Investigation of Charge Transfer Between Porous Silicon and Metal Halide Perovskites

Type: Graduate
Author(s): William Burnett Chemistry & Biochemistry Bong Lee Physics & Astronomy
Advisor(s): Jeffery Coffer Chemistry & Biochemistry Ignacy Gryczynski Physics & Astronomy Zygmunt Gryczynski Physics & Astronomy
Location: Third Floor, Table 5, Position 1, 1:45-3:45

Silicon-Perovskite tandem solar cells are some of the leading emerging technology solar cells due to their high photoconversion efficiency or the ability to turn light into electricity. These solar cells rely on the ability to harvest a higher percentage of the solar spectrum due to the differences in the two materials. MHPs are an ionic crystal that have the chemical formula ABX3 where A is a monovalent cation (+1) such as cesium, methylammonium or formamidinium; B is a divalent cation (+2) such as lead or tin, and X is a halide such as chloride, bromide, or iodide. Porous silicon is crystalline silicon that has been etched to form pores with properties dependent upon the etching conditions. Porous silicon that has been etched such that the silicon area between the pores is between 1-4nm becomes photoluminescent (PL). It has been shown that the optoelectronic properties of metal halide perovskite (MHPs) grown within porous silicon (pSi) are highly dependent upon the surface area, pore size, and surface chemistry of the pSi. This interaction has led us to investigate the fundamental interactions that occur when nanoscale porous silicon encounters nanoscale MHP, namely the possibility of energy/charge transfer.
We have evaluated two different experimental designs. The first entails adsorbing ligand passivated MHP quantum dots onto a solid piece of luminescent mesoporous Si membrane and allow the solvent to evaporate. The change in luminescence from the pSi can be used to monitor the impact the perovskite has upon the pSi by monitoring the change in intensity and wavelength. The second approach as previously described utilizes MHP quantum dots (QDs) dispersed in toluene which is then titrated with non-luminescent pSi and the PL monitored. The primary impact of the pSi upon the light emission of the perovskite QDs is a significant reduction in the intensity of the emission. Comparisons of different pSi with hydride terminated versus oxide terminated surfaces show a dependence upon the surface chemistry to the change in PL. The PL lifetimes will be measured, and comparisons made to determine the mechanism of energy transfer.

'Fine-Tuning' Potential Alzheimer's Therapeutics through Pyridinophane Substitution

Type: Undergraduate
Author(s): Will Campa Chemistry & Biochemistry Sarah Dunn Chemistry & Biochemistry Christina Mantsorov Chemistry & Biochemistry Shrikant Nilewar Chemistry & Biochemistry Kristof Pota Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry
Location: Basement, Table 14, Position 1, 11:30-1:30

Pyridinophane molecules have recently been shown to have both antioxidant and pharmacological properties suitable for therapeutic applications targeting neurodegenerative diseases, including Alzheimer’s Disease. We have synthesized derivatives of this parent molecule with added moiety substitutions. These substitutions are designed to enhance the permeability and antioxidant activity beyond that of the parent molecule in the hopes of producing a molecule suitable for pharmacological testing in animal models. To establish a principle between moiety location on the parent molecule and its activity, we have placed 8-hydroxyquinoline, a moiety established in our lab to improve the antioxidant activity of parent molecules, in varying locations. The results presented here will detail our evaluation of the substitution of 8-hydroxyquinoline in varying locations and its impact on the molecule’s permeability and reactivity through a series of statistics, including a DPPH assay, determination of logBB, and the determination of chelating equilibrium quotients at varying pH (“log beta”).

New Approaches to Macrocycle Synthesis

Type: Graduate
Author(s): Liam Claton Chemistry & Biochemistry
Advisor(s): Eric Simanek Chemistry & Biochemistry
Location: Second Floor, Table 1, Position 2, 11:30-1:30

Creating a diverse array of structurally distinct, triazine-containing, macrocycles remain the focus of the Simanek group. Until now, this goal has been accomplished through a straightforward 3 step synthetic route with variation of amino acid incorporation and acetal length. Currently two new approaches to macrocycle synthesis are being pursued. The first approach relies on two like monomers coming together: by changing the relative position of groups in the macrocycle, the persistence of shape can be probed. The second approach relies on two different monomers coming together. Using a similar synthetic route, this strategy, if successful, will allow much finer control over design and engineering these molecules for specific purposes. These libraries of structurally diverse macrocycles are important for the long-term goals of establishing rules that can guide pharmaceutical drug design in these under-explored types of molecules.

