During apoptosis, beta actin is cleaved by activated caspase 3 between Asp244 and Gly245. This cleavage results in the release of an approximately 130 amino acid (15 kDa) fragment from the C-terminus of beta actin and a 32 kDa (244 amino acid) N-terminal fragment of actin, known as fractin. The C -terminus of the fractin fragment represents an apoptosis-specific neoepitope that is not antigenic in native full-length beta actin and therefore presents a novel and specific marker for distinguishing apoptotic from necrotic cells.