Proton Equilibria in the Manganese Cluster of Photosystem II Control the Intensities of the S0 and S2 State g ~ 2 Electron Paramagnetic Resonance Signals
We have studied the pH effect on the S0 and S2 multiline electron paramagnetic resonance (EPR) signals from the water-oxidizing complex of photosystem II. Around pH 6, the maximum signal intensities were detected. On both the acidic and alkaline sides of pH 6, the intensities of the EPR signals decreased. Two pKs were determined for the S0 multiline signal; pK1 = 4.2 ± 0.2 and pK2 = 8.0 ± 0.1, and