Open Theses & Dissertations

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1,2-asymmetric induction in carbonyl compounds: a computational study
(University of New Brunswick, 2019) Retallick, Jeffrey; Deslongchamps, Ghislain
In asymmetric synthesis, it is important to reliably predict the major stereoisomeric product of a reaction. One such reaction is the nucleophilic addition to a carbonyl compound featuring an adjacent chiral carbon. Several reaction models exist in literature to predict the facial selectivity of these reactions. These models provide simple visual drawings to quickly predict the major product of such a reaction without requiring exhaustive quantum mechanical calculations. These models are used on a daily basis, and some models perform better than others, making it valuable to investigate which ones are the most effective. For the first time in this thesis, high-level computations have been performed on all of the literature models to verify their efficacy. The results of this thesis offers a definitive answer that the Felkin-Anh and Wintner models are the most effective, and that bent bond theory offers an interesting insight on the mechanics of these reactions.
A Formal Synthesis of Himachalene Sesquiterpenes
(University of New Brunswick, 2022-03) Algamal, Muhammad AbdAllah; MaGee, David I.
Insect communications rely on chemical signalling, using chemical substances called pheromones. These chemicals are specific to individuals of the same species and are used for different purposes, such as gathering for food, mating, alerting other individuals to dangers, setting boundaries, or limiting the number of individuals in a certain space or on one host and to follow other individuals. The use of pheromones to disrupt insect behaviour, more specifically mating, became one of the most important and environmentally friendly pest control strategies as a core element of integrated pest management (IPM) programs. Pheromones are also used to monitor insect populations and in traps with other toxic substances to reduce the risks and losses caused by invasive species. In an endeavour to study the pheromonal activity of four himachalene sesquiterpenes as an insect pest management strategy for the control of the blueberry flea beetle Altica sylvia Malloch (a major insect pest of the blueberry plantations in North America), attempts to repeat literature synthetic routes were found to be low yielding. Where the nor-himachalene ketone was considered a convenient precursor to the rest of the target himachalenes, several strategies were investigated, of which two new routes to achieve the desired compound were found to be more efficient. The first furnished the 6,7-bicyclic core of the himachalenes via a sequence of allylic alkylation (AA), Cope rearrangement, and ring-closing metathesis (RCM). The second route relied on RCM to construct the required 2,2,6-trimethylcycloheptanone that could then be subjected to Robinson annulation to furnish the target precursor. These routes are easily amenable to result in an asymmetric version. Other routes examined included a formal [2+2] cycloaddition to construct a cyclobutane intermediate that can go in a ring opening-annulation sequence to form the six-membered ring, the use of Mukaiyama-Michael addition (MMA) to introduce the carbon sidechain required for the annulation of the 2,2,6-trimethylcycloheptanone and an intramolecular Diels-Alder (IMDA) cycloaddition to construct the fused 6,7-bicyclic system from an open chain. During the investigation of the MMA reaction, we developed new organocatalytic conditions using bis(trifluoromethane)sulfonimide (TFI) as the catalyst that was found to be effective at low catalyst loading.
A hyperfine analysis of the [4th power]Π–X[4th power]Σˉ transition of rhenium monocarbide
(University of New Brunswick, 2016) Hall, Ryan; Adam, Allan
In this thesis, the first spectroscopic study of rhenium monocarbide, ReC, is presented. ReC molecules were produced via a supersonic molecular jet apparatus. The ReC spectrum was studied utilizing both high and low-resolution spectroscopic techniques, including laser induced fluorescence (LIF) and dispersed fluorescence (DF). The low-resolution survey scan was performed and four bands from this system were identified, and studied using high-resolution. This clearly revealed the [superscript 187]ReC and [superscript 185]ReC isotopologues, and extensive hyperfine structure, which resulted in a complex spectrum. This experimental data appears to be consistent with a [4th power]Π–X[4th power]Σˉ transition, which agrees with Dr. Grein’s [1] calculations. A program has been written using the Hamiltonian matrix for a [4th power]Π–X[4th power]Σˉ transition, as reported in the literature [2]. After performing a fit using assigned transitions in our spectrum, molecular constants were extracted to describe the molecular system. Dispersed fluorescence spectra were used to extract vibrational information.
