Table 4.

Relative Energy of Different Protonation States of BNC Cluster Residues in the Fully Oxidized BNC^a

state energy, pH 7 (ΔpK units)	OH− heme a3	OH− CuB	His I-334b	Tyr I-288	site pK′7c
neutral state
16.4	0	0	0	0
single anion
0	0	−1	0	0	−9.4
4.4	−1	0	0	0	−5.0
10.7	0	0	0	−1	1.3
11.7	0	0	−1	0	2.3
dianionic states
1.6	0	−1	0	−1
3.3	−1	0	−1	0
3.7	−1	−1	0	0
10.1	0	0	−1	−1

^aEnergies are relative to the state with a single OH⁻ on CuB (in bold). Ionization of all other key residues are given in Table 1.

^bUsing the model for His in complex with water–CuB with a pKa,sol of 9.0 (40).

^cpK′7 for groups assigned a −1 charge. This is different from that given in Table 2 since those are calculated with the ionization given in Table 1 while here the BNC residues are in the explicitly defined, nonequilibrium ionization states. 1 ΔpK unit is 1.36 kcal/mol.