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- Title
Excitation transfer and trapping kinetics in plant photosystem I probed by two-dimensional electronic spectroscopy.
- Authors
Akhtar, Parveen; Zhang, Cheng; Liu, Zhengtang; Tan, Howe-Siang; Lambrev, Petar H.
- Abstract
Photosystem I is a robust and highly efficient biological solar engine. Its capacity to utilize virtually every absorbed photon's energy in a photochemical reaction generates great interest in the kinetics and mechanisms of excitation energy transfer and charge separation. In this work, we have employed room-temperature coherent two-dimensional electronic spectroscopy and time-resolved fluorescence spectroscopy to follow exciton equilibration and excitation trapping in intact Photosystem I complexes as well as core complexes isolated from Pisum sativum. We performed two-dimensional electronic spectroscopy measurements with low excitation pulse energies to record excited-state kinetics free from singlet-singlet annihilation. Global lifetime analysis resolved energy transfer and trapping lifetimes closely matches the time-correlated single-photon counting data. Exciton energy equilibration in the core antenna occurred on a timescale of 0.5 ps. We further observed spectral equilibration component in the core complex with a 3-4 ps lifetime between the bulk Chl states and a state absorbing at 700 nm. Trapping in the core complex occurred with a 20 ps lifetime, which in the supercomplex split into two lifetimes, 16 ps and 67-75 ps. The experimental data could be modelled with two alternative models resulting in equally good fits-a transfer-to-trap-limited model and a trap-limited model. However, the former model is only possible if the 3-4 ps component is ascribed to equilibration with a 'red' core antenna pool absorbing at 700 nm. Conversely, if these low-energy states are identified with the P reaction centre, the transfer-to-trap-model is ruled out in favour of a trap-limited model.
- Subjects
PHOTOSYSTEMS; LIGHT-harvesting complex (Photosynthesis); ENERGY transfer; FLUORESCENCE spectroscopy; PEA research; SINGLE photon generation
- Publication
Photosynthesis Research, 2018, Vol 135, Issue 1-3, p239
- ISSN
0166-8595
- Publication type
Article
- DOI
10.1007/s11120-017-0427-2