fluorescein 5-isothiocyanate2-(6-Hydroxy-3-oxo-(3H)-xanthen-9-yl)-5-isothiocyanatobenzoic acid3',6'-dihydroxy-5-isothiocyanatospiro(isobenzofuran-1(3H),9'-(9H)xanthen)-3-one5-FITC5-isothiocyanatofluoresceinF5ITCFITC isomer 1FITC-IFluorescein-5-isothiocyanatFluoreszein-5-isothiocyanatfluorescein isothiocyanate isomer 1fluorescein-5-isothiocyanate