Figure 2.

Photoactivation of CP47RC dimers as measured by flash-induced oxygen evolution. (A) Solution contained 40 μM MnCl₂, 80 mM CaCl₂, protein equivalent to 10 μM RCs, and 0.8 mM ferricyanide. (B) As in A plus 1 mM DCBQ. Each trace represents illumination by 400 flashes of increasing duration and spaced by 3-s dark time. (I) First illumination, flash length increasing linearly from 5 ms to 205 ms (A) or from 5 ms to 405 ms (B). (II) Second illumination, flash length increasing linearly from 5 ms to 405 ms. The lag time parameter (t_lag) was determined by extrapolating the slope of the flash-induced yield to the baseline as indicated in the figure. The maximal oxygen yield refers to the value estimated at the end of the second cycle of illumination (i.e., with 405-ms flash length).