Adjusting the water-sensitivity of sugar/boronate-based organogels.

During the investigation of the water-sensitivity of (arylboronate alkylglucoside)-based organogels, we evaluated a series of twelve potential organogelators. They were synthesised in a single step from the corresponding arylboronic acids and alkylglucosides. Eight of them showed organogelation abilities in three solvents (toluene, cyclohexane, and ethyl myristate). Conformational minimisations of the potential organogelators permitted a clear relationship between the arylboronate orientation and the gelation effectiveness to be established. These gels were characterised by rheometry and SEM which revealed a gel-state originating from the self-assembly of the organogelators into long entangled fibres. SAXS confirmed the mode of packing in a hexagonal phase. Gels in toluene were found to be water-sensitive both after addition of a small amount of water and immersion into water. This study demonstrated that the main parameter impacting the water-sensitivity was the length of the alkyl chain at the anomeric position of the glucoside unit, much more than the functionalisation of an arylboronate moiety.

Synthesis of an Exhaustive Library of Naturally Occurring Galf-Manp and Galp-Manp Disaccharides. Toward Fingerprinting According to Ring Size by Advanced Mass Spectrometry-Based IM-MS and IRMPD.

Nature offers a huge diversity of glycosidic derivatives. Among numerous structural modulations, the nature of the ring size of hexosides may induce significant differences on both biological and physicochemical properties of the glycoconjugate of interest. On this assumption, we expect that small disaccharides bearing either a furanosyl entity or a pyranosyl residue would give a specific signature, even in the gas phase. On the basis of the scope of mass spectrometry, two analytical techniques to register those signatures were considered, i.e., the ion mobility (IM) and the infrared multiple photon dissociation (IRMPD), in order to build up cross-linked databases. d-Galactose occurs in natural products in both tautomeric forms and presents all possible regioisomers when linked to d-mannose. Consequently, the four reducing Galf-Manp disaccharides as well as the four Galp-Manp counterparts were first synthesized according to a highly convergent approach, and IM-MS and IRMPD-MS data were second collected. Both techniques used afforded signatures, specific to the nature of the connectivity between the two glycosyl entities.

Isolation of Bioactive Compounds from Calicotome villosa Stems.

A phenylethanoid, two steroids, a flavone glucoside and a chalcone have been isolated for the first time from the stems of Calicotome villosa together with a previously isolated flavone glucoside. Their structures were determined by spectroscopic analyses (NMR, HRMS) as basalethanoïd B (1), ß-sitosterol and stigmasterol (2), chrysine-7-O-ß-d-glucopyranoside (3), chrysine 7-((6''-O-acetyl)-O-ß-d-glucopyranoside) (4) and calythropsin (5). The crude extracts and the isolated compounds (except 4), were evaluated for their antioxidant, antimicrobial (against two Gram-positive bacterial strains: Staphylococcus aureus, Bacillus cereus, four Gram-negative bacterial strains: Staphylococcus epidermidis, Klebsiella pneumonia, Acinetobacter baumanii, and three yeasts: Candida albicans, Candida tropicalis, and Candida glabrata), hemolytic, antidiabetic, anti-inflammatory and cytotoxic activity. The crude extracts showed good ability to scavenge the free radical DPPH. Methanol stem extract followed by the dichloromethane stem extract showed moderate antimicrobial potency; furthermore, at 1 mg/mL the methanol extract showed an inhibition of C. albicans growth comparable to nystatin. Dichloromethane, methanol, and aqueous extracts inhibited 98%, 90%, and 80% of HeLa cell proliferation at 2 mg/mL respectively. Weak hypoglycemic and hemolytic effects were exhibited by the crude extracts. Among all the tested compounds, compound 3 showed remarkable hypoglycemic potential (93% at 0.1 mg/mL) followed by compound 5 (90% at 0.3 mg/mL). Compound 5 was the most effective in the DPPH. scavenging assay (100% at 0.1 mg/mL) and cytotoxic assay on HeLa cells (99% and 90% after 24 and 48 h of treatment at 0.1 mg/mL, respectively). No anti-inflammatory effects were displayed by any of the crude extracts or the isolated compounds at any of the tested concentrations.

