- Dr. Dustin E. Gross - Organic, Supramolecular, and Macromolecular Chemistry
Using dynamic covalent reactions, it is possible to prepare large and structurally complex molecules from relatively simple small-molecule precursors in a single synthetic transformation. Research in the Gross lab takes advantage of these reactions to allow for systematic development of diverse molecular systems in relatively few steps. Specific interest revolves around tri-coordinate boronate esters, which have found their niche in covalent organic frameworks (COFs) and other discrete molecular architectures. The REU participant will take on a project to investigate novel benzoborole-based systems. This will involve the investigation of benzodiazaboroles for dynamic covalent chemistry (DCC) and the design and synthesis of diazaborole-based polymers, oligomers, and macrocycles from symmetric and asymmetric monomers. In addition to synthetic work, students will also gain hands-on experience with IR, UV-vis, fluorescence and NMR spectroscopy (including multinuclear), GC/MS, and gel permeation chromatography (GPC). The experience with this instrumentation will not only allow the students to monitor their experiments and characterize their products, but it will also make them more marketable when applying for graduate schools or positions in industry.
- Dr. Donovan C. Haines - Biochemistry and Organic Chemistry of Lipids, Enzymes, and Drug Metabolism
The enzyme superfamily known as Cytochrome P450 is one of the most widely studied classes of enzymes in biochemistry, due in part to the important roles of these enzymes. In addition to the metabolism of xenobiotics like pharmaceuticals, the family can metabolize lipids, especially fatty acids and fatty acyl amides like anandamide. We have developed small molecule probes (substrates and inhibitors) of important parts of the mechanism of lipid metabolizing P450s. We also have a library of mutants of a key member of this important class of enzyme, P450BM-3, that has been studied for about 40 years as a model of P450 structure and function. These mutants perturb important mechanistic triggers, like the change in iron spin state, that occurs upon substrate binding due to changes in water dynamics in the active site. Students will synthesize new N-acylamino acids using organic synthesis, purify them, characterize them and confirm their identity and purity using spectroscopic techniques like Nuclear Magnetic Resonance spectroscopy and gas chromatography/mass spectrometry, and use those probes to study the mechanistic triggers in wild type enzyme and in mutants where the triggers malfunction (or at least function differently). For example, when alanine 328 is mutated to valine, the hydrophobic molecules bind much more efficiently and tightly and the rate of catalysis goes up (coupled to efficient spin state change). However, when the same residue is mutated to a serine (just addition of a single hydroxyl group to wild type enzyme), the spin state change appears to be largely broken. Initially, it was believed that substrate was not binding to this enzyme significantly, but re-examination of the original data reveals that not only do substrates bind (though weakly), the effect on binding depends significantly on the amino acid headgroup on the substrate even though that group binds 17 angstroms away from the heme iron. The combined tools of the mutants and the library of small molecules allows us to probe how substrate binding triggers the spin state change that makes the enzyme easier to reduce (the next step of the mechanism). In addition to the organic techniques, students will learn how to study the spin state change by UV-vis spectroscopy and how to carry out enzyme kinetic assays.
