Engine of Life: Biophysics and Tyrosine

Carbon dioxide emissions have increased sharply within the last few decades, which has resulted in climate change and pollution. This has led to the search for alternative energy sources, using photosynthesis as an inspiration. Within photosynthesis, photosystem II (PSII) uses light energy to drive the energetically demanding four-electron oxidation of water to dioxygen. There are two symmetric redox-active tyrosine residues, Y_Z and Y_D, in the D1 and D2 protein subunits of PSII. While these tyrosine residues are chemically identical, they are functionally distinct. It is proposed that Y_Z is directly involved in the primary electron transfer pathway of PSII. In contrast, the Y_D residue is proposed to be involved in the assembly of the catalytic Mn₄Ca-oxo cluster. My research is focused on understanding the structure and function of the Y_Zand Y_Dresidues of PSII. In my presentation, I will describe the methodology of cyanobacterial cell cultures, isolation and purification of PSII and the application of pulsed electron paramagnetic resonance spectroscopy to study the Y_Z and Y_D radicals of PSII.