Overexpression of ALDH10A8 and ALDH10A9 Genes Provides Insight into Their Role in Glycine Betaine Synthesis and Affects Primary Metabolism in Arabidopsis thaliana.

Betaine aldehyde dehydrogenases oxidize betaine aldehyde to glycine betaine in species that accumulate glycine betaine as a compatible solute under stress conditions. In contrast, the physiological function of betaine aldehyde dehydrogenase genes is at present unclear in species that do not accumulate glycine betaine, such as Arabidopsis thaliana. To address this question, we overexpressed the Arabidopsis ALDH10A8 and ALDH10A9 genes, which were identified to code for betaine aldehyde dehydrogenases, in wild-type A. thaliana. We analysed changes in metabolite contents of transgenic plants in comparison with the wild type. Using exogenous or endogenous choline, our results indicated that ALDH10A8 and ALDH10A9 are involved in the synthesis of glycine betaine in Arabidopsis. Choline availability seems to be a factor limiting glycine betaine synthesis. Moreover, the contents of diverse metabolites including sugars (glucose and fructose) and amino acids were altered in fully developed transgenic plants compared with the wild type. The plant metabolic response to salt and the salt stress tolerance were impaired only in young transgenic plants, which exhibited a delayed growth of the seedlings early after germination. Our results suggest that a balanced expression of the betaine aldehyde dehydrogenase genes is important for early growth of A. thaliana seedlings and for salt stress mitigation in young seedlings.

Characterization and Luminescence Properties of Lanthanide-Based Polynuclear Complexes Nanoaggregates.

For the first time, hexanuclear complexes with general chemical formula [Ln6O(OH)8(NO3)6(H2O)n](2+) with n = 12 for Ln = Sm-Lu and Y and n = 14 for Ln = Pr and Nd were stabilized as nanoaggregates in ethylene glycol (EG). These unprecedented nanoaggregates were structurally characterized by (89)Y and (1)H NMR spectroscopy, UV-vis absorption and luminescence spectroscopies, electrospray ionization mass spectrometry, diffusion ordered spectroscopy, transmission electron microscopy, and dynamic light scattering. These nanoaggregates present a 200 nm mean solvodynamic diameter. In these nanoaggregates, hexanuclear complexes are isolated and solvated by EG molecules. The replacement of ethylene glycol by 2-hydroxybenzyl alcohol provides new nanoaggregates that present an antenna effect toward lanthanide ions. This results in a significant enhancement of the luminescence properties of the aggregates and demonstrates the suitability of the strategy for obtaining highly tunable luminescent solutions.

Synthesis and evaluation of 1,2-trans alkyl galactofuranoside mimetics as mycobacteriostatic agents.

The simple octyl ß-D-galactofuranoside was previously described as a good bacteriostatic agent against Mycobacterium smegmatis, a non-pathogenic model of M. tuberculosis. In order to decipher its mechanism of action, STD NMR on whole M. smegmatis cells was implemented. It outlined the crucial role of the alkyl chain and the possibility of modulation on the furanosyl entity. Then, 16 new alkyl furanosides were synthesized in order to optimize the mycobacteriostatic activity. They all present the pending alkyl chain in a 1,2-trans configuration relative to the sugar ring. Three families were studied that differ by a substituent on the primary position of the galactofuranose ring, the series or the pending alkyl chain. Four of these neofuranosides showed growth inhibition inferior to the parent octyl ß-D-galactofuranoside. Double alkyl chains at C-1 and a polar substituent on the primary position of the furanoside significantly favored the activity. Finally, a mixed biantennary alkyl/aryl ß-D-galactofuranoside exhibited the best growth inhibition concentration at 90 µM.

