Table 1. Spectroscopic and Electrochemical Data for the Ni–CODHs from Different Sources.

	A-cluster		B-cluster		C-cluster
	g-values (−CO)	E0′	g-values	E0′	g-values	E0′
R. rubrum(74,89)			2.04, 1.94, 1.89	–418	2.03, 1.88, 1.71	–110
					1.97, 1.87, 1.75
C. hydrogenoformans(88)			2.04, 1.93, 1.89		2.01, 1.89, 1.73
					1.96, ?, 1.77
M. thermoaceticum(79b)	2.08, 2.07, 2.03		2.04, 1.94, 1.90	–440	2.01, 1.81, 1.65	–220
	2.06, 2.05, 2.03	–530			1.97, 1.87, 1.75	–530
M. thermoaceticum with azide90					2.34, 2.07, 2.03
					2.34, 2.11, 2.04
M. barkeri(91)			2.05, 1.94, 1.90	–390	2.01, 1.91, 1.76	–35
					?, ?, 1.73
M. soehngenii(92)			2.05, 1.93, 1.86	–410	2.01, 1.89, 1.73	–230
M. thermophila(93)	2.06, 2.05, 2.03		2.04, 1.93, 1.89	–444	2.02, 1.87, 1.72	–154
					?, ?, 1.79