Fig. 2.

Effect of valinomycin and nigericin on NR color change. In the absence of ionophores, buildup of a transmembrane potential inhibits proton translocation. The ionophore valinomycin rapidly collapses the potential, allowing proton release that closely matches the kinetics of electron transfer. The pH gradient decays more slowly than Δψ and can lower the yield if flash groups are closely spaced (30 s here). Addition of nigericin at low concentration (0.1 μM) allows relaxation between groups of flashes to overcome that effect, to allow maximal yield. (Flashes indicated by arrows on time axis.)