EPR kinetic studies of the S-1 state in spinach thylakoids.

The Y(Z)* decay kinetics in a formal S(-1) state, regarded as a reduced state of the oxygen evolving complex, was determined using time-resolved EPR spectroscopy. This S(-1) state was generated by biochemical treatment of thylakoid membranes with hydrazine. The steady-state oxygen evolution of the sample was used to optimize the biochemical procedure for performing EPR experiments.