Vibronic Wavepackets and Energy Transfer in Cryptophyte Light-Harvesting Complexes

Chanelle C. Jumper, Ivo H.M. Van Stokkum, Tihana Mirkovic, Gregory D. Scholes*

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

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Determining the key features of high-efficiency photosynthetic energy transfer remains an ongoing task. Recently, there has been evidence for the role of vibronic coherence in linking donor and acceptor states to redistribute oscillator strength for enhanced energy transfer. To gain further insights into the interplay between vibronic wavepackets and energy-transfer dynamics, we systematically compare four structurally related phycobiliproteins from cryptophyte algae by broad-band pump-probe spectroscopy and extend a parametric model based on global analysis to include vibrational wavepacket characterization. The four phycobiliproteins isolated from cryptophyte algae are two "open" structures and two "closed" structures. The closed structures exhibit strong exciton coupling in the central dimer. The dominant energy-transfer pathway occurs on the subpicosecond timescale across the largest energy gap in each of the proteins, from central to peripheral chromophores. All proteins exhibit a strong 1585 cm-1 coherent oscillation whose relative amplitude, a measure of vibronic intensity borrowing from resonance between donor and acceptor states, scales with both energy-transfer rates and damping rates. Central exciton splitting may aid in bringing the vibronically linked donor and acceptor states into better resonance resulting in the observed doubled rate in the closed structures. Several excited-state vibrational wavepackets persist on timescales relevant to energy transfer, highlighting the importance of further investigation of the interplay between electronic coupling and nuclear degrees of freedom in studies on high-efficiency photosynthesis.

Original languageEnglish
Pages (from-to)6328-6340
Number of pages13
JournalJournal of Physical Chemistry B
Issue number24
Early online date30 May 2018
Publication statusPublished - 21 Jun 2018


We thank Jacob Dean, Shahnawaz Rafiq, Rienk van Grondelle, and Pavel Malý for helpful discussions. G.D.S. acknowledges the Canadian Institute For Advanced Research (CIFAR). C.C.J. acknowledges funding for her doctoral studies from NSERC Canada Graduate Scholarships and the University of Toronto. I.H.M.v.S. acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no 654148 Laserlab-Europe. G.D.S. acknowledges the United States Air Force Office of Scientific Research (AFOSR) (FA9550-13-1-0005).

FundersFunder number
Air Force Office of Scientific ResearchFA9550-13-1-0005
Horizon 2020 Framework Programme654148
Natural Sciences and Engineering Research Council of Canada
University of Toronto


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