<p><p>One of the most significant discoveries from mutational analysis of protein interfaces is that often a large percentage of interface residues negligibly perturb the binding energy upon mutation, while residues in a few critical "hotspots" drastically reduce affinity when mutated. The organization of protein interfaces into hotspots has a number of important implications. For example, small interfaces can have high affinity, and when multiple binding partners are generated to the same protein, they are predisposed to binding the same regions and often have the same hotspots. Even small molecules that bind to interfaces and disrupt protein-protein interactions (PPIs) tend to bind at hotspots. This suggests that some hotspot-forming sites on protein surfaces are <italic>intrinsically</italic> more apt to form protein interfaces. These observations paint a hotspot-centric picture of PPI energetics, and present a question of fundamental importance which remains largely unanswered: <italic>why are hotspots hot?</italic></p></p><p><p>In order to gain insight into the nature of hotspots I experimentally examined the small, but high-affinity interface between the synthetically evolved ankyrin repeat protein Off7 with E. coli maltose binding protein by characterization of mutant variants and redesigned interfaces. In order to characterize many mutants, I developed two high-throughput assays to measure protein-protein binding that integrate with existing technology for the high-throughput fabrication of genes. The first is an ELISA-based method using in vitro expressed protein for semi-quantitative analysis of affinity. Starting from DNA encoding protein partners, binding data is obtained in just a few hours; no exogenous purification is required. For the second assay, I develop data fitting methods and thermodynamic framework for determination of binding free energies from binding-induced shifts in protein thermal stability monitored with Sypro Orange.</p></p><p><p>Analysis of Off7/MBP variants using these methods reveals that conservative mutagenesis or local computational repacking is tolerated for many residues in the interface without drastic loss of affinity, except for a single essential hotspot. This hotspot contains a Tyr-His-Asp hydrogen bonding network reminiscent of a common catalytic motif. Substitution of the tyrosine with phenylalanine shows that a single hydrogen bond across the interface is critical for binding. Analysis of the protein database by structural bioinformatics shows that, although rare, this motif is present in other naturally evolved interfaces. Such a triad was found in the homodimeric interface of PH0642 from Pyrococcus horikoshii, and is conserved between many homologues in the nitrilase superfamily, meeting one of the key criteria by which potential hotspots can be identified. This analysis supports a number of analogies between hotspot residues and catalytic residues in enzyme active sites, and raises the intriguing possibility that hotspots may be associated with other structural motifs that could be used for identification or design of PPIs.</p></p> / Dissertation

The aim of this thesis is to analyze Ukrainian foreign policy and its domestic sources since 1991, with a focus on the post-Orange Revolution era. The thesis argues that contrary to neo-realist approaches to the study of Ukrainian foreign policy, in the final analysis, it is Ukraine&#039 / s domestic factors which determines the direction of Ukrainian foreign policy in the post-Soviet era. This thesis demonstrates that the existing neo-realist studies of Ukrainian foreign policy exaggerates the role of external factors and neglects the crucial role of domestic factors in Ukrainian foreign policy. The thesis begins with an introduction, which is followed by the second chapter on the interaction between domestic and external factors in Ukrainian foreign policy in the pre-Orange Revolution era. The third chapter examines the characteristics of Ukrainian foreign policy in the post-Orange Revolution era. The following four chapters discuss the impact of political, economic and cultural factors on Ukrainian foreign policy as well as the Crimean question. Finally the last chapter will be the conclusion of this thesis.

Silver (Ag) was loaded to three different kinds (P-25, NT-22, and TiO(OH)2) of titanium dioxide (TiO2) powders through adding three different quantities (4.6, 9.2, and 13.8 ml) of silver nitrate (AgNO3) solution by mechanical ball milling process. X-Ray diffraction analysis suggested that Ag was loaded on the TiO2 powders in the form of silver oxide (AgO). SEM, particle size, and BET surface area analyses revealed that TiO2 particles agglomerated after ball milling, resulting in the decrease of specific surface area of the TiO2 powders. Powders P-25, NT-22, and TiO(OH)2 degraded 94 %, 46 %, and 26 %, respectively of MO solution under 1 h UV irradiation. Increasing amount of Ag loading enhanced photocatalytic activity of TiO2 powders under UV irradiation. The best photocatalytic performance was achieved by 13.8 ml AgNO3 solution added NT-22 powders. Percent methyl orange (MO) degradation of 13.8 ml AgNO3 solution added P-25, NT-22, and TiO(OH)2 powders under 1 h UV irradiation was 85 %, 96 %, and 67 %, respectively. Contact angle measurements revealed that hydrophilic properties of TiO2 powders were also improved by Ag loading. Moreover, TiO2 powders gained antibacterial prospect after Ag addition. Ag loaded TiO2 powders could be used effectively for the applications requiring better photocatalytic activity and antibacterial effect.

