Table 2. Charges of the Active Site Residues for Each Model System.

system	Cys647	Asp473	His471	Asp351
PS-I	0	–1	0	–1
PS-II	–1	0	0	–1
PS-III	–1	–1	+1	–1
PS-IV	–1	0	+1	–1
PS-V	0	–1	+1	–1