Chemistry Commons^™

Design And Synthesis Of Novel Azasteroids And Pseudoazulenyl Nitrones, Nagaraju Birudukota

FIU Electronic Theses and Dissertations

Steroids are one of the essential classes of bioactive compounds and are involved in many biological functions which include their role as signaling compounds, the alteration of membrane fluidity and the regulation of a variety of metabolic processes. In order to identify novel compounds with beneficial pharmacological action, the synthesis of modified steroids is gaining much attention in recent years. Among those analogs, azasteroids are one of the most important classes which display a variety of biological activities, often free from undesirable side effects. The challenges in the synthesis of steroids, particularly azasteroids, and the potential of azasteroids as novel …

Going Beyond The Analysis Of Common Contaminants: Target, Suspect, And Non-Target Analysis Of Complex Environmental Matrices By High-Resolution Mass Spectrometry, Anna Katarina Huba

FIU Electronic Theses and Dissertations

The advancements in the field of analytical chemistry, and especially mass spectrometry, have been redefining the field of contaminant detection. While more traditional analysis was sufficient to screen for a small number of well-known compounds, new techniques such as high-resolution mass spectrometry, have enabled a fairly comprehensive screening for previously unknown contaminants. This is enormously beneficial with respect to the analysis of water, air, or soil quality in a society that continuously introduces novel anthropogenic compounds into the environment. This dissertation, thus, focused on the analysis of the uncharacterized portion of compounds in two types of complex environmental matrices (i.e., …

Carbon Nanotube- And Gold Nanoparticle-Based Materials For Electrochemical And Colorimetric Sensing Applications, Janak Paudyal 9255967

FIU Electronic Theses and Dissertations

Carbon nanotubes (CNTs) and gold nanoparticles (AuNPs) are widely used for sensing applications due to their distinctive electrical and optical properties, and we have explored the development of methods that enable the incorporation of these nanomaterials into new and improved sensing devices.

As a means for fabricating simple, low-cost and fast detection platforms for various applications, we have developed paper-based electrochemical detection platforms based on CNTs or platinum nanoparticle (PtNP)-CNT composite materials. We describe the use of a paper-based, low density, a three-dimensional thin film of interconnected CNTs as an electrode material. We studied the electrochemical properties of these paper-based …

Synthesis And Characterization Of A Hydrolytically Stable Photochromic Copolymer Containing An N-Alkylindolylfulgimide, Samina Yasmeen

FIU Electronic Theses and Dissertations

Fulgides and fulgimides comprise one class of thermally irreversible photochromic organic compounds. Light dependent isomerization, has made these organic molecules promising materials for several applications, including optical memory devices, and switches. Hydrolytic stability of fulgides and fulgimides is crucial for their practical applications in biological systems and humid environments. Fulgimides, the most important derivative of fulgides, have a succinimide ring, which, unlike the anhydride ring, of fulgides, is resistant to hydrolytic degradation. A novel N-alkylindolylfulgimide was synthesized and copolymerized with acrylamide. The photochromic and hydrolytic properties of the copolymer in phosphate (pH 7.4) and acetate (pH 5.0) buffer solutions …

Mercury Sulfide Dissolution In Environmental Conditions: Thermodynamic And Kinetic Approaches, Ping Jiang

FIU Electronic Theses and Dissertations

Mercury (Hg) is a global contaminant of ecosystems and human health risk, with complicated biogeochemical processes. Mercury sulfide (HgS) dissolution has been suggested as a key process in Hg cycling, as it could potentially increase the pool of inorganic Hg (iHg) for the production of methylmercury (MeHg). Despite previous sporadic observations of enhanced HgS dissolution under certain conditions, much remains unclear on mechanisms of HgS dissolution. The objective of my research was to advance the mechanistic understanding of HgS dissolution, concerning re-adsorption of released Hg, effects of thiol-ligands, and Hg speciation.

