Matching Items (2)
Filtering by
- Genre: Masters Thesis
Description
To mimic the membrane environment for the photosynthetic reaction center of the photoheterotrophic Heliobacterium modesticaldum, a proteoliposome system was developed using the lipids found in native membranes, as well as a lipid possessing a Ni(II)-NTA head group. The liposomes were also saturated with menaquinone-9 to provide further native conditions, given that menaquinone is active within the heliobacterial reaction center in some way. Purified heliobacterial reaction center was reconstituted into the liposomes and a recombinant cytochrome c553 was decorated onto the liposome surface. The native lipid-attachment sequence of cytochrome c553 was truncated and replaced with a hexahistidine tag. Thus, the membrane-anchoring observed in vivo was simulated through the histidine tag of the recombinant cytochrome binding to the Ni(II)-NTA lipid's head group. The kinetics of electron transfer in this system was measured and compared to native membranes using transient absorption spectroscopy. The preferential-orientation of reconstituted heliobacterial reaction center was also measured by monitoring the proteoliposome system's ability to reduce a soluble acceptor, flavodoxin, in both whole and detergent-solubilized proteoliposome conditions. These data demonstrate that this proteoliposome system is reliable, biomimetic, and efficient for selectively testing the function of the photosynthetic reaction center of Heliobacterium modesticaldum and its interactions with both donors and acceptors. The recombinant cytochrome c553 performs similarly to native cytochrome c553 in heliobacterial membranes. These data also support the hypothesis that the orientation of the reconstituted reaction center is inherently selective for its bacteriochlorophyll special pair directed to the outer-leaflet of the liposome.
ContributorsJohnson, William Alexander (Author) / Redding, Kevin E (Thesis advisor) / Van Horn, Wade D (Committee member) / Jones, Anne K (Committee member) / Arizona State University (Publisher)
Created2018
Description
Alkylphosphine- and alkylpyridine-substituted 2,6-bis(imino)pyridines (pyridine diimines, PDI) have recently been used as polydentate, redox non-innocent ligands that support the development of highly active catalysts. The alkyl phosphine-substituted ligand, Ph2PPrPDI, was added to (Ph3P)3CoCl and subsequent reduction using excess sodium amalgam yielded (Ph2PPrPDI)Co. Electronic structure analysis revealed a cobalt(I) complex that features a singly reduced PDI chelate. Additionally, low valent Ph2PPrPDI complexes of Fe and Ni were synthesized and structurally characterized. Furthermore, a series of Ph2PPrPDI Mn, Fe, Co, and Ni complexes were investigated to evaluate ligand denticity and redox activity. Finally, the catalytic hydrosilylation of carbonyls was investigated to compare the activity of the series and determine whether electron count plays a role in catalysis. An analogous ligand system featuring alkylpyridine substituents, PyEtPDI, was added to CoCl2, affording a cobalt dichloride complex with the formula [(PyEtPDI)CoCl][Cl]. Single crystal X-ray diffraction revealed a high-spin cobalt(II) center that possesses an octahedral geometry and an outer-sphere chloride ion. Further treatment using 2 equivalents of NaEt3BH resulted in the formation of (κ4-N,N,N,N-PyEtIPCHMeNEtPy)Co, which has been verified by multinuclear NMR spectroscopy and single crystal X-ray diffraction. (κ4-N,N,N,N-PyEtIPCHMeNEtPy)Co was then used in the catalytic hydroboration of nitriles at ambient conditions to yield the corresponding N,N-diborylamines, which were used as precursors for amide formation.
ContributorsMena, Matthew Ray (Author) / Trovitch, Ryan J (Thesis advisor) / Jones, Anne K (Committee member) / Ackerman, Laura K.G. (Committee member) / Arizona State University (Publisher)
Created2021