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Description
In my thesis, I characterize multi-nuclear manganese cofactors in modified reaction
centers from the bacterium Rhodobacter sphaeroides. I characterized interactions
between a variety of secondary electron donors and modified reaction centers. In Chapter
1, I provide the research aims, background, and a summary of the chapters in my thesis.
In Chapter 2 and Chapter 3, I present my work with artificial four-helix bundles as
secondary electron donors to modified bacterial reaction centers. In Chapter 2, I
characterize the binding and energetics of the P1 Mn-protein, as a secondary electron
donor to modified reaction centers. In Chapter 3, I present the activity of a suite of four
helix bundles behaving as secondary electron donors to modified reaction centers. In
Chapter 4, I characterize a suite of modified reaction centers designed to bind and oxidize
manganese. I present work that characterizes bound manganese oxides as secondary
electron donors to the oxidized bacteriochlorophyll dimer in modified reaction centers. In
Chapter 5, I present my conclusions with a short description of future work in
characterizing multiple electron transfers from a multi-nuclear manganese cofactor in
modified reaction centers. To conclude, my thesis presents a characterization of a variety
of secondary electron donors to modified reaction centers that establish the feasibility to
characterize multiple turnovers from a multi-nuclear manganese cofactor.
centers from the bacterium Rhodobacter sphaeroides. I characterized interactions
between a variety of secondary electron donors and modified reaction centers. In Chapter
1, I provide the research aims, background, and a summary of the chapters in my thesis.
In Chapter 2 and Chapter 3, I present my work with artificial four-helix bundles as
secondary electron donors to modified bacterial reaction centers. In Chapter 2, I
characterize the binding and energetics of the P1 Mn-protein, as a secondary electron
donor to modified reaction centers. In Chapter 3, I present the activity of a suite of four
helix bundles behaving as secondary electron donors to modified reaction centers. In
Chapter 4, I characterize a suite of modified reaction centers designed to bind and oxidize
manganese. I present work that characterizes bound manganese oxides as secondary
electron donors to the oxidized bacteriochlorophyll dimer in modified reaction centers. In
Chapter 5, I present my conclusions with a short description of future work in
characterizing multiple electron transfers from a multi-nuclear manganese cofactor in
modified reaction centers. To conclude, my thesis presents a characterization of a variety
of secondary electron donors to modified reaction centers that establish the feasibility to
characterize multiple turnovers from a multi-nuclear manganese cofactor.
ContributorsEspiritu, Eduardo (Author) / Allen, James P. (Thesis advisor) / Jones, Anne K (Committee member) / Redding, Kevin (Committee member) / Arizona State University (Publisher)
Created2019
Description
The utilization of solar energy requires an efficient means of its storage as fuel. In bio-inspired artificial photosynthesis, light energy can be used to drive water oxidation, but catalysts that produce molecular oxygen from water are required. This dissertation demonstrates a novel complex utilizing earth-abundant Ni in combination with glycine as an efficient catalyst with a modest overpotential of 0.475 ± 0.005 V for a current density of 1 mA/cm2 at pH 11. The production of molecular oxygen at a high potential was verified by measurement of the change in oxygen concentration, yielding a Faradaic efficiency of 60 ± 5%. This Ni species can achieve a current density of 4 mA/cm2 that persists for at least 10 hours. Based upon the observed pH dependence of the current amplitude and oxidation/reduction peaks, the catalysis is an electron-proton coupled process. In addition, to investigate the binding of divalent metals to proteins, four peptides were designed and synthesized with carboxylate and histidine ligands. The binding of the metals was characterized by monitoring the metal-induced changes in circular dichroism spectra. Cyclic voltammetry demonstrated that bound copper underwent a Cu(I)/Cu(II) oxidation/reduction change at a potential of approximately 0.32 V in a quasi-reversible process. The relative binding affinity of Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) to the peptides is correlated with the stability constants of the Irving-Williams series for divalent metal ions. A potential application of these complexes of transition metals with amino acids or peptides is in the development of artificial photosynthetic cells.
ContributorsWang, Dong (Author) / Allen, James P. (Thesis advisor) / Ghirlanda, Giovanna (Committee member) / Redding, Kevin (Committee member) / Arizona State University (Publisher)
Created2014