- Dr. Meagan Hinze - Chemical Biology, Biocatalysis
Students in the Hinze lab will profile the biocatalytic activity of Baeyer-Villiger monooxygenases (BVMOs) toward both native and non-native reactions in addition to using the products in the synthesis of bioactive compounds. BVMOs are flavin-dependent enzymes, which natively mediate the oxidation of a ketone to produce an ester or lactone, and the active intermediate is a C4a-peroxyflavin species, which reacts via a Criegee intermediate. BVMOs have the potential to be a powerful tool in the resolution of chiral molecules. Cyclic meso ketones are often included in substrate libraries to assess the general reactivity profile of newly isolated BVMOs; however, the inclusion of meso 1,3-diketone scaffolds has been limited. The newly formed acetyl group is readily hydrolyzed to reveal the α-hydroxyl group of the benzoin product, and the benzoin motif itself is present in harmandianone and phenatic acid, compounds with antibacterial and antifungal properties. For application in the following research interests, three BVMOs will be overexpressed in E. coli: phenylacetone monooxygenase from Thermobifida fusca (PAMO), cyclohexanone monooxygenase from Thermocrispum municipale DSM 44069 (TmCHMO), and BVMO from Leptospira biflexa (BVMOLepto). Expression protocols in E. coli for all three enzymes have been established. A library of 1,3-diketone substrates will be synthesized from commercial materials in 1-3 steps using CuI-mediated arylation, Claisen condensation, and alkylation methodologies. Once confirmation of native enzyme reactivity is established, purified enzymes will be subjected to a substrate screen of the 1,3-diketones. The accessibility of different substrate motifs will provide opportunities for students to analyze reactivity trends and discern differences between the substrate scope of each enzyme. Additionally, effective implementation of dynamic kinetic resolution conditions would enhance the utility and impact of the oxidative transformation.
Students in the lab will develop a diverse skillset with an emphasis in organic synthesis, chemical biology, or a blend of the two disciplines. Also, they will be guided to collaborate, learn from, and mentor each other. Organic synthesis methods employed in the lab will include Schlenk technique, experimental design, small molecule purification, and spectroscopic characterization. Chemical biology techniques in the lab will include DNA manipulation, heterologous expression in E. coli, protein purification, and biochemical characterization. At the interface of these disciplines, students will gain exposure and proficiency in biocatalysis protocols, including analysis of reactions with GC/MS and HPLC, rigorous design of control experiments, and development of preparative scale biocatalytic transformations.
- Dr. Christopher E. Hobbs - Polymer Chemistry, Catalysis
Considering that many homogeneous catalysts contain expensive and potentially toxic transition metals, their sequestration, recovery, and reuse is an important “green” endeavor. This is often achieved through the covalent linkage of a ligand/catalyst to a soluble polymer support whose selective solubility can allow for catalyst recovery as either a solution or a solid. However, the use of the polymer support is limited to only the specific reaction that is facilitated by the catalyst attached. Furthermore, upon catalyst death (after multiple uses) the polymer support, ligand and transition metal are disposed of along with other laboratory waste. An idea that has been explored much less is the preparation and use of re-loadable polymer supports, systems in which a used ligand/catalyst can be removed from the support and a new catalyst installed. Typical covalent bonds used to attach catalysts to supports (C-C, C-O, C-N, etc.) render this highly challenging. However, there are some covalent bonds (like Si-O) that can undergo facile hydrolysis. REU students working in Prof. Hobbs’ laboratory will explore the preparation and use of detachable ligands and catalysts that are anchored to a polymer support through silyl ether linkages. This will allow for the removal of the catalyst from a polymer-support catalyst after multiple cycles, followed by subsequent installation of another catalyst. This will result in a more streamlined approach to synthetic processes. Students working on this project will gain experience in synthesis, catalysis, polymer and green chemistry.
- Dr. Ilona Petrikovics - Chemical Defense, Nanotechnology, and Enzymes in Drug Antagonism
As part of the nationwide network including other universities e.g. UCSD, UCI, SDSU, UC, led by the U.S. Army Medical Research Institute of Chemical Defense and funded by the NIH, the Petrikovics lab is working on developing therapeutic agents to treat cyanide intoxication. Students in the Petrikovics lab are involved in the wide range of the drug development process such as formulation; solubility studies; drug stability studies; particle size determination; in vivo toxicity and antidotal efficacy studies on mice and rats; pharmacokinetics (PK) studies on rats and mice e.g. drug absorption to blood, blood-brain-barrier (BBB) penetration studies, and organ distribution studies. More recently, the lab is equipped to do brain distribution studies, in vitro and in vivo BBB penetration studies, and PK studies with a newly developed advanced formulation (developed by the Southwest Research Institute in San Antonio Texas). We are also focusing on drug protein-binding studies with Dr. Thompson’s lab involving DMTS metabolism and hemoglobin interactions with DMTS. Students in the Petrikovics lab work on animal models, analytical methods development to analyze DMTS in blood and brain, and other organs (GC-MS, HPLC).