An Investigation of Pyclen Metal Chelator Release on the Aggregation of Amyloid Beta

Type: Undergraduate
Author(s): Caroline Crittell Chemistry & Biochemistry
Advisor(s): Jeffrey Coffer Chemistry & Biochemistry
Location: First Floor, Table 2, Position 2, 1:45-3:45

Alzheimer’s Disease (AD) affects over 6.5 million Americans over the age of 65. Previous research links AD with Amyloid-Beta-40 (AB40) aggregation in the brain, which creates neurotoxic plaques, associated with AD. A potential mechanism in the treatment of AD is using therapeutics that will prevent the formation of these plaques, which is possible with Metal Chelation Therapy.
Metal ion chelation ideally stops metal ions from aiding in the aggregation of AB40. However, to deliver metal chelating agents to the brain, a drug-delivery mechanism is required that will be able to deliver this medicine across the Blood-Brain Barrier. Porous silica is a potential drug delivery material due to its small particle size, high loading capacity, surface tunability, and biocompatibility. Along with these characteristics, porous silica can create a “sustained” release of a given drug, allowing for a slow and steady release profile, reducing the risks of medication side effects.
This project seeks to establish the optimal loading capacities of a class of potential metal ion chelate therapeutic molecules known as pyclens into porous silica, each with different pyridyl moieties and chemical functionalities along the rim of the molecule. Encapsulation efficiencies measurements for these pyclen derivatives reveal loading percentages in the 10-19% range, varying by pyclen identity. Additionally, release studies monitored diffusion over time to find which pyclen molecule achieved “sustained” release. All loaded pyclen species were able to show sustained release after 20 minutes, both in the presence and absence of copper (II) ions. Turbidity assays with AB40 present showed that all pyclen species decreased protein aggregation in the presence of copper (relative to non-pyclen controls), showing that all pyclen species were able to successfully prevent the aggregation of AB40 in the presence of copper.
Release studies in a more authentic BBB model remain to be completed.

ROS Breakdown By Catalase Macrocycle Ligand Mimics

Type: Graduate
Author(s): Nora Del Bosque Chemistry & Biochemistry Kayla Green Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry
Location: Basement, Table 11, Position 2, 1:45-3:45

Neurodegenerative diseases affect more than 50 million people worldwide. This condition damages and destroys parts of the nervous system, specifically the brain. Our goal is to synthesize a macrocycle ligand mimic of catalase, test the reactivity, and compare it to the current Green ligand library.

The effect of anionic surfactant on the fluorescence of polyvinyl pyrrolidone in water

Type: Undergraduate
Author(s): Ngan Dinh Chemistry & Biochemistry Shamberia Thomas Chemistry & Biochemistry
Advisor(s): Onofrio Annunziata Chemistry & Biochemistry
Location: Basement, Table 4, Position 1, 11:30-1:30

Polyvinyl pyrrolidone (PVP) is a nonionic synthetic polymer often employed in drug formulations. Due to its hydrophilicity, it is often found in aqueous solutions where it can act as a solubilizing agent for organic molecules with poor water solubility. Interestingly, PVP also exhibits fluorescence in water. Furthermore, PVP fluorescence intensity is known to decrease as the concentration of salt increases. This effect has been attributed to the affinity of inorganic anions to PVP chains. In this poster, we examine the effect of an anionic surfactant, sodium dodecyl sulfate (SDS), on PVP fluorescence. In contrast with inorganic anions, we found that PVP fluorescence intensity increases with SDS concentration. We attribute this effect to the binding of SDS anions to PVP chains. This hypothesis is supported by a crystallization assay showing that PVP suppresses formation of SDS crystals. Our experimental results indicate that PVP fluorescence could be used to determine concentration of other types of anionic surfactants in water. These include perfluoroalkyl substances (PFAS), which are relevant environmental chemistry.

Polyethylene Glycol as an LLPS Temperature Promoter for Protein Crystallization

Type: Undergraduate
Author(s): Joel Dougay Chemistry & Biochemistry Shamberia Thomas Chemistry & Biochemistry
Advisor(s): Onofrio Annunziata Chemistry & Biochemistry
Location: Second Floor, Table 8, Position 2, 1:45-3:45

Protein purification is a critical step in the downstream processing of protein. Although chromatography is the most employed technique for protein purification, novel strategies that reduce operational costs and increase the amount of purified protein are being developed. These strategies have the possibility to reduce the price of protein-based pharmaceutical and biotechnological products through the reduction of purification cost. Preparative protein crystallization is one such economically-sustainable alternative to chromatography, however protein crystallization is very slow and is difficult to implement in current protein purification protocols. In our lab, we explore the use of metastable liquid-liquid phase separation (LLPS) to enhance protein crystallization. LLPS is typically induced by cooling protein aqueous samples below a well-defined temperature, called the LLPS temperature. We have previously shown that cooling aqueous samples of lysozyme in the presence of NaCl (0.15 M) and HEPES (0.10 M, pH 7.4) below LLPS temperature reproducibly produces yields of lysozyme crystallization above 90%. However, this process requires sample cooling to relatively low temperatures
(below –10 °C). In this poster, we examine the use of polyethylene glycol (PEG) as an additive that increases LLPS temperature. Our experimental results show that PEG increases LLPS temperature without appreciably altering formation of lysozyme crystals. The effect of PEG concentration on LLPS temperature is explained by considering the mechanism of macromolecular crowding.

