Primary photochemistry of iron-depleted and zinc-reconstituted reaction centers from Rhodopseudomonas sphaeroides
Authors:
- 1 September 1986
- journal article
- research article
- Published by National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 83 (17) , 6407-6411
Abstract
The primary photochemistry of Fe-depleted and Zn-reconstituted reaction centers from Rhodopseudomonas sphaeroides R-26.1 was studied by transient absorption spectroscopy and compared with native, Fe 2+ -containing reaction centers. Excitation of metal-free reaction centers with 30-ps flashes produced the initial charge-separated state P + I - (P + BPh - , where P is the primary donor and BPh is bacteriopheophytin) with a yield and visible/near-infrared absorption difference spectrum indistinguishable from that observed in native reaction centers. However, the lifetime of P + I - was found to increase approximately 20-fold to 4.2 ± 0.3 ns (compared to 205 ps in native reaction centers), and the yield of formation of the subsequent state P + Q A - (Q A is the primary quinone acceptor) was reduced to 47 ± 5% (compared to essentially 100% in native reaction centers). The remaining 53% of the metal-free reaction centers were found to undergo charge recombination during the P + I - lifetime to yield both the ground state (28 ± 5%) and the triplet state P R (25 ± 5%). Reconstitution of Fe-depleted reaction centers with Zn 2+ restored the “native” photochemistry. Possible mechanisms responsible for the reduced decay rate of P + I - in metal-free reaction centers are discussed.Keywords
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