Controllable model membranes and new quantitative analyses to interrogate light harvesting proteins

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This proposal will develop new model systems and analysis methods to quantify the biophysical properties of important Light Harvesting (LH) proteins with high spatiotemporal resolution. This will provide insight into the physical basis of photosynthetic processes which are crucial for life on Earth but poorly understood. It will also have wider relevance for the potential use of LH proteins in nanotechnology, photonics and plasmonics. We need to develop a suite of "model membranes" (idealized experimental models of biomembranes) which incorporate LH proteins and offer a balance between complexity, controllability and amenability to tools that can quantify structure and optical properties. We need the ability to manipulate the density of LH proteins within these model membranes. We need to quantify how the organization and optical properties of these LH proteins change in response to important physicochemical stimuli. The proposed project will develop three types of model membranes for studying LH proteins, which progress from mostly synthetic to close-to-natural membranes. These "model membranes" will be manipulated by applying external electric fields to direct the migration of LH proteins within membranes, for the first time. The nanoscale organization and photophysical properties of these LH proteins will be compared in each type of membrane by an advanced microscopy and spectroscopy combined system. My previous research has demonstrated that the clustering of LH proteins is correlated to energy dissipation (fluorescence quenching) and my expertise with correlative microscopy and spectroscopy tools make me uniquely well-placed for performing quantitative studies of energy transfer processes. In Leeds, we have a new Fluorescence Lifetime Imaging Microscope combined with Atomic Force Microscopy (FLIM+AFM) instrument which will allow unprecedented direct correlation and quantification of optical properties and nanoscale organization (I was co-investigator on the grant acquiring this instrument). This combined microscope is ideal to study LH proteins and gives us a competitive edge. In summary, this project will provide a comparative analysis of the advantages and limitations of new membrane models and, in doing so, quantify the crucial relationship between organization and optical properties of light harvesting proteins. These new models could be applied to bacterial and mammalian membranes of relevance for health and agriculture. Furthermore, knowledge of the important LHCII protein could be relevant for the development of alternative solar nanotechnologies or the production of enhanced crops.