Dual genetic selection of synthetic riboswitches for TMAO as genetic and analytical tools

Type: Undergraduate
Author(s): Isabelle Galvan Chemistry & Biochemistry
Advisor(s): Youngha Ryu Chemistry & Biochemistry
Location: Basement, Table 6, Position 2, 1:45-3:45

The goal of this project is to develop synthetic riboswitches for trimethylamine N-oxide
(TMAO). TMAO has been shown to regulate various physiological processes involved in the
development of atherosclerosis. A riboswitch is a non-coding RNA molecule that specifically
binds to a ligand and thereby controls the expression of genes in the downstream. A synthetic
riboswitch for TMAO could be useful for regulating gene expression in response to TMAO and
detecting TMAO in complex biological samples such as urine and blood. The 17 nucleotides in
the aptamer domain of a naturally occurring glycine riboswitch were randomized to generate a
library containing billions of different variants. The library was placed in the upstream of the
cat-upp fusion gene for a series of dual genetic selections. The positive selection is done in the
presence of TMAO to identify functional riboswitches that make cells resistant to
chloramphenicol. The negative selection is performed in the presence of 5-fluorouracil to kill
the cells containing the riboswitch variants activated by any endogenous molecules. Once
identified by several rounds of dual genetic selections, the synthetic TMAO riboswitches will
be tested by colorimetric and fluorescence assays.

Impact of Selected Ionic Liquids on the Properties of Metal Halide Perovskites

Type: Graduate
Author(s): Maegyn Grubbs Chemistry & Biochemistry Sergei Dzyuba Chemistry & Biochemistry
Advisor(s): Jeff Coffer Chemistry & Biochemistry
Location: Basement, Table 8, Position 1, 11:30-1:30

Metal-halide perovskites are crystalline materials that work as a semiconductor in both Light Emitting Diodes (LEDs) and solar cells. In general, perovskites possess the formula ABX3. For this project, the A site is an organic molecule such as Methylammonium (MA), the B site is Lead, and the X site is Bromide. While perovskites are easily fabricated, their crystal size and number of defects present are challenging to control. Defects cause LEDs to be less stable and/or less photoluminescent (bright) and cause solar cells to be less efficient at converting light to energy. One approach to reduce the number of defects is to use ionic liquids during perovskite formation. Ionic liquids are compounds made of ions in the liquid state due to a low melting temperature. They can be added to the perovskite precursor solution to slow down the crystallization process so that fewer defects are created. The goal of this project is to create new metal halide perovskites in the presence of selected ionic liquids, evaluate their structure and photophysical properties, with the long-term goal of creating new LEDs that are both stable and efficient.

In this project, cetyl-ionic liquids (cetyl meaning 16 carbon chains) were investigated for their effects on perovskite structure and light emission. The three ionic liquids were investigated: [C16-mim]Br (referred to as "IL1"), [C16-py]Br ("IL2"), [C16-C1pyrr]Br ("IL3"), and CTAB (“IL4”). Variations in the deposition method of the perovskite films were studied as well. It was hypothesized that the inclusion of cetyl-ionic liquids will protect the perovskite films from the environment (increasing stability) by providing a hydrophobic layer on the surface and will improve the electronic properties by filling in pinholes that cause defects. It is found that perovskite films with IL1 produced through a two-step spin coat deposition method are more photoluminescent than the perovskite films formed with IL2, IL3, IL4 or no IL (control). These results, along with detailed structural characterization of a given perovskite film, will be discussed in this presentation.

Isolating Chiral Nanoparticles from Paper: Templates for Chiral Semiconductor Nanoparticles

Type: Undergraduate
Author(s): Sarafina Gutterres Chemistry & Biochemistry
Advisor(s): Jeff Coffer Chemistry & Biochemistry
Location: Second Floor, Table 6, Position 2, 11:30-1:30

Chirality is a property of two molecules of the same composition to not be structurally superimposable on each other. Chiral structures are both common and essential throughout nature. Porous material can be used as templates for creating chirality. The use of cellulose as a template provides environmentally friendly alternatives for templating chirality onto materials such as silica. New research in this field includes using chiral silica templates for the synthesis of chiral perovskite films, a semiconductor material with bright light emission found in light sources like light emitting diodes (LEDs).

This project began by testing cellulose obtained from several different vendors to determine which product has the ideal properties for use in chiral films. An important aspect of cellulose product is its relative acidity/basicity (quantified in terms of pH), which can be regulated to control the degradation of cellulose into nanocrystals as well as the formation of chiral structures. Initially, the cellulose was acidified using sulfuric acid which causes aggregation and kinetic arrest within particles. A technique known as ion exchange chromatography is now being used in these experiments as the method of choice for acidifying cellulose samples.