A Metabolomic Investigation of Radula complanata
(University of New Brunswick, 2022-04) Blatt-Janmaat, Kaitlyn; Qu, Yang
Bibenzyls are a medicinally interesting class of specialized metabolites that are found throughout the plant kingdom. Liverworts (Phylum Marchantiophyta) are one of the most prolific producers of bibenzyls, specifically plants of the Radula genera, however the in planta function and biosynthesis of these metabolites has been largely unexplored. To investigate the role of these metabolites in planta, six prenylated bibenzyls were isolated from Radula complanata and their response to various phytohormones was investigated. The whole metabolic response was also explored through untargeted metabolomics to investigate larger metabolic shifts that were occurring. Unfortunately, due to the small size and slow growing nature of liverworts, harvesting these natural products directly from the plant is not feasible or sustainable. To address this, transcriptome mining was conducted to identify candidate genes involved in the biosynthetic pathway that could be expressed in heterologous systems for in vitro bibenzyl production.
A new synthetic route to the himachalene family
(University of New Brunswick, 2024-07) Keyes, Cameron; MaGee, David I.
Himachalene sesquiterpenes are believed to play a significant role in the chemical signaling between Blueberry Flea beetles, a pest of interest in Atlantic Canada. Due to their role in blueberry crop loss, controlling the outbreak of this pest is of significant economic importance, especially in Atlantic Canada. Synthesis of himachalenes will allow for pheromone replication of the blueberry flea beetle for monitoring and trapping purposes. Attempts to synthesize the himachalenes using previously reported schemes in the literature have proved inconsistent. A new synthetic approach to the himachalene skeleton is investigated, building upon the work of Dr. Algamal and his attempts at reaching the himachalene skeleton. This new synthetic approach begins with cheap and readily available starting materials and aims to eliminate the common challenges associated with established syntheses. The 12-step synthesis developed in this thesis provides a more consistent route to the himachalenes of interest.
A positively charged, diffusion resistant, bispyridinylidene derivative as an anolyte for organic redox flow batteries
(University of New Brunswick, 2016) Wheeler, Hillary; Dyker, Adam
Redox flow batteries represent a leading technology for large scale energy storage, which is necessary as the use of renewable energy becomes more important. Organic redox flow batteries are a new class of redox flow batteries that have the potential to provide higher cell voltages and improved energy densities. Organic materials with high redox potentials are suitable for applications as cathode materials and are readily available. Research in our group has focused on developing anode materials, which are much less common. Previously, the Dyker group has evaluated non-flowing cells with bispyridinylidene as an anolyte material and TEMPO as a catholyte material separated by an anion exchange membrane (AEM). Cyclic voltammetry (CV) studies showed that the battery degrades due to diffusion of the neutral active materials across the AEM. This thesis describes the preparation and evaluation of a new anolyte couple which lessened the problem of diffusion through the anion exchange membrane owing to the permanent positive charge in both charged and discharged states. Cells exhibited high coulombic, voltage, and energy efficiencies, though also exhibited a drop in capacity after the first charge, thought to perhaps be associated with the impurity present in the electrolyte or crossover of catholyte materials. In order to determine the relative diffusion rates, cells were assembled with active material on one side of the cell and blank electrolyte on the other side. These cells were left to allow for possible diffusion after which CV was carried out on the disassembled cell to determine the extent of active material diffusion. These results led to the belief that the amount of positive charge affects the extent to which the species cross the AEM. Therefore, as a tetracation / dication redox couple, the new anolyte was successful in reducing the amount of active material diffusion across the AEM.
