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CHEM2019CASTILLO16416 CHEM

RATIOMETRIC MOLECULAR ROTORS FOR DETERMINING PHASE-TRANSITIONS OF SOFT MATERIALS

Type: Graduate
Author(s): Marlius Castillo Chemistry & Biochemistry Zygmunt Gryczynski Physics & Astronomy Zhangatay Nukureyev Physics & Astronomy
Advisor(s): Sergei Dzyuba Chemistry & Biochemistry
Location: Session: 1; Basement; Table Number: 3

presentation location

Soft matter, such as organogels, waxes and polymer films have found numerous applications in various areas of sciences, engineering and medicine. Ability to assess and monitor their structural organization and physical properties is of the outmost importance. However, there are no convenient methods to accomplish this task.
Small molecule environmental probes have been instrumental in providing information about changes of various types of media upon exposure to external stimuli. Our group has demonstrated the validity of using these probes, also known as molecular rotors, for investigating various types of media. This poster will highlight our efforts on the developments and applications of ratiometirc molecular rotors that allow determining structural integrity as well as properties of various industrially important, medically- and energy-relevant soft matter materials.

(Presentation is private)

CHEM2019CLARK13102 CHEM

Synthesis of Pancratistatin and similar analogs

Type: Undergraduate
Author(s): Brian Clark Chemistry & Biochemistry
Advisor(s): David Minter Chemistry & Biochemistry
Location: Session: 1; 1st Floor; Table Number: 6

presentation location

Pancratistatin is a natural alkaloid that can be isolated from the bulbs of Hymenocallis littoralis, which is a tropical plant commonly referred to as the Spider Lily. Pancratistatin has been shown to have potent cytotoxic anti-tumor activity in biological testing, meaning that it could be a key component for designing natural anti-cancer drugs. The key structural component responsible for the cytotoxic activity of Pancratistatin is the phenanthridone ring system. Pancratistatin has also been proven to combat RNA-containing flaviviruses such as Yellow Fever, Zika, and West Nile Virus. Previously reported procedures for synthesizing Pancratistatin have been reasonably successful, but they all involve the use of lengthy sequences that produce low yields in order to reach the desired product. The purpose of this research project is to provide a more efficient synthesis by increasing the final yield and decreasing the number of steps required. Through successfully synthesizing Pancratistatin, several different analogs of the molecule that contain the phenanthridone ring will also be obtained.

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CHEM2019EBER15332 CHEM

Synthesis of 1,1’-Dideaza-Quinine: A Proof of Concept

Type: Undergraduate
Author(s): Jackson Eber Chemistry & Biochemistry David Minter Chemistry & Biochemistry Adam Montoya Chemistry & Biochemistry
Advisor(s): David Minter Chemistry & Biochemistry
Location: Session: 1; 3rd Floor; Table Number: 3

presentation location

Quinine is a naturally occurring alkaloid found in the bark of the cinchona tree.1 Its medicinal relevance cannot be overstated as it is one of the most widely used anti-malarial drugs in the world.1 While the synthetic pathway to derive quinine is of limited relevance due to its abundance and ease of extraction, the puzzle of engineering reactions to isolate a stereochemically pure product of quinine captivated chemists for generations. The purpose of this study was to prove the conceptual route proposed by Stotter, Friedman, and Minter2 for the stereochemically pure total synthesis of quinine via a non-nitrogenous analog where the two nitrogen atoms of quinine are substituted with carbon atoms. The product of the analogous route is 1,1’-Dideaza-Quinine. Quinine is stereochemically complex, containing four separate stereocenters, thus the synthesis of quinine opens up the possibility of generating sixteen different isomeric structures.3 While the total synthesis of quinine with the correct stereochemistry was accomplished in 2001,3 the proposed route simplifies the process by relying on a stereospecific aldol condensation to eliminate potential isomerization.2 The results of the study validate the proposed route and add to the field of Organic Synthesis by illustrating an example of a stereoselective aldol condensation. Additionally, due to the analogous nature of the synthetic route utilized, many novel compounds were generated adding to the body of knowledge available to the Chemistry community.

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CHEM2019FAHIM64637 CHEM

Unusual Liquid-liquid Phase Separation of Lysozyme Aqueous Solutions at Physiological pH and Salt Concentration

