Purity >99% by HPLC. A synthetic peptide that irreversibly inhibits ICE (interleukin-1Beta converting enzyme, Ki = 0.76 nM) activity. YVAD is the preferred recognition sequence for ICE/caspase-1. The inhibitor is designed as a methyl ester to facilitate cell permeability. (CAUTION: If the intended use is on purified or recombinant enzymes, esterase should be added to generate free carboxyl groups).