between Ar–O<Subscript>2</Subscript> Post-Discharge and Stearic Acid II: Behaviour of Thick Films

We study the interaction of thick films (~4 mm) of stearic acid (SA), a C₁₈ alkane skeleton with an acid function, with late Ar–O₂ post-discharge. Contrary to what is observed with thin films of SA (~2–3 μm) which are efficiently etched (part I), only functionalization is observed over the first 2 h of treatment with a plasma source operated in the continuous mode, whatever the temperature. The heat released by surface reactions affects non-linearly the temperature of the substrate. Pulsing the source at a frequency ranging from 0.1 to 1 kHz slows down the functionalization process but does not allow any etching of the material. On the contrary, the SA can be etched as thick films by pulsing the oxygen flow rate at a frequency below 50 mHz. By pulsing the reactive gas, the time averaged value of the [O]/[O₂] ratio is decreased, limiting the functionalization processes due to oxygen atoms, and the mean temperature is lowered, decreasing the diffusion length of O₂ (and/or possibly O₂*) species in the SA which are responsible for the scission of C–C bonds of radicals.     

Anion exchange in trimethyl‐ and triphenyltin complexes with chromogenic ligands: solution equilibria and colorimetric anion sensing

A series of organotin(IV) compounds R₃Sn(A) where R = Me or Ph and A is a chromogenic nitrophenolate ligand were prepared and studied as possible colorimetric sensors for anions (F⁻, Cl⁻, Br⁻, AcO⁻, H₂PO₄⁻). Equilibrium constants for a complete set of reactions between R₃Sn(A) with A = 2‐amino‐4‐nitrophenolate (ANP) or 4‐nitrophenolate and anions (X⁻) involving formation of complexes R₃Sn(A)(X)⁻ and substitution products R₃Sn(X) and R₃Sn(X)₂⁻ were determined by UV‐vis and ¹H NMR titrations in MeCN and DMSO. The binding selectivity was AcO⁻ > F⁻ > H₂PO₄⁻ > Cl⁻ ≫ Br⁻ in both solvents and both for R = Me and Ph with higher affinity for R = Ph. Compounds with A = ANP were found to have the optimum properties as anion sensors allowing optical detection of F⁻, AcO⁻ and H₂PO₄⁻ anions in the 5–100 µM range by appearance of an intense absorption band of free ANP resulting from its substitution with the analyte. Selectivity and affinity of anion interactions with R₃Sn(ANP) are similar to those for thiourea receptors, but the organotin receptor produces a much larger naked eye detected optical signal, operates equally well in nonpolar and polar solvents and tolerates the presence of up to 20% vol. of water in DMSO. Copyright © 2011 John Wiley & Sons, Ltd.     

Inelastic X-ray scattering and vibrational effects at the K-edges of gaseous N2, N2O, and CO2

We report non-resonant inelastic X-ray scattering experiments of several gaseous samples in the inner-shell excitation energy range. The experimental near-edge spectra from all the K-edges of N(2), N(2)O, and CO(2) including the momentum transfer dependence are presented. The results are analyzed using density functional theory calculations that accurately reproduce the experimental spectral features. We observe vibrational effects in the measured spectrum and in the calculations the atomic motion is modeled using the Franck-Condon approximation and the linear coupling model. Our findings show that vibrational effects cannot be neglected in the analysis of high resolution inelastic X-ray scattering spectroscopy. The results also support the validity of the transition potential approximation for calculating core excited state potential energy surfaces.     

Non-invasive vibrational SFG spectroscopy reveals that bacterial adhesion can alter the conformation of grafted "brush" chains on SAM

Understanding bacterial adhesion on a surface is a crucial step to design new materials with improved properties or to control biofilm formation and eradication. Sum Frequency Generation (SFG) vibrational spectroscopy has been employed to study in situ the conformational response of a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film to the adhesion of hydrophilic and hydrophobic ovococcoid model bacteria. The present work highlights vibrational SFG spectroscopy as a powerful and unique non-invasive biophysical technique to probe and control bacteria interaction with ordered surfaces. Indeed, the SFG vibrational spectral changes reveal different ODT SAM conformations in air and upon exposure to aqueous solution or bacterial adhesion. Furthermore, this effect depends on the bacterial cell surface properties. The SFG spectral modeling demonstrates that hydrophobic bacteria flatten the ODT SAM alkyl chain terminal part, whereas the hydrophilic ones raise this ODT SAM terminal part. Microorganism-induced alteration of grafted chains can thus affect the desired interfacial functionality, a result that should be considered for the design of new reactive materials.     

