Table 2.

Redox potential of Phe a in the PS II core complex from Synechocystis sp. PCC 6803 and A. marina

Samples and conditions	Em, mV
Synechocystis
Control	−525 ± 3
CHES treatment	−594 ± 3
Restored after CHES treatment with Mn and HCO3−	−543 ± 4
NH2OH treatment	−609 ± 2
Restored after NH2OH treatment with Mn and HCO3−	−557 ± 3
Tris treatment	−580 ± 5
A. marina
Control (without Mn clusters)	−478 ± 4
Control (with Mn clusters)	−401 ± 5*

The redox state of Phe a was estimated by the absorption change either at 683 nm (Synechocystis) or at 452 nm (A. marina) (Materials and Methods).

*Represents a value estimated from the value for Synechocystis.