ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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To understand how a spider converts the unfolded protein spinning dope into a highly structured and oriented in the super fiber,the effect of acidification on spider silk assembly was investigated on native spidroins from the major ampullate (MA) gland fluid excised from Latrodectus hesperus (Black Widow) spiders. The in vitro spider silk assembly kinetics were monitored as a function of pH with a 13C solid-state Magic Angle Spinning (MAS) NMR approach. The results confirm the importance of acidic pH in the spider silk self-assembly process with observation of a sigmoidal nucleation-elongation kinetic profile. The rates of nucleation and elongation and the percentage of β-sheet structure in the grown fibers depend on pH.
The secondary structure of the major ampullate silk from Peucetia viridians (Green Lynx) spiders was characterized by X-ray diffraction (XRD) and solid-state NMR spectroscopy. From XRD measurement, β-sheet nano-crystallites were observed that are highly oriented along the fiber axis with an orientational order of 0.980. Compare to the crystalline region, the amorphous region was found to be partially oriented with an orientational order of 0.887. Further, two dimensional 13C-13C through-space and through-bond solid-state NMR experiments provide structural analysis for the repetitive amino acid motifs in the silk proteins. The nano-crystallites are mainly alanine-rich β-sheet structures. The total percentage of crystalline region is determined to be 40.0±1.2 %. 18±1 % of alanine, 60±2 % glycine and 54±2 % serine are determined to be incorporated into helical conformations while 82±1 % of alanine, 40±3 % glycine and 46±2 % serine are in the β-sheet conformation.
Presented here are a series of studies toward this goal. First, self-assembled seven-helix DNA bundles (7HB) with cyclic arrays of three distinct chromophores were developed. The spectral properties and energy transfer mechanisms in the artificial light-harvesting antenna were studied extensively using steady-state and time-resolved methods. Next, engineered cysteine residues in the reaction center of the purple photosynthetic bacterium Rhodobacter sphaeroides were each covalently conjugated to fluorophores in order to explore the spectral requirements for energy transfer between an artificial light harvesting system and the reaction center. Finally, a structurally well-defined and spectrally tunable artificial light-harvesting system was constructed, where multiple organic dyes were conjugated to 3-arm DNA nanostructure. A reaction center protein isolated from the purple photosynthetic bacterium Rhodobacter sphaeroides was linked to one end of the 3-arm junction to serve as the final acceptor, which converts the photonic energy absorbed by the chromophores into chemical energy by charge separation. This type of model system is required to understand how parameters such as geometry, spectral characteristics of the dyes, and conformational flexibility affect energy transfer, and can be used to inform the development of more complex model light-harvesting systems.
computing, nano-robotics, disease diagnosis, and drug delivery.
This dissertation focuses on developing the structural design rules for "static" DNA nano-architectures with increasing complexity. By using a modular self-assembly method, Archimedean tilings were achieved by association of different DNA motifs with designed arm lengths and inter-tile sticky end interactions. By employing DNA origami method, a new set of design rules was created to allow the scaffolds to travel in arbitrary directions in a designed geometry without local symmetry restrictions. Sophisticated wireframe structures of higher-order complexity were designed and constructed successfully. This dissertation also presents the use of "dynamic" DNA nanotechnology to construct DNA origami nanostructures with programmed reconfigurations.