Figure 5

Comparison of the kinetics of M formation and decay with kinetics of ET release and uptake. The time trace of the M-like intermediate was measured at 400 nm (upper panel). Time-resolved H⁺ concentration changes (lower panel) were measured with the pH indicator dye Cresol Red. A negative Cresol Red absorbance change at 580 nm is indicative of a transient decrease in the pH of the solution, i.e. of H⁺ release by pR. Solid lines represent multiexponential fits, with the main rise and decay times indicated for the M intermediate. The H⁺ release and uptake time constants obtained from the fit are marked with arrows pointing down for release and pointing up for uptake. Sample and excitation conditions are as in fig. 4.