Considering the lack of feasible techniques to differentiate dissolution …

Kinetics And Reaction Mechanisms For Methylidyne Radical Reactions With Small Hydrocarbons, Joao Marcelo Lamim Ribeiro

FIU Electronic Theses and Dissertations

The chemical evolution with respect to time of complex macroscopic mixtures such as interstellar clouds and Titan’s atmosphere is governed via a mutual competition between thousands of simultaneous processes, including thousands of chemical reactions. Chemical kinetic modeling, which attempts to understand their macroscopic observables as well as their overall reaction mechanism through a detailed understanding of their microscopic reactions and processes, thus require thousands of rate coefficients and product distributions. At present, however, just a small fraction of these have been well-studied and measured; in addition, at the relevant low temperatures, such information becomes even more scarce. Due to the …

The Optimization Of Pressure Cycling Technology (Pct) For Differential Extraction Of Sexual Assault Casework, Vanessa Martinez

FIU Electronic Theses and Dissertations

A two-step protocol has been devised as a rapid and selective alternative to conventional differential extraction techniques with an increased recovery of DNA. The protocol involves pressure cycling with the Barocycler^® NEP 2320 from Pressure Biosciences. Inc. in alkaline conditions for epithelial cell lysis and removal. This step is followed by alkaline lysis at 95^º C for extraction of sperm cell DNA. At 1:1 or 2:1 female to male cell ratios, high selectivity and complete separation can be achieved. But at higher ratios, male allelic dropout is observed. This protocol has been modified to generate a clean male …

Carotenoids And Fatty Acids In Early Lactation: A Study Of A Peruvian Population, Vanesa Mendez

FIU Electronic Theses and Dissertations

Lipid soluble carotenoids are micronutrients present in human milk that serve as precursors of vitamin A and also play an important role protecting cells from damage arising from photooxidative processes and reactive oxygen species. Fatty acids comprise about 3-5% of human milk and are mainly present as triglycerides. They are a major energy source for the infant and are necessary to support cell growth required for normal development and maturation of critical organs. Transport of carotenoids into milk has been little studied and there has been no previous investigation of the relationship of carotenoid transport with that of individual fatty …

Qualitative Analysis For The Characterization And Discrimination Of Printing Inks, Rhett J. Williamson

FIU Electronic Theses and Dissertations

Improvements in printing technology and the wide accessibility of advanced printers has resulted in an increase in counterfeiting. Of particular interest to forensic document examiners, ink analysis of security documents has emerged as an important tool for the analysis, comparison, and association of inks to a potential production source. In this study, methods were developed for Py-GC/MS, ATR-FTIR, DART-MS, and MALDI-MS analyses of printing inks of four classes: 78 inkjet inks, 76 toners, 79 offset inks, and 86 intaglio inks in order to generate information on the organic chemical characterization of the inks to determine the ability to associate and …

Synthetic Studies Toward A Novel Hydroxylamine Of Potential Utility In The Preparation Of Mitochondriotropic Nitrones, Gloria Patricia Perez

FIU Electronic Theses and Dissertations

Mitochondrial dysfunction and oxidative stress have been linked with many pathological conditions. Studies suggest that antioxidants able to accumulate in the inner regions of the mitochondria as well as possessing the chemical entities to cross membranes such as the blood brain barrier, could potentially overcome many of the limitations found with current antioxidants.

Nitrones have demonstrated great antioxidant potential due to their free radical scavenging properties, cardio and neuro-protective activities. In this research, several synthetic studies were performed with the aim of synthesizing a novel hydroxylamine of potential utility for the preparation of mitochondria targeted nitrones. These studies resulted in …

Qualitative Detection Of Selected Designer Drugs And Relevant Metabolites In Environmental Water Samples, Marley Pruyn

FIU Electronic Theses and Dissertations

Designer drugs are compounds which have been synthetically derived from illicit drugs. After consumption, drugs and their metabolites are introduced into the sewage water which is treated and disposed into the environment. A combined target, suspect and non-target workflow was created to detect designer drugs in environmental water samples. Multiple water samples were spiked with an unknown mixture of drugs and metabolites to assess the efficiency of the method. Samples were collected from sewage influent and effluent pipes, downstream from a sewage outfall and reclaimed water. Analysis was conducted with high resolution MS using the QExactive Orbitrap. Screening was performed …

Dna Aptamer Confirmation And Utilization For The Cyanotoxin, Cylindrospermopsin, Diane M. Catlin

FIU Electronic Theses and Dissertations

Cyanotoxins are posing an increasing threat to the health of humans and wildlife. Cylindrospermopsin is a cyanotoxin that occurs in warm climates and is harmful when ingested. The toxic effects of CYN can affect multiple organ systems. The effects, coupled with the evidence of a mass contamination of a water supply in Australia, prove that CYN needs to be investigated further.

