Open AccessSubpicosecond equilibration of excitation energy in isolated photosystem II reaction centers.
Author(s) -
James R. Durrant,
Gary Hastings,
D. M. Joseph,
Jim Barber,
George Porter,
David R. Klug
Publication year - 1992
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.89.23.11632
Subject(s) - p680 , delocalized electron , excited state , chemistry , photochemistry , photosystem ii , electron transfer , photosynthetic reaction centre , femtosecond , ultrafast laser spectroscopy , excitation , spectroscopy , photosystem i , atomic physics , photosynthesis , physics , laser , biochemistry , organic chemistry , quantum mechanics , optics
Photosystem II reaction centers have been studied by femtosecond transient absorption spectroscopy. We demonstrate that it is possible to achieve good photoselectivity between the primary electron donor P680 and the majority of the accessory chlorins. Energy transfer can be observed in both directions between P680 and these accessory chlorins depending on which is initially excited. After excitation of either P680 or the other chlorins, the excitation energy is observed to equilibrate between the majority of these pigments at a rate of 100 +/- 50 fs-1. This energy-transfer equilibration takes place before any electron-transfer reactions and must therefore be taken into account in studies of primary electron-transfer reactions in photosystem II. We also show further evidence that the initially excited P680 excited singlet state is delocalized over at least two chlorins and that this delocalization lasts for at least 200 fs.