Type: Graduate
Author(s): Aisha Fahim Chemistry & Biochemistry
Advisor(s): Onofrio Annunziata Chemistry & Biochemistry
Location: Session: 1; 3rd Floor; Table Number: 1

presentation location

Liquid-liquid phase separation (LLPS) of protein aqueous mixtures is the reversible condensation of protein-rich micro droplets occurring below a well-defined LLPS temperature. LLPS studies of protein mixtures are fundamental for understanding the membrane-less compartmentalization inside living cells, protein-aggregation diseases, protein-based drug formulations, enzyme-based materials and molecular interactions. It is known that aqueous solutions of the protein lysozyme in the presence of phosphate buffer at neutral pH and physiological salt concentration undergo LLPS upon cooling below ≈ 0 °C. The obtained lysozyme-rich micro droplets rapidly dissolve upon heating above the LLPS temperature. In this work, it will be shown that an apparently undisruptive substitution of phosphate buffer with another well-known buffer, 4-(2-hydroxyethyl)-1-piperazineethanesulfonate (HEPES), to lysozyme aqueous solutions significantly alter the LLPS mechanism. Specifically, contrary to the case of phosphate buffer, the micro droplets produced below ≈ 0 °C remain surprisingly stable upon heating even at ≈ 30-40 °C. Related LLPS studies in both acidic and basic conditions show similar anomalous LLPS behavior. Our results indicate that HEPES triggers a second protein self-assembly process that is catalyzed by LLPS. These findings show that protein aqueous mixtures in the presence of HEPES buffer could be exploited for the preparation of protein-based materials. They also suggest that the combination of a protein self-assembly with LLPS may be a mechanism involved in the formation of membrane-less globular compartments inside the cytoplasm of living cells.

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CHEM2019HENDERSON2011 CHEM

Chemical hardness and orbital overlap in substituted aromatics

Type: Undergraduate
Author(s): Nicholas Henderson Chemistry & Biochemistry Arshad Mehmood Chemistry & Biochemistry
Advisor(s): Benjamin Janesko Chemistry & Biochemistry
Location: Session: 2; Basement; Table Number: 5

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Hard-soft acid base theory is often used to explain the selectivity of chemical reactions, under the assumption that hard (soft) nucleophiles prefer to react with hard (soft) electrophiles. Computationally, quantifying the relative hardness and softness of different sites in a molecule remains challenging. Our "orbital overlap distance function" allows us to quantify which regions in a molecule contain compact vs. diffuse molecular orbitals. Here we explore the idea that compact molecular orbitals correspond to chemically hard regions, and that diffuse and polarizable orbitals correspond to chemically soft regions. We combine the orbital overlap distance with electrostatic potentials to quantify the hardness and electrophilicity of different sites in heterocyclic aromatic compounds. Results are compared to known experimental trends in aromatic reactivity

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CHEM2019LE4831 CHEM

Formation of Platinum Nanocrystals on Silicon Nanotubes and in vitro Anti-cancer Activity of the composites

Type: Graduate
Author(s): Nguyen Le Chemistry & Biochemistry
Advisor(s): Jeffery Coffer Chemistry & Biochemistry Giridhar Akkaraju Biology
Location: Session: 2; 1st Floor; Table Number: 3

