Columbus State University Honors College: Senior Theses, Fall 2020/Spring 2021

This is a collection of senior theses written by honors students at Columbus State University during the Fall 2020 and Spring 2021 semesters.https://csuepress.columbusstate.edu/honors_theses/1002/thumbnail.jp

Hemoglobin Biosynthesis in Vitreoscilla stercoraria DW: Cloning, Expression, and Characterization of a New Homolog of a Bacterial Globin Gene

In the strictly aerobic, gram-negative bacterium Vitreoscilla strain C1, oxygen-limited growth conditions create a more than 50-fold increase in the expression of a homodimeric heme protein which was recognized as the first bacterial hemoglobin (Hb). The recently determined crystal structure of Vitreoscilla Hb has indicated that the heme pocket of microbial globins differs from that of eukaryotic Hbs. In an attempt to understand the diverse functions of Hb-like proteins in prokaryotes, we have cloned and characterized the gene (vgb) encoding an Hb-like protein from another strain of Vitreoscilla, V. stercoraria DW. Several silent changes were observed within the coding region of the V. stercoraria vgb gene. Apart from that, V. stercoraria Hb exhibited interesting differences between the A and E helices. Compared to its Hb counterpart from Vitreoscilla strain C1, the purified preparation of V. stercoraria Hb displays a slower autooxidation rate. The differences between Vitreoscilla Hb and V. stercoraria Hb were mapped onto the three-dimensional structure of Vitreoscilla Hb, which indicated that the four changes, namely, Ile7Val, Ile9Thr, Ile10Ser, and Leu62Val, present within the V. stercoraria Hb fall in the region where the A and E helices contact each other. Therefore, alteration in the relative orientation of the A and E helices and the corresponding conformational change in the heme binding pocket of V. stercoraria Hb can be correlated to its slower autooxidation rate. In sharp contrast to the oxygen-regulated biosynthesis of Hb in Vitreoscilla strain C1, production of Hb in V. stercoraria has been found to be low and independent of oxygen control, which is supported by the absence of a fumarate and nitrate reductase regulator box within the V. stercoraria vgb promoter region. Thus, the regulation mechanisms of the Hb-encoding gene appear to be quite different in the two closely related species of Vitreoscilla. The relatively slower autooxidation rate of V. stercoraria Hb, lack of oxygen sensitivity, and constitutive production of Hb suggest that it may have some other function(s) in the cellular physiology of V. stercoraria DW, together with facilitated oxygen transport, predicted for earlier reported Vitreoscilla Hb

Efficient photocatalytic hydrogen generation by silica supported and platinum promoted titanium dioxide

Titanium dioxide was supported on mesoporous silica and promoted with Pt and Ru. The supported photocatalysts show high surface area and better photocatalytic activity in visible light as compared to the benchmark Degussa P25. These photocatalysts were characterized using XRD, BET-SA, and UV-DRS techniques. The surface area of supported photocatalyst was 140.6 m2/g which is higher than Degussa P- 25. Supported photocatalyst was evaluated for hydrogen evolution via water splitting reaction using ethanol as a sacrificial donor. Hydrogen yield observed is 4791.43 mmol/h/g of TiO2 and that for P-25 is 161 mmol/h/g of TiO2 under visible light irradiation. The value is 30 times higher than benchmark material Degussa P-25. This photocatalyst is also found stable up to 24 h without replenishing with sacrificial donor ethanol. However silica gel/TiO2/Ru does not show any exciting result for hydrogen generation. The effect of various operating parameters like photocatalyst loading, Illumination time and intensity of light on supported photocatalyst also has been studied

Influence of zeolitic structure on photoreduction property and hydrogen evolution reaction