Trimethylaluminum and borane complexes of primary amines.

Trimethylaluminum (TMA) complexes of methyl-, n-propyl-, cyclopropyl-, allyl-, and propargylamine were synthesized and their experimental properties and theoretical characteristics were compared with the respective amine-borane analogues. The amine ligand of an amine-TMA Lewis acid-base complex can be easily changed by another amine through a 2:1 amine-TMA intermediate in pentane at room temperature. The exchange of the same ligands in the case of amine-boranes requires remarkably more time in line with the calculated relative energy of the respective transition state. The (1)H and (13)C NMR experiments examining the addition of one or more equivalent of amine to the respective Lewis acid-base complex conclude in the fast exchange of the amine ligand in the NMR time scale only in the cases of amine-TMA complexes, which could also be caused by similar 2:1 complexes. However, in gas phase, only 1:1 amine-TMA complexes are present as evidenced by ultraviolet photoelectron spectroscopy (UPS). The observed UP spectra, which are the first recorded photoelectron spectra of primary amine-TMA compounds, indicate that the stabilization effect of the lone electron pair of nitrogen atom in amines during the borane complexation is stronger than that of the TMA complexation. In line with this observation, the destabilization of the σ(Al-C) orbitals is lower than that of σ(B-H) orbitals during the formation of amine-TMA and amine-borane complexes, respectively. As showed by theoretical calculations, the CH(4) elimination of the studied amine-TMA complexes is exothermic, indicating the possibility of using these compounds in metal organic chemical vapor deposition techniques (MOCVD). On the other hand, our experimental conditions avoid this methane elimination and constitutes the first procedure employing distillation to isolate primary amine-TMA complexes.

Heteroleptic silylamido phenolate complexes of calcium and the larger alkaline earth metals: ß-agostic Ae⋠⋠⋠Si-H stabilization and activity in the ring-opening polymerization of L-lactide.

The factors governing the stability and the reactivity towards cyclic esters of heteroleptic complexes of the large alkaline earth metals (Ae) have been probed. The synthesis and stability of a family of heteroleptic silylamido and alkoxide complexes of calcium [{LO(i)}Ca-Nu(thf)(n)] supported by mono-anionic amino ether phenolate ligands (i = 1, {LO(1)}(-) = 4-(tert-butyl)-2,6-bis(morpholinomethyl)phenolate, Nu(-) = N(SiMe(2)H)(2)(-), n = 0, 4; i = 2, {LO(2)}(-) = 2,4-di-tert-butyl-6-{[2-(methoxymethyl)pyrrolidin-1-yl]methyl}phenolate, Nu(-) = N(SiMe(2)H)(2)(-), n = 0, 5; i = 4, {LO(4)}(-) = 2-{[bis(2-methoxyethyl)amino]methyl}-4,6-di-tert-butylphenolate, Nu(-) = N(SiMe(2)H)(2)(-), n = 1, 6; Nu(-) = HC≡CCH(2)O(-), n = 0, 7) and those of the related [{LO(3)}Ae-N(SiMe(2)H)(2)] ({LO(3)}(-) = 2-[(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)methyl]-4,6-di-tert-butylphenolate Ae = Ca, 1; Sr, 2; Ba, 3) have been investigated. The molecular structures of 1, 2, [(4)(2)], 6, and [(7)(2)] have been determined by X-ray diffraction. These highlight Ae⋅⋅⋅H-Si internal ß-agostic interactions, which play a key role in the stabilization of [{LO(i)}Ae-N(SiMe(2)H)(2)] complexes against ligand redistribution reactions, in contrast to regular [{LO(i)}Ae-N(SiMe(3))(2)]. Pulse-gradient spin-echo (PGSE) NMR measurements showed that 1, 4, 6, and 7 are monomeric in solution. Complexes 1-7 mediate the ring-opening polymerization (ROP) of L-lactide highly efficiently, converting up to 5000 equivalents of monomer at 25 °C in a controlled fashion. In the immortal ROP performed with up to 100 equivalents of exogenous 9-anthracenylmethanol or benzyl or propargyl alcohols as a transfer agent, the activity of the catalyst increased with the size of the metal (1<2<3). For Ca-based complexes, the enhanced electron-donating ability of the ancillary ligand favored catalyst activity (1>6>4≈5). The nature of the alcohol had little effect over the activity of the binary catalyst system 1/ROH; in all cases, both the control and end-group fidelity were excellent. In the living ROP of L-LA, the HC≡CCH(2)O(-) initiating group (as in 7) proved superior to N(SiMe(2)H)(2)(-) or N(SiMe(3))(2)(-) (as in 6 or [{LO(4)}Ca-N(SiMe(3))(2)] (B), respectively).

