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. Cy5, when bound to Amaranthus caudatus Lectin (ACL/ACA), can show the binding pattern of this lectin in cellular imaging and flow cytometry. The excitation wavelength required for Cy5 to fluoresce is high enough to avoid overlap with most other fluorochromes, making it useful for dual-labeling experiments. Because of this high excitation, there is typically less background from autofluorescence of biological specimens.