TABLE 5.

Structural parameters obtained by fitting the spectrum of the bacterial cyt bc₁ complex to additional clusters containing two His residues

Model	Ligand cluster n	Zn-N (Å)	Zn-O (Å)	β (°) His	γ (°) Asp/Glu	η (°) Gln/Asn	R (%)
a	2 His (2 Nɛ2)	2.05 (3)		115 (5)			10.6	7.4 (2.2)
	2 Asp/Glu m		2.11 (2)		124 (2)
	1 Gln/Asn		2.18 (5)			116 (4)
	n = 5
b	2 His (2 Nɛ2)	2.08 (3)		137 (7)			15.4	18.4 (5.5)
	1 Asp/Glu m		2.18 (8)		122 (4)
	1 Asp/Glu b		2.11 (7)		121 (4)
	n = 5
c	2 His (2 Nɛ2)	2.02 (3)		118 (4)			11.5	13.1 (3.8)
	2 Asp/Glu m		2.15 (3)		123 (1)
	2 H2O		2.09 (1)
	n = 6
d	2 His (2 Nɛ2)	2.05 (5)		134 (7)			11.8	12.8 (3.9)
	1 Asp/Glu m		2.19 (6)		123 (4)
	1 Asp/Glu b		2.16 (9)		126 (2)
	1 H2O		1.93 (7)
	n = 6
e	2 His (2 Nɛ2)	2.02 (3)		135 (6)			10.2	10.6 (3.3)
	1 Asp/Glu m		2.13 (10)		123 (11)
	1 Asp/Glu b		2.13 (9)		124 (2)
	1 Gln/Asn		2.13 (10)			116 (15)
	n = 6
f	2 His (2 Nɛ2)	2.07 (3)		135 (5)			23.6	37.9 (10.8)
	2 Asp/Glu b		2.14 (3)		122 (2)
	n = 6
g	2 His (2 Nɛ2)	2.09 (4)		135 (5)			17.8	34.2 (10.2)
	1 Asp/Glu b		2.25 (7)		124 (3)
	2H2O		2.11 (3)
	n = 6
h	2 His (2 Nɛ2)	2.06 (2)		137 (5)			11.7	13.2 (3.8)
	1 Asp/Glu m		2.28 (5)		118 (3)
	3 H2O		2.12 (2)
	n = 6

Symbols are as in Table 2. See text for details.