Metabolome and water homeostasis analysis of Thellungiella salsuginea suggests that dehydration tolerance is a key response to osmotic stress in this halophyte.

Thellungiella salsuginea, a Brassicaceae species closely related to Arabidopsis thaliana, is tolerant to high salinity. The two species were compared under conditions of osmotic stress to assess the relationships between stress tolerance, the metabolome, water homeostasis and growth performance. A broad range of metabolites were analysed by metabolic fingerprinting and profiling, and the results showed that, despite a few notable differences in raffinose and secondary metabolites, the same metabolic pathways were regulated by salt stress in both species. The main difference was quantitative: Thellungiella had much higher levels of most metabolites than Arabidopsis whatever the treatment. Comprehensive quantification of organic and mineral solutes showed a relative stability of the total solute content regardless of the species or treatment, meaning that little or no osmotic adjustment occurred under stress. The reduction in osmotic potential observed in plants under stress was found to result from a passive loss of water. Thellungiella shoots contain less water than Arabidopsis shoots, and have the ability to lose more water, which could contribute to maintain a water potential gradient between soil and plant. Significant differences between Thellungiella and Arabidopsis were also observed in terms of the physicochemical properties of their metabolomes, such as water solubility and polarity. On the whole, the Thellungiella metabolome appears to be more compatible with dehydration. Osmotic stress was also found to impact the metabolome properties in both species, increasing the overall polarity. Together, the results suggest that Thellungiella copes with osmotic stress by tolerating dehydration, with its metabolic configuration lending itself to osmoprotective strategies rather than osmo-adjustment.

Enzymatic degradation of κ-carrageenan in aqueous solution.

Enzymatic degradation of standard κ-carrageenan and the low-gelling hybrid κ-/µ-carrageenan were conducted using recombinant Pseudoalteromonas carrageenovora κ-carrageenase. The initial velocity of the enzyme was determined as a function of varying Tris or NaI concentrations and at constant 200 mM cosolutes concentration, adjusting NaI and Tris concentrations accordingly. In both cases, we observed strong inhibition of the enzyme with increasing amounts of iodide. The characterization of the κ- and κ-/µ-carrageenan ordering by optical rotation and the visualization of iodide binding on carrageenan by (127)I NMR revealed that inhibition was not caused by the disordered-ordered transition of carrageenan in NaI, but by iodide binding. These results were confirmed by analysis of the degradation products by gel permeation chromatography. Degradation of carrageenan in the disordered state led to a rapid decrease in molecular mass and the production of all possible neo-κ-carrabiose oligomers. In the ordered conformation, the degradation kinetics, the decrease of average molecular weight, and the chain population distribution of degradation products varied with iodide concentration. These observations were interpreted to be the result of increasing amounts of bound iodide on carrageenan helices that, in turn, impede enzyme catalysis. Based on these results, we propose a single-helix ordered conformation state for κ-carrageenan and reject the previously advocated double-helix model.

Activation of olefin metathesis complexes containing unsymmetrical unsaturated N-heterocyclic carbenes by copper and gold transmetalation.

