Date of Award

Fall 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular Biophysics and Biochemistry

First Advisor

Brudvig, Gary

Abstract

Oxygenic photosynthesis — performed on all seven continents by green plants, algae, and cyanobacteria — supports the global biome through its ability to capture and store light energy. This is achieved through a series of protein complexes collectively known as the photosynthetic apparatus. During my PhD research, I’ve investigated the structural basis for how these protein complexes capture this light energy and transduce it to redox energy. My thesis work, summarized in this dissertation, can be grouped in two broad research themes: (i) structural studies on Nature’s water oxidation reaction, explored in Part I of this dissertation; and (ii) the structural basis of far-red light photosynthesis, explored in Part II of this dissertation. In Part I, the reaction mechanism of water oxidation performed by the photosystem II enzyme is explored through cryogenic-electron microscopy structural studies on photosystem II point mutants. My findings have provided new insight into the role of conserved water channels in orchestrating the proton removal steps during the water oxidation mechanism. Furthermore, I demonstrated a need to reinterpret previous biochemical and biophysical data using a structural perspective. In Part II, the structural basis of far-red light photosynthesis is explored with an emphasize on methodology development to identify the important far-red light absorbing chlorophyll pigments in the structural data. Our findings identified several of the far-red light absorbing chlorophyll pigment binding sites in both the photosystem II and photosystem I enzymes in a cyanobacterium acclimated to far-red light. Furthermore, we developed quantitative tools to support these conclusions and provided recommendations on how to best interpret these experimental data. Overall, my PhD research has advanced the photosynthesis research field using structural biology methods.

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