20-BBSRC/NSF-BIO Quantum-enhanced long-range energy capture

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Natural photosynthesis in major crop plants shows an overall efficiency of solar energy to biomass conversion of just 2-3%. There is great interest in improving this figure through genetic manipulation because global crop production must increase by an estimated 100-110% by 2050 to feed the projected 9-10 billion population. One option is to widen the spectral range of absorbed solar energy beyond the current limit of 720 nm. Because bacterial photosynthetic complexes use bacteriochlorophyll to absorb light in the 700-1050 nm region, synthetic biology could be used to augment plants with similar abilities. As a first step towards this goal, realising efficient energy transfer from the plant protein, LHCII, to the bacterial protein, RC-LH1, is crucial and will be furthered by the proposed work.While the overall efficiency of photosynthesis is low, the initial steps exhibit high quantum efficiency as up to 95% of absorbed photons drive a charge separation event. Understanding how the organisation and interactions within the light-harvesting network achieve this efficiency, including the proposed, yet debated, role of quantum phenomena, would provide a blueprint for artificial light-harvesting devices. Recent observations in lithographically patterned systems of in- creased energy propagation and exciton-plasmon coupling to the substrate suggest that nanoscale interactions can be enhanced through the design of these photonic systems. Previous work has probed for quantum phenomena in LHCs, and found evidence of delocalised vibrational and vibronic coherences persisting for hundreds of femtoseconds. To date, such effects have been studied with sophisticated spectroscopic techniques, yet exclusively within isolated proteins. The extent to which quantum coherence may be enhanced by non-native conformations and interactions is an open question.We propose to engineer these effects through non-native interactions within lithographically patterning arrays of LHCs and RCs, benchmarking them to near-native liposomal systems. Previously, such arrays were constructed from a single component and have only been interrogated with basic microscopic and spectroscopic methods to ensure their functionality. Here we will engender a step-change in our understanding by constructing more complex non-natural network architectures and interrogating them in unprecedented detail using the latest advanced 2D electronic and correlation spectroscopy and electron-tunnelling AFM methods. These efforts will progress biological understanding by providing mechanistic insight into the factors that promote quantum coherence at physiological temperatures and revealing the regimes where such behaviours enhance function.