The activation of ruthenium-indenylidene complexes containing two unsymmetrical unsaturated N-heterocyclic carbenes (u2-NHCs) by a transmetalation process is reported. The use of copper(i) or gold(i) chlorides promotes the rapid trapping of one NHC ligand, which releases the catalytically active Ru-species. Impressive initiation rates with full-conversions are observed within one minute. This practical protocol demonstrates excellent catalytic performances in various ring-closing metathesis (RCM) and self-metathesis (SM) reactions.

Synthesis, spectral characterization, molecular modeling, antibacterial and antioxidant activities and stability study of binuclear Pd(II) and Ru(III) complexes with novel bis-[1-(2-[(2-hydroxynaphthalen-1-yl)methylidene]amino}ethyl)-1-ethyl-3-phenylthiourea] ligand: Application to detection of cholesterol.

A novel bis-[1-(2-[(2-hydroxynaphthalen-1-yl) methylidene]amino}ethyl)-1-ethyl-3-phenylthiourea] Schiff base (L) and its binuclear palladium and ruthenium complexes have been prepared and characterized by ESI-MS, elemental analysis, NMR (1H NMR, 13C NMR, COSY, NEOSY and HSQC), FT-IR, ATR, UV-Visible spectra, TGA measurements, conductivity and cyclic voltammetry. The experimental results and the molecular parameters calculated using DFT method revealed a square planar geometry around Pd and octahedral geometry around ruthenium metal. The antibacterial activity of the ligand L and its complexes was evaluated against different human bacteria. In addition, the formation constants of the synthesized Schiff base-metal complexes and the systems formed with these chelates and cholesterol were estimated using spectrophotometric technique. The detection of cholesterol using novel Pd and Ru Schiff base complexes was studied using fluorometric method, and the measurements showed that the sensitive fluorometric response towards cholesterol analysis was determined using palladium complex. The limit of detection (LOD) of cholesterol calculated using this complex (4.6 µM) is lower (better) than LOD found using ruthenium complex (19.1 µM) and different compounds previously published around linear range of 0-5 mM.

Probing ß-(1→3)-D-glucans interactions with recombinant human receptors using high-resolution NMR studies.

A full characterization of the high-resolution NMR spectrum of the laminarihexaose is described and used for the determination of the binding epitope of the more complex but structurally related laminarin. These biophysical data extend the current knowledge of ß-glucans/Dectin-1 interactions and suggest different biological mechanisms in close relation with the size of the saccharidic chain.

Polyhydroxylated ammonium chloride salt: a new efficient surfactant for nanoparticles stabilisation in aqueous media. Characterization and application in catalysis.

A trihydroxyammonium chloride has proved to be an efficient protective agent for Rh(0) nanoparticles and the hydrogenation of arene compounds has been investigated. Significant formation of cyclohexanone in the reduction of anisole has been demonstrated.

First o-glycosylation from unprotected 1-thioimidoyl hexofuranosides assisted by divalent cations.

The preparation of O-hexofuranosides was accomplished from unprotected 1-thioimidoyl furanosides as donors. The present methodology was first used for the synthesis of octyl galactofuranoside and further extended to D-galactofuranose-containing disaccharides. Within this study, we emphasized the need for additional complexing cations to maintain the furanose ring in its initial size. After experimentation, calcium ion was first used concomitantly with trimethylsilyl trifluoromethanesulfonate, the latter being able to activate the thioimidate and the former being likely to inhibit ring expansion. Moreover, an improvement was performed by using copper(II) trifluoromethanesulfonate which could then meet the requirements as both promoter and complexing agent.

Synthesis, structural studies, theoretical calculations, and linear and nonlinear optical properties of terpyridyl lanthanide complexes: new evidence for the contribution of f electrons to the NLO activity.