The time allotted for cellulose nanocrystals to obtain chiral conformation is also an important aspect of creating chiral films. Initially, samples were not left to stand motionless and were immediately converted into silica films. Currently however, our procedure has been modified to allow the chiral cellulose nanocrystals at least seven days of sitting undisturbed before the addition of a silica precursor molecule, thereby facilitating the chiral product from the rest of the product mixture. Upon successful isolation of chiral cellulose-silica films, experiments will be initiated to template the formation of chiral light-emitting perovskite structures by infiltration.

First Year engagement - Chemistry Club

Type: Undergraduate
Author(s): Tatum Harvey Chemistry & Biochemistry Saba Anjum Biology Grace Bobo Chemistry & Biochemistry Jack Bonnell Chemistry & Biochemistry Braden Chadwick Biology Kathryn Collins Biology Caroline Crittell Chemistry & Biochemistry Delaney Davis Biology Audrey Dolt Biology Annie Downum Chemistry & Biochemistry Izzie Galvan Chemistry & Biochemistry Mark Sayegh Chemistry & Biochemistry Sam Shah Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry Heidi Conrad Chemistry & Biochemistry Julia Fry Chemistry & Biochemistry
Location: First Floor, Table 5, Position 2, 11:30-1:30

Texas Christian University’s Chemistry Club has always made a conscious effort to interest and include first year students through events and volunteering. This year’s project was focused on boosting numbers and cultivating a stronger community within the Chemistry and Biochemistry Department by specifically holding events to engage first year students. Events included the citrus social, periodic table of cupcakes, murder mystery play, tie dye event, and jeopardy night. This gave students a chance to get to know their peers better, to interact with a wide range of professors, and to gain knowledge about chemistry from outside the classroom. The success of these events has lead to record high attendance not only for the events but also for the Chemistry Club meetings held bi-weekly. The success of this initiative will ensure these and other events will be hosted for years to come, hopefully growing to the size where other schools can join and collaborate, further building a community within the field of chemistry and biochemistry.

Predicting pKas of flexible polybasic pyclen derivatives: A pKa challenge

Type: Undergraduate
Author(s): Tatum Harvey Chemistry & Biochemistry
Advisor(s): Benjamin Janesko Chemistry & Biochemistry Kayla Green Chemistry & Biochemistry
Location: Third Floor, Table 2, Position 1, 1:45-3:45

Predicting pKas is an outstanding challenge in computational chemistry. The Green group
at TCU is working to develop a library of pyclen derivatives that can successfully reduce oxidative
stress within the brain of people afflicted with neurodegenerative diseases1. Predicting the various
pKas of these flexible molecules, which are charged at neutral pH, challenges conventional
approaches to predicting pKas. For each pyclen derivative, we combine an extensive survey of
protonation site isomers, with conformational sampling using the CREST package2, DFT
calculations with continuum solvent models, followed by a linear fit to correct the solvent models
limitations for calculating energy of highly charged species. We can predict three to five measured
pKa values for each pyclen derivative with a RMSD of 0.9 pKa units, which is competitive with
the best-physics based method in the SAMPL6 blind challenge for the first pKa3. We are pushing
the boundaries of computational chemistry and its abilities to predict multiple pKas of flexible
molecules.

Models for the Next Generation of Drugs: Design, Synthesis, and Conformational Analysis of a 26-Atom Macrocycle

Type: Undergraduate
Author(s):
Advisor(s):
Location: First Floor, Table 4, Position 1, 1:45-3:45

To fight disease, pharmaceutical companies have historically prepared small molecules
designed to interfere with specific sites on proteins (enzymes) to prevent chemical reactions
from taking place. However, a second paradigm for interfering with proteins has gone largely
unexplored--blocking protein-protein interactions. To accomplish the latter, large molecules are
needed to bind to large areas on the protein target. However, large molecules present additional challenges. Typically, they are hard to synthesize, not orally available, and typically cannot cross cell membranes. Nature has designed large molecules like cyclosporin that should not work as drugs based on our current understanding. Despite its size, cyclosporin is orally available and can cross cell membranes. This research explores the design, synthesis, and conformational analysis of similar large ring-shaped molecules, so-called macrocycles. In this work, we are increasing the size of the ring-shaped molecule. By increasing the size of the ring-shaped molecule and varying the amino acid (in this case, valine), we are expanding the possible ways in which our macrocycle may interfere with protein-protein interactions. Here, a 26-atom macrocycle is reported. 1H NMR spectroscopy reveals a protonated molecule that is highly dynamic which has access to a beta-sheet conformation.

