Crossed immunoaffinoelectrophoresis

The crossed immunoaffinoelectrophoresis technique (CIAE) combines the principle of biospecific interaction with the principle of identification of proteins by immunoprecipitation in CIE. Biospecific interaction of macro-molecular components during electrophoresis was first described by Nakamura et al. (1). Lectins, or plant agglutinins, are proteins that react with carbohydrate groups with high specificity. Very rapidly, a combination of CIE and affinity electrophoresis with lectins was developed for identification and characterization of glycoproteins. Among the lectins, concanavalin A (Con A) is the most commonly used. Originally, Con A was introduced into an intermediate gel as immobilized Con A bound to Sepharose or free Con A (2). Glycoproteins can be partially characterized with respect to the number of lectin binding sites per molecule (e.g., ref. 3). Bøg-Hansen et al. (4) modified the procedure by introducing the lectin into the first dimension gel. Con A is electrophoretically immobile under the experimental conditions used for CIAE. The procedure can be used with other lectins, but their electrophoretic mobility must be checked beforehand. This procedure allows detection and separation of microheterogeneous forms of a glycoprotein. The degree of retardation during the first dimension electrophoresis in the gel with lectin is an expression of the affinity between the glycoprotein and the lectin. Higher affinity means stronger binding, which in turn means a higher degree of retardation.