It is extremely important in our age to look for alternative, more environmentally favorable energy sources. The Sun is a largely unused and widely available energy source to power human industry which can be utilized in different ways. Photovoltaic cells directly convert solar energy to electricity but only provide power when illuminated. Supplying solar-sourced energy during night hours and inclement weather requires conversion to another form, for instance into chemical fuel by means of water splitting into oxygen and hydrogen. This strategy, inspired by natural photosynthesis, is currently a promising and actively researched approach. However, achieving a high energy conversion efficiency, which is essential for industrial implantation of the method, remains a primary goal.
A Dye-Sensitized Photoelectrochemical Solar Cell (DSPEC) is specifically designed for using solar energy to generate hydrogen from water. We are pursuing the formation of photoanodes with polymer surface coatings prepared by electropolymerization. The polymer interfaces are designed to promote directional electron transfer at the interface, thereby resulting in a better solar energy conversion efficiency. The structure of the surface polymer enables the incorporation of catalyst units to the interface. To this end, we have prepared several novel iridium-oxide nanoparticle suspensions, using two different synthetic methods, to serve as the water-oxidation catalysts in our system. During the synthesis, the nanoparticles are functionalized with specific capping groups that contain terminal double bonds, through which they can be incorporated to the surface polymer electrochemically. Using acrylic acid and acrylamide as small molecule precursors, electro-polymer coatings have been prepared on FTO (fluorine-doped tin oxide) surfaces. Future research work will involve the incorporation of functionalized iridium oxide nanoparticles in the poly(acrylic acid/acrylamide) films and the characterization of their catalytic activity toward water oxidation. The method will then be extended to tin-oxide and titanium-dioxide semiconductor electrodes for preparing photo-active interfaces.
Ion solvation is fundamental in biochemistry. It controls the biophysical processes of protein solubility, reactivity, phase separation, crystallization and informational equilibria involving proteins and polypeptides. Ion solvation depends on the solute-solvent interactions which are governed by the properties of solvent like polarity, hydrogen bonding and ability to donate or accept electrons. These properties are subject to Pearson’s hard–soft acid–base (HSAB) effect and are characterized as hardness and softness of solvents. There have been attempts to connect the solvent hardness-softness to molecular properties and some empirical scales have been devised like μ-scale, DS scale and difference between the IR wavenumber shift of the C-I stretch of ICN and the O-H stretch of phenol. Only limited attempts have been reported to correlate the properties of solvents obtained from quantum chemical calculation to these empirical scales of solvent hardness-softness.
Our new quantum chemical descriptor, Orbital Overlap Distance, D(r), measures the size of orbital lobes that best overlap with the wavefunction around an atom. Compact, chemically stable atoms in the molecule tend to have overlap distances smaller than chemically soft, unstable atoms. Plots of D(r) on computed molecular surfaces, like electron density or spin density, distinguishes and quantifies the chemically soft and hard regions of a molecule. We propose that D(r) can be considered in terms of HSAB theory in order to predict solvation of ions. Our initial studies exhibit that D(r) of many common solvents correlates well with Marcus’s empirical μ-scale of solvent softness. Our studies provide a direct method to estimate the softness-hardness of solvents by using standard quantum chemical calculations.
Author(s): Allison Buckingham Chemistry & Biochemistry Keira Clotfelter Chemistry & Biochemistry Jack Dietz Biology Tommy Gifford Chemistry & Biochemistry Waylan Kisor Chemistry & Biochemistry
Advisor(s): Magnus Rittby Chemistry & Biochemistry
Location: Session: 2; Basement; Table Number: 9
This is experiment is designed to test how Nylon 6-10 is constructed and responds in a microgravity environment. Nylon 6-10 is a very flexible fiber. It consists of two chemicals called polypropylene and sebacoyl chloride to make the nano-structure for Nylon 6-10. We have developed several of ideas on what will happen to Nylon 6-10 in micro-gravity. We think that it will change the molecular structure of the Nylon 6-10 in micro-gravity for the better or worse. The good variable is that Nylon 6-10 might change into a very flexible, durable substance for many different applications both on Earth and in space. One concern we have is that Nylon 6-10 might change the molecular structure to not form any fibers or it might not dry by absorbing air molecules.
