Aqueous Micellar Two-Phase Systems for Protein Separation

Abstract

The extractive technique for protein purification based on two-phase separation in aqueous micellar solutions (aqueous micellar two-phase system (AMTPS)) is reviewed. The micellar solution of a nonionic surfactant, such as polyoxyethylene alkyl ether, which is most frequently used for protein extraction, separates into two phases upon heating above its cloud point. The two phases consist of a surfactant-depleted phase (aqueous phase) and a surfactant-rich phase. Hydrophilic proteins are partitioned to the aqueous phase and hydrophobic membrane proteins are extracted into the surfactant-rich phase. Because of the methodological simplicity and rapidity, this technique has become an effective means, and thus has been widely used for the purification and characterization of proteins. In contrast to polyoxyethylene alkyl ether, micellar solutions of a zwitterionic surfactant, such as alkylammoniopropyl sulfate, separate below the critical temperature. Alkylglucosides can also separate into two phases upon adding water-soluble polymers. Recently, these twophase systems have been exploited for protein separation. Additionally, hydrophobic affinity ligands, charged polymers, and ionic surfactants have been successfully used for controlling the extractability of proteins in AMTPS.

Pyruvate:Quinone Oxidoreductase from Corynebacterium glutamicum : Purification and Biochemical Characterization

“…Phosphatidylglycerol and the fatty acids palmitic and oleic acid were found to be the main constituents of the C. glutamicum membrane (31), and thus it seems reasonable to assume that the pyruvate:quinone oxidoreductase enzyme is much more active when in contact with the inner surface of the corynebacterial membrane than when located within the cytoplasm. Third, similar to the case with other membrane proteins (7,62), the C. glutamicum pyruvate:quinone oxidoreductase was found to bind to the detergent Triton X-114. The binding to Triton X-114 was completely reversible and dependent on the presence of the substrate pyruvate and the cofactors TPP and Mg 2ϩ .…”

Plant Extraction with Aqueous Two‐Phase Systems

“…In particular, nonionic surfactants in high concentration can form a two-phase system in aqueous environment. Increasing the surfactant concentration in an aqueous solution above the critical micelle concentration (CMC) will lead to ball-like micelle formation [18]. By heating mixtures up above a certain temperature, which is defined as the cloud point (CP), separation into two phases is forced.…”

“…Aqueous two-phase extraction has already been successfully used with downstream processing in the field of biotechnology [23], as well as for the extraction of enzymes, proteins, and other biological products [18,[24][25][26][27]. Since many of these nonionic surfactants as, e.g., lecithine have the advantage that they are admitted for food, cosmetic, and pharmaceutical areas, it is not always necessary to elaborate separation techniques for the back-extraction of the target substances.…”

Alternating Current Cloud Point Extraction on a Microfluidic Chip: the Use of Ferrocenyl Surfactants

“…[6][7][8][9] ACPE is based on the principle of cloud point extraction (CPE). 10 In CPE, a test solution containing membrane proteins solubilized in nonionic surfactant micelles is initially heated above its cloud point. The solution is separated into a surfactant-poor phase and a surfactant-rich phase, the latter containing membrane proteins solubilized in the micelles.…”