Seeing photosynthesis at the nanoscale: mapping physical properties of light-harvesting biomembranes by high-resolution microscopy and spectroscopy

Understanding photosynthesis could provide valuable clues for future solar technology and help our understanding of food crops. Solar photons are absorbed by the biomembranes within chloroplasts, where large numbers of Light-Harvesting Complex (LHC) proteins act as a satellite dish for channelling energy to Photosystem (PS) proteins. However, we need a better understanding of the dynamic structure and biophysical properties of the system. We can map the protein structure and arrangement to nanoscale resolution using a technique called Atomic Force Microscopy (AFM). Recent developments in AFM also allow video-speed imaging and measurements of the protein dynamics at the millisecond to microsecond timescale. Fluorescence spectroscopy and microscopy (FM) then allows us to quantify the important optical properties and energy transfer processes which occur within these proteins.

In this project, you will quantify the nanoscale structural dynamics of these proteins using high speed AFM and fluorescence techniques. Firstly, you will study how the so-called supercomplexes of PS/LHC proteins can assemble and disassemble in real time with AFM and FM imaging. You will systematically assess the effect of membrane composition and the effect of temperature. This will reveal the interaction strength and remodelling capabilities of these critically important Photosystem clusters. Secondly, you will quantify the flexibility and rearrangement of single LHC proteins with a newly developed ultra-fast height spectroscopy mode of AFM. Here, you will assess the effect of pH, which is thought to trigger changes to these proteins. Finally, you will quantify energy transfer processes of different configurations of proteins using advanced fluorescence spectroscopy. Characterizing the structural arrangement and biophysical properties of these membrane proteins will greatly advance our understanding photosynthesis.