Affinity-purified Amaranthus caudatus (ACL/ACA) is a dimer glycoprotein made up of two subunits. ACL has preferential specificity to oliogsacharrides containing the galactosyl disacharride GalÎ²3GalNAc. ACL tolerates sialic acid substitution at the 3 position of galactose in the â€œTâ€ antigen. It does not have specificity for blood groups but does have a higher affinity for type O erythrocytes over B and A. Colloidal gold can be used to visualize localization of specific saccharide moieties and examine the distribution of plasma membrane glycoproteins based on the binding pattern of Amaranthus caudatus Lectin (ACL/ACA). Colloidal gold labeled lectins can be viewed via electron microscopy.