The photocatalytic activity of semiconductor metal oxides can be improved by the addition of sensitizer which enhances the band gap by considerable red shift of the absorption edge of semiconductor. In the present study, the effect of ascorbic acid as sensitizer on the photocatalytic activity of titania-silica binary mixtures was studied. The SiO2-TiO2 mixtures having 50wt%Ti:Si composition were prepared with sol-gel method. The surface area and porosity of the samples were modified by using various amounts of polyethylene glycol (PEG) as template. The thin films of the samples were obtained by dip coating of glass plates to colloidal solutions. The samples were characterized by methylene blue adsorption method and UV-Vis spectrophotometry. The photocatalytic activities of the samples were measured with methylene blue degradation, methyl orange degradation and direct water splitting in the presence and absence of ascorbic acid. Increase in the surface area and reaction rate with increasing PEG addition until a threshold value was observed. Highest methylene blue degradation activity was observed for 27g PEG added sol-gel derived film and surface area of this film is measured as 44m2/m2. Ascorbic acid presence shows a significant increase in the photocatalytic degradation activity of methyl orange. The sensitization effect of ascorbic acid was also compared with the effect of EDTA. It was found that the effect of ascorbic acid on the methyl orange degradation rate is significantly higher than the effect of EDTA. However, the effect of EDTA is more pronounced in water splitting reaction.

Thesis (D. Min.)--New Orleans Baptist Theological Seminary, 2000. / Includes abstract and vita. Includes bibliographical references (leaves 115-120).

Thesis (D.W.S.)--Institute for Worship Studies, 2002. / Abstract. Includes bibliographical references (leaves 231-236) and webography (leaves 237-239).

Thesis (M.S.)--University of Central Florida, 2009. / Adviser: Haitham Al-Deek. Includes bibliographical references (p. 173-177).

Thesis (D.W.S.)--Institute for Worship Studies, 2002. / Abstract. Includes bibliographical references (leaves 157-162).

Titanium Dioxide (TiO 2) has been considered an ideal photocatalyst due to factors such as its photocatalytic properties, chemical stability, impact on the environment and cost. However, its application has been primarily limited to ultraviolet (UV) environments due to its high band gap (3.2 eV). This high band gap limits the harvesting of photons to approximately 4% of sunlight radiation. Research today is focused on lowering this gap by doping or coupling TiO 2 with other semiconductors, transition metals and non-metal anions, thereby expanding its effectiveness well into the visible range. This thesis explores the effects of thermal and thermochemical ammonia treatment of nano-particulated TiO 2. The objective is to synthesize a photocatalytic activity in the visible range while at the same time retaining its photocatalytic properties in the UV range. Specifically, this study utilizes pure commercial nano-particulated TiO 2 powder (Degussa P-25), and uses this untreated TiO2 as a baseline to investigate the effects of thermal and thermochemical treatments. Nitrogen-doping is carried out by gas phase impregnation using anhydrous ammonia as the nitrogen source and a tube furnace reactor. The effects of temperature, time duration and gas flow rate on the effectiveness of thermally and thermochemically treated TiO 2 are examined. Thermally treated TiO 2 was calcinated in a dry inert nitrogen (N2) atmosphere and the effects of temperature and treatment duration are investigated. The band gap of the thermally treated and thermochemically ammonia treated TiO 2 have been measured and calculated using an optical spectrometer. The photocatalytic properties of all materials have been investigated by the degradation of methyl orange (MO) in an aqueous solution using both visible simulated solar spectrum (VSSS) and simulated solar spectrum (SSS) halogen light sources. Methyl orange degradation has been measured and calculated using an optical spectrometer. The phase structure and particle size of the materials is determined using x-ray diffraction (XRD). The BET surface area of the samples has been obtained using an Autosorb. Surface or microstructure characterization has also been obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

From 1961 to 1971 the United States and the Republic of South Vietnam used chemicals to defoliate the coastal and upload forest areas of Viet Nam. The most notorious of these chemicals was named Agent Orange, a weaponized herbicide made up of two chemicals that, when combined, produced a toxic byproduct called TCDD-dioxin. Studied suggest that TCDD-dioxin causes significant human health problems in exposed American and Vietnamese veterans, and possibly their children (Agency, U.S. Environmental Protection, 2011). In the years since the end of the Vietnam War, volumes of discourse about Agent Orange has been generated, much of which is now digitally archived and machine-readable, providing rich sites of study ideal for “big data” text mining, extraction and computation. This study uses a combination of tools and text mining scripts developed in Python to study the descriptive phrases four discourse communities used across 45 years of discourse to talk about key issues in the debates over Agent Orange. Findings suggests these stakeholders describe and frame in significantly different ways, with Congress focused on taking action, the New York Times article and editorial corpus focused on controversy, and the Vietnamese News Agency focused on victimization. Findings also suggest that while new tools and methods make lighter work of mining large sets of corpora, a mixed-methods approach yields the most reliable insights. Though fully automated text analysis is still a distant reality, this method was designed to study potential effects of rhetoric on public policy and advocacy initiatives across large corpora of texts and spans of time.