Matching Items (5)
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- All Subjects: Photosynthetic reaction centers
- All Subjects: Coral Reef
- Creators: Redding, Kevin
- Status: Published
Description
There is a critical need for the development of clean and efficient energy sources. Hydrogen is being explored as a viable alternative to fuels in current use, many of which have limited availability and detrimental byproducts. Biological photo-production of H2 could provide a potential energy source directly manufactured from water and sunlight. As a part of the photosynthetic electron transport chain (PETC) of the green algae Chlamydomonas reinhardtii, water is split via Photosystem II (PSII) and the electrons flow through a series of electron transfer cofactors in cytochrome b6f, plastocyanin and Photosystem I (PSI). The terminal electron acceptor of PSI is ferredoxin, from which electrons may be used to reduce NADP+ for metabolic purposes. Concomitant production of a H+ gradient allows production of energy for the cell. Under certain conditions and using the endogenous hydrogenase, excess protons and electrons from ferredoxin may be converted to molecular hydrogen. In this work it is demonstrated both that certain mutations near the quinone electron transfer cofactor in PSI can speed up electron transfer through the PETC, and also that a native [FeFe]-hydrogenase can be expressed in the C. reinhardtii chloroplast. Taken together, these research findings form the foundation for the design of a PSI-hydrogenase fusion for the direct and continuous photo-production of hydrogen in vivo.
ContributorsReifschneider, Kiera (Author) / Redding, Kevin (Thesis advisor) / Fromme, Petra (Committee member) / Jones, Anne (Committee member) / Arizona State University (Publisher)
Created2013
Description
The heliobacterial reaction center (HbRC) is widely considered the simplest and most primitive photosynthetic reaction center (RC) still in existence. Despite the simplicity of the HbRC, many aspects of the electron transfer mechanism remain unknown or under debate. Improving our understanding of the structure and function of the HbRC is important in determining its role in the evolution of photosynthetic RCs. In this work, the function and properties of the iron-sulfur cluster FX and quinones of the HbRC were investigated, as these are the characteristic terminal electron acceptors used by Type-I and Type-II RCs, respectively. In Chapter 3, I develop a system to directly detect quinone double reduction activity using reverse-phase high pressure liquid chromatography (RP-HPLC), showing that Photosystem I (PSI) can reduce PQ to PQH2. In Chapter 4, I use RP-HPLC to characterize the HbRC, showing a surprisingly small antenna size and confirming the presence of menaquinone (MQ) in the isolated HbRC. The terminal electron acceptor FX was characterized spectroscopically and electrochemically in Chapter 5. I used three new systems to reduce FX in the HbRC, using EPR to confirm a S=3/2 ground-state for the reduced cluster. The midpoint potential of FX determined through thin film voltammetry was -372 mV, showing the cluster is much less reducing than previously expected. In Chapter 7, I show light-driven reduction of menaquinone in heliobacterial membrane samples using only mild chemical reductants. Finally, I discuss the evolutionary implications of these findings in Chapter 7.
ContributorsCowgill, John (Author) / Redding, Kevin (Thesis advisor) / Jones, Anne (Committee member) / Fromme, Petra (Committee member) / Arizona State University (Publisher)
Created2012
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
A novel underwater, open source, and configurable vehicle that mimics and leverages advances in quad-copter controls and dynamics, called the uDrone, was designed, built and tested. This vehicle was developed to aid coral reef researchers in collecting underwater spectroscopic data for the purpose of monitoring coral reef health. It is designed with an on-board integrated sensor system to support both automated navigation in close proximity to reefs and environmental observation. Additionally, the vehicle can serve as a testbed for future research in the realm of programming for autonomous underwater navigation and data collection, given the open-source simulation and software environment in which it was developed. This thesis presents the motivation for and design components of the new vehicle, a model governing vehicle dynamics, and the results of two proof-of-concept simulation for automated control.
ContributorsGoldman, Alex (Author) / Das, Jnaneshwar (Thesis advisor) / Asner, Greg (Committee member) / Marvi, Hamidreza (Committee member) / Arizona State University (Publisher)
Created2020
Description
Coral reefs are diverse marine ecosystems, where reef building corals provide both the structure of the habitat as well as the primary production through their symbiotic algae, and alongside algae living on the reef itself, are the basis of the food web of the reef. In this way, coral reefs are the ocean's "forests" and are estimated to support 25% of all marine species. However, due to the large size of a coral reef, the relative inaccessibility and the reliance on in situ surveying methods, our current understanding of reefs is spatially limited. Understanding coral reefs from a more spatially complete perspective will offer insight into the ecological factors that contribute to coral reef vitality. This has become a priority in recent years due to the rapid decline of coral reefs caused by mass bleaching. Despite this urgency, being able to assess the entirety of a coral reef is physically difficult and this obstacle has not yet been overcome. However, similar difficulties have been addressed in terrestrial ecosystems by using remote sensing methods, which apply hyperspectral imaging to assess large areas of primary producers at high spatial resolutions. Adapting this method of remote spectral sensing to assess coral reefs has been suggested, but in order to quantify primary production via hyper spectral imaging, light-use efficiencies (LUEs) of coral reef communities need to be known. LUEs are estimations of the rate of carbon fixation compared to incident absorbed light. Here, I experimentally determine LUEs and report on several parameters related to LUE, namely net productivity, respiration, and light absorbance for the main primary producers in coral reefs surrounding Bermuda, which consist of algae and coral communities. The derived LUE values fall within typical ranges for LUEs of terrestrial ecosystems, with LUE values for coral averaging 0.022 ± 0.002 mol O2 mol photons-1 day-1 at a water flow rate of 17.5 ± 2 cm s^(-1) and 0.049 ± 0.011 mol O2 mol photons-1 day-1 at a flow rate of 32 ± 4 cm s^(-1) LUE values for algae averaged 0.0335 ± 0.0048 mol O2 mol photons-1 day-1 at a flow rate of 17.5 ± 2 cm s^(-1). These values allow insight into coral reef productivity and opens the door for future remote sensing applications.
ContributorsFlesher, David A (Author) / Neuer, Susanne (Thesis director) / Redding, Kevin (Committee member) / School of Molecular Sciences (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05