Yield of protein crystallization from metastable liquid-liquid phase separation
Aisha Fahim, Shamberia Thomas, Jenny Pham, Onofrio Annunziata

The high demand in pharmaceutical and biotechnological products has motivated the need for economically sustainable alternatives to chromatography for protein purification. One promising alternative for protein purification is protein crystallization. However, protein crystallization is a complex, not well understood process. In our previous work, a new strategy for enhancing protein crystallization from metastable protein-rich droplets was examined. This requires the use of two additives. The first additive (inducer) promotes liquid-liquid phase separation (LLPS) in a protein aqueous sample. The second additive (modulator) alters the composition of droplets and their thermodynamic stability. A protocol for determining yields of LLPS-mediated protein crystallization was developed. This protocol was used to examine the effect of various inducer-modulator pairs on crystallization of lysozyme, a model protein.

There are a wide variety of unnatural amino acids whose properties could be used to study the structure and function of proteins and create proteins with enhanced or novel functions. The purpose of this research is to develop a method to add unnatural amino acids to proteins via site-specific modification. This is done through aminoacyl tRNA synthetases (aaRSs) which are proteins that attach the correct amino acid to its corresponding tRNA. The loaded tRNA then transports the amino acid to the ribosome where it is incorporated into an elongating protein. Usually, aaRSs have editing domains that remove any amino acids that the synthetase is not specific to. To solve this problem, we have paired Methanobacterium thermoautotrophicum leucyl tRNA synthetase (MLRS) with a removed editing domain with Halobacterium sp. NRC-1 leucyl tRNA to incorporate unnatural amino acids into proteins in Escherichia coli. The binding site of MLRS has been identified, and we have created millions of MLRS variants by randomizing the five amino acids in the binding sites. Using genetic screening procedures, we have identified variants with larger binding sites, and we are currently testing for successful incorporation of unnatural amino acids like dansyl-DAP into the z-domain model protein.

Utilizing the supportive structure of hydrogels, the semiconducting character of porous silicon (pSi) membranes, and the biodegradability of both, a unique biosensor for the chemical analysis of health-relevant analytes can ideally be created.
Alginate-based hydrogels are water-infused, biodegradable polymer networks. These are particularly useful because of their environmental abundance, and their ability to interface well with human skin. These characteristics also make them an ideal medium for supporting pSi membranes and simultaneously assimilating them into a wide range of tissues.
Porous silicon (pSi), a highly porous form of the elemental semiconductor, is utilized to measure and conduct electrical signals throughout the hydrogel matrix. In diode form, these membranes exhibit measurable current values as a function of voltage, which can be used to detect bioelectrical stimuli such as the concentration of physiologically relevant ionic species (e.g. Na+, K+, and Ca2+).
Recent experiments center on integrating pSi membranes into various aqueous environments and hydrogels to test how variations in ion concentration affect the flow of electrical current as a function of applied voltage. pSi membranes are fashioned into diodes upon the attachment of 0.25 mm diameter copper wire using silver epoxy and annealing. An electrochemical cell is created by placing two pSi membranes parallel each other in an electrolyte composition. Current is measured as a function of applied voltage (typically from 0-5 V) for systems with differing NaCl concentration.
As expected, the magnitude of maximum current response is proportional to ion concentration present in the electrolyte, with an order of magnitude amplification or more of measured current for a given voltage upon immersion of the electrodes in an alginate hydrogel matrix relative to water alone.
This presentation will focus on initial diode fabrication protocols, as well as establishing limits of detection for simple ions species present in human sweat. More refined strategies are also envisioned, including the development of methods for stabilization of sensor performance along with miniaturization of the sensing platform itself.

