Table 1. Observed rate constants for 2- and 4-electron reduction of CPR monitored as a change in 600 nm absorbance (flavin reduction) and fluorescence emission of extrinsic fluorophores (domain motion).

Reduction Level of CPR	Observed Rate Constants and Enthalphy Changes for 2- and 4-Electron Reduction	Flavin Reduction	Domain Motion
2e−	k obs1 (s−1)a	16.2±0.2	24.5±1.0
	ΔH‡ 1 (kJ mol−1)	61.1±0.3	62.4±3.4
4e−	k obs2 (s−1)a	4.0±0.1	4.2±0.1
	ΔH‡ 2 (kJ mol−1)	64.1±0.2	67.6±2.8

^aMeasurement at 25°C.