Aptamers have become a desirable method for detection of CYN as a result of an aptamer’s high specificity and the ability to scale up experiments. Aptamers have been designed to bind with a variety of targets, including cyanotoxins. An …

Analysis Of Improvised Explosives By Electrospray Ionization - Mass Spectrometry And Microfluidic Techniques, Inge Corbin

FIU Electronic Theses and Dissertations

Improvised explosives may be based on smokeless gunpowder, fertilizers, or inorganic oxidizers such as nitrate (NO3-), chlorate (ClO3-), and perchlorate (ClO4-) salts.

Identification is a priority for the military and law enforcement but due to their varying physical properties and complexity, identification can be challenging. Consequently, three methods have been developed to aid in presumptive and confirmatory detection.

Smokeless powder contains plasticizers, stabilizers, dyes, opacifiers, flash suppressants, and other compounds. Identification of these additives can narrow down or identify the brands of smokeless powder used in a device. Fourteen organic smokeless powder components were identified by capillary electrochromatography (CEC) using …

Development Of A Primary Ion Column For Mass Spectrometry-Based Surface Analysis, Raul A. Villacob

FIU Electronic Theses and Dissertations

Secondary Ion Mass Spectrometry (SIMS) is a powerful technique for high spatial resolution chemical mapping and characterization of native surfaces. The use of massive cluster projectiles has been shown to extend the applicable mass range of SIMS and improve secondary ion yields 100 fold or beyond. These large projectiles however, present a challenge in terms of focusing due to the initial spatial and kinetic energy spreads inherent to their generation. In the present work, we describe the development and construction of a novel primary ion (PI) column employing a gold nanoparticle – liquid metal ion source (AuNP-LMIS) and the coupling …

Insight Into The Inhibition Of Ribonucleotide Reductases By 2'-Chloro-2'-Deoxynucleotides And 2'-Azido-2'-Deoxynucleotides: Biomimetic Studies With Model Substrates, Mukesh M. Mudgal Dr.

FIU Electronic Theses and Dissertations

Ribonucleotide Reductases (RNRs) are crucial enzymes that catalyze reduction of ribonucleotides to deoxyribonucleotides, required for the biosynthesis of DNA. Vital role played by RNR in the biosynthesis of DNA and its control on cell growth made it one of the main targets for anticancer therapy. Several laboratories clarified the aspects of reaction cascades at active site of RNR. Biochemical studies of RNR by Stubbe for the inactivation of RDPR by 2'-chloro-2'-deoxyuridine-5'-diphosphate emphasizes departure of chlorine as an anion, while biomimetic studies by Robins with 6'-O-nitro-2'-chloro-homonucleosides emphasizes the elimination of chlorine substituent from 2'-position as a radical. To clarify …

Gold Nanoparticle-Based Colorimetric Sensors For Detection Of Dna And Small Molecules, Pingping Liang

FIU Electronic Theses and Dissertations

Biosensors have proven to be a powerful tool for detecting diverse targets, such as proteins, DNA, and small molecules representing disease biomarkers, toxins, drugs and their metabolites, environmental pollutants, agrichemicals, and antibiotics with high sensitivity and specificity.

The major objective of the research described in this dissertation was to develop low cost, low sample volume, highly sensitive and specific AuNP-based colorimetric sensor platforms for the detection of DNA and small molecules. With this in mind, we propose an instrument-free approach in chapter three for the detection of NADH with a sensor constructed on a paper substrate, based on the target-induced …

Conformational Dynamics And Stability Associated With Magnesium Or Calcium Binding To Dream In The Regulation Of Interactions Between Dream And Dna Or Presenilins, Khoa Ngoc Pham

FIU Electronic Theses and Dissertations

Downstream regulatory element antagonist modulator (DREAM) is involved in various interactions with targets both inside and outside of the nucleus. In the cytoplasm, DREAM interacts with the C-terminal fragments of presenilins to facilitate the production of β-amyloid plaques in Alzheimer’s disease. In the nucleus, Ca²⁺ free DREAM directly binds to specific downstream regulatory elements of prodynorphin/c-fos gene to repress the gene transcription in pain modulation. These interactions are regulated by Ca²⁺ and/or Mg²⁺ association at the EF-hands in DREAM. Therefore, understanding the conformational dynamics and stability associated with Ca²⁺ and/or Mg²⁺ binding to DREAM …

