abstract
A long-standing problem in enzymatic catalysis in organic media is finding a buffer that keeps a constant pH, as there are no commercially available biological buffers for such media. The biological buffers such as Good's buffers that are commonly used in aqueous media are insoluble in almost all organic solvents, and there is nowadays a pressing need for a buffer for organic media. Good's buffers were designed based on sets of criteria which make them extensively used in biochemical and biological research. In this context, we show that when Good's buffers turned into ionic liquids, so-called Good's buffer ionic liquids (GB-ILs), they became highly soluble in polar organic media, such as methanol and ethanol. This implies that a huge number of organo-soluble buffers are expected to be commercially available for such solvents. Twenty five GB-ILs (tetramethylaminonium, tetraethylammonium, tetrabutylammonium, 1-ethyl-3-methy limidazolium, and choline salts of Tricine, TES, MES, HEPES, and CHES) were tested as organic-phase buffers for pure methanol, and their buffer capacities in methanol were found to be very closet) that in water. A series of mixed GB-ILs was also formulated as universal buffers in methanol. Conductor-like screening model for real solvents (COSMO-RS) calculations were performed to show why GB-ILs gained high solubility in methanol. (C) 2016 Elsevier B.V. All rights reserved.
keywords
HYDROGEN-ION BUFFERS; ACID-BASE BUFFERS; NONAQUEOUS BIOCATALYSIS; CATALYTIC-ACTIVITY; ACID/BASE BUFFERS; LIQUIDS; SOLVENTS; WATER; PH; ENZYME
subject category
Chemistry; Physics
authors
Taha, M; Coutinho, JAP
our authors
Mohamed Taha Ahmed Amin
Post-doc Fellowshipacknowledgements
This work was financed by national funding from Fundacao para a Ciencia e a Tecnologia (FCT, Portugal), European Union, QREN, FEDER and COMPETE for funding the CICECO (project PEst-C/CTM/LA0011/2013), QOPNA (project PEst-C/QUI/UI0062/2013) and LSRE/LCM (project PEst-C/EQB/LA0020/2013). M. Taha acknowledges FCT for the postdoctoral grants SFRH/BPD/78441/2011.