IONIC COMPOSITION OF THE LIVER FLUKE FASCIOLA-HEPATICA FROM DIFFERENT MAMMALIAN HOSTS AND COMPARISON WITH HOST BILE

A qualitative analysis of the cationic profile of bovine and ovine biles and of bovine, ovine and rat liver flukes has been carried out by DC are emission spectrography. A quantitative assessment of the concentrations of Na+, K+, Ca2+ and Mg2+ ions in bovine, ovine and rat flukes has been determined by atomic absorption spectrophotometry. The levels of these ions in bovine and ovine bile samples have also been assessed and compared with those of Hedon-Heig saline. The ionic composition of the two biles is similar and the concentration of each ion is greater than that in Hedon-Heig saline. Despite the similarity in biles, ion levels in bovine flukes are generally higher than those in ovine flukes. Ion levels in rat flukes are different again but show closer similarity to those in bovine, not ovine, flukes. The results are discussed in relation to the proposed operation of the osmoregulatory system in the fluke.

A conserved spider silk domain acts as a molecular switch that controls fibre assembly

A huge variety of proteins are able to form fibrillar structures(1), especially at high protein concentrations. Hence, it is surprising that spider silk proteins can be stored in a soluble form at high concentrations and transformed into extremely stable fibres on demand(2,3). Silk proteins are reminiscent of amphiphilic block copolymers containing stretches of polyalanine and glycine-rich polar elements forming a repetitive core flanked by highly conserved non-repetitive amino-terminal(4,5) and carboxy-terminal(6) domains. The N-terminal domain comprises a secretion signal, but further functions remain unassigned. The C-terminal domain was implicated in the control of solubility and fibre formation(7) initiated by changes in ionic composition(8,9) and mechanical stimuli known to align the repetitive sequence elements and promote beta-sheet formation(10-14). However, despite recent structural data(15), little is known about this remarkable behaviour in molecular detail. Here we present the solution structure of the C-terminal domain of a spider dragline silk protein and provide evidence that the structural state of this domain is essential for controlled switching between the storage and assembly forms of silk proteins. In addition, the C-terminal domain also has a role in the alignment of secondary structural features formed by the repetitive elements in the backbone of spider silk proteins, which is known to be important for the mechanical properties of the fibre.

Photo-ionized neon plasmas induced by radiation pulses of a laser-plasma EUV source and a free electron laser FLASH

In this work, a laser-produced plasma extreme ultraviolet source and a free electron laser were used to create Ne photo-ionized plasmas. In both cases, a radiation beam was focused onto a gas stream injected into a vacuum chamber synchronously with the radiation pulse. Extreme ultraviolet radiation from the plasma spanned a wide spectral range with pronounced maximum centered at lambda = 11 +/- 1 nm while the free electron laser pulses were emitted at a wavelength of 32 nm. The power density of the focused plasma radiation was approximately 2 x 10(7) W/cm(2) and was seven orders of magnitude lower compared with the focused free electron laser beam. Radiation fluences in both experimental conditions were comparable. Despite quite different spectral characteristics and extremely different power densities, emission spectra of both photo-ionized plasmas consist of the same spectral lines within a wavelength range of 20 to 50 nm, however, with different relative intensities of the corresponding lines. The dominating spectral lines originated from singly charged ions (Ne II); however, Ne III lines were also detected. Additionally, computer simulations of the emission spectra, obtained for photo-ionized plasmas, driven by the plasma extreme ultraviolet source, were performed. The corresponding measured and calculated spectra are presented. An electron temperature and ionic composition were estimated. Differences between the experimental spectra, obtained for both irradiation conditions, were analyzed. The differences were attributed mainly to different energies of driving photons.

Non-ideal behaviour of a room temperature ionic liquid in an alkoxyethanol or poly ethers at T = (298.15 to 318.15) K

Non-ideal behaviour of 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] in ethylene glycol monomethyl ether; CH3OCH2CH2OH (EGMME), ethylene glycol dimethyl ether; CH3OCH2CH2OCH3 (EGDME) and diethylene glycol dimethyl ether; CH3(OCH2CH2)2OCH3 (DEGDME) have been investigated over the whole composition range at T = (298.15 to 318.15) K. To gain insight into the mixing behaviour, results of density measurements were used to estimate excess molar volumes, image, apparent molar volumes, Vphi,i, partial molar volumes, image, excess partial molar volumes, image, and their limiting values at infinite dilution, image, image, and image, respectively. Volumetric results have been analyzed in the light of Prigogine–Flory–Patterson (PFP) statistical mechanical theory. Measurements of refractive indices n were also performed for all the binary mixtures over whole composition range at T = 298.15 K. Deviations in refractive indices ?phin and the deviation of molar refraction ?xR have been calculated from experimental data. Refractive indices results have been correlated with volumetric results and have been interpreted in terms of molecular interactions. Excess properties are fitted to the Redlich–Kister polynomial equation to obtain the binary coefficients and the standard errors.

