Kinetics of phyllosemiquinone oxidation in the Photosystem I reaction centre of Acaryochloris marina.
Light-induced electron transfer reactions in the chlorophyll a/d-binding Photosystem I reaction centre of Acaryochloris marina were investigated in whole cells by pump-probe optical spectroscopy with a temporal resolution of ~5ns at room temperature. It is shown that phyllosemiquinone, the secondary electron transfer acceptor anion, is oxidised with bi-phasic kinetics characterised by lifetimes of 88±6ns and 345±10ns. These lifetimes, particularly the former, are significantly slower than those reported for chlorophyll a-binding Photosystem I, which typically range in the 5-30ns and 200-300ns intervals. The possible mechanism of electron transfer reactions in the chlorophyll a/d-binding Photosystem I and the slower oxidation kinetics of the secondary acceptors are discussed.
Institute de Biologie Physico-Chimique, Paris, France. stefano.santabarbara@cnr.it
Stefano
S
Santabarbara
Benjamin
B
Bailleul
Kevin
K
Redding
James
J
Barber
Fabrice
F
Rappaport
Alison
A
Telfer
D016227:Benzoquinones / Q000378:metabolism*; D000458:Cyanobacteria / Q000737:chemistry / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D007700:Kinetics; D010084:Oxidation-Reduction; D045331:Photosystem I Protein Complex / Q000737:chemistry* / Q000378:metabolism*; D059748:Proteolysis; D013057:Spectrum Analysis; D046939:Synechocystis / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D013997:Time Factors; D010837:Vitamin K 1 / Q000737:chemistry / Q000378:metabolism*
D016227:Benzoquinones; D045331:Photosystem I Protein Complex; C025232:semiquinone radicals; D010837:Vitamin K 1