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.
Displaying 41 - 43 of 43
Description
Interactions between proteins form the basis of almost all biological mechanisms. The majority of proteins perform their functions as a part of an assembled complex, rather than as an isolated species. Understanding the functional pathways of these protein complexes helps in uncovering the molecular mechanisms involved in the interactions. In this thesis, this has been explored in two fundamental ways. First, a biohybrid complex was assembled using the photosystem I (PSI) protein complex to translate the biochemical pathways into a non-cellular environment. This involved incorporating PSI on a porous antimony-doped tin oxide electrode using cytochrome c. Photocurrent was generated upon illumination of the PSI/electrode system alone at microamp/cm2 levels, with reduced oxygen apparently as the primary carrier. When the PSI/electrode system was coupled with ferredoxin, ferredoxin-NADP+ reductase (FNR), and NADP+, the resulting light-powered NADPH production was coupled to a dehydrogenase system for enzymatic carbon reduction. The results demonstrated that light-dependent reduction readily takes place. However, the pathways do not always match the biological pathways of PSI in nature. To create a complex self-assembled system such as the one involving PSI that is structurally well defined, there is a need to develop ways to guide the molecular interactions. In the second part of the thesis, this problem was approached by studying a well-defined system involving monoclonal antibodies (mAbs) binding their cognate epitope sequences to understand the molecular recognition properties associated with protein-protein interactions. This approach used a neural network model to derive a comprehensive and quantitative relationship between an amino acid sequence and its function by using sparse measurements of mAb binding to peptides on a high density peptide microarray. The resulting model can be used to predict the function of any peptide in the possible combinatorial sequence space. The results demonstrated that by training the model on just ~105 peptides out of the total combinatorial space of ~1010, the target sequences of the mAbs (cognate epitopes) can be predicted with high statistical accuracy. Furthermore, the biological relevance of the algorithm’s predictive ability has also been demonstrated.
ContributorsSingh, Akanksha (Author) / Woodbury, Neal (Thesis advisor) / Liu, Yan (Committee member) / Gould, Ian (Committee member) / Arizona State University (Publisher)
Created2021
Description
MAX phases are an intriguing class of materials with exotic combinations of properties, essentially turning them into metallic ceramics. Despite this unique feature, no commercialization has been accomplished yet. Looking at the state of the art within the MAX phase community, almost all published studies can be summarized using the term “traditional high temperature synthesis”. Contrasting the scientific interest that has been on the rise especially since the discovery of MXenes, the synthetic spectrum has been largely the same as it has been over the past decades.Herein, the newly-emerging sol-gel chemistry is being explored as an alternative non-conventional synthetic approach. Building on the successful sol-gel synthesis of Cr2GaC, this study focuses around the expansion of sol-gel chemistry for MAX phases. Starting with a thorough mechanistic investigation into the reaction pathway of sol-gel synthesized Cr2GaC, the chemical understanding of this system is drastically deepened. It is shown how the preliminary nano-structured metal-oxide species develop into bulk oxides, before the amorphous and disordered
graphite partakes in the reaction and reduces the metals into the MAX phase.
Furthermore, the technique is extended to the two Ge- based MAX phases V2GeC and Cr2GeC, a critical step needed to prove the viability and applicability of the newly developed technique. Additionally, by introducing Mn into the Cr-Ga-C system, a Mn-doping was achieved, and for the first time for (Cr1–xMnx)2GaC, a unit cell increase could be recorded. Based on magnetometry measurements, the currently widely accepted assumption of statistically distributed Mn in the M-layer is challenged.
The versatility of wet chemistry is explored using the model system Cr2GaC. Firstly, the MAX phase can be obtained in a microwire shape leveraging the branched biopolymer dextran, eliminating the need for any post-synthesis machining. Via halide intercalation, the electrical transport properties could be purposefully engineered.
Secondly, leveraging the unique and linear biopolymer chitosan, Cr2GaC was obtained as thick films and dense microspheres, drastically opening potential areas of application for MAX phases. Lastly, hollow microspheres with diameters of tens of μm were synthesized via carboxymethylated dextran. This shape once more opens the door to very specific applications requiring sophisticated structures.
ContributorsSiebert, Jan (Author) / Birkel, Christina (Thesis advisor) / Gould, Ian (Committee member) / Kouvetakis, John (Committee member) / Arizona State University (Publisher)
Created2022
Description
Deoxyribonucleic acid (DNA), a biopolymer well known for its role in preserving genetic information in biology, is now drawing great deal of interest from material scientists. Ease of synthesis, predictable molecular recognition via Watson-Crick base pairing, vast numbers of available chemical modifications, and intrinsic nanoscale size makes DNA a suitable material for the construction of a plethora of nanostructures that can be used as scaffold to organize functional molecules with nanometer precision. This dissertation focuses on DNA-directed organization of metallic nanoparticles into well-defined, discrete structures and using them to study photonic interaction between fluorophore and metal particle. Presented here are a series of studies toward this goal. First, a novel and robust strategy of DNA functionalized silver nanoparticles (AgNPs) was developed and DNA functionalized AgNPs were employed for the organization of discrete well-defined dimeric and trimeric structures using a DNA triangular origami scaffold. Assembly of 1:1 silver nanoparticle and gold nanoparticle heterodimer has also been demonstrated using the same approach. Next, the triangular origami structures were used to co-assemble gold nanoparticles (AuNPs) and fluorophores to study the distance dependent and nanogap dependencies of the photonic interactions between them. These interactions were found to be consistent with the full electrodynamic simulations. Further, a gold nanorod (AuNR), an anisotropic nanoparticle was assembled into well-defined dimeric structures with predefined inter-rod angles. These dimeric structures exhibited unique optical properties compared to single AuNR that was consistent with the theoretical calculations. Fabrication of otherwise difficult to achieve 1:1 AuNP- AuNR hetero dimer, where the AuNP can be selectively placed at the end-on or side-on positions of anisotropic AuNR has also been shown. Finally, a click chemistry based approach was developed to organize sugar modified DNA on a particular arm of a DNA origami triangle and used them for site-selective immobilization of small AgNPs.
ContributorsPal, Suchetan (Author) / Liu, Yan (Thesis advisor) / Yan, Hao (Thesis advisor) / Lindsay, Stuart (Committee member) / Gould, Ian (Committee member) / Arizona State University (Publisher)
Created2012