Structure of Ionic Liquid-Benzene Mixtures

Neutron diffraction has been used to investigate the structure of liquid mixtures of 1,3-dimethylimidazolium hexafluorophosphate with benzene. Two concentrations of benzene were investigated, namely, 33 mol % and 67 mol %, and show similar structures in each case. The presence of benzene significantly alters the ionic liquid structure, in particular, in the cation-cation interactions, in agreement with the single-crystal structure described recently (Holbrey, J. D.; Reichert, W. M.; Nieuwenhuyzen, M.; Sheppard, O.; Hardacre, C.; Rogers, R. D. Chem. Commun. 2003, 476). In each case, the data was analyzed using an empirical potential structure refinement process.

Adsorption isotherm models for basic dye adsorption by peat in single and binary component systems

Coloured effluents from textile industries are a problem in many rivers and waterways. Prediction of adsorption capacities of dyes by adsorbents is important in design considerations. The sorption of three basic dyes, namely Basic Blue 3, Basic Yellow 21 and Basic Red 22, onto peat is reported. Equilibrium sorption isotherms have been measured for the three single component systems. Equilibrium was achieved after twenty-one days. The experimental isotherm data were analysed using Langmuir, Freundlich, Redlich-Peterson, Temkin and Toth isotherm equations. A detailed error analysis has been undertaken to investigate the effect of using different error criteria for the determination of the single component isotherm parameters and hence obtain the best isotherm and isotherm parameters which describe the adsorption process. The linear transform model provided the highest R2 regression coefficient with the Redlich-Peterson model. The Redlich-Peterson model also yielded the best fit to experimental data for all three dyes using the non-linear error functions. An extended Langmuir model has been used to predict the isotherm data for the binary systems using the single component data. The correlation between theoretical and experimental data had only limited success due to competitive and interactive effects between the dyes and the dye-surface interactions.

Liquid-liquid equilibria of ternary 2M1B/2M2B-2M1BOH-H2O and quaternary 2M1B-2M2B-2M1BOH-H2O mixtures

Liquid-liquid equilibria of two ternary mixtures 2M1B-2M1BOH-H[2]O] and 2M2B-2M1BOH-H[2]O were measured at 5, 15 and 25 C. UNIQUAC and NRTL models were fitted to the experimental data using ASPEN PLUS. Both experimental and correlated values of equilibrium compositions were compared with the values predicted by UNIFAC method. The same procedure was extended to the quaternary mixture 2M1B-2M2B-2M 1BOH-H[2]O. The regressed results were in good agreements with experimental data. Original UNIFAC model performed better representation than Dortmund UNIFAC model.

A possible model of benzimidazole binding to beta-tubulin disclosed by invoking an inter-domain movement.

Although it is well established that benzimidazole (BZMs) compounds exert their therapeutic effects through binding to helminth beta-tubulin and thus disrupting microtubule-based processes in the parasites, the precise location of the benzimidazole-binding site on the beta-tubulin molecule has yet to be determined. In the present study, we have used previous experimental data as cues to help identify this site. Firstly, benzimidazole resistance has been correlated with a phenylalanine-to-tyrosine substitution at position 200 of Haemonchus contortus beta-tubulin isotype-I. Secondly, site-directed mutagenesis studies, using fungi, have shown that other residues in this region of the protein can influence the interaction of benzimidazoles with beta-tubulin. However, the atomic structure of the alphabeta-tubulin dimer shows that residue 200 and the other implicated residues are buried within the protein. This poses the question: how might benzimidazoles interact with these apparently inaccessible residues? In the present study, we present a mechanism by which those residues generally believed to interact with benzimidazoles may become accessible to the drugs. Furthermore, by docking albendazole-sulphoxide into a modelled H. contortus beta-tubulin molecule we offer a structural explanation for how the mutation conferring benzimidazole resistance in nematodes may act, as well as a possible explanation for the species-specificity of benzimidazole anthelmintics.