Table 1.

Measured rate constants for native and mutant RCs in the presence and absence of Cd²⁺ (pH 7.7; 21°C)

RC*	kAD, s−1	kBD, s−1	kAB(1)† s−1	kAB(2), s−1
Native	8.8	0.8	7,000	1,200
DN(M17)	9.0	0.6	1,000	500
DN(L210)	8.9	1.0	900	600
Native + Cd2+	9.0	0.8	700	60
DN(M17) + Cd2+	8.9	0.8	300	8
DN(L210) + Cd2+	9.0	2.2	150	8

Errors (statistical) 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⁾. It should be noted that the forward rate constants are dependent on conditions, such as type and concentration of detergent, and can vary by factors of 2 between different measurement conditions. 

^*Conditions for kinetic measurements as described in the text. The samples labeled “+ Cd²⁺” were measured in the presence of 1 mM CdSO₄. 

^† The observed rate constant was obtained by using a single exponential fit to the data. A better fit can be obtained with a sum of two exponentials (23, 24), but we opted for the simple analysis, which shows all the salient features of the metal binding.