FIGURE 5.

Flash-induced absorption changes for P700⁺ reduction at 820 nm. A, decay kinetics of samples containing: 1) 1 μm P700-F_X cores, 20 μm apo-PsaC, 20 μm PsaD, 4 mm DTT, and 0.04% (w/v) DM; 2) 1 μm P700-F_X cores, 20 μm holo-PsaC, 4 mm DTT, and 0.04% (w/v) DM; 3) 1 μm P700-F_X cores, 42 μm holo-NfuA, 20 μm PsaD, 4 mm DTT, and 0.04% (w/v) DM; 4) 1 μm P700-F_X cores, 20 μm holo-PsaC, 20 μm PsaD, 4 mm DTT, and 0.04% (w/v) DM; 5) 1 μm P700-F_X cores, 42 μm holo-NfuA, 20 μm apo-PsaC, 20 μm PsaD, 4 mm DTT, and 0.04% (w/v) DM. After a 1-h incubation, 10 μm DCPIP and 10 mm ascorbate were added and flash-induced kinetics at 820 nm were measured. B, decay kinetics of samples containing: 1) 1 μm P700-F_X cores, 42 μm holo-NfuA that had been boiled for 1 min, 20 μm apo-PsaC, 20 μm PsaD, 4 mm DTT, and 0.04% (w/v) DM; and 2) 1 μm P700-F_X cores, 20 μm apo-PsaC, 20 μm PsaD, 4 mm DTT, and 0.04% (w/v) DM. Fe/S clusters were assembled by mixing 168 μm Fe²⁺ and 168 μm S^2- and 4 mm DTT. Prior to addition of these reagents to the solution containing apo-PsaC, the Fe/S reagents were boiled for 1 min. After a 1-h incubation, 10 μm DCPIP and 4 mm ascorbate were added and flash-induced kinetics at 820 nm were measured. The discontinuity in the noise level is a consequence of fusing two kinetic traces taken at different time bases on the same laser flash.