Protein conjugates purification and characterization

Abstract

Methods for separation and characterization of PEGylated proteins are reviewed in this chapter. It is explained that these methods are challenging because PEG itself is a relatively inert, neutral, hydrophilic polymer and the starting point for PEGylation is a pure protein. Other than changes to molecular weight and size, differences between the properties of the PEGylated forms of a pure pro- tein are relatively small, since they arise only from the addition to the protein of relatively inert, neu- tral polymer chains, which tend to shield interactions. Physicochemical properties that are routinely used to characterize and purify proteins are discussed with regard to their applications for PEGylated proteins, including molecular mass, size and shape (mass spectrometry, size exclusion chromatography, membranes, capillary electrophoresis, gel elec- trophoresis), electrostatic charge (cation and anion exchange chromatography, isoelectric point gel electrophoresis, capillary electrophoresis) and relative hydrophobicity (hydrophobic interaction, reversed phase).