Special considerations for glycoproteins and their purification.

This unit begins by describing some properties of glycoproteins (e.g., subcellular location and solubility) that may be useful in determining which purification techniques to try. This discussion is followed by two protocols describing preparative glycoprotein purification using lectin-affinity chromatography, as well as an outline for a small-scale pilot procedure designed to check lectin binding and elution conditions. Lectins are often used for purifying glycoproteins because, in contrast to conventional purification procedures (e.g., gel filtration and ion-exchange chromatography) that exploit general physical properties of glycoproteins, lectins recognize specific three-dimensional structures created by a cluster of sugar residues. Conventional purification procedures are generally tried before applying lectin-affinity chromatography.