Exhaled Breath Analysis Of Smokers Using Cmv-Gc/Ms, D'Nisha D. Hamblin

FIU Electronic Theses and Dissertations

The aim of this research was to demonstrate the potential of the novel pre-concentration device, capillary microextraction of volatiles (CMV), for breath analysis. The CMV offers dynamic sampling of volatile organic compounds with its simple coupling to a GC inlet for GC/MS analysis, avoiding expensive thermal desorption instrumentation needed for sorbent tubes, as well as an increased surface area over a single SPME fiber. CMV collectively identified 119 compounds in the breath of 13 self-reported smokers and 7 nonsmokers. The presence and intensity of twelve compounds were used to classify all the nonsmokers 100% of the time using Principal Component …

Characterizing The Molecular Structure And Reactivity Of Natural Organic Matter In The Everglades, Wenxi Huang

FIU Electronic Theses and Dissertations

Mangroves are the dominant vegetation in Everglades estuarine environment and are known to contain polyphenols such as tannins, which present similar fluorescence properties as some amino acid fluorophores. In the present study, gas chromatography–mass spectrometry (GC/MS) was used to quantify gallic acid, which is a normal monomer of polyphenols. The quantitative GC/MS analytical method was developed using gallic acid and tannic acid standards to quantify the false ‘protein-like’ fluorescence in DOM. The present study also compared the optical properties, reactive species (RS) production and radical scavenging ability of DOM from different regions of the Everglades and a correlation was observed …

Hydrogeochemical Modeling Of Saltwater Intrusion And Water Supply Augmentation In South Florida, Yonas T. Habtemichael

FIU Electronic Theses and Dissertations

The Biscayne Aquifer is a primary source of water supply in Southeast Florida. As a coastal aquifer, it is threatened by saltwater intrusion (SWI) when the natural groundwater flow is altered by over-pumping of groundwater. SWI is detrimental to the quality of fresh groundwater sources, making the water unfit for drinking due to mixing and reactions with aquifer minerals. Increasing water demand and complex environmental issues thus force water utilities in South Florida to sustainably manage saltwater intrusion and develop alternative water supplies (e.g., aquifer storage and recovery, ASR).

The objectives of this study were to develop and use calibrated …

Physical And Chemical Characterization Of Crude Oil-Water Mixtures: Understanding The Effects Of Interfacial Process To Chemical Bioavailability, Kathia A. Sandoval

FIU Electronic Theses and Dissertations

This work detailed the physical and chemical characterization of oil water mixtures prepared using fresh and weathered Macondo related oils under different conditions of mixing energy/time and in the presence/absence of chemical dispersants. The results indicated that WAFs produced consistent, droplet free solutions for both source and weathered oils with concentration ranges that represented the soluble components of the oil used. Chemically enhanced WAFs prepared with the source oil generated a large amount of micron-size droplets; however the viscosity of the weathered oils were a limiting factor for the preparation of CEWAFs with weathered oils. Droplet size distributions were influenced …

Determination Of Human Scent Biomarkers For Race, Ethnicity And Gender, Lauren J. Colόn Crespo

FIU Electronic Theses and Dissertations

Human scent has been the focal point of diverse scientific interests and research initiatives for the past several years. The knowledge gained about its composition has favored the advancement of multiple disciplines, and promoted the development of a wide variety of applications. Among these applications is the use of human scent as a resource for Forensic investigations, where scent profiles are often used as evidence to associate individuals to the scene of a crime. The characteristic nature of individual human scent has enabled this type of evidence to be used as a biometric tool for the differentiation of subjects. Nevertheless, …

Conjugated Polymer-Based Biomaterials Through Controlled Self-Assembly, Megan Twomey

FIU Electronic Theses and Dissertations

Synthetic polymeric materials have gained significant use as biological materials (biomaterials) in biomedical and pharmaceutical applications. As a result, a demand for well-defined polymers with tunable properties has emerged. The synthetic versatility of polymeric biomaterials allows the opportunity to understand the structure-property relationship of materials and their cellular interactions. A novel class of polymeric biomaterials are conjugated polymers (CPs), which possess desirable physicochemical and excellent photophysical properties, including inherent fluorescence. The synthetic versatility of CPs allows easy modification of the conjugated backbone to tune emission and side chain structures to adjust biocompatibility through increased water solubility, controlled biodegradability, and incorporation …