Photoreaction centres are nature’s solar batteries. These complexes of protein, chlorophyll, quinone and other cofactors use the energy of sunlight to create an electrical potential difference across a charge-impermeable membrane. The potential difference generated by photoreaction centres is used to power a wide range of energy-requiring reactions in biology, and these proteins can be exploited for a variety of applications in photovoltaics, photosensing, chemical sensing, photocatalysis and biocomputing. 

Reaction centres are found in plants, algae and bacteria, and the best understood of these multicomponent integral membrane proteins is the relatively simple variant found in the purple photosynthetic bacteria. As electron transfer in the reaction centre is triggered by light, the kinetics of this process can be monitored by laser spectroscopy, on time scales as short as picoseconds or femtoseconds. As a result the purple bacterial reaction centre has made a unique contribution to our understanding of biological electron transfer. This tractable and robust protein is also used to study generic features of complex integral membrane proteins, such as the relationship between structure and stability, and the interplay between protein dynamics and catalysis.

Studies in my laboratory are focused on understanding: 

• how the protein controls the rate and efficiency of electron transfer during light energy transduction
• interactions of the reaction centre with the proteins and lipids that form the membrane environment
• the relationship between structure and the thermal stability of the protein, including the use of mutagenesis to engineer reaction centres with enhanced thermal stability
• adaptation and enhancement of the native photovoltaic properties of the reaction centre for exploitation in novel protein solar cells, biosensors and as energy-generating modules for synthetic biology and photocatalysis.

We tackle these issues through the application of protein engineering, membrane protein biochemistry, X-ray crystallography, kinetic spectroscopy, fluorescence and vibrational spectroscopy and measurements of photovoltaic capacity. In all of these areas mutant complexes are generated and analysed in Bristol, with further analysis using specialised spectroscopic techniques accessed through a network of collaborations with research groups in the UK, Netherlands, France, Italy, Poland, Singapore and the USA.