Table 1.

Measured rate constants for RCs in the presence and absence of metal ions (pH 8.0, T = 21°)

RCs178	kAD (s−1)	kBD (s−1)	kAB(1) (s−1)†	kAB(2) (s−1)
Native	8.8	0.8	7,000	1,200
Native + Zn2+	8.8	0.7	700	120
Native + Cd2+	9.0	0.8	700	60

Errors in the rates are estimated to be ∼8% for the charge recombination rate constants k_AD and k_BD and ∼15% for the forward electron transfer rate constants k_AB⁽¹⁾ and k_AB⁽²⁾ 

¹⁷⁸Conditions for kinetic measurements as described in Materials and Methods. The samples labeled Native + Zn²⁺ and Native + Cd²⁺ were measured in the presence of 10μM ZnSO₄ and CdSO₄, respectively. 

^†This is the observed rate constant using a single exponential fit to the data. This reaction can be better fitted with a sum of two exponentials (24), but the effect of the metal binding is clearly shown by using this simple analysis.