Alkaline polymer electrolyte with sub-zero conductivity for zinc-air batteries
(University of New Brunswick, 2022-07) Khor, Chun Keat; Ignaszak, Anna
Due to the increasing demand for flexible electronics that can function in harsh environments, research on flexible solid-state batteries, especially zinc-air batteries (ZAB), is expanding. However, the electrolyte in the current commercially available ZAB still suffers from drying out after prolonged exposure to air. Here, the synthesis of a flexible conductive hydrogel electrolyte that can function at low temperatures was attempted. The polymer chain was made up of potassium polyacrylamide-co-acylate and crosslinked using N,N’-methylenebisacrylamide. Three variants of cellulose were added to improve the stretchability of the hydrogel. We found out that acrylamide decomposed in the high concentration of base required for ZAB electrolyte. Further understanding of the polymer chains had helped improve our hydrogel design, which can tolerate high molarity of base and functions at -23°C. Electrochemical studies were carried out to understand the charge transport properties of the electrolyte in the hydrogel.
Approaches toward white light emission and programmable fluorescence, along with the serendipitous discovery of a series of pericyclic cascade reactions
(University of New Brunswick, 2023-06) Price, Jayden T.D.; Eisler, Sara
Research in molecular fluorescence has led to more energy-efficient LED displays, single-molecule level detection limits in microscopy, and increasingly complex anti-counterfeiting measures. However, synthetic and design challenges associated with the realization of white, red, and blue light-emitting systems with the properties required for commercialization still exist. First, we explore the use of multicomponent photoluminescent systems, containing a mixture of simultaneously emitting organic molecules to access white light and programmable emission color. By mitigating the potential for energy transfer through the control of concentration, we show that the emission color is approximated as a linear combination of the emitting components and their corresponding brightness. Based on these results, we demonstrate that the ratio of red, green, and blue emitters needed to achieve hard-to-reach WLE can be predictably determined. Second, we show that one molecular scaffold, thioarylmaleimide (TAM), can be used to access blue to deep-red emission colors with high quantum yields in just one synthetic step. A series of mono and bis-substituted TAMs are synthesized from commercially available starting material in moderate to excellent yields via Suzuki-Miyaura (SM) cross-coupling. Photophysical properties, including wavelength and quantum yield, are controlled by adjusting the conjugation, connectivity, and the number of thioaryl groups attached to the maleimide. A marked decrease in the SM coupling yield of monosubstituted TAMs prompted the serendipitous discovery of a series of pericyclic cascade reactions leading to crowded thienyl and benzo[b]thienyl fused architectures. Stereochemical assignment is achieved using a combination of NMR studies, chemical shift calculations and DP4+ analysis. Transition-state calculations support an asynchronous concerted mechanism and provide support to rationalize the regio- and diastereoselectivity that is observed.
Bipolar electrochemistry for the synthesis of functionalized carbon-polypyrrole supercapacitor electrodes
(University of New Brunswick, 2023-04) Patterson, Nigel; Ignaszak, Anna
Supercapacitors belong to the family of electrical energy storage systems alongside batteries and fuel cells. Their unique feature is having both high power and energy density making them suitable options where fast charging and long-lasting power are desired. Supercapacitance comes in two flavours, electric double layer capacitance (EDLC) and pseudocapacitance (PC). This thesis combines both in a single electrode using carbon EDLC base and polypyrrole PC coating. Various methods to bind the two using bipolar electrochemistry are the major focal points of this thesis. Bipolar electrochemistry is a wireless electrochemical setup that is green, scalable, and easily produces asymmetric/gradient products. The first project functionalizes carbon electrodes through diazonium salt reduction to electrochemically graft a linker group. Polypyrrole then binds to this linker in a copolymer-like fashion. Results showed that aqueous conditions produced a better product than non-aqueous conditions at 200 mF cm−2 compared to 11 mF cm−2. The second project incorporates metal-organic frameworks (MOFs) as the binding agent. This class of materials has some of the largest surface area densities ever measured. Filling this space with polypyrrole transforms the MOF from an electrical insulator to a conductor. Plain powder forms of three different MOFs synthesized using the solvothermal method were used to test the proof of concept. The results showed specific capacitances ranging from 300 to 600 mF cm−2. From this the MOF synthesis was adapted to use bipolar electrochemistry for direct electroplating. Once again carbon featured as the base while Cu MOF was deposited by the anodic dissolution method. The MOF layers were fragile and prone to detachment, but thermal oxidation of pyrrole in air was found to leave the MOFs intact. Loading solutions with higher pyrrole content resulted in greater improvements to the supercapacitance, up to 28 mF cm−2.
