TABLE 1.

Sulfide (S²⁻) and sulfur (S⁰) content of [4Fe-4S] FNR pre- and post-NO treatment

S²⁻ measurements were made by the method of Beinert (45).

Sample	Concentration	Before treatment with NO			After treatment with NO (∼530 μm)a
		[4Fe-4S]	S2−	S2−/[4Fe-4S]	S2−	S2−/[4Fe-4S]	S0	S0/[4Fe-4S]
	μm	μm	μm		μm		μm
1	37	33	134 (± 7)	4.0 (± 0.2)	7.6 (± 0.5)	0.23 (± 0.01)	76 (± 2)	2.3 (± 0.1)
2	39	35	139 (± 7)	4.0 (± 0.2)	24.5 (± 1.2)	0.70 (± 0.04)	50 (± 7)	1.4 (± 0.2)
3b	26	23	92 (± 5)	4.0 (± 0.2)	17.6 (± 0.2)	0.77 (± 0.10)	43 (± 10)	1.9 (± 0.4)

^a Samples had a final [NO]:[4Fe-4S] ratio of ∼15.

^b Low molecular weight reactants and products were removed via gel filtration (PD10, GE Healthcare).