**4.1 General applications**

Currently, many proteins of pharmacological and industrial interest are obtained through highly optimized purification processes, typically consisting of two or three chromatographic separation stages. Usually these processes involve one or two IEC steps followed by a HIC step (Asenjo & Andrews, 2004). In addition, most recombinant proteins can be obtained at therapeutic grade of purity, by processes of the same structure (Asenjo & Andrews, 2008). Then, HIC often forms part of processes to yield a purified macromolecule of biomedical interest, such as therapeutic proteins (Seely & Richey, 2001), DNA vaccines (Diogo et al., 2000), and enzymes (Teng et al., 2010), among others. Besides, the use of HIC to purify protein complexes (McCue et al., 2008), as well as to study protein folding from a thermodynamic point of view (Geng & Wang, 2007), have been reported. Some applications of HIC for purifying enzymes and protein complexes, and to studying protein folding are described below.