Light-driven reactions, such as those utilized in photoelectrosynthetic applications, focus on capturing and transferring light energy to drive chemical reactions. For this purpose, light-active metal oxide semiconductor materials are used, such as BiVO4, 𝛼-Fe2O3, and WO3 to list a few. Previous work demonstrated the use of BiVO4 electrodes to drive the oxidation of benzyl alcohol to benzaldehyde in the presence of a TEMPO (2,2,6,6-tetramethylpiperidine) mediator.1 This study seeks to improve the photoelectrochemical performance of this reaction by using a heterojunction WO3-BiVO4 electrode. We hypothesize that the heterojunction would decrease charge carrier recombination and improve the photochemical yield of the reaction compared to a BiVO4 electrode.2,3 The WO3-BiVO4 interface forms a type II band alignment allowing electrons from photoexcited BiVO4 to transfer into WO3 and holes to accumulate at the BiVO4-electrolyte interface.4 Two techniques, UV-visible spectroscopy and incident photon-to-current efficiency (IPCE) measurements, were applied to better understand why the heterojunction improved the photocurrent density in the presence of reaction components in solution. UV-visible spectroscopy was used to determine the band gaps of the materials. Information about the efficiency of light energy conversion to chemical energy was obtained by IPCE measurements. IPCE values are determined by relating the proportion of incident light power to the current produced by illuminating the WO3­-BiVO4 photoanode over a small wavelength range. Photoanodes exhibiting higher IPCE % are more effective at driving photoelectrosynthetic reactions.1 To test the effect of WO3 on the energy conversion efficiency, IPCE experiments were run for the WO3-only, BiVO4-only, and WO3-BiVO4 samples. Comparing IPCE values for WO3-BiVO4 samples shows a clear increase compared to BiVO4-only photoanodes. These results demonstrate how coupled materials (WO3-BiVO4) can generate higher current densities upon illumination for driving photoelectrosynthetic reactions.

The long-term goal of exploring macrocycles is to be able to produce drugs that can interfere with certain protein-protein interactions within cells. This strategy could have the potential to change the way scientists think about drug design. Aspartic acid is a particularly useful to incorporate because it is one of the top five amino acids that contribute to binding at protein-protein interfaces. The acid sidechain of aspartic acid presents significant challenge because of the potential for side reactions. This research has established that an aspartic acid macrocycle can be synthesized quickly in three steps. The route is remarkably efficient and has the characteristics of those that could be used to make drugs. This poster details the chemical synthesis and characterization of this molecule, discusses potential side reactions, and identifies the next steps in advancing this project.

N-terminal acetylation plays an important role in the stability, activity, and targeting of proteins in eukaryotes. Most proteins expressed in bacteria are not acetylated, although the N-terminal acetylation is critical for the activities of a handful of biologically important proteins. Therefore, it is of practical significance to control N-terminal acetylation of recombinant proteins in bacteria. This study is aimed to alter the substrate specificity of RimJ, a protein N-terminal aminotransferase (NAT) that is known to acetylate a few recombinant proteins including the Z-domain in E. coli. The RimJ-mediated protein acetylation occurs at a higher rate when the substrate’s N-terminal amino acid is small. Because of this narrow substrate specificity, RimJ is not applicable for a broad range of recombinant proteins. Based on the AlphaFold-predicted structure of E. coli RimJ (AF-P0A948_F1), we predicted that five amino acids (Y106, M142, N144, Y170, and L171) may recognize substrate proteins in the active site. We created RimJ variants, in which one or two of these five amino acids are changed to alanine, a small neutral amino acid, so that the active site becomes larger to accommodate substrate proteins containing bigger N-terminal amino acid residues. Then, the substrate specificity of RimJ was investigated by co-expressing two Z-domain variants T2I and S3K, which were not acetylated by the wild-type RimJ. The expressed Z-domain variants were purified by immobilized metal affinity chromatography and subsequently analyzed by mass spectrometry, by which a 42-Da mass increment indicates the presence of an N-terminal acetyl group. The RimJ single mutants such as N144A, M142A, and Y106A showed little acetylation on both T2I and S3K Z-domain variants. In contrast, the RimJ double mutants, Y106A M142A, Y106A N144A, and Y170A L171A showed higher acetylation rates on the Z-domain T2I variants. Little acetylation was observed for the Z-domain S3K variant by any of these double mutants. We also created more RimJ variants in which three different amino acids located on the other side of the active site were changed to alanine. These variants will be used to co-express the Z-domain variants, whose N-terminal acetylation patterns will be analyzed by mass spectrometry.