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The semiconductor Silicon (Si) remains a significant material in the electronic device and photovoltaic industries [1]. Especially, nanostructured forms of Si with a porous morphology (pSi) exhibit interesting properties which can be controlled via modulating pore structure and surface chemistry [1]. Recently, synthesis of a unique one-dimensional form of Si, namely nanotubes, with tunable structure (shell thickness, length, inner diameter and porous morphology) has been demonstrated, thereby suggesting newly emerging applications [2]. For instance, recent works have indicated Si nanotubes (SiNTs) can efficiently serve as a reaction vessel for formation of organometal perovskite nanostructures and a template for superparamagnetic iron oxide (Fe3O4) loading [3], [4]. In an observation of dissolution of SiNTs with a porous morphology (pSiNTs), the material readily resorbed in buffered media at physiological conditions in a similar manner to bioactive nanostructured porous silicon, thereby implying potential therapeutic applications of this material [2].
In chemotherapy, platinum-based cancer drugs, such as cisplatin and carboplatin, are widely used as effective drugs against various types of cancer [5]. Interestingly, while elemental platinum nanoparticles (Pt NPs) have been well investigated in diverse catalytic processes, in recent years, Pt NPs have also been discovered as a potent anti-cancer agent in nanomedicine, implying the use of the nanodrug to counteract chemoresistance in some cancer cell lines [6], [7]. Recent reports have also indicated that enhanced cytotoxicity against selected cancer cell lines is ascribed to ultra-small Pt NPs, especially those with size less than 3 nm [7]. In this report, pSiNTs were investigated as a template for the formation of Pt NPs, and in vitro cytotoxicity of the composites was evaluated against HeLa cancer cells.
Regarding fabrication, pSiNTs with short lengths (~500 nm) and thin walls (~10 nm) were synthesized via a ZnO nanowire sacrificial template method. Based on a combination of characterization techniques [High resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray analysis (TEM-EDX)], it is suggested that pSiNTs surface functionalized with 3-aminopropyltriethoxysilane can facilitate formation of Pt nanocrystals (Pt NCs) with size ranging from 1-3 nm utilizing a K2PtCl4 precursor. By varying reaction conditions (concentration of Pt salt and incubation time), the amount of Pt NCs deposited on SiNTs can be sensitively tuned from 20 to 55 wt%. In terms of cytotoxicity evaluation of the composites against HeLa cells, cellular viability was assessed using CellTiter-Glo assays, which quantified the amount of ATP in metabolically active cells. Our findings suggest that Pt NCs-SiNTs composites were toxic to HeLa cells, and less than 50% cells were still viable after 3 days of treatment with the composites at doses of 35 μg/ml and 50 μg/ml. Results from caspase 3/7 assays also showed that caspase 3/7 level in cells treated with Pt NCs-SiNTs approximately ranged from 1.5 to 2-fold increase compared to cells without treatment, thereby suggesting apoptosis as the likely mechanism. In vitro cellular uptake studies analyzed by confocal microscopy also confirmed accumulation of the composites within the cytoplasm of the cells after the treatment, consistent with a “Trojan horse” mechanism in which high concentrations of Pt NCs are internalized within cells assisted by pSiNTs and subsequently released via dissolution of the nanotube matrix.
The studies presented herein describe a novel strategy to form and immobilize highly compact clusters of Pt NCs by using pSiNTs as a template. In terms of bio-relevant applications, in vitro studies provide new insights into the anti-cancer properties of the newly discovered composites in inducing apoptosis in HeLa cells, thereby providing significant potential uses of Pt NCs-SiNTs in cancer treatment. Further investigations into gene expression profile(s) may be necessary in order to clarify the impact of the composites on cell survival in terms of molecular mechanisms.
References
1. H. Santos, Porous Silicon for Biomedical Applications, Ed. Cambridge: Woodhead Publishing, (2014).
2. X. Huang, R. Gonzalez-Rodriguez, R. Rich, Z. Gryczynski and J. L. Coffer, Chem. Commun., 49, 5760 (2013).
3. R. Gonzalez-Rodriguez, N. Arad-Vosk, N. Rozenfeld, A. Sa'ar and J. L. Coffer, Small, 12(33), (2016).
4. P. Granitzer, K. Rumpf, R. Gonzalez, J. Coffer, M. Reissner, Nanoscale Res. Lett., 9, 413 (2014).
5. T. C. Johnstone, K. Suntharalingam and S. J. Lippard, Chem. Rev., 116 (5), 3436–3486, (2016).
6. X. Li, G. Li, W. Zang, L. Wang and X. Zhang, Catal. Sci. Technol., 4, 3290-3297 (2014).
7. H. Xia, F. Li, X. Hu, W. Park, S. Wang, Y. Jang, Y. Du, S. Baik, S. Cho, T. Kang, D. Kim, D. Ling, K. M. Hui and T. Hyeon, ACS Cent. Sci., 2, 802−811 (2016).

(Presentation is private)

CHEM2019MEHMOOD38923 CHEM

An Orbital-overlap Scale for Solvent Hardness and Softness: Method and Application to Ionic Liquids

Type: Graduate
Author(s): Arshad Mehmood Chemistry & Biochemistry
Advisor(s): Benjamin G. Janesko Chemistry & Biochemistry
Location: Session: 1; 2nd Floor; Table Number: 1

presentation location

The chemical hardness of a solvent can play a decisive role in solubility and reactivity in solution. Several empirical scales of solvent softness have been proposed. We explore whether computed properties of solvent molecules can reproduce these empirical scales. Our "orbital overlap distance" quantifying the size of orbitals at a molecule's surface effectively reproduces the Marcus μ-scale of solvent softness. The orbital overlap distance predicts that the surfaces of chemically hard solvent molecules is dominated by compact orbitals possessing a small orbital overlap distance. In contrast, the surface of chemically soft solvent molecules has a larger contribution from diffuse orbitals and a larger orbital overlap distance. Other "conceptual density functional theory" descriptors, including the global hardness and electronegativity, can also reproduce empirical solvent scales. We further introduce a "solvent versatility" RMSD Dsurf scale quantifying variations in the surface orbital overlap distance. "Good" solvents such as DMSO, which combine chemically "hard" and "soft" sites within a single molecule, possess a large RMSD Dsurf. We conclude by applying this approach to predict the Marcus μ-parameters for widely-used ionic liquids and ionic liquid - cosolvent systems.