- Dr. David E. Thompson - Analytical Chemistry of Cyanide Antagonism, Nanosensing, Calibration
Dimethyl Trisulfide (DMTS) is a molecule that has shown promise as a cyanide antidote. DMTS has been shown to accelerate the conversion of hemoglobin to metHb in blood. This project would focus on tracking the sulfur as this and other conversion processes occur upon addition of DMTS to blood; or as DMTS degrades in non-hermetically sealed containers.50 The laboratory work would likely include UV-vis spectroscopy, headspace sampled GC-MS, combustion analysis, and HPLC-MS experiments. The goal would be to complete one experiment per week. Students would initially be given detailed experimental protocols, and in later experiments would be expected to help write up such protocols. Similarly, students would be carefully guided through initial data analysis and would be expected to work more independently later in the summer. Training in methods, instruments and safety would be a key component of the work. Each week of the summer, time would be allotted for students to work on growing a unified research report, and preparing a presentation. The writing would describe the work of that week and would summarize a related reading from the peer-reviewed literature. The student would be expected to make regular presentations to the research group on their progress, and to listen to other students doing the same. The target will be a peer-reviewed paper and a student presentation at an ACS conference.
- Dr. Tarek Trad - Materials Chemistry, Nanotechnology
Piezoelectric and semiconducting properties of zinc oxide led to a large commercial demand for ZnO based optoelectronic devices that operate at the blue-ultraviolet regions. Therefore, a wide range of techniques have been explored to synthesize ZnO nanostructures which could open the door for advanced applications. Doped ZnO structures with Al, Si, In, and Ga showed enhanced electrical/optical properties.51 Doped ZnO has been synthesized using chemical methods such as hydrothermal growth,52,53 and electrodeposition.54 However, physical methods such as thermal evaporation or chemical vapor deposition55–57 have the advantage of producing high crystalline quality products which are essential for photovoltaic applications. Progress has been made in conductivity type studies, but the effect of dopants is not yet fully understood. In this project, ZnO nanostructures will be synthesized using a modified chemical vapor deposition technique. Copper will be introduced with the zinc starting material in a one-step growth process to obtain high crystalline quality P-type semiconducting nanostructures with uniformly distributed dopant within the structures. Preliminary results show the possibility of synthesizing nanoscale ZnO hexagonal columns on gold-catalyzed silicon substrates. The comparative study proposed here will evaluate the photoluminescence properties of doped and un-doped ZnO nanocolumns, or other possible structures, and provide a better understanding on the effect of doping over structure, morphology, and crystal quality. Depending on the metal oxide structure performance, a complementary study will follow and involve the fabrication and testing of a dye-sensitized solar cell using the produced metal oxide nanostructures prepared.
Students will be involved in determining particle shape, distribution, and morphology by using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Energy dispersive X-ray (EDX) spectroscopy will be used to determine the chemical composition of the products. Photoluminescence (PL) spectra will be evaluated using fluorescence spectroscopy available in the chemistry department at SHSU. The students will also gain experience with a novel synthesis process involving nanostructures and will participate in all aspects of the research methodology including literature search, writing, proper scientific reporting and referencing, instrumental training, and safety.