Metal Halide Perovskites (MHPs) are an emerging type of semiconductor for use in electronic devices that produce or utilize light. MHPs have shown advantages over traditional semiconductors such as silicon due to ease of solution processing, high defect tolerance (defects are strained chemical bonds and/or missing atoms in the crystal lattice) and tunable emission of light color. MHPs have the chemical structure 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. Their favorable properties have resulted in solar cells capable of 32.5% power conversion efficiency in a tandem perovskite/silicon solar cell. However, MHPs suffer from issues with long term stability brought about by exposure to air and moisture, as well as ion migration under illumination.
Crystal engineering and chemical passivation using small molecules have been implemented to improve the long-term stability and reduce ion migration. Incorporation of small molecules with charged groups onto a MHP helps to mitigate surface defects by occupying surface sites of missing atoms or strained bonds. Recent work has shown incorporation of these small molecules during MHP synthesis results in the formation of two dimensional layers on top of the three-dimensional perovskite crystal resulting in increased long-term stability, resistance to heat and moisture, and reduction in ion migration at grain boundaries. Current work in our lab involves synthesizing thin films of methylammonium lead tribromide by spin coating and incorporating a macrocycle based on triazine molecules for this purpose. This presentation focuses on the effects of triazine treatment on the above perovskite, as evaluated by photoluminescence microscopy, powder x-ray diffraction, and scanning electron microscopy.

In the lab, molecules used as drugs are made either in solution (wherein the reactive agents dissolve) or on solid supports referred to as 'beads' (wherein reactive agents are washed over beads and become attached only to be liberated later). The virtue of bead-based synthesis comes with the savings in time and energy normally required to purify the reaction products. That is, solution phase synthesis is work intensive. Here, a route to cyclic molecules synthesized on beads is described. The molecules produced by these bead-based methods have already been prepared in solution for comparison. In addition to evaluating the relative efficiencies of these two routes, the bead-based method can be used to rapidly make 100s-1000s of cyclic molecules. Such numbers are not possible using solution phase methods due to the burdens of purification. The effort relies on tethering an acetal to a reactive bead, followed by a protection and deprotection sequence, the addition of an amino acid using standard peptide coupling strategies and a reaction with a core group that offers the potential for the attachment of 100s-1000s of different groups. Cleavage of this linear molecule from the bead leads to spontaneous cyclization to the desired products. The products will be characterized by NMR spectroscopy and mass spectrometry as well as be assayed for biological activity in a disease model of breast cancer.

Salt-induced diffusiophoresis is the migration of a colloidal particle in water caused by a salt concentration gradient. Recent studies have shown that diffusiophoresis can be used for controlling particle motion, with potential applications in separation science, microfluidics, and enhanced oil recovery. These applications are especially appealing for nanoparticles with host-guest properties such as micelles. In this work, Rayleigh interferometry was used to experimentally characterize diffusiophoresis of tyloxapol micelles in the presence of the strong salting-out agent, sodium sulfate, in water at 25oC. Our results show that micelle diffusiophoresis occurs from high to low salt concentration. A model based on micelle preferential hydration was used to quantitatively explain our findings. At relatively high salt concentrations, liquid-liquid phase separation (LLPS) was observed. Near this phase transition, micelle Brownian mobility was found to dramatically decrease, making micelle diffusiophoresis the dominant transport mechanism. Our work suggests that salting-out agents and proximity to LLPS can be used to control the motion of micelles and hydrophilic nanoparticles in general.

Tissue engineering encompasses many important medical applications that pertain to the repair and regeneration of various tissues throughout the human body that have been adversely affected by disease or injury. Through combining the body’s cells with synthetic scaffolds, tissue engineering promotes proliferation of cells at damaged sites. Recent advances have demonstrated that using biocompatible materials such as alginate hydrogels—polymer networks derived from brown algae—are a cheap and environmentally-friendly approach to this. Alginate hydrogels are effective because they mimic the extracellular matrix of tissues, which provides structural support to cells that comprise human tissues.
One necessary modification to these scaffold materials is to load them with drugs that can facilitate healing. More complex designs can ideally deliver more than one therapeutic species simultaneously. In addition to hydrogels, drugs can also be loaded into a material known as porous silicon (pSi). pSi nanoparticles can be physically entrapped inside alginate hydrogels to create a two-system drug delivery mechanism with sustained release. This allows drugs such as growth factors, substances that stimulate cell growth, to be released at different times as the pSi and alginate hydrogel degrade.
This project entails the construction of alginate hydrogels that incorporate model dye-loaded pSi particles. The release of two dye molecules known as curcumin and rhodamine were monitored to assess the efficacy of the two-system drug delivery mechanism. It was first found that curcumin was too hydrophobic of a dye to achieve significant loading in the pSi. Rhodamine was found to be released from the pSi/alginate hydrogel system in a more incremental (sustained) manner over time compared to a relatively large initial ‘burst’ release observed for the release of rhodamine from pSi only. Sustained release in drug delivery is important to ideally reduce the amount of drug necessary and contrasts a burst release where large amounts of the loaded molecules are released prior to achieving a stable release profile. Furthermore, the localization of pSi in the alginate hydrogels was achieved by inserting loaded pSi membranes into pre-gelled alginate hydrogels, which is important to control the spatial delivery of the loaded molecule from pSi. Overall, it is believed that this pSi/alginate hydrogel material can greatly benefit the field of tissue engineering by creating dual delivery platforms with more diverse control over drug release.