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CHEM2019MEKHAIL60535 CHEM

Functional groups effect on the electronics of macrocyclic pyridinophane

Type: Graduate
Author(s): Magy Mekhail Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry
Location: Session: 2; 3rd Floor; Table Number: 8

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The use of macrocyclic pyridinophane has been growing in the fields of bioinorganic modeling, catalysis and imaging. However, the functionalization of the pyridine has not been fully explored. Therefore, the Green Research Group we produce a series of 12-membered tetra-aza N-heterocyclic amines, derived from pyclen with different functional groups substituted at the para position. Using Hammett plot analysis, X-ray diffraction, electrochemistry and C-C coupling catalytic results, we aim to understand the impact of these functional groups on the donating) of the ligand. From the Hammett plot results we predict how other functional groups will affect the electronics and reveal whether the resonance or inductive effects will mitigate the coordination environment.
The use of macrocyclic pyridinophane has been growing in the fields of bioinorganic complexes modeling, catalysis, and imaging. However, the functionalization of the pyridine has not been fully explored. Therefore, the Green Research Group produced a series of 12-membered tetra-aza macrocycles derived from pyclen with different functional groups substituted at the para position. Using Hammett plot analysis, X-ray diffraction, electrochemistry, and C-C coupling catalytic results, we aim to understand the impact of these functional groups on the donor ability of each ligand. From the Hammett plot results we hope to predict how other functional groups will affect the electronics and reveal whether the resonance or inductive effects will mitigate the coordination environment and reactivity of each complex.

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CHEM2019MONTOYA22550 CHEM

Steps Towards the Total Synthesis of Amaryllidaceae Alkaloids

Type: Graduate
Author(s): Adam Montoya Chemistry & Biochemistry
Advisor(s): David Minter Chemistry & Biochemistry
Location: Session: 1; 3rd Floor; Table Number: 6

presentation location

Phenanthridone-type alkaloids isolated from certain plants of the Amaryllidaceae family are of interest due to their pharmaceutically active nature. The compounds are commonly used in research concerning cancer, Alzheimer’s disease and other human illnesses. One of the main hindrances to such research is the limited availability of many of these compounds. The Minter group is interested in the development of procedures for synthesizing such alkaloids in a cost-effective and time efficient manner, while at the same time maintaining fair to excellent yields.
Techniques toward the synthesis of natural products of the Phenanthridone type are presented herein. Manipulations were tested and optimized on a model system in order to save both time and funds while developing a synthetic pathway to be utilized in the formation of more complex compounds. Setbacks such as controlling the stereochemistry of a tetra-substituted double bond reduction have been encountered. However, adjustments are being made to avoid such difficulties in the future. Ideally, the proposed scheme will ultimately allow for the synthesis of multiple phenanthridone analogs.

(Presentation is private)

CHEM2019NEWELL46942 CHEM

Preparation of Clickable Monomers Compatible with Automated PNA Synthesis

Type: Undergraduate
Author(s): Grace Newell Chemistry & Biochemistry
Advisor(s): Jean-Luc Montchamp Chemistry & Biochemistry
Location: Session: 2; Basement; Table Number: 1

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Peptide nucleic acids (PNA) are artificially synthesized monomers or polymers that mimic DNA or RNA sequences. Due to their stability in biological conditions and their ability to bind complementary to DNA or RNA, PNAs have potential medicinal value since they can be used to block processes like replication or protein synthesis. Though most PNAs are commercially synthesized, the goal of this project was to begin the synthesis with propargyl bromide. This would allow the final monomer to have a propargyl group which allows functional groups (like a polyamine tail, fluorescent tag, or alkylating group) to be added at the end or any time throughout the synthesis. The PNA monomer will be made with all four DNA bases (thymine, cytosine, adenine, and guanidine) attached. Another importance of this PNA monomer is its ability to undergo click reactions to create a PNA oligomer. Click chemistry is a chemical reaction that uses copper-catalyzed coupling to combine an azide with an alkyne. The ability to use click chemistry is vital since it can be done in biological conditions, has an excellent yield with few byproducts, and is relatively quick to perform. In conclusion, this project is useful since these PNA sequences can be used to modulate processes and treat a variety of diseases while having the ability to add functional groups to track the PNA oligomer.

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CHEM2019NIEBUHR27253 CHEM

Functional Modifications and Electronic Influences on Macrocyclic Tetra-aza Copper (II) Complexes

Type: Undergraduate
Author(s): Brian Niebuhr Chemistry & Biochemistry Marianne Burnett Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry
Location: Session: 2; Basement; Table Number: 2

presentation location

A library of novel pyridinophane tetra-aza macrocyclic molecules derived from 1,4,7,10-tetraaza-2,6-pyridinophane (pyclen) capable of chelating biologically relevant metal ions have been synthesized. Applications of these types of molecules currently being pursued are 1) therapeutic, focusing on radical scavenging and metal chelation and 2) diagnostic, focusing on magnetic resonance imaging (MRI) contrast agents when complexed with specific metal ions. Despite wide interest in these molecules, a full study of the electronic effects imparted by substitution to the pyridyl moiety and the subsequent impact on the metal center has not yet been conducted. The objective of the present study is to characterize metal complexes of four, new tetra-aza macrocyclic metal chelating molecules. The pyridyl functional groups studied include: A) unmodified pyridyl (L1), B) 14-hydroxyl (L2), C) 14-nitrile (L3), and D) 14--nitro (L4) modified pyclen structures. Procedures for metal ion chelation with copper (II) ion, followed by characterization and analysis of the electronic environments of each are presented.

