Caspase colorimetric substrate set

Assay Procedure:
1. Induce apoptosis in cells by desired method. Concurrently incubate a control culture without induction.
2. Count cells and pellet 1-5x10⁶ cells.
3. Resuspend cells in 50µl of chilled Cell Lysis Buffer and incubate cells on ice for 10 min.
4. Centrifuge for 1 min. in a microcentrifuge (10’000 x g).
5. Transfer supernatant to a fresh tube and assay protein concentration.
6. Dilute 50-200µg protein to 50µl Cell Lysis Buffer for each assay.
7. Add 50µl of 2x Reaction Buffer containing 10mM DTT to each sample.
8. Add 5µl of the 4mM pNA conjugated substrates (200µM final conc.) into each tube individually and incubate at 37°C for 1-2 hours.
9. Read samples at 400 or 405nm in a microtiter plate reader, or spectrophotometer using a 100 µl micro quartz cuvet, or dilute sample to 1ml with Dilution Buffer and using regular cuvet (Note: Dilution of the samples proportionally decreases the reading).
Fold-increase in caspase activity can be determined by comparing these results with the level of the uninduced control.
 Note: Background reading from cell lysates and buffers should be subtracted from the readings of both induced and the uninduced samples before calculating fold increase in caspase activity.