The molecule is the 5-isomer of fluorescein isothiocyanate. Acts as a fluorescent probe capable of being conjugated to tissue and proteins; used as a label in fluorescent antibody staining procedures as well as protein- and amino acid-binding techniques.
3',6'-dihydroxy-6-isothiocyanatospiro[2-benzofuran-3,9'-xanthene]-1-one