Capture of sulfur dioxide using sulfur oxydianions: synthesis and characterization of two novel compounds
(University of New Brunswick, 2013) Richardson, Stephanie; Passmore, Jack
One mole equivalent of SO2 reversibly reacts with [N(CH3)4]2SO4(s) to give [N(CH3)4]2S2O6(s) (1) containing the [O3SOSO2]2- ion, shown by Raman and IR to be an isomer of the [O3SSO3]2- dianion. The experimental and calculated (B3PW91/6-311+G(3df)) vibrational spectra are in excellent agreement and the IR spectrum is similar to that of the isoelectronic O3ClOClO2. Crystals of [N(CH3)4]2(O2SO)2SO2•SO2 were isolated from a solution of [N(CH3)4]2SO4 in liquid SO2. The X-ray structure showed that it contained the [(O2SO)2SO2]2- dianion (2). The characterized N(CH3)4 + salts 1 and 2 are the first two members of the (SO4)(SO2)x 2- sulfur oxydianions analogous to the well-known small cation salts of the SO4(SO3)x 2- polysulfates.
Carbon-based polymeric materials for stretchable supercapacitors
(University of New Brunswick, 2017) Radtke, Mariusz; Ignaszak, Anna
The urgent need for the development of efficient and environmentally-friendly energy storage devices has led to the exploration of new materials with chemically tailored properties. More specifically, the field of super- and ultracapacitors is currently moving forward to incorporate carefully modified carbon allotropes in the modern capacitor design. The main goal for previous research in designing capacitive materials has been to maximize their efficiency, without sacrificing environmental safety. This thesis presents a preparation of highly stretchable and heavy-metal-free electrodes based on polyacrylamide/ poly (N, N’- methylenebis(acrylamide)) hydrogels, which contained nanostructured carbons (e.g., graphene, multi-walled carbon nanotubes; MWCNTs, single-walled carbon nanohorns; SWCNHs) covalently bonded to conjugated polymer (polypyrrole; PPy). Carbon cores provided a large electrochemical double layer capacitance, whereas a conjugated polymer was the source of pseudocapacitance. The approach of joining two capacitance mechanisms within one molecule was completed by utilizing nanostructured carbons as polymerization initiators, while the pyrrole or 2-(1H-pyrrol-1-yl) ethyl methacrylate were used as monomers. Polymers were uniformly distributed around the carbon cores via oxidative radical polymerization, electrochemically aided atom transfer polymerization (e-ATRP), and reversible addition-fragmentation chain transfer polymerization (RAFT). The highest specific gravimetric capacitance of active nanocomposite was 456.86 F g[superscript -1], and was found to be highly dependent on the nature of the operating electrolyte. The detailed mechanistic computations, electrochemical quartz microbalance, and electrochemical studies have revealed that potassium chloride is the most suitable electrolyte for maximizing the electrochemical output of obtained nanocomposites. A series of stretchable (up to 1475 %) electrodes were prepared with emphasis on their conductivity, elasticity, and translucent properties. The task of dispersion of nanocomposites within the solid-state electrolyte, based on pAAm/pMBAA hydrogels containing KCl, was addressed by enhancing the zeta potential of active materials through the incorporation of perfluorated long aliphatic molecules (i.e., Nafion 117®). Electrochemical analysis by alternating the current electrochemical admittance spectroscopy, cyclic voltammetry, and the theoretical modeling of an equivalent circuit based on impedance spectroscopy have revealed a large interfacial specific gravimetric capacitance of the stretchable electrodes (up to 516.86 F g[superscript -1]). Prepared materials are stable up to 7500 charge/discharge cycles in liquid electrolytes and up to 717 cycles in hydrogels. Obtained products are market-grade materials for modern supercapacitors.
