Wheat germ agglutinin (WGA) contains a group of closely related isolectins, with an isoelectric point about pH 9. The receptor sugar for WGA is N-acetylglucosamine, with preferential binding to dimers and trimers of this sugar. WGA can bind oligosaccharides containing terminal N-acetylglucosamine or chitobiose, structures which are common to many serum and membrane glycoproteins. Bacterial cell wall peptidoglycans, chitin, cartilage glycosaminoglycans, and glycolipids can also bind WGA. Native WGA has also been reported to interact with some glycoproteins via sialic acid residues (see succinylated WGA). This lectin is used for the purification of insulin receptors and for neuronal tracing. Rhodamine labeled WGA has an appropriate number of fluorochromes bound to provide the optimum staining characteristics for this lectin. This conjugate is supplied essentially free of unconjugated fluorochromes. The excitation maximum is at 550 nm and the emission maximum is at 575 nm.