From Förster resonance energy transfer to coherent resonance energy transfer and back

Abstract

Photosynthesis converts solar energy into chemical energy. It provides food and oxygen; and, in the future, it could directly provide bioenergy or renewable energy sources, such as bio-alcohol or hydrogen. To exploit such a highly efficient capture of energy requires an understanding of the fundamental physics. The process is initiated by photon absorption, followed by highly efficient and extremely rapid transfer and trapping of the excitation energy. We first review early fluorescence experiments on in vivo energy transfer, which were undertaken to understand the mechanism of such efficient energy capture. A historical synopsis is given of experiments and interpretations by others that dealt with the question of how energy is transferred from the original location of photon absorption in the photosynthetic antenna system into the reaction centers, where it is converted into useful chemical energy. We conclude by examining the physical basis of some current models concerning the roles of coherent excitons and incoherent hopping in the exceptionally efficient transfer of energy into the reaction center.

Chlorophyll a fluorescence induction: a personal perspective of the thermal phase, the J–I–P rise

“…The time dependence of the fluorescence yield depends on several processes including excitation energy transfer in the antenna complexes (fs-ps time domain) (Schatz et al 1987(Schatz et al , 1988Renger and Holzwarth 2005;Clegg et al 2010), and electron transfer reactions (ps-ms) (Crofts and Wraight 1983;Eaton-Rye and Govindjee 1988a, b;Leibl et al 1989;Steffen et al 2005;Kern and Renger 2007). Since the reduction of Q A after a saturating STF should be completed within 1 ns (Nuijs et al 1986;Eckert et al 1988), the maximum fluorescence yield should be observed instantaneously after the application of the actinic flash.…”

“…Depending on its protein environment, Chl a functions either as a light harvester, or as a redox participant in the primary charge separation in the reaction centers (RCs) of Photosystems II (PSII) and Photosystem I (PSI) (Clegg et al 2010;Renger 2010Renger , 2011. A small part of the light energy absorbed by Chl a is dissipated as heat (internal conversion), and as fluorescence (*2-10 %, Latimer et al 1956Latimer et al , 1957Trissl et al 1993).…”

Excitation energy transfer in intact cells and in the phycobiliprotein antennae of the chlorophyll d containing cyanobacterium Acaryochloris marina

“…The generated excited states are then funnelled by excitation energy transfer (EET) to the photosynthetic reaction centers (RCs) (Clegg et al, 2010) where they induce primary charge separation and secondary electron transfer. Eventually, this leads to oxidation of water and the formation of the energy rich compounds ATP and NADPH which are used in the Calvin cycle to synthesize the organic compounds that are the basis of all life on earth.…”

Conservation and dissipation of light energy in desiccation-tolerant photoautotrophs, two sides of the same coin

“…Light is harvested by the pigments of photosynthetic membranes. Excitation energy migrates within the pigment bed until it is trapped by the reaction centres where charge separation initiates photosynthetic energy conservation (Clegg et al 2010). In the reaction centres of photosystem II, an electron is donated from a chlorophyll molecule to a pheophytin molecule within a few picoseconds (Greenfield et al 1997;Holzwarth et al 2006).…”