From curiosities to commodities: ionic liquids begin the transition.
Explore the source record for details and available documents.
Journal Article↗
Biomedical subjects
James H Davis
Publications and source records attributed to James H Davis.
Comparison of proto-oncogenic and mutant forms of the transmembrane region of the Neu receptor in TFE.
A single mutation within the transmembrane region of the Neu receptor (Val664-->Glu) is known to enhance tyrosine kinase activity, by promoting receptor dimerization. In order to gain insight into potential structural changes that arise as a result of the mutation, peptides corresponding to the complete transmembrane domain of proto-oncogenic and mutant forms of Neu have been studied by 1H nuclear magnetic resonance in the solvent trifluoroethanol (TFE). The chemical shifts are similar for both forms of the peptide, with the exception of amide residues close to the mutation site. Both peptides adopt a helical conformation, with a distinct bend one turn downstream of the mutation site. This deformation gives rise to several nuclear Overhauser effects, the majority of which were detected in both peptides, that are atypical for a straight canonical alpha-helix. Our data in this solvent do not support a conformational change in the transmembrane domain of monomeric Neu as a result of the mutation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicates that proto-oncogenic Neu peptides have a higher propensity to oligomerize in the solvent TFE than the Glu664 oncogenic form.
Amino Acid Substitution↗
15N,(1)H Heteronuclear correlation NMR of gramicidin A in DMPC-d(67).
We have studied gramicidin A, an environmentally sensitive polymorphic pentadecapeptide, fully 15N-labelled and dispersed in a highly deuterated phospholipid bilayer system. By submitting the sample to fast magic angle spinning, we were able to reduce the polypeptide amide hydrogen linewidths to 160 Hz, and hence to partially resolve them. By correlating these resonances with the 40 Hz wide dipolar coupled 15N in a 2D-CROPSY (cross-polarization spectroscopy) experiment, it was possible to observe the 20 partially overlapping 1H-15N signal pairs from the polypeptide backbone and sidechains. Both chemical shift distributions closely match those of the same peptide in SDS micelles, but only poorly match those of conformationally different gramicidin A in trifluoroethanol, dimethylsulfoxide, or methanol/chloroform mixture. Our results are indicative of the N-to-N right-handed beta6.3-helix conformation of gramicidin A and offer sufficient resolution to encourage development of experiments to measure orientational or distance restraints using through-space dipolar couplings.
Anti-Bacterial Agents↗
Task-specific ionic liquids incorporating novel cations for the coordination and extraction of Hg2+ and Cd2+: synthesis, characterization, and extraction studies.
A series of hydrophobic task-specific ionic liquids designed to extract Hg2+ and Cd2+ from water were prepared by appending urea-, thiourea-, and thioether-substituted alkyl groups to imidazoles and combining the resulting cationic species with PF6-. The new ionic liquids were characterized and investigated for their metal ion extraction capabilities. When used in liquid/liquid extraction of Hg2+ and Cd2+ from aqueous solutions, the metal ion distribution ratios increased several orders of magnitude, regardless of whether the ionic liquids were used as the sole extracting phase or doped into a series of [1-alkyl-3-methylimidazolium][PF6] (alkyl = n-C4-C8) ionic liquids to form a 1:1 solution. In the 1:1 mixtures, as the length of the alkyl chain increased from butyl to hexyl to octyl, the metal ion distribution ratios increased. Increasing the ratio TSIL/[C4mim][PF6] resulted in higher distribution ratios for both Hg2+ and Cd2+. Overall, the thiourea- and urea-derivatized cations yielded the highest distribution ratios, and those for Hg2+ were higher than those for Cd2+; however, a change in aqueous-phase pH does not promote the stripping of metal ions from the extracting phase. The combination of these imidazolium cations and PF6- produced ionic liquids with decreased thermal stability in comparison to [C(n)mim]-[PF6]. Gaussian98 restricted Hartree-Fock geometry optimizations for one of the thiourea-appended cations shows the charge delocalization around the ring and suggests that the thiourea group may aid in deprotonating the imidazolium ring and may be responsible for the lowered thermal stability of these cations.
Cadmium↗
Novel Brønsted acidic ionic liquids and their use as dual solvent-catalysts.
The reaction of triphenylphosphine or N-butylimidazole with cyclic sultones gives zwitterions that are subsequently converted into ionic liquids by reaction with trifluoromethane sulfonic acid or p-toluenesulfonic acid. The resulting ionic liquids have cations to which are tethered alkane sulfonic acid groups. These Brønsted acidic ionic liquids are useful solvent/catalysts for several organic reactions, including Fischer esterification, alcohol dehydrodimerization and the pinacol rearrangement. The new ionic liquids combine the low volatility and ease of separation from product normally associated with solid acid catalysts, with the higher activity and yields normally found using conventional liquid acids.
Journal Article↗
CO(2) capture by a task-specific ionic liquid.
Reaction of 1-butyl imidazole with 3-bromopropylamine hydrobromide, followed by workup and anion exchange, yields a new room temperature ionic liquid incorporating a cation with an appended amine group. The new ionic liquid reacts reversibly with CO2, reversibly sequestering the gas as a carbamate salt. The new ionic liquid, which can be repeatedly recycled in this role, is comparable in efficiency for CO2 capture to commercial amine sequestering reagents, and yet is nonvolatile and does not require water to function.
Journal Article↗