Griffonia simplicifolia lectin (GSL I) is affinity purified from a woody climbing shrub native to Africa. GSL I is composed of two types of subunits A and B that combine to form tetrameric structures, resulting in five isolectins. This lectin has affinity for terminal Î±-D-galactosyl residues and terminal N-acetyl-Î±-D-galactosaminyl residues. The A-rich lectin preferentially agglutinates blood group A erythrocytes and thus appears to be specific for Î±-N-acetylgalactosamine residues, while the B-rich lectin preferentially agglutinates blood group B cells and is specific for Î±-galactose residues. This lectin shows specificity for blood group B greater than blood group A1.GSL I has been reported to bind several glycoproteins including laminin. Since some Î±-D-galactosyl residues are expressed in endothelial cells of mouse tissues, GSL I can present a highly specific surface of glycosylation pattern in these cells.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. Griffonia simplicifolia Lectin (GSL I) is conjugated to HRP at an appropriate ratio to provide optimal staining characteristics.