We decided to use Nylon 6-10 because of its overall construction. The industrial process for Nylon 6-10 is stronger and more flexible than Nylon 6-6. It is basically liquid rope. It can be used for repairs and manufacturing. It is an industrial chemical. A variety of products are created using Nylon 6-10, toothbrushes, paint brushes and even your underwear. It is a very common product in many of different industries and is a very useful product. It behaves like nylon fiber for thread or can be used for manufacturing different tools such as epoxy or fiberglass. The industrial ideas are very extensive and there are many suppliers.
Author(s): Hannah Carey Chemistry & Biochemistry Jason Mars Chemistry & Biochemistry
Advisor(s): Eric Simanek Chemistry & Biochemistry
Location: Session: 1; 2nd Floor; Table Number: 5
(Poster is private)
Recent trends in drug discovery research are directed at targeting protein-protein interactions. Blocking these interactions could be an effective strategy for treatment. Here, the synthesis of a macrocycle, a large ring-shaped molecule that is the same size as many protein-protein interaction sites, is described. The synthesis relies on the preparation of two different, crescent-shaped molecules through short, multistep syntheses. When these two molecules are combined together and subjected to acid to reveal reactive groups, a spontaneous assembly process occurs. The macrocycle is characterized by conventional methods including 1H NMR (which reveals a diagnostic signal for cyclization), 13C NMR, and mass spectrometry.
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
(Poster is private)
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.
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.
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
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.
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.
Author(s): Nicholas Henderson Chemistry & Biochemistry Arshad Mehmood Chemistry & Biochemistry
Advisor(s): Benjamin Janesko Chemistry & Biochemistry
Location: Session: 2; Basement; Table Number: 5
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
(Poster is private)
The semiconductor Silicon (Si) remains a significant material in the electronic device and photovoltaic industries . Especially, nanostructured forms of Si with a porous morphology (pSi) exhibit interesting properties which can be controlled via modulating pore structure and surface chemistry . 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 . 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 , . 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 .
In chemotherapy, platinum-based cancer drugs, such as cisplatin and carboplatin, are widely used as effective drugs against various types of cancer . 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 , . 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 . 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.
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).
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.
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.
(Poster is private)
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.
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.
Author(s): Brian Niebuhr Chemistry & Biochemistry Marianne Burnett Chemistry & Biochemistry
Advisor(s): Kayla Green Chemistry & Biochemistry
Location: Session: 2; Basement; Table Number: 2
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.
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.
Drug design has historically involved identifying a protein target and synthesizing molecules to affect its activity. This strategy ignores all of the interactions between proteins that can also be responsible for disease progression. Analysis of the molecular basis of protein-protein interactions from crystal and solution structures shows that amino acids including tryptophan are over-represented at these interaction sites. By making molecules that are rich in tryptophan, these protein-protein interactions might be disrupted. Macrocycles were chosen as targets of synthesis over linear molecules because the former can arrange the tryptophan groups into shapes that are potentially more favorable for protein binding. Importantly, these macrocycles have sizes and shapes that are commonly associated with real drugs. Here, the macrocycle forms spontaneously when two complementary halves dimerize through condensation reactions between the tryptophan-containing bis-aldehyde half and the bis-hydrazine half. Each molecule is available in five or fewer steps. The bis-hydrazine half also displays a biotin group that can be used as a hook to fish proteins out of the proteome using the tryptophan-rich half as bait.
Author(s): Nate Schmitt Chemistry & Biochemistry Adam Montoya Chemistry & Biochemistry
Advisor(s): David Minter Chemistry & Biochemistry
Location: Session: 2; 1st Floor; Table Number: 4
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.
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
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.
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.
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
(Poster is private)
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.
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.
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
(Poster is private)
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.
(Poster is private)
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.
Author(s): Nelli Bodiford Chemistry & Biochemistry Steven McInnes Chemistry & Biochemistry Nathan Shurtleff Chemistry & Biochemistry Nicolas Voelcker Chemistry & Biochemistry
Advisor(s): Jeffery Coffer Chemistry & Biochemistry
(Poster is private)
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.