Direct observation of the immediate electron donor to chlorophyll‐a+II(P‐680+) in oxygen‐evolving photosystem II complexes Resolution of nanosecond kinetics in the UV

Flash‐induced absorption changes in the UV have been monitored with nanosecond time resolution in oxygen‐evolving photosystem II complexes fromSynechococcussp. At 260 nm, the oxidation of the immediate donor to Chl‐a+II(P‐680+) in the 10–500 ns range could be observed directly. The difference extinction coefficient for its oxidation is estimated to be 6000–8000 M−1·cm−1at 260 nm. The observed kinetics for the oxidation of the donor is identical with the reduction kinetics of Chl‐a+IIas monitored at 824 nm. At 320 nm, the reduction of QAwas found to be faster than 1 ns.