Excitation transfer and trapping kinetics in plant photosystem I probed by two-dimensional electronic spectroscopy

Parveen Akhtar, Cheng Zhang, Zhengtang Liu, Howe Siang Tan, Petar H. Lambrev

Research output: Contribution to journalArticle

6 Citations (Scopus)

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 P700 reaction centre, the transfer-to-trap-model is ruled out in favour of a trap-limited model.

Original languageEnglish
Pages (from-to)239-250
Number of pages12
JournalPhotosynthesis research
Volume135
Issue number1-3
DOIs
Publication statusPublished - Mar 1 2018

Keywords

  • Excitation energy transfer
  • Light harvesting
  • Light-harvesting complexes
  • Multidimensional spectroscopy
  • Ultrafast spectroscopy

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

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