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CHEM2019PHAM64839 CHEM

Optimization of Tin(IV) Oxide Particles For Improved Performance of Dye-Sensitized Solar Cell

Type: Undergraduate
Author(s): Bach Pham Chemistry & Biochemistry
Advisor(s): Benjamin Sherman Chemistry & Biochemistry
Location: Session: 1; 3rd Floor; Table Number: 10

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The dye-sensitized solar cells (DSSCs) are a possible alternative tool to harvest solar energy instead of the traditional silicon-based solar cells. DSSCs offer various advantages, such as good energy conversion efficiencies in low-light condition, simple fabrication, low cost, and the ability to modify key properties of the solar cell such as the absorbance wavelengths. We are interested in developing new types of semiconductor supports for use in DSSCs based on tin(IV) oxide nanoparticles (NPs). Tin(IV) oxide offers a wide band gap and higher electron mobility as compared with the more widely used titanium dioxide. In this study, two morphologies of tin(IV) oxide, spherical and flower-like NPs, are synthesized. These two types of tin(IV) oxide NPs and mixtures of both at various ratios are used to fabricate DSSCs. We find that nanoflowers usually give the cells higher open circuit voltages but with lower photocurrent. Nanospheres give much higher photocurrent but with lower open circuit voltage. A mixture that has a 1:2 molar ratio of nanoflowers and nanospheres gave the best performance in terms of photocurrent and voltage. Furthermore, we are investigating the effect of a deposited layer of titanium(IV) oxide on top of the tin(IV) oxide to further enhance the photoperformace of the solar cells.

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CHEM2019SCHMITT50258 CHEM

The Synthesis of Amaryllidaceae Alkaloid Analogs

Type: Undergraduate
Author(s): Nate Schmitt Chemistry & Biochemistry Adam Montoya Chemistry & Biochemistry
Advisor(s): David Minter Chemistry & Biochemistry
Location: Session: 2; 1st Floor; Table Number: 4

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Amaryllidaceae isoquinoline alkaloids as well as their analogs have long been of interest as lead compounds in drug discovery due to their range of biological activity. Many of these alkaloids are cytotoxic anti-tumor agents. Moreover, there have also been studies showing the effectiveness of these molecules against yellow fever and other diseases caused by RNA- containing flaviviruses. The study of these compounds as pharmaceutical agents is hampered by their low natural abundance, which necessitates the development of laboratory syntheses of these alkaloids and their analogs.
This project focuses on the total syntheses of the Pancratistatin-type natural products that contain the phenanthridone ring system. In stage one, model systems are being investigated to develop the methodology required to introduce requisite functionality found in natural systems. Previous research from this laboratory gives the basic phenanthridone skeleton with several different functional groups, but there are no reported methods for converting these functions into polyhydroxycyclohexenes with stereochemical control. Two of the problems under investigation involve the ring expansion of a spiro ring containing an epoxide and the production of a specific trihydroxycyclohexene with control of stereochemistry. In stage two, a specific phenanthridone alkaloid will be targeted for total synthesis that uses the new methodology developed in stage one.

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CHEM2019SCHWARTZ27386 CHEM

Synthesis and Characterization of N,N,N,-Copper Pincer Complexes

Type: Undergraduate
Author(s): Timothy Schwartz Chemistry & Biochemistry Marianne Burnett Chemistry & Biochemistry Akop Yepremyam Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry
Location: Session: 2; 1st Floor; Table Number: 2

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Organometallic catalysts are useful in many organic reactions by exploiting the Lewis acidity of the metal complex. Most catalysts available rely on precious metals like platinum and rhenium. These catalysts pose a financial and environmental barrier to many scientists. Thus, there is a need for catalysts that use less expensive and toxic metals, such as copper. A library of copper catalysts with different electronic functionalities have been synthesized and characterized by cyclic voltammetry, UV-VIS, NMR, and X-ray crystallography. It was found that the complexes with electron donating groups better stabilize the copper center, when compared to the complexes with electron withdrawing groups. However, the planar characteristics of each ligand makes them unsuitable candidates for copper catalysis because they cannot bind to the tetrahedral geometry of reduced copper. This work warrants the complexation of these ligands with other metals, like nickel or cobalt, to determine their viability as applicable organometallic catalysts.

