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

[摘要]

Flash-induced absorption changes in the UV have been monitored with nanosecond time resolution in oxygen-evolving photosystem II complexes from Synechococcus sp. 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⁻¹ at 260 nm. The observed kinetics for the oxidation of the donor is identical with the reduction kinetics of Chl-a ⁺ _II as monitored at 824 nm. At 320 nm, the reduction of Q_A was found to be faster than 1 ns.

[学科分类] 生物化学/生物物理

[关键词] Oxygen evolution;Photosystem II;P-680;Electron transfer;Absorbance difference spectroscopy;(Synechococcus sp.);Chl;chlorophyll;D;electron donor to Chl-a + II in O2-evolving PS II;FWHM;full width at half maximum;Mes;4-morpholineethanesulphonic acid;PS II;photosystem II;QA;primary quinone acceptor of PS II;S;water oxidizing enzyme system;Z;electron donor to Chl-a + II in PS II devoid of its O2-evolving capability