Proteins in Ionic Liquids: Reactions, Applications, and Futures

Biopolymer processing and handling is greatly facilitated by the use of ionic liquids, given the increased solubility, and in some cases, structural stability imparted to these molecules. Focussing on proteins, we highlight here not just the key drivers behind protein-ionic liquid interactions that facilitate these functionalities, but address relevant current and potential applications of protein-ionic liquid interactions, including areas of future interest

Proteins in Ionic Liquids: Reactions, Applications and Futures

Biopolymer processing and handling is greatly facilitated by the use of ionic liquids, given the increased solubility, and in somecases, structural stability imparted to these molecules. Focussing on proteins, we highlight here not just the key drivers behind protein-ionic liquid interactions that facilitate these functionalities, but address relevant current and potential applications of protein-ionic liquid interactions, including areas of future interest

Controlling the outcome of SN2 reactions in ionic liquids: from rational data set design to predictive linear regression models

Rate constants for a bimolecular nucleophilic substitution (SN2) process in a range of ionic liquids are correlated with calculated parameters associated with the charge localisation on the cation of the ionic liquid (including the molecular electrostatic potential). Simple linear regression models proved effective, though the interdependency of the descriptors needs to be taken into account when considering generality. A series of ionic liquids were then prepared and evaluated as solvents for the same process; this data set was rationally chosen to incorporate homologous series (to evaluate systematic variation) and functionalities not available in the original data set. These new data were used to evaluate and refine the original models, which were expanded to include simple artificial neural networks. Along with showing the importance of an appropriate data set and the perils of overfitting, the work demonstrates that such models can be used to reliably predict ionic liquid solvent effects on an organic process, within the limits of the data set

parameter and coordinate files to start an MD simulation of Haloferax volcanii ADH2

<p>parameter and coordinate files to start an MD simulation of Haloferax volcanii ADH2 in Amber</p>halophilic proteins ionic liquid

Ion-combination specific effects driving enzymatic activity of halophilic Alcohol Dehydrogenase 2 from Haloferax volcanii in aqueous ionic liquid solvent mixtures

Biocatalysis in ionic liquids enables novel routes for bioprocessing. Enzymes derived from extremophiles promise greater stability and activity under ionic liquid (IL) influence. Here, we probe the enzyme Alcohol Dehydrogenase 2 from the halophilic archaeon Haloferax volcanii in thirteen different ion combinations for relative specific activity and analyse the results against MD simulations of the same IL systems. We probe the ionic liquid property space based on ion polarizability and molecular electrostatic potential. Using radial distribution functions, survival probabilities and spatial distribution functions of ions we show that cooperative ion-ion interactions determine ion-protein interaction, specifically, strong ion-ion interactions equate to higher enzymatic activity if neither of the ions interact strongly with the protein surface. We further demonstrate a tendency for ions interacting with the protein surface to be least detrimental to enzymatic activity if they show a low polarizability and a small range of molecular electrostatic potential. We also find that the IL ion influence is not mitigated by the surplus of negatively charged residues of the halophilic enzyme. This is shown by free energy landscape analysis in root mean square deviation and distance variation plots of active site gating residues (Trp43 and His273) demonstrating no protection of specific structural elements relevant to preserving enzymatic activity. On the other hand, we observe a general effect across all IL systems that a tight binding of water at acidic residues is preferentially interrupted at these residues through the increased presence of potassium ions. Overall, this study demonstrates a co-ion interaction dependent influence on allosteric surface residues controlling the active/inactive conformation of halophilic Alcohol Dehydrogenase 2 and the necessity to engineer ionic liquid systems for enzymes that rely on the integrity of functional surface residues regardless of their halophilicity or thermophilicity for use in bioprocessing

Target and identify:triazene linker helps identify azidation sites of labelled proteins via click and cleave strategy

A method for identifying probe modification of proteins via tandem mass spectrometry was developed. Azide bearing molecules are immobilized on functionalised sepharose beads via copper catalysed Huisgen-type click chemistry and selectively released under acidic conditions by chemical cleavage of the triazene linkage. We applied this method to identify the modification site of targeted-diazotransfer on BirA