Natural deep eutectic solvents as thermostabilizer for Humicola insolens cutinase

As a new generation of green solvents, deep eutectic solvents (DESs) are considered a promising alternative to current harsh organic solvents and find application in many chemical processing methods such as extraction and synthesis. DESs, normally formed by two or more components via various hydrogen bond interactions, offer high potential as medium for biocatalysis reactions where they can improve efficiency by enhancing substrate solubility and the activity and stability of the enzymes. In the current study, the stabilization of Humicola insolens cutinase (HiC) in natural deep eutectic solvents (NADESs) was assessed. The best hydrogen bond donor among sorbitol, xylitol, erythritol, glycerol and ethylene glycol, and the best acceptor among betaine, choline chloride, choline acetate, choline dihydrogen citrate and tetramethylammonium chloride, were selected, evaluating binding energies and molecular orientations through molecular docking simulations, and finally used to prepare NADES aqueous solutions. The effects of component ratio and NADES concentration on HiC thermostability at 90 degrees C were also investigated. The choline dihydrogen citrate:xylitol, in a 1:1 ratio with a 20 wt% concentration, was selected as the best combination in stabilizing HiC, increasing its half-life three-fold

Étude des grandeurs caractéristiques de la tache cathodique d'un arc électrique

The cathode of an electric arc burning freely in air was studied during a half-wave of a sinusoidal, 50 Hz current. For mean intensities ranging from 500 to 2 000 A, five characteristic parameters for the cathode spot were determined : the mean radius a, the temperature T, the electric field E, the total current density J, and the fraction s of the current density due to electrons. The experimental measurement of the erosion of the cathode together with five simultaneous equations enabled the parameters above to be obtained for copper and silver electrodes. The first part of the results gives mean values. The second part shows the changes occuring in the cathode spot as a function of time for the half-wave of the current.On étudie la cathode d'un arc électrique brulant librement dans l'air pendant une demi-alternance d'un courant sinusoïdal de fréquence 50 Hz. Nous avons déterminé pour des intensités moyennes variant entre 500 et 2 000 A cinq grandeurs physiques caractéristiques de la tache cathodique : le rayon moyen a, la température T, le champ électrique E, la densité totale de courant J et la fonction s de la densité de courant due aux électrons. La mesure expérimentale de l'érosion de la cathode associée à un système de cinq équations a permis d'obtenir ces grandeurs pour des électrodes en cuivre et en argent. La première partie des résultats donne des valeurs moyennes, tandis que la deuxième partie montre l'évolution de la tache cathodique en fonction du temps pour la demi-alternance de courant

Ionic association and interactions in aqueous methylsulfate alkyl-imidazolium-based ionic liquids

International audienceSeveral experimental techniques were used to study ionic association and interactions in aqueous [C1C2Im][MeSO4], 1-ethyl-3-methylimidazolium methylsulfate, and [C1C4Im][MeSO4], 1-butyl-3-methylimidazolium methylsulfate. Two transport properties, viscosity and electrical conductivity, were determined for these two binary mixtures. For a better assessment of the ionic association and the perturbation of water into the molecular structure of the ionic liquid, diffusion coefficients of ions and water molecules were obtained by NMR spectroscopy while molecular interactions were probed by IR spectroscopy.The comparison of the two ionic liquids shows that for the shorter alkyl chain the viscosity was lower and the electrical conductivity was higher. While the viscosity of the mixture drops already with small additions of water, the electrical conductivity of the solution is only significantly increased for high water concentrations. A maximum is observed for compositions around xwater = (0.90 to 0.95). The SO3 asymmetric stretching band of the IR spectrum can be used as a probe to observe the evolution of the structure around the anion which was mainly occurring for high concentrations of water. Several experimental techniques show than the main change in the ionic association was only observed for high water contents (water mole fraction > 0.8)

Using bio-based solvents as CO2 absorbents in refrigeration processes.

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Thermodynamics of Cellulose Dissolution in an Imidazolium Acetate Ionic Liquid

International audienceThe heat of dissolution of cellulose in one imidazolium acetate ionic liquid was determined experimentally. The value of −132 ± 8 J g−1 indicates that the dissolution is exothermal thus confirming energetically favourable cellulose–ionic liquid interactions but indicating that an increase in temperature does not thermodynamically favour the dissolution process

Elaboration of Bi-based Nanoparticles by reactive magnetron sputtering on Ionic Liquid for photocatalytic applications.

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Experimental thermodynamic study of CO2-Acetone system.

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Quantification of the impact of water as an impurity on standard physico-chemical properties of ionic liquids

International audienceThe objective of this work was to quantify the effect of the presence of water as impurity in ionic liquids. First, density and viscosity of five ionic liquids as well as their aqueous solutions were measured. For hydrophobic dried ionic liquids, traces of water (50 ppm) have measurable impact neither on the density nor on the viscosity values. In the concentration range studied (up to 5000 ppm), a linear evolution of the molar volume of the mixture with the mole fraction composition is observed. Practically, this allows to estimate the density of an neat ionic liquid provided (i) the water quantity and (ii) the density of the undried sample are known. This is particularly useful for hydrophilic ionic liquids that are difficult to dry. In the studied concentration range, a linear evolution of the relative viscosity was also depicted as a function of the mass fraction composition. It is thus possible to evaluate the viscosity of the pure ionic liquid knowing the water quantity and the viscosity of the undried sample. The comparison of the results obtained using two viscosimeters confirms that a Stabinger viscosimeter is appropriate to precisely measure ionic liquids viscosities. Second, NMR and IR spectroscopies were used to characterize the pure ionic liquids and their solutions with water. The sensitivity of IR spectroscopy does allow neither the quantification nor the detection of water below 1 mol%. With NMR spectroscopy, water can be quantified using either the intensity or the chemical shift of the water proton peak for mole fractions as low as 200 ppm. It is even possible to detect water in the dried hydrophobic ionic liquids, few ppm of water, as long as the water peak does not overlap the ionic liquid signal

Design and study of new tunable hydrophobicity solvents.

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