Yes, the majority of R&D Systems Caspase Inhibitors have a Fluoromethyl ketone (FMK) functional group on the C-terminus of the peptide, and act as effective irreversible inhibitors with no added cytotoxic effects. Inhibitors synthesized with a benzyloxycarbonyl group (also known as BOC or Z) at the N-terminus and O-methyl side chains exhibit enhanced cellular permeability.R&D Systems also offers a General Caspase Inhibitor, Q-VD-OPh, Catalog # OPH001, as well as a FITC-conjugated pan-caspase inhibitor (ApoStat), Catalog # FMK012, which are both cell-permeable, irreversible inhibitors of caspase activity.