Ianatul Khoiroh

Phase behavior and molecular dynamics simulation studies of new aqueous two-phase separation systems induced by HEPES buffer.

Here, for the first time, we show that with addition of a biological buffer, 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), into aqueous solutions of tetrahydrofuran (THF), 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone, the organic solvent can be excluded from water to form a new liquid phase. The phase diagrams have been determined at ambient temperature. In order to understand why and how a zwitterion solute (HEPES) induced phase separation of the investigated systems, molecular dynamics (MD) simulation studies are performed for HEPES + water + THF system. The MD simulations were conducted for the aqueous mixtures with 12 different compositions. The reliability of the simulation results of HEPES in pure water and beyond the phase separation mixtures was justified by comparing the densities obtained from MD with the experimental values. The simulation results of HEPES in pure THF and in a composition inside the phase separation region were justified qualitatively. Interestingly, all HEPES molecules entirely aggregated in pure THF. This reveals that HEPES is insoluble in pure THF, which is consistent with the experimental results. Even more interestingly, the MD simulation for the mixture with composition inside the phase separation region showed the formation of two phases. The THF molecules are squeezed out from the water network into a new liquid phase. The hydrogen bonds (HBs), HB lifetime, HB Gibbs energy (ΔG), radial distribution functions (RDFs), coordination numbers (CNs), electrostatic interactions, and the van der Waals interactions between the different species have been analyzed. Further, MD simulations for the other phase separation systems by choosing a composition inside the two liquids region for each system were also simulated. Our findings will therefore pave the way for designing new benign separation auxiliary agents.

Aqueous Two-Phase Flotation for the Recovery of Biomolecules

Aqueous two-phase flotation (ATPF), a novel technique which integrates the principles of aqueous two-phase systems and mass transfer mode of solvent sublation, has been successfully applied for the separation and purification of biological materials in the field of biotechnology. From the studies done so far, ATPF has demonstrated as an effective, economical and environment-friendly technique for separation of labile biomolecules from their crude aqueous extracts of natural plants or fermentation broths, under mild separation condition. In this article, the basic principles, experimental apparatus set up, key design variables of ATPF, ATPF applications and a comparative study between ATPF and other conventional methods are discussed. This review is intended to present a comprehensive summary on the research works carried out so far related to ATPF since its introduction in 2009 until present, which will be helpful for further research in ATPF.

Recent Advances in Protein Extraction Using Ionic Liquid-based Aqueous Two-phase Systems

Since its inception in 2003, ionic liquid (IL)-based aqueous two-phase system (ATPS) has been perceived to give a boost to the application of ATPS in protein separation. Given the green and tunable nature of ILs, the functionality of IL-ATPS can be well designed to suit the specificities required by the bioseparation field. Aside from the conventional imidazolium-based ILs, the types of IL investigated have also expanded to other families of cations (e.g., cholinium, ammonium, phosphonium and guanidinium) and benign anions (e.g., carboxylic acids, amino acids and biological buffers). This review aims to provide a comprehensive assessment of the recent literature targeting the applications of IL-ATPSs in the separation and purification of proteins. Different IL families were addressed in terms of their protein-compatibility, and the applicability of the IL-ATPS formed for the separation of a specific protein of interest. Additionally, the present review highlights the possible directions for future developments.

Isobaric vapor-liquid equilibrium of 2-propanone+2-butanol system at 101.325 kPa: Experimental and molecular dynamics simulation

Isobaric vapor-liquid equilibrium (VLE) data for binary mixtures of 2-propanone+2-butanol have been measured at 101.325 kPa. The measurements were in a modified recirculating type of Othmer equilibrium still. All the data passed the thermodynamics consistency test and no azeotropic behavior was exhibited. The experimental VLE data were correlated with the Wilson, non-random two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) activity coefficient models. The correlation results showed that the experimental data were well correlated with those models. The experimental data also showed slight deviations from the predicted results using UNIFAC and modified UNIFAC (Dortmund) models. To gain more insight into the nature of interactions between 2-propanone molecule and alcohol, we analyzed the hydrogen-bonds, the electrostatic (Coulomb) interactions, and the van der Waals (Lennard- Jones) interaction energies extracted from MD simulations. In addition, the structural property of liquid phase was characterized through radial distribution function (RDF) to establish favorable interactions between 2-propanone and 2-butanol in the mixture.