The Apoptosis western blot cocktail (ab136812) is designed to study the induction of apoptosis in response to various stimuli. The two main components of this cocktail are monoclonal antibodies specific to caspase 3 and PARP. Caspase 3 is one of the executioner caspases activated by proteolytic cleavage during apoptosis. The rabbit caspase 3 antibody of this cocktail detects both the 32 kDa pro-caspase 3 as well as the p17 subunit of the active caspase 3 generated by cleavage of the pro-caspase 3 at Asp175. Thus the induction of apoptosis can be followed by a decrease of the pro-caspase 3 or by an increase of the p17 caspase 3. Monitoring the changes in the pro-caspase 3 is particularly advantageous, since the proportion of caspase activation can be determined from the reduction of the pro-form from analysis of control and stimulated samples. Poly [ADP-ribose] polymerase 1 (PARP) is a DNA repair enzyme that is cleaved during apoptosis by activated caspases. The mouse PARP antibody of this cocktail detects only the apoptosis-specific 89 kDa PARP fragment (cleaved-PARP). This antibody does not react with the full-length PARP. Combined, these two antibodies provide biomarkers of apoptosis. The rabbit muscle actin antibody is provided as a loading control for sample to sample normalization. Since the primary antibodies are both mouse and rabbit, the cocktail of HRP-conjugated goat anti-rabbit and anti-mouse secondary antibodies is provided for convenience. The targets are easily resolved by Western blot given their different molecular weights.