D2R (Rhodamine 110, bis-(L-aspartic acid amide), ditrifluoroacetic acid salt) is a general substrate for caspases including caspases 3 and 7. Unlike other fluorogenic substrates for caspases, D2R appears to be membrane-permeant, and thus can be used to measure caspase activity in live cells without osmotic shock for flow cytometry studies, as well as for cell extracts.