Catalases are a class of metalloenzymes responsible for the protection of cells from damage caused by hydrogen peroxide by converting it into water and oxygen. Manganese-based catalase (MnCAT) has been identified in different organisms as an antioxidant, raising the interest in developing small molecules as biomimetic models. A Mn(III) complex of pyclen, a 12-membered ring pyrinophane macrocycle, has previously shown to be a functional mimic of MnCAT in our laboratory. In the present study, modifications of the pyridinophane macrocycle were used to evaluate their impact on the catalytic disproportionation of hydrogen peroxide. Two series of ligands were studied: (1) varying the number of pyridine moieties within the macrocycle, and (2) substitutions in the 4-position of the pyridine ring. pH-potentiometric titrations were used to determine the formation constants (log ß) of each manganese complex, which allowed us to derive speciation curves in solution. The initial rates method was used to calculate the kinetic-relevant parameters for the disproportionation reaction. The results emphasize the effect of structural differences of the ligand on modulating the reactivity of manganese, which are the basis of a mechanistic study of the reaction that is currently underway.

N-alkylation of amino acid-containing pharmaceuticals has been shown to increase their respective oral availability and membrane diffusion. Macrocycles, too, have been an interest in modern drug design due to their ability to have a dynamic conformation and adopt a chameleon-like property to enhance the ability for the drug to be properly delivered in a multitude of environments, and similarly macrocycle's ability to fully envelope an active site to block enzymatic activity. In this project, four novel N-alkylated amino acid-linked triazine macrocycles were synthesized from cyanuric chloride using BOC-hydrazine, an N-alkylated amino acid, and dimethylamine. Coupling of the amino acids with EDC to form the acetal product and further acidification and removal of protecting groups with trifluoroacetic acid yielded macrocycles in good yield. Characterization via 1D and 2D NMR reveals the emergence of different conformations in varying proportions. These conformations result from by the restricted rotation around the Ar-N bonds of both the hydrazine and amino acid of the macrocycles. A previous, non N-alkylated, glycine macrocycle was used as a reference compound, and the emergence of the different conformations was not observed for this molecule. Furthermore, the N-methylated glycine macrocycle displayed an asymmetric configuration, whereas the proline macrocycle was too rigid around the Ar-N of the amino acid to form the different rotamers. The successful synthesis of these N-alkylated amino acid macrocycles shows that further customization of these triazine macrocycles is possible.

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"), and [C16-C1pyrr]Br ("IL3"). Variations on the addition method of ionic liquids to the perovskite precursor 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 IL3 are more photoluminescent than the perovskite films formed with IL1, IL2, or no IL (control). Preliminary experiments varying the addition method of IL3 during film formation have shown that the perovskite films are brightest when IL3 is added to both the precursor and the antisolvent layers at the beginning of the fabrication process. These results, along with detailed structural characterization of a given perovskite film, will be discussed in this presentation.

