Hemoproteins Purification and Characterization by Using Aqueous Two-Phase Systems

There are many techniques that can be used to purify and characterize proteins, but one especially caught my attention about 10 years ago. Is it possible to purify a protein using just water? A smart trick that does the job is aqueous 2-phase extraction. In 1958, Albertsson (2 ) found that when 2 aqueous solutions of hydrophilic polymers such as polyethyleneglycol (PEG) and dextran (Dx) are mixed above critical concentrations, a liquid-liquid phase separation occurs. Moreover, when he added these 2 polymers to a disrupted cell broth, he found that proteins or enzymes and cell debris tend to partition unequally between the 2 phases or between the phases and the interface, thus allowing for the extraction of a particular protein. The high water content of these systems, which gives the technique its name, provides a gentle environment for biologically active proteins, cells, and cell organelles. Many proteins have been partitioned in aqueous 2-phase and 3-phase systems, and the subject has been described in several reviews (2 ,22 ,50 ,52 ,56 ). A comprehensive database containing all the publications in this topic since 1956 can be found in (http://bama.ua.edu/-rdrogers/aq2phase/ ). Detail recipes for most of the protocols used in different applications of aqueous 2-phase systems can be found in Reference 22 .