FIGURE 6.

Reduction kinetics of Na⁺-NQR by NADH in the presence of different cations. Time course at 450 nm showing the phases of reduction of the enzyme in the absence of cations (black line), or in the presence of 100 mm NaCl (black dotted line), 100 mm LiCl (gray dashed line), 100 mm KCl (black dashed line), or 100 mm RbCl (solid gray line). Inset shows the time course of the accumulation of the four-electron reduced enzyme (FADH₂-2Fe-2S_red-RibH₂), whose rate of appearance is dependent on sodium or lithium.