This project aims to incorporate unnatural amino acids into proteins using an ortogonal pair composed by a leucyl synthetase from Methanobacterium thermoutotropicum (MLRS) and tRNA from Halobacterium sp. NRC-1 (HL-TAG3). A plasmid called pRCG was designed to contain a cat-upp fusion gene with amber stop codons at permissible sites of the chloramphenicol acetyl transferase protein (CAT). Three variations of the pRCG plasmid were tested: Q98TAG, D111TAG, and a double mutant containing both mutations. To study the amber codon suppression ability of the mutants, a functional leucyl-tRNA synthetase lacking the editing domain was tested for the incorporation of its endogenous amino acid using the three pRCG variants. To show that the amber stop codon is being suppressed, E. coli GH371 cells must survive when grown in the presence of leucine and chloramphenicol because the full-length CAT is expressed. In contrast, when grown in the presence of 5-fluorouracil (5-FU) and leucine, cells will not survive because the MLRS produces a full-length uracil phosphoribosyl transferase protein (UPRT) that converts 5-FU to a toxic product, causing the cells to die. Only Q98TAG or D111TAG mutant was able to suppress the amber stop codon when E. coli GH371 cells were grown in the presence of leucine under positive and negative selection conditions. The Q98TAG variant showed higher suppression ability. A library of MLRS with five randomized amino acids in the active site was designed and selected using the pRCG Q98TAG system and two unnatural amino acids (UAAs): 4-nitro-1-phenylalanine and 2-amino-3-(5-(dimethylamino)naphthalene-1-sulfonamide)propanoic acid (Dansyl-Dap). The obtained variants are currently under study to test their ability to incorporate these UAAs into a model protein called Z-domain

It is estimated that 50 million individuals worldwide live with Alzheimer’s disease (AD), a neurodegenerative progressive disorder that, along with other chronic dementias, cost the United States $355 billion in 2021. Previous research links AD with amyloid beta (A𝛽) aggregation in the brain. Possible therapeutic drugs, including antioxidants and metal chelating agents, need efficient delivery systems that can cross the blood-brain barrier and release drugs appropriately. Recent discoveries in nanoscale materials as targeted drug delivery and controlled release agents have shown that such materials can release therapeutic drugs in a slow manner and increase efficacy. Chief among these carriers are porous materials with high surface areas because of their tunable pore structure, surface chemistry and drug loading capacity. This project focuses on using porous silicon derivatives as a carrier because, in addition to the above properties, it is a known biocompatible material.
This research deals with developing efficient protocols for loading mesoporous silica (pSiO2) with selected metal ion binding agents through systematic manipulation of external variables in order to achieve the highest percentage of loading. Once this has been determined, release and complexation studies are conducted. Known spectrophotometric methods are used to monitor diffusion over time and evaluate the profile of the sustained release. Different derivatives of chelating agents are tested and compared to determine the best suited candidates. The macrocyclic molecule Pyclen was the first tested candidate, followed by its dimer form, and finally a halogen substituted derivative. Stoichiometric complexation ratios with copper ions are measured followed by testing their success of inhibiting amyloid beta aggregation. Developing a slow and steady rate at which drugs capable of inhibiting neurotoxic A𝛽 aggregates in the brain can be released should be more effective and lead to more promising solutions for AD.

The misregulation of reactive oxygen species (ROS) and transition metal ions contributes to the onset of Alzheimer’s Disease (AD). A series of new pyridinophane ligands with indole (L2 and L3) and 4-methyl-8-hydroxyquinoline (L4) modifications were evaluated as a means of targeting the molecular features of AD. These studies contribute to the overall understanding of the therapeutic potential of the pyridinophane backbone as a means of treating AD. In comparison to the parent molecule L1, the order of radical scavenging activity was determined to be L4 > L1 ~ L3 > L2, which is likely related to the reactivity and position of the substitutions. These results demonstrate that the addition of (1) the indole moiety to the pyridine, and (2) the addition of the 4-methyl-8-hydroxyquinoline moiety to the secondary amine on the tetra-aza macrocyclic pyridinophane both disrupt radical scavenging ability, warranting future exploration of these modifications in therapeutic design for AD.

Catalase is one of the most efficient antioxidants metalloenzymes in biology responsible for the decomposition of hydrogen peroxide into water and oxygen. The desired antioxidant activity of catalase for medical and industrial application has inspired the study of metal-based mimics of catalase activity. However, very few of these studies explored iron-based mimics, their mechanism of action and the impact of the metal center environment on the activity of the complex. In this study, the first goal is to investigate pyridine containing macrocyclic Fe (III) complex (L1) as catalase mimic. Mass spectroscopy and UV-Visible spectrophotometry were used to follow the mechanistic activity of FeL1. The second goal is to evaluate the impact of adjusting the electronic properties (L2 and L3) and the structural rigidity (L1 and L4) of the ligand on the activity of the complex. Cyclic voltammetry, X-ray structural analysis, potentiometric titration, and UV-Visible spectrophotometry were conducted to characterize and study the properties of all the complexes. Kinetic studies following the initial rate method and TON studies were conducted to compare their activity.