Preparation of AgX (X = Cl, I) nanoparticles using ionic liquids

Nanoparticles of silver halides have been prepared by mixing silver halide powder with a single liquid phase consisting of an ionic liquid, isooctane, n-decanol and water. Much higher nanoparticle concentrations may be formed with ionic liquids using this new simple method than are found with conventionally applied surfactants. This method also emphasizes the applicability of ionic liquids as versatile components in microemulsions and as solvents for the synthesis of nanomaterials. The effect on the nanoparticles of changing the composition of the liquid mixtures and the nature of the ionic liquid is analysed. High nanoparticle concentrations were only found with chloride based ionic liquids, indicating the importance of the ionic liquid anion in the mechanism of the reaction.

Ionic Liquids Containing Boron Cluster Anions

The combination of different boron cluster anions and some of the cations typically found in the composition of ionic liquids has been possible by straightforward metathetic reactions, producing new low melting point salts; the imidazolium cations have been systematically studied, [C(n)mim](+) (when [C(n)mim](+) = 1-alkyl-3-methylimidazolium; n = 2, 4, 6, 8, 10, 12, 14, 16, or 18). Melting points increase in the anionic order [Co(C2B9H11)(2)](-) =-34 degrees C). The salts [C(n)mim](2)[X] ([X](2-) = [B10Cl10](2-) or [B12Cl12](2-), n = 16 or 18) show liquid crystal phases between the solid and liquid states. Tetraalkylphosphonium salts of [B10Cl10](2-) have also been prepared. Physical properties, such as thermal stability, density, or viscosity, have been measured for some selected samples. The presence of the perhalogenated dianion [B12Cl12](2-) in the composition of the imidazolium salts renders highly thermally stable compounds. For example, [C(2)mim](2)[B12Cl12] starts to decompose above 480 degrees C in a dynamic TGA analysis under a dinitrogen atmosphere. Crystal structures of [C(2)mim][Co(C2B9H11)(2)] and [C(2)mim](2)[B12Cl12] have been determined. H-1 NMR spectra of selected imidazolium-boron cluster anion salts have been recorded from solutions as a function of the concentration, showing trends related to the cation-anion interactions.

Mesophases in Nearly 2D Room-Temperature Ionic Liquids

Computer simulations of (i) a [C(12)mim][Tf2N] film of nanometric thickness squeezed at kbar pressure by a piecewise parabolic confining potential reveal a mesoscopic in-plane density and composition modulation reminiscent of mesophases seen in 3D samples of the same room-temperature ionic liquid (RTIL). Near 2D confinement, enforced by a high normal load, as well as relatively long aliphatic chains are strictly required for the mesophase formation, as confirmed by computations for two related systems made of (ii) the same [C(12)mim][Tf2N] adsorbed at a neutral solid surface and (iii) a shorter-chain RTIL ([C(4)mim][Tf2N]) trapped in the potential well of part i. No in-plane modulation is seen for ii and iii. In case ii, the optimal arrangement of charge and neutral tails is achieved by layering parallel to the surface, while, in case iii, weaker dispersion and packing interactions are unable to bring aliphatic tails together into mesoscopic islands, against overwhelming entropy and Coulomb forces. The onset of in-plane mesophases could greatly affect the properties of long-chain RTILs used as lubricants.

Volumetric properties and enthalpies of solution of alcohols CkH2k+1OH (k = 1, 2, 6) in 1-methyl-3-alkylimidazolium bis(trifluoromethylsulfonyl)imide {[C1CnIm][NTf2] n = 2, 4, 6, 8, 10} ionic liquids

