UC Berkeley

Biological systems perform some of the most energetically demanding, life sustaining reactions. Metal containing enzymes such as photosystem II facilitate fundamental processes (water splitting) with high levels of efficiency. The use of high-power x-ray beams provides a window into electronic and geometric structure. Time resolved studies can be used to produce a molecular movie of the progression of the reaction on the atomic scale. Understanding the steps nature takes provides insight for artificial systems. With climate change effects becoming more prominent every day, solutions for food shortages, greenhouse gas sequestration, and high-efficiency liquid fuels sources are more important than ever. Artificial systems can be built to mimic nature’s blueprint for overcoming some of the largest energetic barriers. This dissertation outlines the steps necessary to use x-rays to track metal facilitated catalysis. Specifically, Iron in soluble methane monooxygenase (MMO) and Mn in photosystem II (PS II) which facilitate methane to methanol conversion and water oxidation respectively. These systems were studied using synchrotrons and x-ray free electron lasers to look at atomic level changes in both stable and transient intermediates. This dissertation presents work in instrumentation development, synchrotron assisted initial model compound studies for MMO, and electronic and geometric structures studies of PS II through both x-ray free electron lasers (XFEL) and synchrotrons. Instrumentation was developed to minimize sample waste and maximize signal during XFEL experiments. X-ray emission spectroscopy of model compounds and MMO provided electronic structure information on stable intermediates which can be used to guide future XFEL studies. PS II analysis probed both stable and transient intermediates during the final two steps of water oxidation, thus, finally illuminating some of the most important steps of O-O bond formation. These three projects outline the different steps for efficient studies of multi-electron catalysis in metalloenzymes using x-ray spectroscopy; while also providing fundamental findings of the chemistry and physics of MMO and PS II specifically.