MMC interstrand crosslink DNA adduct was prepared using a protocol similar to intrastrand crosslinking, except the incubation was performed in a closed lid PCR tube, and a total of 60 µmol of Na2S2O4 was added in five portions of 12 µmol at a five-minute interval. MMC-treated DNA was purified by using 1.8x Ampure XP beads and eluted in 20 µl 10 mM Tris-HCl, pH 8.0.                