To accomplish many critical reactions and interactions mediated by metals like zinc and copper, Nature uses the amino acid cysteine—often in pairs—that are preorganized in space by a protein. Cysteine proteases are illustrative of the former; zinc finger transcription factors of the latter. Small molecule models of these proteins can serve many roles. They can shed light on the chemical process or ape them for therapeutic gain. Here, a macrocycle is used to preorganize two cysteine residues. These macrocycles are synthesized in three steps. The route begins with a stepwise substitution of a BOC-protected hydrazine group, a protected cysteine, and dimethylamine onto a triazine ring. Next, an acetal is appended onto the compound. Finally, a macrocycle is produced using an acid-promoted homodimerization. The macrocycle product has been characterized using 1H and 13C NMR in 1D and 2D experiments. Additionally, logP, variable temperature NMR, and H/D exchange experiments will be performed to understand the shape of the macrocycle in solution. These studies conclude with a study of how these cysteines bind metal ions. The results of this work will guide their development for biomedical applications including their use as drugs.

Three b-branch substituted macrocycles featuring a b-branched amino acid linked acetal, a trans-hydrazone, and dimethyl amine were synthesized via acid condensation to yield homodimer macrocycles near quantitative yield without need for further purification. Previous attempts at the dimerization of triazine monomers utilized glycine or b-alanine that do not contain steric bulk. Here, L-valine, L-threonine, and L-isoleucine were used to probe the effects of steric bulk upon macrocycle formation. The resulting macrocycles are symmetrical species that are characterized by 1H-NMR, 13C-NMR, 1H-COSY spectroscopy, and 1H-rOesy spectroscopy. The symmetrical macrocycles containing valine exists as one species while threonine and isoleucine macrocycles exist as two isomers in a 9:1 and 6:4 ratio respectively. All three macrocycles exist as one rotamer state out of four possible. The minor isomer of the threonine macrocycle has an inconclusive rotamer state where the isoleucine macrocycle shows the same rotamer state as the major isomer. Well-tempered MetaDynamics Simulations tell us the rotamer state seen in the rOesy favors a folded state in all cases with barriers to interconversion decreasing as size of the side chain increases.

Various semiconductor metal oxides such as ZnO, TiO2, WO3, and BiVO4 have been utilized for photoelectrochemical (PEC) water-splitting as well as for value added alternative reactions. However, single-phase materials often face multiple challenges including poor charge separation efficiency and surface degradation especially in aqueous environment. BiVO4 is well known as a promising photoanode material, but the above-mentioned shortcomings are still present. Therefore, in order to enhance the PEC performance of BiVO4,our group has focused on doping techniques for BiVO4 with tungsten (W) to yield tungsten doped BiVO4 (W:BiVO4). In addition, polyethylene glycol (PEG) has also been introduced to the material as a morphological control agent. The addition of polymer to the precursor solution helps to control the porosity of the resulting surface film by promoting a less porous and more compact formation of BiVO4 on FTO. The mixture of PEG (1% MW 100,000 : 1% MW 20,000) has been tested. The photochemical oxidation of a solution containing (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) has been performed in acetonitrile with 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) electrolyte. As a result, photocurrent density of PEG (1% MW 100,000 : 1% MW 20,000) - W:BiVO4 (0.58 mAcm-2 with an applied biased of 0.3 V vs. SCE) has outperformed that of W:BiVO4 without PEG (0.32 mAcm-2). Based on the data obtained, PEG(1% MW 100,000 : 1% MW 20,000) -W:BiVO4 outperformed W:BiVO4 by about 2 times. In the future, the best performing electrode samples will be studied for driving TEMPO-mediated benzyl alcohol oxidation.