Implication of Steric Congestion on Sheet Formation: 26-Atom Macrocycles

Type: Undergraduate
Author(s): Lola Kouretas Chemistry & Biochemistry Luke Homfeldt Chemistry & Biochemistry Alex Menke Chemistry & Biochemistry
Advisor(s): Eric Simanek Chemistry & Biochemistry
Location: Second Floor, Table 1, Position 1, 1:45-3:45

Molecular engineering of larger macrocyclic compounds offers new avenues to disrupt protein-protein interfaces and potentially halt pathways that lead to neurodegenerative diseases, such as Alzheimer’s. The hallmark of Alzheimer’s disease involves the aggregation of so-called amyloid peptides that exhibit characteristic β-sheet structures. Thus, designing macrocycles that structurally/topologically mimic β-sheets should enhance the affinity of these macrocycles towards the amyloid aggregates and lead to rational design of more advanced scaffolds with superior structures. This will potentially present opportunities to interrogate protein-protein interactions, thus preventing amyloid plaque formation.

This work will describe the synthesis of structurally and functionally-diverse macrocyclic scaffolds containing leucine and isoleucine to understand the factors that contribute to β-sheet formation. Here, 26-atom macrocycles prepared in three steps will be described. Using a triazine core, a protected hydrazine group, and an amino acid constitute the base acid. In the second step the addition of an acetal of variable length forms the monomer. Acetals ranging from 2-4 carbons can be used to yield rings of 22-28 atoms. Previous work proves acetal length dictates morphology; three-carbon acetals demonstrate folded conformations and five-carbon acetals yield crinkled b-sheets. Four-carbon acetals yield the flattened b-sheets described here. Treatment with acid leads to dimerization in very high yields. Varying the amino acid choice can give way to synthesis of different homodimers and heterodimers.

These studies also address the optimization of the macrocyclization step. Early results indicate that a >300x reduction in the time of reaction (from 7 days to 30 min) might be realized. NMR spectroscopy provides confirmation of synthesis and 2D-NMR techniques offer opportunities to probe solution structure more efficiently.

Fabrication Process And Efficiency Analysis Of Organic Light-Emitting Diodes (OLEDs)

Type: Undergraduate
Author(s): Nhu Le Engineering
Advisor(s): Jeffery Coffer Chemistry & Biochemistry
Location: Second Floor, Table 1, Position 3, 1:45-3:45

Display technology is one of the industries of great significance, providing benefits for consumers with applications such as smartphones, televisions, and computer monitors. One of the current research topics in this industry of extensive interest is the development of new organic light-emitting diodes or OLEDs.

While such devices are common, fundamental challenges remain. Three pressing needs are: (1) longer device lifetimes, (2) lower fabrication costs, and (3) better control over emission color for ultrahigh definition displays and white-light lighting. Today, high-quality displays are built using high-vacuum deposition of molecular precursors, an expensive method unsuitable for ultra-large displays. Methods that rely on spin coating or printing of solutions of such precursors are far more economical, but present fabrication challenges of their own.

Our goal here is to improve device function and stability in OLEDs through simple solution-based routes with innovative fluorescent structures known as perovskites as building blocks. Ideally these new OLEDs will perform well at low voltage ranges and maintain good light emission intensity, as evaluated using techniques known as photoluminescence and electroluminescence spectroscopies.

In this research project, single-layer OLED and three-layer OLED devices are analyzed. Single-layer OLED devices consist of the substrate, anode, emissive layer, and cathode. Fluorine-doped Tin Oxide (FTO)/glass and Indium Tin Oxide (ITO)/plastic are the main substrates used, acting as anode. Ga-In eutectic, Silver Nanowire (AgNW), and Silver Epoxy are used as the interconnect / cathode layer to the emissive layer. To fabricate a three-layer OLED, the electron transport layer (ETL) is added between the cathode and emissive layer and a hole transport layer (HTL) added between emissive layer and anode, both to ideally improve energetics of electron/hole injection to the emissive layer. In our experiments, a species known as PEDOT:PSS is typically the hole transport layer and for the electron transport layer, we use ZnO or a mixture of ZnO and polyethylenimine.

The most success to date has been achieved with [Ru(bpy)3]2+ as the active emitting species in a thin polymer matrix referred to poly-vinylalcohol (PVA). Our current results show that the photoluminescence spectroscopy intensities were relatively high while the electroluminescence needs to be improved. The best result was recorded with the single-layer red OLED, which is made of FTO, [Ru(bpy)3]2+, and Ga-In eutectic. Visible light emission at low voltages from 3.5V-7V could be observed with the unaided eye under these conditions.

From Macroscopic to Molecular: Investigating the Behavior of Self-Assembling Hinges

Type: Graduate
Author(s): Alexander Menke Chemistry & Biochemistry
Advisor(s): Eric simanek Chemistry & Biochemistry
Location: First Floor, Table 2, Position 1, 11:30-1:30

Hinges are pervasive in the world today. Most common is a simple mortise door hinge  - defined by the flush stacking of leaves and fully revolute motion. Chemists have long sought to reproduce such structures on the molecular scale. Here, the hinge behavior of large, cyclic molecules is described.  Moreover, hinge motion can be controlled by "gumming up" the parts responsible for motion. While dirt and debris work in the macroscopic world, additional atoms are used in these molecular mimics. Specifically, by increasing the size of groups in the hinge domain, the rate of hinging decreases. Hinge motion is visualized by variable temperature NMR spectroscopy where in, at low temperatures the hinging both faces of the leaves (inside and outside) can be observed. At high temperatures, the hinging speeds up and the inside and outside exchange too quickly to be observed. Unlike hinges of everyday use that require human assembly, the molecular hinges described here assemble themselves. As a result, hinges with identical leaves as well as hinges with mismatched leaves can be prepared. Surprisingly, the results of this assembly process are biased: a statistical distribution of hinges is not observed.  Further studies to understanding this steric (gumming) sorting are ongoing.