The synthesis and structural, photophysical, and second-order nonlinear optical (NLO) properties of a novel lanthanide terpyridyl-like complex family LLn(NO(3))(3) (Ln = La, Gd, Dy, Yb, and Y) are reported. The isostructural character of this series in solution and in the solid state has been established on the basis of X-ray diffraction analysis in the cases of yttrium and gadolinium complexes, theoretical optimization of geometry (DFT), and NMR spectroscopy. The absorption, emission, and solvatochromic properties of the free terpyridyl-like ligand L were thoroughly investigated, and the twist intramolecular charge transfer (TICT) character of the lowest energy transition was confirmed by theoretical calculation (TDDFT and CIS). The similar ionochromic effect of the different lanthanide ions was evidenced by the similar UV-visible spectra of the complete family of complexes. On the other hand, the quadratic hyperpolarizability coefficient beta, measured by the harmonic light scattering (HLS) technique, is clearly dependent on the nature of the metal, and a careful examination of the particular case of yttrium unambiguously confirms the contribution of metal f electrons to the NLO activity.

Glucan-like synthetic oligosaccharides: iterative synthesis of linear oligo-beta-(1,3)-glucans and immunostimulatory effects.

Small reducing and linear oligo-beta-(1,3)-glucans, which are able to act as phytoallexin elicitors or as immunostimulating agents in anticancer therapy, were synthesized according to an iterative strategy that involved a unique key monosaccharidic donor. To avoid anomeric mixtures, the reducing entity of the target oligomers was first locked with benzyl alcohol and further selective deprotection of the 3-OH with DDQ afforded the desired building block as an acceptor. The latter was then used in a second cycle of glycosylation/deprotection to afford the desired disaccharide, and successive reiterations of this process provided the desired oligomers. Unusual conformational behaviors were observed by standard NMR sequences and supported by NOESY studies. Finally, removal of protecting groups afforded free tri-, tetra-, and pentaglucosides in good overall yields. Two oligosaccharides representing linear laminaritetraose and laminaripentaose were compared to the recently described beta-(1,3)-glucan phycarine. Following an intraperitoneal injection, the influx of monocytes and granulocytes into the blood and macrophages into the peritoneal cavity was comparable to that caused by phycarine. Similarly, both oligosaccharides stimulated phagocytic activity of granulocytes and macrophages. Using ELISA, we also demonstrated a significant stimulation of secretion of IL-1beta. Together these results suggest that the synthetic oligosaccharides have similar stimulatory effects as natural beta-(1,3)-glucans.

Synthesis, linear, and quadratic-nonlinear optical properties of octupolar D3 and D2d bipyridyl metal complexes.

A series of D3 (Fe(II), Ru(II), Zn(II), Hg(II)) and D2d (Cu(I), Ag(I), Zn(II)) octupolar metal complexes featuring different functionalized bipyridyl ligands has been synthesized, and their thermal, linear (absorption and emission), and nonlinear optical (NLO) properties were determined. Their quadratic NLO susceptibilities were determined by harmonic light scattering at 1.91 microm, and the molecular hyperpolarizability (beta0) values are in the range of 200-657 x 10(-30) esu for octahedral complexes and 70-157 x 10(-30) esu for tetrahedral complexes. The octahedral zinc(II) complex 1 e, which contains a 4,4'-oligophenylenevinylene-functionalized 2,2'-bipyridine, exhibits the highest quadratic hyperpolarizability ever reported for an octupolar derivative (lambdamax=482 nm, beta1.91(1 e)=870 x 10(-30) esu, beta0(1 e)=657 x 10(-30) esu). Herein, we demonstrate that the optical and nonlinear optical (NLO) properties are strongly influenced by the symmetry of the complexes, the nature of the ligands (donor endgroups and pi linkers), and the nature of the metallic centers. For example, the length of the pi-conjugated backbone, the Lewis acidity of the metal ion, and the increase of ligand-to-metal ratio result in a substantial enhancement of beta. The contribution of the metal-to-ligand (MLCT) transition to the molecular hyperpolarizability is also discussed with respect to octahedral d6 complexes (M=Fe, Ru).