Maclura pomifera agglutinin or lectin (MPA/MPL) is tetrameric plant protein purified by fractionation. MPA has a molecular weight of about 44,000 and consists of four subunits. It has an isoelectric point between pH 4.8 and pH 5.3, and blood group specificity towards A, B, and O (-SA). This lectin has a high affinity for tumor-associated T-antigen disaccharide (GalÎ²1,3GalNAcÎ±) and many O-linked glycopeptide structures. The structure of GalÎ²1,3GalNAcÎ± occurs on the surface of tumor cells as a mucin-associated antigenic marker, termed as T-antigen. It is also the central element in O-linked glycopeptide structures on other mammalian glycoproteins.Maclura pomifera Lectin (MPL/MPA)Â is labeled with tetramethylrhodamine isothiocyanate (TRITC) and has an appropriate number of fluorochromes bound to provide the optimum staining characteristics for this lectin. TRITC is a bright orange or red-fluorescent dye with excitation ideally suited to the 532-nm laser line. TRITC labeled MPL/MPAÂ can be used for cellular imaging applications.