Table 3. NBO Orbital Stabilization Results (from Perturbation Theory Contributions) for the Interactions between O₁ and All of Its Interacting Residues for Each Protonation State^a.

protonation state	residue	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	Thr301	15.8	9%	2.81	1.78	1.38
II	Ser62	3.1	2%	3.10	1.90	0.51
II	Thr301	12.3	8%	2.01	1.79	0.38
III	Ser62	1.8	1%	3.24	2.55	1.11
III	Thr301	12.6	9%	2.94	1.81	1.39
IV	Ser62	7.3	4%	4.28	1.97	0.64
IV	Thr301	11.8	6%	3.07	1.77	0.91
V	Thr301	16.0	11%	5.81	1.77	1.29
VI	Arg285	26.6	14%	4.20	1.69	1.22

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

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