Isolectin GS-IB4 is a 114,000-dalton glycoprotein that is part of a family of five tetrameric type I isolectins (IA4, IA3B, IA2B2, IAB3, and IB4) isolated from the seeds of the tropical African legume Griffonia simplicifolia. The A subunit prefers N-acetyl-D-galactosamine end groups while the B subunit is selective for terminal a-D-galactosyl residues. The red fluorescent Alexa Fluor™ 594 isolectin GS-IB4 conjugate can be used in fluorescence microscopy.