We present a study on the effect of the alkyl chain length of the imidazolium ring in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [C1CnIm][NTf2] (n = 2 to 10), on the mixing properties of (ionic liquid + alcohol) mixtures (enthalpy and volume). We have measured small excess molar volumes with highly asymmetric curves as a function of mole fraction composition (S-shape) with more negative values in the alcohol-rich regions. The excess molar volumes increase with the increase of the alkyl-chain length of the imidazolium cation of the ionic liquid. The values of the partial molar excess enthalpy and the enthalpy of mixing are positive and, for the case of methanol, do not vary monotonously with the length of the alkyl side-chain of the cation on the ionic liquid – increasing from n = 2 to 6 and then decreasing from n = 8. This non-monotonous variation is explained by a more favourable interaction of methanol with the cation head group of the ionic liquid for alkyl chains longer than eight carbon atoms. It is also observed that the mixing is less favourable for the smaller alcohols, the enthalpy of mixing decreasing to less positive values as the alkyl chain of the alcohol increases. Based on the data from this work and on the knowledge of the vapour pressure of {[C1CnIm][NTf2] + alcohol} binary mixtures at T = 298 K reported in the literature, the excess Gibbs free energy, excess enthalpy and excess entropy could be then calculated and it was observed that these mixtures behave like the ones constituted by a non-associating and a non-polar component, with its solution behaviour being determined by the enthalpy.

Protic ionic liquids based on the dimeric and oligomeric anions: [(AcO)(x)Hx-1](-)

We describe a fluidity and conductivity study as a function of composition in N-methylpyrrolidine-acetic acid mixtures. The simple 1 : 1 acid-base mixture appears to form an ionic liquid, but its degree of ionicity is quite low and such liquids are better thought of as poorly dissociated mixtures of acid and base. The composition consisting of 3 moles acetic acid and 1 mole N-methylpyrrolidine is shown to form the highest ionicity mixture in this binary due to the presence of oligomeric anionic species [(AcO)(x)Hx-1](-) stabilised by hydrogen bonds. These oligomeric species, being weaker bases than the acetate anion, shift the proton transfer equilibrium towards formation of ionic species, thus generating a higher degree of ionicity than is present at the 1 : 1 composition. A Walden plot analysis, thermogravimetric behaviour and proton NMR data, as well as ab initio calculations of the oligomeric species, all support this conclusion.

Physico-chemical properties of non-newtonian shear thickening diisopropyl-ethylammonium-based protic ionic liquids and their mixtures with water and acetonitrile

New protic ionic liquids (PILs) based on the diisopropyl-ethylammonium cation have been synthesized through a simple and atom-economic neutralization reaction between the diisopropyl-ethylamine and selected carboxylic acid. Densities and rheological properties were then measured for two original diisopropyl-ethylammonium-based protic ionic liquids (heptanoate and octanoate) at 298.15 K and atmospheric pressure. The effect of the presence of water or acetonitrile on the measured values was also examined over the whole composition range at 298.15 K and atmospheric pressure. From these values, excess properties were calculated and correlated by using a Redlich-Kister-type equation. Finally, a qualitative analysis of the evolution of studied properties with the alkyl chain length of the anion and with the presence or not of water (or acetonitrile) was performed. From this analysis, it appears that selected PILs and their mixtures with water or acetonitrile have a non-Newtonian shear thickening behavior, and the addition of water or acetonitrile on these PILs increases this phenomena by the formation of aggregates in these media.

Volumetric Properties, Viscosities, and Isobaric Heat Capacities of Imidazolium Octanoate Protic Ionic Liquid in Molecular Solvents

Densities (F), viscosities (?), and isobaric heat molar capacities (Cp) of binary mixtures containing imidazolium octanoate, [Im][C7CO2], a protic ionic liquid (PIL), with four molecular solvents, water, acetonitrile, ethanol, and 1-octanol, are determined as a function of temperature from (298.15 to 323.15) K and within the whole composition range at atmospheric pressure. Excess molar volumes, VE, excess molar heat capacities, Cp E, and the deviation from additivity rules of viscosities, ??, of imidazolium octanoate solutions were then deduced from the experimental results, as well as apparent molar volumes, Vfi, and partial molar volumes, V j m,i. Results are discussed according to the nature of the interaction between the PIL and the molecules and the effect of temperature. The excess Gibbs energies of activation of viscous flow (?G*E) for these systems were then calculated at 298.15 K. The excess isobaric heat capacities, Cp E, of binary ([Im][C7CO2] + solvent) systems, depend also of the nature of the molecular solvent in mixture. The excess properties were then correlated, at each temperature, as a function of composition by a Redlich-Kister-type equation. Finally results have been discussed in terms of molecular interactions and molecular structures in these binary mixtures, and thermodynamic properties of investigated binary mixtures were then compared to literature values together to investigate the impact of the nature of the solvent on these reported properties.

