Table 2 pKa of the Mn4CaO5 cluster in water. Supplementary Table 2 for anti-ferromagnetic spin configuration.

From: pKa of the ligand water molecules in the oxygen-evolving Mn4CaO5 cluster in photosystem II

S state

Mn1, Mn2, Mn3, Mn4a

W1

W2

W3

W4

S0

III, IV, III, III

11.3

10.1

17.7

16.4

S0 [O4-H]b

III, IV, III, III

9.5

9.0

16.6

16.0

S0 [O5-H]c

III, IV, III, III

10.0

8.5

16.1

15.4

S1

III, IV, IV, III

10.2

9.0

15.6

15.1

S2 [open]d

III, IV, IV, IV

8.3

8.2

15.6

15.9

S2 [closed]e

IV, IV, IV, III

9.7

7.1

14.2

15.6

  1. aFerromagnetic spin configuration.
  2. bO4 is protonated.
  3. cO5 is protonated.
  4. dOpen-cubane structure.
  5. eClosed-cubane structure.
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