Repair of N3-EtdT by Alkbh2in vitro.(a) A schematic diagram illustrating the repair of N3-EtdT by Alkbh2. (b,c) LC-MS for monitoring the products from the in vitro incubation reactions of a duplex DNA, that is, d(5′-ATGGCG(N3-EtdT)GCTAT-3′)/d(5′-TTATAGCACGCCATGG-3′) in the absence (b) or presence (c) of purified human Alkbh2 protein. Shown are the high-resolution “ultra zoom-scan” MS results for monitoring the [M-3H]3− ions of the initial 12mer N3-EtdT-bearing ODN (i.e., 12mer N3-EtdT) as well as its repaired product d(5′-ATGGCGTGCTAT-3′) (i.e., 12mer dT) and an intermediate product (i.e., 12merHO-N3-EtdT).