Affinity purified Vicia villosa lectin or agglutinin (VVL/VVA) is a tetramer composed of four subunits. VVL consists of A and B subunits, with a dominant isolectin that appears to be B subunit-rich. A4 isolectin agglutinates specifically A1 erythrocytes. B4 isolectin does not agglutinate A, B, or O-erythrocytes; however, B4 binds the Tn antigen, a molecule expressed on the surface of most tumor cells. A2B2 and similar tetramer isolectins display properties characteristic of both A4 and B4 isolections.Biotin is a small molecule involved in a wide range of metabolic processes. This ligand forms a complex with Avidin and Streptavidin, resulting in the strongest non-covalent protein-ligand interaction known. Biotinylated Vicia villosa Lectin (VVL/VVA) has an appropriate amount of biotin bound to provide optimum detection characteristics when using an Avidin-HRP or Streptavidin-HRP conjugate. Biotinylated lectins allow for more sensitive detection in ELISA and Western-blotting applications.