Inhibition of pol β by “Met-Im” dTTP analogues. (A) Representative gels for inhibition by 1a. Aliquots were quenched at 5, 15, and 30 min, and the DNA was run on denaturing polyacrylamide gels to separate unextended from extended primer. The first lane corresponds to reaction without inhibitor. The final lane in each set is the reaction without dTTP, showing that the inhibitor is not incorporated into DNA by pol β. (B) Hyperbolic decay fits of data from inhibition reactions. Filled circles represent 1a, and open circles, 1b. Error bars represent σ for three independent experiments.