A new photocatalytic material developed by supporting TiO2 in combination with transition metal ion like cobalt and heteropolyacid (HPA) on the surface is facilitating enhanced photoreduction of water and methyl orange. Zeolites being a solid acid play an important role in the electron transfer reaction, facilitated by the Lewis acid sites in the form of aluminium ions. In the present work, four different zeolite matrices namely, NaY zeolite, ultrastable zeolite Y, beta zeolite and titanium silicate-1 have been used for the synthesis of new photocatalytic materials. These materials have been evaluated for water splitting by an initial screening procedure using methyl orange photoreduction. The photocatalyst containing Na Y has emerged as a potential photocatalyst with hydrogen evolution rate of 2730 mmol/h/g of TiO2. Hydrogen evolution was not observed for the composite photocatalysts synthesized using the other zeolite matrices. It has been observed that physicochemical properties like Si/Al ratio, acidity and basicity of the zeolite support have a tremendous influence on the photoreduction property of these zeolite matrices

Chlorophyll-based photocatalysts and their evaluations for methyl orange photoreduction

Immobilization of chlorophyll on different functionalized mesoporous materials has been attempted. The replacement of butanediol with monoethanol amine has resulted in increase in chlorophyll loading by a factor of two. The maximum immobilization of chlorophyll was on MCM-41 functionalized with monoethanolamine MCM-41/MEA/Chl) as compared to other mesoporous materials. This material has been characterized using XRD, UV–vis diffuse reflectance spectroscopy, scanning electron microscopy (SEM-EDX) and fluorescence spectroscopy. The photocatalytic reduction ofmethyl orange (MO)was studied using MCM-41/MEA/Chl as photocatalyst under the visible light. The photocatalytic reduction of MO was 0.396 mg/g of MCM-41/MEA/Chl photocatalyst as compared to 0.508 mg/g of TiO2 for that of Degussa P-25 photocatalyst. The effect of various operating parameters like catalyst loading, initial concentration and intensity of light has also been studied. Photocatalytic property of chlorophyll-based photocatalytic material indicates that chlorophyll acts as a reaction center, which absorbs visible light and generates electron, which is transferred to different electron acceptors reducing MO into derivative of hydrazine

Hydrogen evolution by a low cost photocatalyst: Bauxite residue

Bauxite residue or red mud which is an aluminium industry waste has been used as a novel low cost photocatalyst active in visible light for the generation of hydrogen from water. The driving force behind the use of bauxite residue as a photocatalyst is not only the fact that it is widely available but also bauxite residue is a fine grained mixture of oxides and hydroxides (Fe2O3, TiO2, SiO2, and Al2O3, Al(OH)3). The photocatalyst was characterized with respect to BET-SA, UV-DRS, XRD, SEM and EDX. Hydrogen yield of 4600 mmol/h/g of TiO2 was achieved as compared to hydrogen evolution rate of 164 mmol/h/g of TiO2 for commercially available titania Degussa P-25. However, the hydrogen evolution was 20.85 mmol/h/g of photocatalyst. The results suggest that bauxite residue appears to be a novel low cost photocatalyst. The various operating conditions of photocatalytic hydrogen generation were studied which include amount of catalyst, illumination intensity, illumination time, effect of various sacrificial donors etc

Nano cobalt oxides for photocatalytic hydrogen production

Nano structured metal oxides including TiO2, Co3O4 and Fe3O4 have been synthesized and evaluated for their photocatalytic activity for hydrogen generation. The photocatalytic activity of nano cobalt oxide was then compared with two other nano structured metal oxides namely TiO2 and Fe3O4. The synthesized nano cobalt oxide was characterized thoroughly with respect to EDX and TEM. The yield of hydrogen was observed to be 900, 2000 and 8275 mmol h�1 g�1 of photocatalyst for TiO2, Co3O4 and Fe3O4 respectively under visible light. It was observed that the hydrogen yield in case of nano cobalt oxide was more than twice to that of TiO2 and the hydrogen yield of nano Fe3O4 was nearly four times as compared to nano Co3O4. The influence of various operating parameters in hydrogen generation by nano cobalt oxide was then studied in detail