- Dr. Darren L. Williams - Physical Chemistry, Spectroscopy, Solvent Blend Formulation, Industrial and Precision Cleaning
The Strategic Environmental Research and Development Program (SERDP) funded research “Development of Azeotropic Blends to Replace TCE and nPB in Vapor Degreasing Operations” with $150,000 from the fall of 2014 through July 2016. The relationships developed with industry during this project led to our development of a two-day hands-on Product Quality Cleaning Workshop held May 16-17, 2018. The 2018 workshop had seven corporate sponsors, was attended by 32 industry professionals, and brought in $37,200 in revenue. The workshop benefitted from the assistance of many undergraduate researchers. This industrial training is unique because it is hands-on. Part of the Cleaning Research Group work is dedicated to developing clear and concise laboratory experiments that teach the principles of precision cleaning chemistry to professionals in industry. One particular experiment will be to study the solvent-swelling of various commercially-available polymeric materials. The undergraduate researcher will be tasked with gathering a large library of polymer samples with varying Hansen solubility parameters. The researcher will select an example test solvent and will perform solvent-polymer interaction tests analyzing the data photographically and potentially, gravimetrically. In addition to creating and troubleshooting a valuable hands-on exercise for the workshop, this research will potentially lead to a paper on the determination of the Hansen solubility parameters of unknown solvents. There is a current need for methods aimed at the analysis of new biological extracts for solvent properties and solvating abilities.
- Dr. Adrian Villalta-Cerdas - Chemical Education, Carbon Nanomaterials
Undergraduate researchers will synthesize carbon-nanomaterials via arc-discharge underwater and use them in the removal of contaminants of concern considering their bioaccumulation potential. The goal is to study the potential application of carbon-based nanomaterials as environmental remediation tools for water treatment plants. In another project, undergraduate researchers will design and evaluate novel laboratory experiences for General and Organic Chemistry laboratory programs. The lab experiences will foster clear connections between fundamental concepts in chemistry via multiple laboratory techniques. The design will implicitly guide learners into developing an overarching comprehension of the chemical phenomenon under investigation. In this way, the chemistry laboratory experience will be aligned with desired goals of laboratory education put forth by the National Research Council in 2005: “development of scientific reasoning, understanding of the nature of science, developing practical skills, and supporting mastery of subject matter.” Undergraduate researchers will test the lab experiences to (1) ensure robustness and reproducibility of the collected data, (2) determine experimental fallouts and limitations, and (3) determine the time frame necessary for the completion of the experience. The participation of undergraduate students supports and provides feedback during the development of the learning materials and laboratory curriculum design. The involvement of undergraduate students is a unique feature ensuring a student-focus redesigned approach.
- Dr. Christopher Zall - Inorganic Chemistry
Research in the Zall group is in the field of inorganic catalysis, focused on developing new catalysts for reactions related to energy storage and conversion. A key goal is to develop catalysts for hydrogenation of low-energy feedstocks, such as CO2. The products of these reactions, such as formic acid and methanol, can be used as renewable fuels or as part of a chemical hydrogen storage strategy. Our research in this field has three main areas of focus: studying the thermodynamics of H2 activation and hydride-transfer reactions involving transition metal-phosphine complexes; incorporating bio-inspired organic hydride donors into the coordination sphere of these metal complexes to facilitate these reactions; and studying the catalytic hydrogenation activity of these catalysts. Research in the group introduces students to a variety of experiences, including organic and inorganic synthesis, equilibrium studies, catalytic kinetics, and computational modeling of reaction energetics. Typically, an undergraduate who is new to research starts by synthesizing a new ligand containing a novel organic hydride donor. This ligand synthesis follows an established template but results in a new potential catalyst, as the various hydride donors are each paired with metal ions that have complementary reactivity. Students will then conduct stoichiometric studies of H2 activation and hydride transfer, followed by studies of catalytic hydrogenation reactions. The modular catalyst design is amenable to undergraduate research, allowing systematic variation of factors such as hydride donor ability and steric bulk. As a result, each student has a unique project that follows a consistent template but results in a catalyst with unique reactivity. Collectively, these projects constitute a cohesive research program, where the interrelated projects facilitate interactions among students, who can learn from and build upon their peers’ projects.