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CHEM2019SHARMA21186 CHEM

Exploring Cyanuric Chloride Chemistry to Synthesize Macrocycles of Different Sizes

Type: Graduate
Author(s): Vishal Sharma Chemistry & Biochemistry
Advisor(s): Eric Simanek Chemistry & Biochemistry
Location: Session: 1; 3rd Floor; Table Number: 4

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In chemistry, cyclic compounds of twelve or more atoms are considered macrocycles. Many bioactive, natural products containing macrocycles have been isolated and synthesized. Still, construction of macrocycles is usually considered a challenging step in their synthesis. Here, a route to different-sized macrocycles is described. These macrocycles arise from spontaneous cyclization of two identical subunits comprising a central triazine displaying both a masked aldehyde and hydrazine group. The aldehyde portion is presented on a linker that can comprise varying number of carbons. By varying this linker, macrocycles of 22, 24, and 26 atoms have been prepared. Future study focuses on probing macrocycle size with increasingly larger linkers.

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CHEM2019TA53316 CHEM

DESIGNER SOLVENTS AND MATERIALS

Type: Undergraduate
Author(s): Daniel Ta Chemistry & Biochemistry Onofrio Annunziata Chemistry & Biochemistry Christian Chen Chemistry & Biochemistry
Advisor(s): Sergei Dzyuba Chemistry & Biochemistry
Location: Session: 2; 2nd Floor; Table Number: 8

presentation location

Room-temperature ionic liquids and deep-eutectic solvents have become unique and almost indispensible materials for various areas of sciences, medicine and engineering. The ability to engineer media with desired properties favorably distinguishes these solvents from traditionally used molecular solvents.

This poster will describe our ongoing efforts on designing various types of ionic, eutectic systems as well as approaches towards modulating their phase transitions. Studies related to controlling the self-assembly process of various solutes in this type of media will also be presented.

(Presentation is private)

CHEM2019WEGENER47813 CHEM

Can Whiskey have Terroir? Assessing sugar differences after mashing heirloom cereals for Bourbon production

Type: Undergraduate
Author(s): Kathleen Wegener Chemistry & Biochemistry
Advisor(s): Eric Simanek Chemistry & Biochemistry Rob Arnold Biology
Location: Session: 1; 1st Floor; Table Number: 7

presentation location

This project will entail assessing several varieties of common and heirloom corn from throughout Texas to identify sugar (and thus alcohol) content.
After obtaining cereal samples from a local distillery, the cereals will be processed by mashing and fermenting.
The resulting mashes will be measured for pH and S.G., then analyzed through chromatography using HPLC-RID. These samples of corn will be assessed for variations in sugar yield, both and composition and quantification. After fermentation, the HPLC-RID will be used for chromatographic analysis of ethanol concentration. Ultimately, this will provide information on the most promising corn varieties, and expose their potential as a future staples of this partner distillery.

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CHEM2019WINTERS65295 CHEM

The Cost of Academic Methodologies

Type: Graduate
Author(s): Karen Winters Chemistry & Biochemistry Olivier Berger Chemistry & Biochemistry Sergei Dzyuba Chemistry & Biochemistry Axel Sabourin Chemistry & Biochemistry
Advisor(s): Jean-Luc Montchamp Chemistry & Biochemistry
Location: Session: 2; 1st Floor; Table Number: 6

presentation location

The cost of reagents and catalysts employed in synthetic methodologies developed in academia is very rarely discussed. Yet these costs are very real as they represent a significant portion of any grant proposal budget. The Cost of Academic Methodologies (CAM) is a novel concept, which should be considered when evaluating synthetic methodologies. CAM will allow for one to quantitatively evaluate with a numerical value a particular synthetic methodology that prepares a particular product. CAM will allow for a comparison among distinctly different reactions conditions, reagents, catalytic versus stoichiometric systems, etc. Cost considerations are almost always avoided in academic publications; however CAM is a parameter that can be useful to gauge seemingly non-comparable methodologies. Unlike specious or poorly-defined considerations often seen in manuscripts, such as “harshness” of conditions, “metal-free”, “precious metals are expensive”, etc., the CAM parameter is a real, tangible, aspect of academic methodologies, which is applicable to any chemical reaction.

(Presentation is private)

CHEM2018BARNETT5923 CHEM

Spectroscopic assays of a novel neurodegenerative therapeutic agent

Type: Undergraduate
Author(s): Maddie Barnett Chemistry & Biochemistry Hannah Johnston Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry

Oxidative stress in the brain is a known contributor to the development of neurodegenerative diseases, including Alzheimer’s. The focus of this project is to target the amyloid-β plaque formations and reactive oxygen species (ROS) derived from mis-regulated metal-ions that lead to disease-causing oxidative stress. The present investigation measures both the antioxidant reactivity and metal chelating ability of 1,4,11,13-tetra-aza-bis(2,6-pyridinophane)-8,17-ol (L4).  L4 contains two radical scavenging pyridol groups along with a metal-binding nitrogen rich ligand system.  It was hypothesized that increasing the number of pyridol groups on the ligands in our small molecule library would increase the radical scavenging activity, which in turn may provide cells protection from oxidative stress.  The radical scavenging ability of L4 was quantified using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay. This was compared to other radical scavenging small molecules to evaluate the effect of the additional radical scavenging group on the antioxidant activity.  The interaction of L4 with redox active metal-ions such as copper(II) was also evaluated using the coumarin-3-carboxylic acid (CCA) assay to show the molecule’s ability to target mis-regulated metal-ions in diseased tissues. With the end goal being to develop a potential biological therapeutic agent, metabolic stability studies were also performed.