Carbonized metal-organic frameworks as bifunctional electrocatalysts for oxygen reduction/evolution reactions
(University of New Brunswick, 2023-10) Parsimehr, Hamidreza; Ignaszak, Anna
Electrochemical energy devices like batteries and fuel cells as benign high-performance solutions for energy issues have been swiftly developed in recent decades. Both metal-air batteries and fuel cells use a positive electrode (cathode) that has a similar chemical composition to facilitate oxygen reduction reactions (ORR) during their operation. The second important reaction involving oxygen species is the oxygen evolution reaction (OER). This process is used in water electrolyzers to generate oxygen. An electrocatalyst incorporated in the electrodes in the above-listed energy systems is key to the efficient ORR and OER processes. Such electrocatalyst plays a critical role in overall performance, stability, and long cycle lifetime. The main objective is to synthesize and evaluate the electrochemical performance of heteroatom-doped carbons made by pyrolysis of metal-organic frameworks (MOFs) and zeolitic imidazole frameworks (ZIFs). Although some of these catalysts demonstrated decent activity, further work is needed to prove their electrocatalytic performance.
Characterization of the biosynthetic pathway for medicinal monoterpenoid indole alkaloid
(University of New Brunswick, 2023-06) Guo, Jun; Qu, Yang
Monoterpenoid indole alkaloids (MIA) are a complex and diverse class of alkaloids found in nature, boasting over 3000 reported structures. Many MIAs exhibit human medicinal properties, such as the anti-cancer drugs vinblastine and camptothecin. In this thesis, two enzymes involved in the biosynthesis of a plant derived MIA was elucidated and functionally characterized. To achieve this, a bioinformatics approach was used to shortlist candidate genes from the source plant, which were then cloned into a heterologous system to characterize the enzymes they encode. Experiment results show that one of the candidate genes codes for the required enzyme responsible for the biosynthesis of this MIA. The discovery from this work will allow assembly of the complete biosynthetic pathway in baker’s yeast (Saccharomyces cerevisiae), facilitating de novo MIA synthesis.
Controlling regioselectivity of cyclization in heterocyclic alkynylamides
(University of New Brunswick, 2021-12) Infante, Genesis; Eisler, Sara
Competitive 5-exo/6-endo anionic intramolecular cyclization reactions in heterocyclic alkynylamides were explored via experimental and computational analysis. The 5-exo-dig cyclization pathway is usually disfavoured in heterocyclic systems, and 6-endo products are often both the kinetic and thermodynamic products. However, it was discovered that it is possible to shift selectivity toward the 5-exo-dig pyrrolone products and away from the less strained pyridinone products that are produced via the 6-endo-dig cyclization. Parameters such as identity of heteroatom, heteroatom positioning within the heterocycle, and functionality on the alkyne were investigated and in many cases were found to strongly influence product ratios. A series of computational studies was performed to provide further insight into the 5-exo and 6-endo-dig pathways in these heterocyclic systems. Theoretical predictions were found to reproduce experimental results, highlighting the predictive capabilities of the computations in determining preferred products. The established experimental and predictive computational protocols were then applied to more complex bisalkynylamides. The subsequent competing tandem cyclization pathways, 5-exo/6-exo-dig and 5-exo/7-endo-dig, were predicted and controlled using established experimental and theoretical concepts from earlier studies.
