Figure 3.

Effect of Zn²⁺ binding on electron transfer k_AB⁽¹⁾ at pH 8.5, measured as the bandshift of the pheophytin cofactor at 750 nm. (A) Native RCs. (B) Glu-L212→Gln mutant RCs. Experimental conditions were as in Fig. 2. Note that the traces with and without Zn²⁺ overlap in B.