(Presentation is private)

CHEM2018BODIFORD8780 CHEM

Drug delivery and degradation behavior of nanostructured porous silicon and polycaprolactone porous fiber composites

Type: Graduate
Author(s): Nelli Bodiford Chemistry & Biochemistry Steven McInnes Chemistry & Biochemistry Nathan Shurtleff Chemistry & Biochemistry Nicolas Voelcker Chemistry & Biochemistry
Advisor(s): Jeffery Coffer Chemistry & Biochemistry

The combination of inorganic porous silicon (pSi) and flexible biocompatible polymers has been shown to yield more beneficial hybrid scaffolds for tissue engineering (i.e. use of synthetic materials to facilitate healing). PSi has a variety of tunable properties, including pore size, pore volume and non-toxic degradation. The addition of a biocompatible polymer such as polycaprolactone (PCL) can provide control over shape and serve as an additional drug delivery component.
In this work, composite materials consisting of oxidized porous silicon (ox-pSi) with a particle size of ~ 30 μm and pore size of 40-100 nm and PCL porous fibers. Porous fibers were fabricated using an electrospinning method into sheets of desired thickness (0.1-0.4 mm), fiber diameter 3-4 μm, and fiber pore size 300-500 nm. Ox-pSi particles previously loaded with the anticancer drug-camptothecin (CPT) were placed between two sheets (6 mm in diameter each) and sealed at the edges, resulting in ~65% loading of ox-pSi. Drug release from the ox-pSi particles alone and ox-pSi/porous PCL fiber composites was monitored fluorometrically in phosphate buffered saline (PBS), showing a distinct release profile for each material.
Ox-pSi/p-PCL fiber composites release a CPT payload in accordance with the Higuchi release model and showed a significant decrease in burst effect compared to ox-pSi particles only. In addition, composite evolution after 5 weeks in PBS at 37 oC was examined using gravimetry, differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM). Overall weight loss of the composites was about 50%, mainly attributed to pSi particles dissolution and some polymer hydrolysis. Preliminary DSC results show that high surface area porous PCL fibers are less crystalline compared to solid PCL fibers, suggesting a faster hydrolysis route.

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CHEM2018BURNETT36214 CHEM

Non-Innocent redox activity of the glycine modified DOTA scaffold and the impact on Eu3+/2+ electrochemistry

Type: Graduate
Author(s): Marianne Burnett Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry

Europium contrast agents have been extensively investigated as an alternative to typical Gd3+ species for imaging. This is due to the dual imaging modalities which can accessed dependent on the oxidation state of the europium metal center (T1 or PARACEST). To achieve these functionalities, the europium containing complex must be stable enough to support both oxidation states (+3 and +2). In collaboration with UTSW, an electrochemical investigation was completed to understand the effects of the ligand environment on the metal center as a direct result of glycine modification to the ligand scaffold, DOTA. Increasing amide functionalities in close proximity to the europium core result in a positive shift in the potential in comparison to the acetate arms associated with DOTA. Furthermore, the addition of the glycine moiety to the pendant arms results in redox activity of the ligand itself, making the ligand non-innocent in nature. Additionally, a crystal structure of Eu4 (the tetraglycinate DOTA derivative) was obtained and compared to known lanthanide complexes.

(Presentation is private)

CHEM2018CIEKER32577 CHEM

EN ROUTE TO DESIGNER MEDIA: synthetic and spectroscopic studies on ionic and eutectic solvents

Type: Undergraduate
Author(s): Chris Cieker Chemistry & Biochemistry Marlius Castillo Chemistry & Biochemistry David Edwards Chemistry & Biochemistry Nico Prieto Chemistry & Biochemistry
Advisor(s): Sergei Dzyuba Chemistry & Biochemistry

Non-conventional solvents, such as room-temperature ionic liquids and deep-eutectic solvents, have attracted a lot of attention in recent years due their diverse applications in various areas of sciences, medicine and engineering. The ability to control physical properties of these solvents by simply adjusting their structure and/or the ratio of the components favorably distinguishes ionic and eutectic solvents from traditionally used molecular solvents as it allows to custom design specific types of media for given applications.

This presentation will highlight our efforts on various aspects of the synthesis of ionic liquids and deep-eutectic solvents as well as it will describe our investigations on the physical properties and nanostructural organization of these liquids using environmental probes, such as those that feature BODIPY and aza-BODIPY motifs. In addition, our initial studies on the design of multiphase systems that utilize ionic, eutectic and molecular solvents will be presented.