Cost efficient, scalable asymmetric synthesis of bronze birch borer kairomone (5s,7s)-7-Methyl-1,6-dioxaspiro[4.5]decane
(University of New Brunswick, 2021) Atwood, Graham Andrew; MaGee, David
With the increased use of birch trees, specifically non-native birches in parks, and beautification projects, an increase of infestations by the bronze birch borer (Agrilus anxius) has occurred. While reactive measures are available to try to remediate infested trees, a proactive strategy is not as widely available. (5S,7S)-7-Methyl-1,6-dioxaspiro[4.5]decane (5S,7S-conophthorin) has been identified as a possible kairomone that attracts bronze birch borers to susceptible trees. These susceptible trees include Eurasian varieties and stressed native North American species. While synthesized in the past, a scalable, cost efficient synthesis of this kairomone will likely enable its production industrially, and help allow for mass detection/trapping strategies of the pest to be implemented before infestations occur.
Design and synthesis of gold monolayer cluster supported catalysts: towards asymmetric synthesis
(University of New Brunswick, 2013) Abeysekera, Sumudu Deepa; MaGee, David
Asymmetric synthesis is the comer stone of the modem pharmaceutical industry. Its success can be attributed to the development of chiral catalysts that provide a high degree of enantioselectivity. The C₂ symmetric bisoxazoline (Box) ligand metal complexes have been a dominant force in the field of asymmetric catalysis. In recent years, the quest for metal free catalysis has resulted in the emergence of organocatalysts, such as the versatile MacMillan’s catalyst, with impressive success. The push towards environmentally friendly processes has ensued in the search for suitable support materials for catalysts since immobilization enhances the recovery, recyclability, and reuse of catalysts. Nanotechnology has become an integral part of science and has opened up the possibility of incorporating gold monolayer protected clusters (Au-MPCs) in asymmetric synthesis. Due to their large surface to volume ratio, Au-MPCs are believed to be ideal candidates for catalyst support materials. In an attempt to combine green chemistry with asymmetric synthesis, hexanethiol, octanethiol, dodecanethiol, and hexadecanethiol stabilized Au-MPCs were synthesized via the Schiffrin reaction as support materials. Thiol ended 10-carbon tethered Box ligand and MacMillan’s catalyst were synthesized and immobilized on the Au-MPCs through place exchange with stabilizing alkanethiols. The supported catalysts were designed to represent homogeneous, heterogeneous and enzyme type catalytic systems. Unfortunately, after the preliminary investigations of the Michael addition reaction between trans-β-nitrostyrene and indole with the Au-MPCs supported Box-Zn(OTf)₂ complexes, further analyses were terminated due to the publication of a similar study by a Japanese research team. The catalytic activity of the Au-MPCs supported MacMillan’s catalyst was tested with the Diels-Alder reaction between trans-cinnamaldehyde and cyclopentadiene and the 1,3-dipolar cycloaddition between trans-crotonaldehyde and nitrone. In addition, catalyst recovery and recyclability were also investigated. The endo/exo selectivity of these reactions was comparable to that of reactions catalyzed by homogeneous catalysts, but the yields and enantioselectivities were lower. The enzyme type catalytic system with catalyst supported on hexadecanethiol stabilized Au-MPCs showed the best catalytic activity with enantioselectivity remaining consistent with the recycled catalyst. A comparison of the catalytic activity with the catalyst supported on Merrifield resin, which is mainly a heterogeneous catalytic system, showed that Au-MPCs are better support materials for the MacMillan’s catalyst.
Detecting spoilage of tomatoes by ultrasound spectroscopy
(University of New Brunswick, 2018) Power, Alison Kathleen; Burns, David
Food spoilage caused by bacterial or fungal contamination can lead to cases of food poisoning and even death. Current techniques for spoilage detection cannot routinely measure packaged products. We present how ultrasound spectroscopy can be used to classify spoiled and non-spoiled samples of tomato juice. Spoilage was induced with a bacterium (Lactobacillus rhamnosus) and mold (Geotrichum candidum) commonly found in spoiled tomatoes and samples analyzed using ultrasound spectroscopy. Frequency profiles of the inoculated samples showed changes with spoilage when compared to control samples. Cross-validated multivariate models separated fresh and spoiled samples with 100% accuracy. A global model was created using the combined inoculation data resulting in a sensitivity and specificity each of 94% with an independent validation set resulting in 100% accuracy of separation. Overall, ultrasound spectroscopy shows promise in the detection of food spoilage. The potential for measuring food samples non-invasively could benefit both the food industry and consumers.