AGR2, a mucinous ovarian cancer marker, promotes cell proliferation and migration

Ovarian cancer is a leading cause of death in women. Early detection of ovarian cancer is essential to decrease mortality. However, the early diagnosis of ovarian cancer is difficult due to a lack of clinical symptoms and suitable molecular diagnostic markers. Thus, identification of meaningful tumor biomarkers with potential clinical application is clearly needed. To search for a biomarker for the early detection of ovarian cancer, we identified human anterior gradient 2 (AGR2) from our systematic analysis of paired normal and ovarian tumor tissue cDNA microarray. We noted a marked overexpression of AGR2 mRNA and protein in early stage mucinous ovarian tumors compared to normal ovarian tissues and serous type ovarian tumors by Western blot analysis and immunohistochemistry. To further elucidate the role of AGR2 in ovarian tumorigenesis, stable 2774 human ovarian cancer cell lines overexpressing AGR2 were established. Forced expression of AGR2 in 2774 cells enhanced the growth and migration of ovarian cancer cells. AGR2 protein was detected in the serum of mucinous ovarian cancer patients by Western blot and ELISA analysis. Thus, AGR2 is a potential biomarker for the diagnosis of mucinous ovarian cancer and an ELISA assay may facilitate the early detection of mucinous ovarian cancer using patient serum.     

Origins of the diastereoselectivity in hydrogen bonding directed Diels-Alder reactions of chiral dienes with achiral dienophiles: a computational study

In this study, the origins of diastereoselectivity in the hydrogen bonding assisted Diels-Alder reactions of chiral dienes with achiral dienophiles have been investigated with density functional methods. The distortion/interaction model has been applied to shed light on the origins of selectivity. C9-Substituted chiral anthracene templates (R = (CH(3))(OCH(3))(H), R = (CH(3))(OH)(H), R = (CH(3))(CH(2)CH(3))(H) and R = (-CH(2)-C(CH(3))(OCH(3))(H)) are used to rationalize the role of a stereogenic center and H-bonding on the product distribution ratio. Even though hydrogen bonding increases the reactivity of the diene, the stereoselectivity is reduced because of the hydrogen bonding capacity of both diastereomeric transition states. The interaction energies of the studied anthracene templates with N-methyl maleimide at the transition state correlate linearly with an increase in reactivity. The selectivity is determined by both favorable distortion and interaction energies. The π-facial selectivity induced by the presence of a chiral auxiliary in 1-substituted 1,3-pentadienes (R1 = (CH(3))(OCH(3))(H) and R1 = (CH(3))(OH)(H)) has also been modeled in order to rationalize the role of the stereogenic center and H-bonding on the stereoselectivity of an aliphatic diene. In both parts, the product distribution ratios calculated from Boltzmann distributions based on Gibbs free energies are in reasonable agreement with the experimental results. Finally the role of OH-substituted five-membered pyrrolidine on C9 of anthracene is investigated since the successful usage of the conformationally rigid pyrrolidines in asymmetric synthesis is well known. Overall, both in the acyclic system and in anthracene, the facilitation due to H-bonding is reflected in the interaction energies: the higher the difference in interaction energies in the transition structures of the two diastereomers, the more selective the H-bonding assisted Diels-Alder reaction is.     

Total synthesis of cirsimarin and evidence of its lipolytic and antilipogenic activities on human adipocytes

A straightforward procedure leading to the flavone cirsimaritin and its 4′-O-β-d-glycosylation to afford cirsimarin, its corresponding flavone glucopyranoside, is described. The biological properties of cirsimarin, measured on human adipocytes, showed potent effects on both lipolysis and lipogenesis. Cirsimarin could therefore be considered as an efficient tool in the struggle against excessive adipose tissue deposition and as a potential candidate in the treatment of obesity.     

Multicompartment micelles from silicone-based triphilic block copolymers

An amphiphilic linear ternary block copolymer was synthesised in three consecutive steps via reversible addition–fragmentation chain transfer polymerisation. Oligo(ethylene glycol) monomethyl ether acrylate was engaged as a hydrophilic building block, while benzyl acrylate and 3-tris(trimethylsiloxy)silyl propyl acrylate served as hydrophobic building blocks. The resulting “triphilic” copolymer consists thus of a hydrophilic (A) and two mutually incompatible “soft” hydrophobic blocks, namely, a lipophilic (B) and a silicone-based (C) block, with all blocks having glass transition temperatures well below 0 °C. The triphilic copolymer self-assembles into spherical multicompartment micellar aggregates in aqueous solution, where the two hydrophobic blocks undergo local phase separation into various ultrastructures as evidenced by cryogenic transmission electron microscopy. Thus, a silicone-based polymer block can replace the hitherto typically employed fluorocarbon-based hydrophobic blocks in triphilic block copolymers for inducing multicompartmentalisation.