Abstract
Photosynthetic oxygen evolution is carried out by machinery that is composed of four manganese ions. A molecular oxygen is produced by a series of reactions with five distinct intermediate state labeled S1 (i=0-4).
We have found a g=2 ESR signal with 200 G width in Ca2+-depleted photosystem (PS) II. The ESR signal was produced by illuminating the Ca2+-depleted PS II in S1 state at 245 K for a short period. By annealing the sample, the signal disappeared with trapped YZ radical signal, and S2 multiline signal appeared. We will discuss the origin of the g=2 broad signal in S1 state.