Volumetric properties, viscosity and refractive index of the protic ionic liquid, pyrrolidinium octanoate, in molecular solvents

Densities ([rho]) and viscosities ([eta]) of binary mixtures containing the Protic Ionic Liquid (PIL), pyrrolidinium octanoate with five molecular solvents: water, methanol, ethanol, n-butanol, and acetonitrile are determined at the atmospheric pressure as a function of the temperature and within the whole composition range. The refractive index of all mixtures (nD) is measured at 298.15†K. The excess molar volumes VE and deviation from additivity rules of viscosities [eta]E and refractive index [Delta][phi]n, of pyrrolidinium octanoate solutions were then deduced from the experimental results as well as apparent molar volumes V[phi]i, partial molar volumes and thermal expansion coefficients [alpha]p. The excess molar volumes VE are negative over the entire mole fraction range for mixture with water, acetonitrile, and methanol indicating strong hydrogen-bonding interaction for the entire mole fraction. In the case of longest carbon chain alcohols (such as ethanol and n-butanol)†+†pyrrolidinium octanoate solutions, the VE variation as a function of the composition describes an S shape. The deviation from additivity rules of viscosities is negative over the entire composition range for the acetonitrile, methanol, ethanol, and butanol, and becomes less negative with increasing temperature. Whereas, [eta]E of the {[Pyrr][C7CO2]†+†water} binary mixtures is positive in the whole mole fraction range and decreases with increasing temperature. the excess Gibbs free energies of activation of viscous flow ([Delta]G*E) for these systems were calculated. The deviation from additivity rules of refractive index [Delta][phi]n are positive over the whole composition range and approach a maximum of 0.25 in PIL mole fraction for all systems. The magnitude of deviation for [Delta][phi]n describes the following order: water†>†methanol†>†acetonitrile†>†ethanol. Results have been discussed in terms of molecular interactions and molecular structures in these binary mixtures.

Transport properties of protic ionic liquids, pure and in aqueous solutions: Effects of the anion and cation structure

Ionic conductivities of twelve protic ionic liquids (PILs) and their mixtures with water over the whole composition range are reported at 298.15 K and atmospheric pressure. The selected PILs are the pyrrolidinium-based PILs containing nitrate, acetate or formate anions; the formate-based PILs containing diisopropylethylammonium, amilaminium, quinolinium, lutidinium or collidinium cations; and the pyrrolidinium alkylcarboxylates, [Pyrr][CnH2n+1COO] with n = 5–8. This study was performed in order to investigate the influence of molecular structures of the ions on the ionic conductivities in aqueous solutions. The ionic conductivities of the aqueous solutions are 2–30 times higher than the conductivities of pure PILs. The maximum in conductivity varies from ww=0.41???to???0.74 and is related to the nature of cations and anions. The molar conductance and the molar conductance at infinite dilution for (PIL + water) solutions are then determined. Self-diffusion coefficients of the twelve protic ionic liquids in water at infinite dilution and at 298.15 K are calculated by using the Nernst–Haskell, the original and the modified Wilke–Chang equations. These calculations show that similar values are obtained using the modified Wilke–Chang and the Nernst–Haskell equations. Finally, the effective hydrodynamic (or Stokes) radius of the PILs was determined by using the Stokes–Einstein equation. A linear relationship was established in order to predict this radius as a function of the anion alkyl chain length in the case of the pyrrolidinium alkylcarboxylates PILs.

Validation of Speciation Techniques: A Study of Chlorozincate(II) Ionic Liquids

The speciation of chlorozincate(II) ionic liquids, prepared by mixing 1-octyl-3-methylirnidazolium chloride, [C(8)mim]Cl, and zinc(II) chloride in various molar ratios, chi zncl(2), was investigated using Raman spectroscopy and differential scanning calorimetry; the Gutmann acceptor number, which is a quantitative measure of Lewis acidity, was also determined as a function of the composition. These results were combined with literature data to define the anionic speciation; in the neat liquid phase, the existence of cl(-), [ZnCl4](2-), [Zn2Cl6](2-), [Zn3Cl8](2-), and [Zn4Cl10](2-) anions was confirmed. From two chlorozincate(H) ionic liquids with [C(2)mim](+) cations (chi zncl(2) = 0.33 and chi zncl(2) = 0.50), crystals have been obtained, revealing the structures of [C(2)mim)(2)[ZnCl4] and [C(2)mim](2)[Zn2Cl6] forming three-dimensional hydrogen-bond networks. The compound [C(2)mim](2){Zn4Cl10} was crystallized from the chi zncl(1) = 0.75 composition, showing an open-framework structure, with the first example of zinc in a trigonal-bipyramidal chloride coordination. Reinvestigation of the electrospray ionization mass spectrometry of these systems demonstrated that it is an unreliable technique to study liquid-phase speciation.