4.9. DNA Fragmentation Assay

Cells were lysed on ice for 30 min in a buffer containing 5 mM Tris-HCl (pH 7.5), 5 mM EDTA, and 0.5% Triton X-100. The lysate was vortexed and then centrifuged at 27,000× g for 20 min. The fragmented DNA in the supernatant was RNase-treated and then treated with proteinase K to degrade any exogenous proteins. The DNA was then extracted with a phenol/chloroform/isoamyl alcohol mixture (25:24:1, v/v/v) and precipitated with isopropanol. DNA was separated from 1.6% agarose gel, stained with 0.1 μg/mL EtBr, and visualized with a UV light source.