Developing new supramolecular tools for biomedical and environmental applications
(University of New Brunswick, 2020) Jennings, Christopher Samuel; Blight, Barry
Supramolecular chemistry has quickly developed from simple host-guest chemistry to the self-assembly of molecular building blocks to form large aggregates, both in solution and the solid state. Currently, supramolecular structures are being developed for several applications, including gas storage technologies, heterogeneous catalysis, chemical sensors and drug delivery systems. Among these structures are metal-organic frameworks (MOFs), metal-organic polyhedra (MOPs) and vesicles. Here, we assess the ability of MOFs to remove cholesterol from the bloodstream. A diverse series of MOFs were first selected from the literature and then synthesised, characterised and their ability to uptake cholesterol quantified by liquid phase ¹H NMR analysis. Further work was undertaken where different methodologies to encapsulate MOF particles within a vesicle - a lipid bilayer cell model - were explored. This process is designed to improve the biostability and bioavailability of the MOF candidates in their role as cholesterol-removal agents. This study led to the serendipitous finding that micron-sized MOF particles can be used to immobilise vesicles, which may provide an alternative strategy to the study of their biophysical and mechanical properties. Finally, two novel, fluorine-rich MOPs have been designed for the selective uptake of chlorofluorocarbons (CFCs), and for eventual use within the environmental chemistry domain. The molecular building blocks that comprise these MOPs have been synthesised and characterised, and the final steps of MOP synthesis and characterisation are currently ongoing.
Development of electrochemical biosensors for the direct detection of infectious disease
(University of New Brunswick, 2020) Flynn, Connor Daniel; Ignaszak, Anna
Infectious disease detection is an extremely important field, as clinicians and scientists around the world continue to seek improved diagnostics. Electrochemical biosensors represent an emerging class of diagnostic techniques that are rapid, inexpensive, and easily scalable. By combining the intricate interactions of biological molecules with the sensitive techniques of electrochemistry, these biosensors hold great promise in the future of infectious disease sensing. The current thesis explores the development of two such devices, for Lyme disease and hepatitis B, by describing their design, assembly, and effectiveness. The Lyme sensor exploits a known protein-protein interaction between bacterial and human cells to produce a biomimetic sensor capable of binding individual bacteria. This biosensor proves effective at capturing the Lyme bacteria and producing a significant electrochemical response. Likewise, the hepatitis B sensor employs highly specialized surface chemistry to detect hepatitis-specific antigens. Through the development of these sensors, we hope to provide insight into potential devices that can combat these dangerous diseases.
Discovery of sarpagan bridge enzyme-mediated pericyclivine biosynthesis
(University of New Brunswick, 2022-08) Paz Galeano, Melina; Qu, Yang
Sarpagan Bridge Enzymes (SBEs) are cytochrome P450 monooxygenases catalyzing the coupling reaction of C5-C16 sarpagan bridge in the biosynthesis of many sarpagan type monoterpenoid indole alkaloids. This includes the anti-arrhythmic drug ajmaline in Rauwolfia serpentina from the Apocynaceae plant family. Despite SBE enzymatic activity first being detected over 20 years ago, only a handful of these enzymes have been identified and characterized. Here, we report the discovery and characterization of two new SBEs in the plants Catharanthus roseus and Tabernaemontana elegans. Through virus-induced gene silencing and a series of in vivo and in vitro assays, we confirmed these enzymes catalyze the cyclization and aromatization reactions characteristic to SBEs. Furthermore, the addition of C. roseus and T. elegans leaf total proteins to in vitro assays confirmed these SBEs’ involvement in pericyclivine biosynthesis. The discovery of these two enzymes continues to expand our knowledge on the pathways SBEs are found in and adds another step in the complete elucidation of perivine and vobasine biosynthetic pathways.

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