Bridging Theory and Practice Enhancing Drug Design Through Molecular Simulations and Solvent Stability Analysis

Type: Undergraduate
Author(s): Alejandro Munoz Chemistry & Biochemistry
Advisor(s): Benjamin Janesko Chemistry & Biochemistry
Location: Second Floor, Table 2, Position 3, 1:45-3:45

SURFACE MODIFIED PLATINUM NANOCRYSTAL-BASED SILICON NANOTUBES FOR ENHANCED CANCER CELL TARGETING

Type: Graduate
Author(s): Leonardo Ojeda Chemistry & Biochemistry
Advisor(s): Jeffery Coffer Chemistry & Biochemistry
Location: Third Floor, Table 1, Position 3, 11:30-1:30

Platinum nanocrystals on Silicon nanotubes (PtNCs-pSiNT) exhibit significant anticancer activity via an apoptotic mechanism. To enhance the specificity of this material, we attach folic acid (FA) to the nanotube surface to target folate receptors (FARs) overexpressed in cancer cells. This conjugation is successfully demonstrated through X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT IR). Cell viability assays show an enhanced cytotoxicity toward HeLa cells relative to its non-FA containing analog.

Platinum-based therapeutics, exemplified by the FDA-approved anti-cancer drug cisplatin, are a mainstay in treatment of a range of different cancer types.3 Although this drug can form an adduct with DNA and induce apoptosis, many studies have confirmed that cancer cells can develop resistance to this treatment. Alternatively, small Pt nanocrystals (Pt NCs) have demonstrated arrested growth and apoptosis in cancer cells as a consequence of DNA platination and enhanced strand-breaks initiated by leaching Pt(II) ions from the NC surface in the acidic intracellular environment. Small Pt nanocrystals whose size is less than 3 nm demonstrate a higher reduction in cell viability than those with larger size, presumably owing to a relatively greater exposed surface area for dissolution. This observation, coupled with the identification of downregulation of multiple genes critical for cancer cell proliferation after treatment with Pt NCs, has led to an observed reduction in addressing drug resistance. Such nanocrystals tend to aggregate extensively in an aqueous environment, however, and we have developed well-defined Silicon nanotubes (pSiNTs) as a scaffold for effective nanocarrier for drug delivery of such PtNCs, taking advantage of nanotube high surface area, biocompatibility, and biodegradability. Functionalization with 3-(aminopropyl)triethoxysilane (APTES), followed by incubation with dilute K2PtCl4 solution results in the formation of PtNCs-pSiNTs well dispersed on the pSiNTs to avoid aggregation and release the platinum as the pSiNTs are resorbed over time, which results in significant cancer cell cytotoxicity-ty. To enhance the specificity of this material we conjugate Folic Acid (FA) to the Pt surface using as a Glutathione (GSH) linker, with the goal of enhanced targeting of overexpressed FARs and more selective cancer cell uptake.

Hinges Affect Permeability: Dynamic and Permeability Studies of Triazine Containing Macrocycles

Type: Graduate
Author(s): Casey Patterson-Gardner Chemistry & Biochemistry
Advisor(s): Eric Simanek Chemistry & Biochemistry
Location: Third Floor, Table 1, Position 1, 1:45-3:45

Chameleonicity, or the ability for a molecule to change its shape to match its environment, is an often-beneficial quality of potential drug candidates, allowing for greater cell permeation. Our group has previously reported several macrocycles exhibiting dynamic hinging motion, allowing the macrocycles to adopt various conformations and giving rise to chameleonic qualities. However, the extent of hinging (e.g., the rate and barrier to hinging) were contingent on the bulk of an amino acid’s side chain. Here, five 24-membered triazine-based macrocycles are introduced with varying alkyl substituents on the hydrazone moiety of our macrocycles, distant from the hinging axis. The macrocycles are obtained by a facile three step process in high yields at each step, with the macrocyclization yielding quantitative folded and dynamic macrocycles. Using rOesy NMR, the macrocycles’ conformation and rotamer state is shown to be preserved. Variable-temperature NMR reveals that the hinging motion is mostly unaffected by the distant hydrazone substitution, further establishing the location and pathway of the hinging axis. The minimal impact of hinging via these substituents allows for varying groups to be placed away from the axis, preserving the dynamic motion but allowing for tuning of pharmaceutically relevant parameters (e.g., lipophilicity/water solubility with varying alkyl chains) or installment of bioactive moieties. Permeability studies with PAMPA show acceptable passive permeation of the alkyl hydrazone macrocycles, with permeability dependent on lipophilicity and dynamic motion. These results further indicate the ability of these macrocycles to be valid scaffolds for intracellular drug development.

