Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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- Creators: Barrett, The Honors College
- Creators: Crozier, Peter
Description
Protein crystallization is a technique for the formation of three-dimensional protein crystals, which is widely utilized by scientists, engineers, and researchers. Protein crystallography allows for protein structures and functions to be studied. As proteins play a central role in biological systems and life itself, a deeper understanding of their structure-function properties is crucial to elucidating fundamental behaviors, such as protein folding in addition to the role that they play in emerging fields, such as, tissue engineering with application to the emerging field of regenerative medicine. However, a significant limitation toward achieving further advancements in this field is that in order to determine detailed structure of proteins from protein crystals, high-quality and larger size protein crystals are needed. Because it is difficult to produce adequate size, high-quality crystals, it remains difficult to determine the structure of many proteins. However, a new method using a microgravity environment to crystallize proteins has proven effective through various studies conducted on the International Space Station (ISS). In the presence of microgravity, free convection is essentially absent in the bulk solution where crystallization occurs, thus allowing for purely random Brownian motion to exist which favors the nucleation and growth of high-quality protein crystals. Many studies from the ISS to date have demonstrated that growing protein crystals in a microgravity environment produces larger and higher-quality crystals. This method provides new opportunities for better structure identification and analysis of proteins. Although there remains many more limitations and challenges in the field, microgravity protein crystallization holds many opportunities for the future of biotechnology and scientific development. The objective of this thesis was to study the crystallization of hen egg white lysozyme (HEWL) and determine the effects of both unit and microgravity on growth/size and quality of HEWL. Through preliminary trials using a universal ground-based reduced-gravity system, the crystallization of HEWL in a simulated microgravity environment was successfully conducted and the results reported are promising. The utility of continuous, scalable ground-based, microgravity platforms for studies on a wide range of material systems and behavior, such as, protein crystallization, has significant implications regarding its impact on many industries, including drug development as well as regenerative medicine.
ContributorsTran, Amanda Marie (Author) / Pizziconi, Vincent (Thesis director) / Alford, Terry (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-12
Description
Two dimensional (2D) Janus Transition Metal Dichalcogenides (TMDs) are a new class of atomically thin polar materials. In these materials, the top and the bottom atomic layer are made of different chalcogen atoms. To date, several theoretical studies have shown that a broken mirror symmetry induces a colossal electrical field in these materials, which leads to unusual quantum properties. Despite these new properties, the current knowledge in their synthesis is limited only through two independent studies; both works rely on high-temperature processing techniques and are specific to only one type of 2D Janus material - MoSSe. Therefore, there is an urgent need for the development of a new synthesis method to (1) Extend the library of Janus class materials. (2) Improve the quality of 2D crystals. (3) Enable the synthesis of Janus heterostructures. The central hypothesis in this work is that the processing temperature of 2D Janus synthesis can be significantly lowered down to room temperatures by using reactive hydrogen and sulfur radicals while stripping off selenium atoms from the 2D surface. To test this hypothesis, a series of controlled growth studies were performed, and several complementary characterization techniques were used to establish a process–structure-property relationship. The results show that the newly proposed approach, namely Selective Epitaxy and Atomic Replacement (SEAR), is effective in reducing the growth temperature down to ambient conditions. The proposed technique benefits in achieving highly crystalline 2D Janus layers with an excellent optical response. Further studies herein show that this technique can form highly sophisticated lateral and vertical heterostructures of 2D Janus layers. Overall results establish an entirely new growth technique for 2D Janus.layers, which pave ways for the realization of exciting quantum effects in these materials such as Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state, Majorana fermions, and topological p-wave superconductors.
ContributorsSayyad, Mohammed Yasir (Author) / Tongay, Sefaattin (Thesis advisor) / Crozier, Peter (Committee member) / Alford, Terry (Committee member) / Arizona State University (Publisher)
Created2020