DNP-INT is a quinone analog that inhibits electron transport in plants by competitively inhibiting plastoquinol oxidation by binding at the Qo site of cytochrome b6f (Kd = 1.4 nM).1 It inhibits electron flow from water to NADP or methylviologen by 50 and 100% when used at concentrations of 0.5 or 5 μM, respectively.2,3