ARE GREEN ROUTES TO RED MOLECULES REAL? Sustainability and cost-effectiveness studies on the synthesis of high-value infrared emitting materials

Type: Undergraduate
Author(s): Hannah Sachs Chemistry & Biochemistry Harley Jacobs Chemistry & Biochemistry Daniel Ta Chemistry & Biochemistry
Advisor(s): Sergei Dzyuba Chemistry & Biochemistry
Location: Basement, Table 10, Position 1, 11:30-1:30

Typically, the costs associated with the synthesis, isolation, and purification of high value molecules/materials as well as environmental/health concerns related to the overall process are disregarded due to perceived profits that could be obtained from the use of the final products. However, as the scale of production of these materials increases, the need for more environmentally benign, sustainable, inexpensive, yet still facile and efficient processes increases exponentially.

Squaraine dyes are versatile, high-value fluorescent molecules, with a very broad and diverse range of applications due to their absorption and emission in the infrared spectral region. However, vast majority of literature syntheses of these dyes utilize toxic, volatile solvents. In this presentation, we will outline our current efforts on the use of green solvents, solvent-free and mechanochemical routes to various types of squaraine dyes. Furthermore, we will present sustainability and cost-effectiveness estimates as guiding tools for the future development of all around-efficient synthetic protocols for various types of squaraine dyes.

Modulation of catalytic reactivity with pyridine ring substitutions of Fe-pyridinophane complexes

Type: Graduate
Author(s): Katherine Smith Chemistry & Biochemistry Jackson Bonnell Chemistry & Biochemistry David M. Freire Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry
Location: Basement, Table 12, Position 1, 1:45-3:45

The inclusion of a pyridine moiety in the skeleton of tetra-aza macrocycles introduces rigidity while also introducing a handle by which the electronics and basicity of the ligand can be tuned. Metallation of these pyridinophanes has resulted in active mimics for metalloenzymes, such as superoxide dismutase mimics. However, recent work has explored their potential for industrially relevant catalytic reactions. Previous studies of iron RPyN3 complexes showed moderate success for a direct Suzuki-Miyaura C-C coupling reaction. In that work, it became clear that the substitution on the 4-position of the pyridine ring offered significant influence over the efficacy of the catalyst: the electron donating groups offer a better handle of modification of the electronic properties of the iron center, but the electron withdrawing groups increased the catalytic activity of the complex. In this presentation we introduce a second pyridine ring to the macrocycle skeleton, which includes a second position for modification, and compare the activity of this new RPy2N2 iron complex series to the previous RPyN3 series. Yields within this new series of iron complexes will be compared along with characterization of the respective complexes to understand what properties mitigate reactivity.

Rings of Power: Controlling SOD Mimic Activity with Pyridinophane Modifications

Type: Graduate
Author(s): Katherine Smith Chemistry & Biochemistry Cameron Bowers Biology Sarah Dunn Chemistry & Biochemistry David M. Freire Chemistry & Biochemistry Timothy M. Schwartz Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry
Location: Basement, Table 7, Position 2, 11:30-1:30

Oxidative stress is caused by the accumulation of reactive oxygen species (ROS) in the body and is a key player in many maladies, including neurological diseases like Parkinson’s and Alzheimer’s disease. Superoxide dismutase (SOD) enzymes are capable of transforming the common ROS molecule superoxide (O2-) into less toxic species such as H2O2 or O2, thus protecting the body from harmful reactions of superoxide. Synthetic metal complexes show promise as SOD mimics and can be effective alternatives to therapeutic dosing of SOD enzyme for oxidative stress. In this work, we present a series of 12-membered tetra-aza pyridinophanes (Py2N2) and the corresponding copper complexes with substitutions on the 4-position of the pyridine ring. The SOD mimic capabilities of the Cu[Py2N2] series were explored using a UV-Visible spectrophotometric assay. Spectroscopic, potentiometric, and crystallographic methods were used to explore how the electronic nature of the 4-position substitution affects the electronics of the overall complex, and the complex’s activity as a SOD mimic. This work is an initial step toward developing these Cu[Py2N2] complexes as potential therapeutics for neurological diseases by mimicking SOD’s capabilities and protecting the body from oxidative stress.

