(Z-DEVD)₂-R110, highly sensitive, photostable fluorogenic substrate for the determination of intracellular caspase-3 activity. The fluorophore Rhodamine 110 (R110) can be detected at an emission wavelength of 535 nm using an excitation wavelength of 485 nm. As with (H-Asp-Glu-Val-Asp)₂-Rhodamine 110 (M-2620) the fluorescence intensity can be measured by flow cytometry, microwell plate reader, or fluorescence microscopy.