Table 4. NBO Orbital Stabilization Results (from Perturbation Theory contributions) for the Interactions between O₂/O₃ and All of Its Interacting Residues for Each Protonation State^a.

protonation state	residue	oxygen interaction	NBO analysis (kcal mol–1)	percentage of total NBO orbital stabilization for the state	AVG MD distanceb (Å)	QM/MM distance (Å)	RMSFb (Å)
I	Arg285	O2	32.4	20%	2.21	1.65	0.83
I	H2O-1	O2	15.0	10%		1.81
I	Arg285	O3	38.7	23%	1.98	1.62	0.46
I	His298	O3	7.2	4%	2.75	1.96	0.65
II	Arg285	O2	24.8	16%	1.88	1.71	0.29
II	Ser62	O2	20.8	13%	3.84	2.73	1.07
II	His298	O2	3.8	2%	3.81	2.25	0.71
II	Arg285	O3	29.5	18%	3.29	1.70	0.67
II	His298	O3	1.3	1%	5.24	2.45	1.04
II	Thr299	O3	42.7	27%	1.74	1.61	0.15
III	Ser62	O2	28.8	20%	2.36	1.71	1.32
III	Tyr159	O2	26.7	18%	1.84	1.67	0.59
III	Arg285	O2			2.36	2.21	0.50
III	Arg285	O3	12.8	9%	2.59	3.18	0.71
III	Thr299	O3	29.2	20%	2.04	1.67	0.78
III	H2O-7	O3	20.0	14%		1.74
IV	Arg285	O2	23.9	13%	1.89	1.74	0.23
IV	His298	O2	4.4	2%	2.86	2.18	0.83
IV	Tyr159	O2	24.6	13%	4.07	2.62	0.99
IV	Arg285	O3	28.3	15%	2.68	1.72	0.46
IV	His298	O3	0.9	<1%	3.28	2.55	0.63
IV	Thr299	O3	39.0	21%	3.70	1.63	1.00
V	Arg285	O2	9.4	7%	3.28	1.73	2.31
V	Arg285	O3	14.8	11%	4.08	1.80	2.91
V	Thr299	O3	2.34	2%	5.48	2.33	3.22
V	H2O-10	O3	25.6	18%		1.64
V	H2O-11	O3	24.0	17%		1.66
VI	H2O-molecule	O2	21.1	11%		1.71
VI	H2O-molecule	O2	22.4	12%		1.68
VI	H2O-molecule	O2	29.7	16%		1.64
VI	H2O-molecule	O3	10.6	5%		1.75
VI	H2O-molecule	O3	21.9	12%		1.70
VI	H2O-molecule	O3	24.1	13%		1.60

^aAll values are in kcal mol^–1 (all interactions LP → σ*).

^bNot reported for H₂O molecules due to fluctuation throughout the MD simulation.