Cancer is a disease worldwide, and every year millions of people are diagnosed with it. Platinum compounds play an important role as anticancer agents. Their ability to bind to DNA in the nucleus (by a process known as intercalation within DNA base pairs) result in DNA damage and cell death. Unfortunately, these platinum-containing compounds lack specificity toward cancer cells and attack normal healthy cells that results in significant side effects as a consequence (loss of hair, nausea, among others).
Drug carriers (inert structures that house a given drug) that can deliver relatively large amounts of one of these drugs in a small volume (which are often chemically metastable) with some degree of specificity toward the tumor (thereby sparing the healthy cells) are clearly desirable. Our research group has developed a straightforward method to produce a well-defined nanoscale drug carrier known as silicon nanotubes (SINTs), along with a way to incorporate platinum on their surface using (3-Aminopropyl) triethoxysilane (APTES) as a functional arm. These silicon nanotubes have attracted great attention in applications relevant to diagnosis and therapy, owing in part to its biocompatibility and biodegradability in cells.
Once inside the cell, platinum is released slowly, thus allowing an interaction with DNA. Our previous results using this technology showed significant toxicity on a type of cancer cell known as HeLa. While these findings are promising, specificity has not yet been achieved.
Cancer activates signaling pathways that translates on overexpression of specific proteins/receptors. Particularly, folate receptors (FR) are present in 90-98% of ovarian, prostate, uterus, breast, as well as some adenocarcinomas. FR expression is very limited in normal cells and generally not accessible to blood flow which makes it a suitable and promising system to target cancer. These receptors are glycopolypeptides that present a high affinity for folic acid (FA). We propose to incorporate folate to our silicon-based Pt nanoparticles to enhance selectivity.
A viable strategy has been identified, involving the conjugation of a molecule known as glutathione to act as a linker to the surface of the silicon-based platinum nanoparticles through N-Hydroxysuccinimide (NHS) activation, followed by substitution with folic acid. This presentation will highlight some of our recent progress in this approach.

Micelles represent an important example of nanoparticles with the ability to host nonpolar molecules in water. Understanding the effect of salts on micelle diffusion is important for enhancing particle insertion into porous materials in the presence of salt brines with application in enhancing oil recovery and soil remediation. In this poster, the effect of two salting-out salts (sodium sulfate and magnesium sulfate) on the diffusion of a non-ionic micelle (tyloxapol) is examined. Micelle diffusion coefficients were experimentally determined in aqueous salt solutions using dynamic light scattering at 25 ˚C. Our experimental results show that the micelle diffusion coefficient is approximately constant until a critical salt concentration is reached. After this concentration, micelle diffusion was found to decrease significantly, and this behavior reflects a corresponding increase in micelle size. To explain our experimental results, we introduce a two-state equilibrium model showing that relatively large surfactant aggregates become thermodynamically more stable than micelles at high salt concentrations. The results of our model were also used to examine the effect of salt gradients on micelle diffusion.

Adamantyl H-phosphinate esters were first introduced by Yiotakis et al. as a protecting group in the synthesis of phosphinopeptides. Gatineau et al. later found adamantyl H- phosphinate esters to be useful in the synthesis of P-stereogenic compounds. Phosphorus compounds have a broad range of applications ranging from pharmaceuticals to agricultural products, making them an area of interest in synthetic chemistry. However, methods for the preparation of P-stereogenic compounds that achieve high enantioselectivity are limited. Gatineau et al. discovered that adamantyl H-phosphinate esters serve as precursors that facilitate this preparation, which they attributed to the ability of the esters to resist racemization when displaced with organometallics. However, their methods were limited by the necessity of chlorophosphine starting materials. In this project, we aimed at developing novel synthetic methods for the preparation of adamantyl H-phosphinate esters which are not limited in terms of available reagents and are less expensive than current known methods. EDC, PivCl, and T3P were utilized in the esterification reactions. Methods were developed to prepare these esters in good yield on a multigram scale without the need for chromatography. An alternative method to the esterification of H-phosphinic acids was also employed that involved the preparation of adamantyl hypophosphite and its conversion into a variety of H-phosphinate esters. However, adamantyl hypophosphite was shown to have limited reactivity.

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.

Small molecular probes, dyes with photophysical properties correlating with various environmental physical properties, such as polarity, pH, viscosity, and temperature, are widely used in various areas of analytical, biological, and material sciences.

This poster will describe spectroscopic behavior of pyrrolyl-squaraine dyes in various types of media (i.e., molecular, ionic and deep-eutectic solvents, and micelles) using a variety of spectroscopic techniques (i.e., absorption, fluorescence, nuclear magnetic resonance and circular dichroism). Some aspects related to the synthesis of these dyes will be presented as well.