Bio-inspired oxygen evolving light driven catalysts (BOLDCATS)

Lead Research Organisation: University of Glasgow
Department Name: College of Medical, Veterinary &Life Sci

Abstract

The major challenge in the area of renewable energy is devise sustainable ways of making fuels, preferably dense portable fuels that can be used for applications such as aviation. There is one major biochemical/chemical process on Earth that can use solar energy to make fuels and this is photosynthesis. The problem, however, of using photosynthesis (P/S) directly to make fuels (biofuels) is the rather low efficiency of conversion of solar energy into fuel. However, if it were possible to 'tap into' P/S at the level of the primary reactions then, in principle, higher energy conversion efficiencies are possible. This is the idea behind the drive for artificial photosynthesis using a strategy that breaks it down into 4 partial reactions. Worldwide there has been a lot of work designed to understand the molecular details of these key four steps in photosynthesis . There has been excellent progress in understanding steps 1 and 2, indeed there are now many artificial reaction centre and antenna mimics that function rather well. The major barriers to building systems capable of using solar energy to make fuels are our current inability to produce robust catalysts that can split water and use the reductant produced to synthesise a fuel. The main aims of this proposal are to work towards the production of novel devices that can overcome these barriers.

Technical Summary

In this CRP we aim to develop novel light-driven water splitting devices capable of providing reducing equivalents for the reduction of carbon dioxide into formate as the first step towards producing a fuel. We will focus on comparing the use of PS1 and PS2 isolated from the thermophilic cyanobacterium Thermosynechococcus elongatus with that of inorganic bio-mimetic analogues. The biological samples provide functioning modules that will be used to develop working systems while the more robust chemical analogues are being designed and synthesised. One side of the cell uses light to split water (PS2) the other uses PS1 and light to reduce CO2 to formate that can later be converted into methanol. In this context the production of formate is just an exemplar for being able to demonstrate light-driven reduction of carbon dioxide. The two sides of the cell are separated so that the PS1 side can be kept anaerobic since formate dehydrogenase is oxygen sensitive. Formate dehydrogenase (FDH) from Syntrophobacter fumaroxidans has been shown to be functional when coupled to a patterned glass electrode system.

Planned Impact

nsuring a stable energy supply is the central challenge of the 21st century, and this team will highlight the importance of the problem and prepare the next generation of scientists. In additional to the technical goals, this project is envisaged to have broader impacts in four distinct domains:

1. The successful completion of the scientific goals of this program will transform thinking about photosynthesis by creating independent modules for studying and optimizing the light and dark processes as well as portable biowires to establish functional contacts between distinct cell types. These modules, as well as the platform for testing them as a system, will be freely shared with other researchers.

2. The RAs will be important stakeholders in team and the proposed project offers extraordinary training opportunities to RAs at all levels. Unique to this project and multidisciplinary team is the range of scientific disciplines and academic institutions involved.

3. The BOLD-CATS team exemplifies the globalization of science and will serve as a model for collaboration in the EU.

4. Dissemination of scientific results will be crucial to this project, both to push the boundaries of photosynthetic research and engage the public in understanding a crucial problem. The geographic location of the participants provides a unique opportunity to develop web-based photosynthetic resources to engage the international community.

Publications

10 25 50
publication icon
Kosumi D (2016) Photoprotection Mechanism of Light-Harvesting Antenna Complex from Purple Bacteria. in The journal of physical chemistry. B

publication icon
Cogdell RJ (2013) The use and misuse of photosynthesis in the quest for novel methods to harness solar energy to make fuel. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

publication icon
Symes MD (2013) Designing artificial photosynthetic devices using hybrid organic-inorganic modules based on polyoxometalates. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

publication icon
Henry SL (2016) DNA-directed spatial assembly of photosynthetic light-harvesting proteins. in Organic & biomolecular chemistry

 
Description We quickly discover the fragility of the biological system (PS1) that we had originally hoped to use. We therefore concentrated on developing a more robust inorganic analogue, based of Cronin's polyoxymetalate complexes. These were highly successful in the area of hydrogen evolution. We also, with our colleagues in Poland, explored the use of plasmon enhancement and developed a system that could strongly enhance the efficiency o the primary photosynthetic light harvesting reactions. This could be used by PS1 and the purple bacterial light harvesting complexes.
Exploitation Route Our findings of plasmon enhancement are relevant to any system that sets out to harvest and use solar energy. It is also a convenient way to enhance florescence in general that could be of use the development of florescence based sensors.
Sectors Chemicals,Education,Energy,Environment

 
Description We have presented our findings at a Cafe Scientifique, on the radio and on television in Scotland. These events have led to impact in the area of general outreach and scientific understanding in the community.
First Year Of Impact 2010
Sector Education,Energy,Environment
Impact Types Societal

 
Description Quantum Coherent Energy Transfer over Varying Pathways in Single Light-Harvesting Complexes 
Organisation University of Bayreuth
Country Germany 
Sector Academic/University 
PI Contribution As a result of the primary collaboratation with Professor Koehler, this extra collaboration was arranged. The initial steps of photosynthesis comprise the absorption of sunlight by pigment-protein antenna complexes followed by rapid and highly efficient funneling of excitation energy to a reaction centre. In these transport processes, signatures of unexpectedly long-lived coherences have emerged in two-dimensional ensemble spectra of various light-harvesting complexes. Here, we demonstrate ultrafast quantum coherent energy transfer within individual antenna complexes of a purple bacterium under physiological conditions. We find that quantum coherences between electronically coupled energy eigenstates persist at least 400 femtoseconds and that distinct energy-transfer pathways that change with time can be identified in each complex. Our data suggest that long-lived quantum coherence renders energy transfer in photosynthetic systems robust in the presence of disorder, which is a prerequisite for efficient light harvesting.
Start Year 2012
 
Description Single-molecule spectroscopy reveals photosynthetic LH2 complexes switch between emissive states 
Organisation University of Bayreuth
Country Germany 
Sector Academic/University 
PI Contribution As a result of the primary collaboratation with Professor Koehler, this extra collaboration was arranged. Photosynthetic organisms flourish under low light intensities by converting photoenergy to chemical energy with near unity quantum efficiency and under high light intensities by safely dissipating excess photoenergy and deleterious photoproducts. The molecular mechanisms balancing these two functions remain incompletely described. One critical barrier to characterizing the mechanisms responsible for these processes is that they occur within proteins whose excited-state properties vary drastically among individual proteins and even within a single protein over time. In ensemble measurements, these excited-state properties appear only as the average value. To overcome this averaging, we investigate the purple bacterial antenna protein light harvesting complex 2 (LH2) from Rhodopseudomonas acidophila at the single-protein level. We use a room-temperature, single-molecule technique, the anti-Brownian electrokinetic trap, to study LH2 in a solution-phase (nonperturbative) environment. By performing simultaneous meas-urements of fluorescence intensity, lifetime, and spectra of single LH2 complexes, we identify three distinct states and observe transitions occurring among them on a timescale of seconds. Our results reveal that LH2 complexes undergo photoactivated switching to a quenched state, likely by a conformational change, and thermally revert to the ground state. This is a previously unobserved, reversible quenching pathway, and is one mechanism through which photosynthetic organisms can adapt to changes in light intensities.
Start Year 2012