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Quantum effects in photosynthesis

Photosynthesis is a process that is vital to all life on earth, with a 3 billion year evolutionary history of plant life photosynthesising both on land and deep in the ocean. During photosynthesis, light coming from the sun is converted into usable chemical energy. Studying photosynthesis allows us to understand this incredibly important process in more detail, as well as potentially using mechanisms in futuristic solar cells.

Overview

Although the overall process of photosynthesis is fairly inefficient, with a practical maximal efficiency of light to energy conversion of 8-9%, the initial step of capturing a photon with a light harvesting molecule and the transportation to a reaction centre happens with an efficiency of near unity [1,2]. There has been speculation for many years that there are quantum effects present in photosynthesis, with the unexpectedly high photon capture efficiency quoted as a reason. Quantum coherence present in antenna complexes would allow for fast and efficient excitonic transport required for the observed efficiencies, due to a possible wavelike search of paths from the exciton location to the reaction centre [3].

Long-lived quantum coherence in photon transfer is supported by experimental observations such as the interference oscillatory signals present in ultrafast optical spectroscopy experiments carried out on the Fenna-Matthews-Olson (FMO) protein [4]. This view, however, faces continuous controversy and is challenged by other observations in which the oscillatory signals are not present leading to the proposal of alternative mechanisms of energy transfer. Investigating whether quantum mechanisms are involved in the initial photon capture by the antenna complex of different microorganisms apart from green-sulphur bacteria represents one of the methods that would contribute greatly for elucidating the phenomenon. 

Research team

University of Surrey

Jeremy Allam profile image

Professor Jeremy Allam

Professor of Ultrafast Optoelectronics

Youngchan Kim profile image

Dr Youngchan Kim

Lecturer in Quantum Biology

Johnjoe McFadden profile image

Professor Johnjoe McFadden

Professor of Molecular Genetics, Associate Dean (International)

Marco Sacchi profile image

Dr Marco Sacchi

Royal Society University Research Fellow

S. Ravi P. Silva profile image

Professor Ravi Silva

Director, Advanced Technology Institute (ATI) and Head of NanoElectronics Centre

External institutions

Jose Jimenez

Dr Jose Jimenez Zarco

Senior Lecturer in Synthetic Biology, Imperial College London

Placeholder image for external profile

Professor Alexandra Olaya-Castro

Professor of Physics, University College London

References 

[1] Bolton JR, Hall DO. The maximum efficiency of photosynthesis. Photochemistry and Photobiology. 1991 Apr;53(4):545-8.

[2] Panitchayangkoon G, Voronine DV, Abramavicius D, Caram JR, Lewis NH, Mukamel S, Engel GS. Direct evidence of quantum transport in photosynthetic light-harvesting complexes. Proceedings of the National Academy of Sciences. 2011 Dec 27;108(52):20908-12.

[3] Engel GS, Calhoun TR, Read EL, Ahn TK, Mančal T, Cheng YC, Blankenship RE, Fleming GR. Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems. Nature. 2007 Apr;446(7137):782.

[4] Cheng YC, Fleming GR. Dynamics of light harvesting in photosynthesis. Annual review of physical chemistry. 2009 May 5;60:241-62.

[5] Hunter CN, Daldal F, Thurnauer MC, Beatty JT, editors. The purple phototrophic bacteria. Springer Science & Business Media; 2008 Oct 11.

Fig. 1. Rhodopseudomonas acidophila strain 7050 growing in modified Pfenning agar.

Fig. 2. View looking down on the top (periplasmic surface) of the LH2 complex from Rhodopseudomonas acidophila strain 10050. Taken from [5].

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