A route to libraries of triazine macrocycles using dynamic covalent chemistry: Application to engineering logP

Type: Graduate
Author(s): Gretel Stokes Chemistry & Biochemistry Casey Patterson-Gardner Chemistry & Biochemistry
Advisor(s): Eric Simanek Chemistry & Biochemistry
Location: Second Floor, Table 1, Position 1, 11:30-1:30

The therapeutic potential of macrocycles provides a tantalizing opportunity in drug discovery. The design criteria, such as solubility properties, for macrocycles is only beginning to be understood. One of the significant limitations to such investigations is the synthetic challenge that macrocycles provide and the need for comparison across similar molecules. This study describes the creation of a library of macrocycles to probe and ultimately to engineer partition coefficients. Recently, the quantitative dimerization of monomers to yield 24-atom macrocycles has been described. Historically, a trichlorotriazine is substituted with BOC-hydrazine, an amino acid, and an auxiliary amine (which has been limited until this point to morpholine or dimethylamine). Subsequently, an acetal is installed and treatment with acid results in quantitative dimerization to form macrocycles. To increase the efficiency of synthesis in this study, the acetal is installed prior to the auxiliary amine—the point of divergence. Here, five auxiliary amines were installed to give five monomers. These five monomers were combined in equimolar amounts and treated with acid to induce dimerization to yield five homodimers and ten heterodimers. The octanol:water partition coefficients of these molecules reveal a compensatory effect of substitution. That is, at pH 7, the partition coefficients of the heterodimers lie between the values of the corresponding homodimers. At this pH, the logP ranges between 1.9 and 4.3, indicating that relatively small molecular changes result in large variation in the logP of these macrocycles. The ability to engineer one property—the partition coefficient—suggests that a secondary property—shape—is conserved, a hypothesis borne out by NMR spectroscopy.

Constructing a database of asphaltenes: Quantum chemistry used to contextualize single-molecule experiments within the ensemble properties of asphaltenes in crude oil

Type: Graduate
Author(s): Gretel Stokes Chemistry & Biochemistry Sydney Mazat Chemistry & Biochemistry
Advisor(s): Benjamin Janesko Chemistry & Biochemistry
Location: Third Floor, Table 8, Position 2, 1:45-3:45

Asphaltenes constitute the heaviest, most diverse, and most chemically unresolved component of petroleum crude oils. Asphaltene mixtures are structurally complex, containing thousands of distinct species with a broad range of molecular weights, functional groups, and aromaticity. The structural diversity of asphaltenes, along with their tendency to aggregate, has hindered a complete understanding of the asphaltene component of crude oil. Modern asphaltene studies have deciphered hundreds of individual asphaltene structures through atomic force microscopy (AFM). The structural diversity and expanding chemical knowledge of asphaltene structures necessitates a way to store and easily retrieve and analyze this information. Additionally, much remains unknown about the connection of these imaged structures to ensemble properties of asphaltenes in crude oil. Herein, we address these two points via creation of a database of 69 published asphaltene structures. Quantum chemistry calculations are run to determine molecular properties of these individual asphaltenes and are stored on the database. These properties include molecular weight, solubility, aromaticity, dipole moment, and HOMO-LUMO gap. The database is exploited to generate graphs—such as the UV-Vis absorbance spectrum—using these computed properties to allow for a more complete chemical description of the ensemble properties of asphaltene mixtures. Our computational predictions give a more complete chemical description of previously determined individual asphaltene structures and help contextualize them with respect to their ensemble properties in crude oil.

Yield of Protein Crystallization from metastable Liquid liquid phase separation

Type: Graduate
Author(s): Shamberia Thomas Chemistry & Biochemistry Joel Dougay Chemistry & Biochemistry Aisha Fahim Chemistry & Biochemistry
Advisor(s): Onofrio Annunziata Chemistry & Biochemistry
Location: Basement, Table 14, Position 1, 1:45-3:45

Although chromatography is a reliable purification method in protein downstream processing, it has several limitations such as loading capacity, scalability and operation costs. These are important drawbacks especially for proteins generated from cell cultures with a high yield. Protein crystallization, which does not suffer these limitations, is regarded as a promising alternative to chromatography for protein purification. However, since protein crystallization is a complex not-well-understood process, protein crystals are often produced at low yield and with poor reproducibility. Thus, its implementation in protein purification protocols remain challenging. In our lab, we designed a new strategy for enhancing protein crystallization from metastable protein-rich droplets generated by liquid-liquid phase separation (LLPS). This strategy is based on the use of two additives; the first additive is needed to induce LLPS in protein aqueous solutions, while the second additive modulates the ability of protein-rich droplets to produce crystals. A protocol for determining yields of LLPS-mediated protein crystallization was also developed. This poster reports our experimental results on yield of lysozyme crystallization in the presence of NaCl (0.15 M) as an LLPS inducer and 4-(2-hydroxyethyl)-1-piperazineethanesulfonate (HEPES) as a modulator. Our results show that addition of HEPES (0.10 M) significantly boosts lysozyme crystallization yield from ≈5% (no HEPES) to 92%. The effect of temperature and incubation time on the yield of protein crystallization yield was also investigated. Our results reveals the key role of LLPS in enhancing protein crystallization.