(Presentation is private)

CHEM2018DACHILLE23489 CHEM

Synthesis and Characterization of Europium-doped Cerium Oxide Nanotubes

Type: Graduate
Author(s): Anne D'Achille Chemistry & Biochemistry Jeff Coffer Chemistry & Biochemistry
Advisor(s): Jeff Coffer Chemistry & Biochemistry

Cerium (IV) oxide, or CeO2, nanomaterials have displayed antioxidant and enzyme mimetic activities due to a Ce3+/Ce4+ redox capability enhanced through oxygen vacancies and mobility. Tri-valent, fluorescent ions such as Eu3+ increase the Ce3+/Ce4+ ratio and oxygen vacancy concentration, while contributing fluorescent properties to the nanomaterial. The combination of these attributes make europium doped cerium oxide (EuCeO¬2) nanomaterials appealing candidates for various biological applications.
To complement our earlier efforts on the synthesis and properties of EuCeO2 nanowires, nanorods, and nanocubes, this presentation addresses a new, complementary structure, EuCeO2 nanotubes. The nanotubes are prepared via deposition and subsequent oxidation of Eu-doped Ce(OH)3 to form a EuCeO2 shell on sacrificial ZnO nanowires.
Previous synthetic routes to CeO2 nanotubes have been reported featuring carbon nanotubes as sacrificial templates, the etching of cerium-based nanorods, and other less-common methods . These routes have struggled with clear evidence for distinct nanotube formation, as well as control over nanotube dimensions. Our use of a ZnO core allows for facile manipulation of inner diameter and length of the nanotube following etching of the core.
The synthesized nanotubes were characterized using scanning and transmission microscopy (SEM and TEM) for morphology, energy dispersive x-ray (EDX) for elemental composition, and photoluminescence to track europium fluorescence. Synthesized nanotubes had inner diameters from 40 nm to 200 nm, based on the ZnO core. Following synthesis and characterization, the nanotubes will be tested for use as a drug delivery vector, using ibuprofen as a model.

(Presentation is private)

CHEM2018DINH49477 CHEM

Genetic selection of leucyl-tRNA synthetase for the production of fluorescent proteins in living cells

Type: Undergraduate
Author(s): Viet Dinh Biology Andrea Guedez Chemistry & Biochemistry
Advisor(s): Youngha Ryu Chemistry & Biochemistry

This project is aimed to modify a leucyl-tRNA synthetase (LeuRS) to incorporate fluorescent amino acids into proteins to produce fluorescent proteins in living cells. Fluorescent proteins are useful because they are easily analyzed and tracked in living organisms. In a small scale, we successfully prepared the library of LeuRS variants in which five amino acids are randomized in the leucine-binding site of a functional LeuRS without its editing domain. Currently, we are working on a large scale production of viable bacterial cells that cover the whole diversity of library (at least 34 million different LeuRS molecules). Initially, we attempted two-step process in which an N-terminal library fragment (for two randomized amino acids) is generated first and a C-terminal fragment (for three randomized amino acids) is added later. However, this two-step cloning process did not produce enough viable cells to cover all the possible variants. In a new approach, a complete library of LeuRS will be produced by overlapping extension PCR and introduced to E. coli in a single step to ensure highest possible transformation efficiency. Consequently, the library of LeuRS variants will be subject to a genetic selection experiment to obtain LeuRS variants that incorporate only fluorescent amino acids into proteins.

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CHEM2018FAHIM52071 CHEM

Amplification of salt-induced protein diffusiophoresis by varying salt nature

Type: Graduate
Author(s): Aisha Fahim Chemistry & Biochemistry
Advisor(s): Onofrio Annunziata Chemistry & Biochemistry

Diffusiophoresis is the migration of a relatively large particle (e.g., protein, polymer, nanoparticle) induced by a gradient of salt concentration. The salt-induced diffusiophoresis of lysozyme, a model protein, at pH 4.5 and 25 °C was examined as a function of salt concentration for three chloride salts: NaCl, KCl and MgCl2. Diffusiophoresis coefficients were theoretically extracted from experimental multicomponent diffusion data by applying irreversible thermodynamics. A selected mass-transfer process was theoretically examined to show that concentration gradients of MgCl2 produce significant lysozyme diffusiophoresis. The dependence of lysozyme diffusiophoresis on salt nature was theoretically examined and linked to protein charge. The effect of salt type on hydrogen-ion titration curves was experimentally characterized to understand the role of salt nature on protein charge. Our findings indicate that diffusiophoresis may be exploited for diffusion-based separation of proteins in the presence of salt concentration gradients and for the enhancement of protein adsorption onto solid surfaces relevant to biosensing applications.

(Presentation is private)