Details of the DFT models.

Model	DFT active site residues	Starting proton position	System net charge	Multiplicity	Final His157 state
Superoxo, His157 NE2-protonated	His1, His84, His157, Gln166, Tyr168	His157 NE2	+1	Triplet	His157 singly NE2-protonated
Hydroperoxyl radical, His157 doubly deprotonated	His1, His84, His157, Gln166, Tyr168	O–O–H	+1	Triplet	Double deprotonated His157
Hydroperoxo, His157 doubly deprotonated	His1, His84, His157, Gln166, Tyr168	O–O–H	0	Doublet	Double deprotonated His157
Hydroperoxo, His157 doubly deprotonated	His1, His84, His157, Gln166, Tyr168	O–O–H	−1	Singlet	Double deprotonated His157