4',5'-Bis(1,3,2-dithiarsolan-2-yl)-3',6'-dihydroxy-3-oxospiro[isobenzofuran-1(3H),9'-[9H]xanthene]-5-carboxylic Acid, is a biarsenical multi-use affinity probe with low non-specific fluorescence. It can be used for site-specific fluorescent labeling of recombinant proteins in living cells.
