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. Horseradish peroxidase (HRP) is a 40 kDa protein that catalyzes the oxidation of substrates by hydrogen peroxide, resulting in a colored or fluorescent product or release of light as a byproduct of the reaction. It is most commonly used for blotting, immunoassays and immunohistochemistry methods. Amaranthus caudatus Lectin (ACL/ACA) is conjugated to HRP at an appropriate ratio to provide optimal staining characteristics.