Table 1.

Calculated and experimental rate constants and equilibrium constant for the diffusion of diatomic gases into and from the active site of studied H-NOXs. Number of global in-and-out events ($№{\mathrm{i}}_{\mathrm{i}\mathrm{n}-\mathrm{o}\mathrm{u}\mathrm{t}})$. The trajectory length used for the simulation and the time that the ligands spent in the distal pocket are given in ns. For comparison, previous results for myoglobin are also added.

Ligand	$№{\mathbf{i}}_{\mathbf{i}\mathbf{n}-\mathbf{o}\mathbf{u}\mathbf{t}}\mathit{s}$	Simulation Time (ns)	Ligand in “Geminate Pair” State [ns]	k1 (M−1 s−1)	k−1 (s−1)	K(k1/k−1) (M−1)	Exp. kon (M−1 s−1)	Exp. koff (s−1)
Ns H-NOX
O2	83	300	91	1.6 × 109	9.1 × 108	1.8	N/A	N/A
NO	34	300	55.8	6.5 × 108	6.0 × 108	1.1	3 × 108 [9]	5 × 10−2
CO	14	300	16.4	2.7 × 108	8.5 × 108	0.3	3 × 106 [9]	3.6
NO/O2 mixture
O2	23	200	15.17	1.3 × 109	1.5 × 109	0.86
NO	9	200	12.1	5.1 × 108	7.5 × 108	0.68
Ka H-NOX
O2	57	300	21.3	1.1 × 109	2.7 × 109	0.4	N/A	N/A
NO	33	300	60.2	6.4 × 108	5.5 × 108	1.2	N/A	N/A
CO	7	300	0.27	1.4 × 108	2.6 × 1010	0.0052	N/A	N/A
NO/O2 mixture
O2	37	200	19	2.1 × 109	2.0 × 109	1.1	N/A	N/A
NO	10	200	7.8	2.6 × 108	1.3 × 109	0.2	N/A	N/A
Cs H-NOX
O2	7	200	63.7	2.6 × 108	1.1 × 108	2.4	4.3 × 107	1.9
NO	1	200	1.42	3.8 × 107	7.1 × 108	0.053	1.5 × 108	3.4 × 10−3
CO	-	-		-	-	-	3.3 × 106	0.5
myoglobin (calculated data from ref. [22])
O2 [34]	N/A	N/A		N/A	N/A		1.7 × 107	15
NO [35]	15	300		1.8 × 108	8 × 107		1.7 × 107	1.2 × 10−4
CO [34]	21	635		1.1 × 108	2.5 × 108		5.1 × 105	1.9 × 10−2