Chemistry Commons^™

Stacked Antiaromatic Porphyrins, Ryo Nozawa, Hiroko Tanaka, Won-Young Cha, Yongseok Hong, Ichiro Hisaki, Soji Shimizu, Ji-Young Shin, Tim Kowalczyk, Stephan Irle, Dongho Kim, Hiroshi Shinokubo

Chemistry Faculty and Staff Publications

Aromaticity is a key concept in organic chemistry. Even though this concept has already been theoretically extrapolated to three dimensions, it usually still remains restricted to planar molecules in organic chemistry textbooks. Stacking of antiaromatic π-systems has been proposed to induce three-dimensional aromaticity as a result of strong frontier orbital interactions. However, experimental evidence to support this prediction still remains elusive so far. Here we report that close stacking of antiaromatic porphyrins diminishes their inherent antiaromaticity in the solid state as well as in solution. The antiaromatic stacking furthermore allows a delocalization of the π-electrons, which enhances the two-photon absorption …

Intramolecular Reductive Heck Approach To Guaipyridine Alkaloids, Samantha Grosslight, Hope Spargo

Scholars Week

The guaipyridine alkaloids are a family of compounds that all share an unusual carbon structure, whose source plants have been used as a traditional medicine in Southeast Asia. Members of the guaipyridine family include cananodine and the rupestines. Cananodine has been isolated from the fruits of the Canaga odorata in Indonesia, Malaysia and the Philippines. Cananodine has been used of decades as a traditional medicine for the treatment of malaria, infections and fever. Studies of cananodine’s biological activity have reveled activity against Hep G2 and Hep 2,2,15 human hepatocarcinoma cell lines, the most common types of liver cancer. Due to …

Evaluating Nucleophile And Substrate Specificities Of Sortase A Homologs For Orthogonal Reactivity, Nicholas Horvath, Jesse Prelesnik

Scholars Week

Enzymes have become an attractive option for protein modification chemistry due to the remarkable site-specificity they afford. Of particular interest is sortase A from taphylococcus aureus (SrtAaur), which has garnered attention for its ability to install a variety of non-natural modifications to a conserved oligopeptide substrate. In addition to SrtAaur it has become apparent that sortase A homologs exist in other bacterial strains, each of which is potentially a novel catalyst for protein engineering. Previous work has demonstrated that eight representative sortase A homologs exhibit unique specificities for synthetic peptide substrates, capable of identifying characteristic combinations of amino acids in …

Gold Catalyzed Lactonization Of Epoxide Esters, Carlos Enciso Lopez

Scholars Week

Lactones are cyclic esters of varying ring size that occur naturally in organic compounds. Organic structures such as these have various useful biological activities applicable to antibacterial drugs, potential anticancer drugs, and participants of metabolic processes. Gold catalysts Au(I) and Au(III) are shown in our experiments to be effective in inducing intramolecular lactonization of epoxide esters to form desired lactone products. In our experiments gold catalysts coordinated with epoxides to develop a positive charge on the carbon nearest to the carbonyl. The result is an intramolecular lactonization of the ester via nucleophilic attack of the carbonyl oxygen onto the positive …

Solving The Molecular Structure Of Hybrid Human-Porcine Factor Viii Through X-Ray Crystallization, Mikko Sayre, Amanda Weis, Brenna Park-Egan

Scholars Week

Factor VIII (fVIII) is a protein that is involved in the coagulation cascade, a collection of reactions that is activated by injury and leads to the formation of blood clots. Deficiencies in fVIII lead to the bleeding disorder hemophilia A, a condition that occurs in 1 in 5000 births. The current treatment for hemophilia A is inefficient and costly; however, there is potential through the use of recombinant hybrid human-porcine fVIII. Hybrid fVIII shows up to 12-fold higher coagulant activity than human fVIII, and can retain its activity even in the presence of inhibitory antibodies. The primary objective of our …

Surface-Enhanced Raman Scattering Optical Fibers As Chemical Sensors, Deanna Myers, Luke Degraaff

Scholars Week

There is a great need to be able to measure chemical environments at both the cellular and sub- cellular levels in real time because chemical irregularities in these environments are indicative of many disease states. In this project, a surface-enhanced Raman scattering (SERS) based optical fiber sensor is designed to monitor pH in real time. SERS spectra of reporter molecules adsorbed on the fiber are used to deliver information on the chemical composition of the environment.

Nickel Phosphide On Boron-Doped Alumina: New Catalysts For Heteroatom Removal Reactions, Catherine E. Miles

WWU Honors College Senior Projects

The effects of boron addition to an alumina (Al₂O₃) support on the hydrodesulfurization (HDS) properties of nickel phosphide (Ni₂P) catalysts have been investigated. The B-Al₂O₃ supports were prepared by a wetness impregnation method using boric acid (H₃BO₃) to dope the alumina support with 0-7.2 wt% B, yielding a boron oxide (B₂O₃) layer of monolayer thickness on the surface of the Al₂O₃ support. Ni₂P precursors were prepared on the B-Al₂O₃ supports in two ways: 1) impregnation …

Mapping Interactions Between The Type-Vi Secretion System Effector Tae1 And Its Putative Substrates Using Nmr Spectroscopy, Robert C. (Robert Corey) Henderson

WWU Graduate School Collection

Tae1 is an amidase produced by gram negative Pseudomonas bacteria that attacks the peptidoglycan layer in the cell walls of neighboring bacteria after secretion through the Type VI secretion system (T6S). The goal of our work is mapping interactions between the type-VI-secretion system effector Tae1 and its putative substrates using nuclear magnetic resonance (NMR) spectroscopy. Tae1 is amenable to NMR in that we are able to collect spectra with resolved, well defined peaks that can be assigned, thereby providing valuable structural information. We have assigned 89.2% of backbone atoms and 87.4% of sidechain atoms. Assignment of Tae1 was performed with …

Acene-Linked Covalent Organic Frameworks As Candidate Materials For Singlet Fission, Viktor Laszlo, Tim Kowalczyk

Chemistry Faculty and Staff Publications

Two-dimensional covalent organic frameworks (COFs) are a versatile class of porous materials that can be tailored for solar energy conversion applications through the incorporation of organic chromophores as linker units. In this work we examine whether such COFs can be engineered to support singlet fission (SF), the generation of two triplet excitons from a single photoexcitation. We simulate the structural and electronic properties of a series of COFs possessing embedded polyacene linkers from benzene through pentacene. Detailed electronic structure calculations suggest that necessary conditions on the energy and electronic coupling for SF can be met with COF architectures closely related …

Development Of 2d And 3d Conductive Biomaterial Composites For Use As Electromechanical Actuators, Sean Severt

WWU Graduate School Collection

Flexible and conductive biocompatible materials are attractive candidates for a wide range of biomedical applications including implantable electrodes, tissue engineering, and controlled drug delivery. Here we demonstrated that chemical and electrochemical polymerization techniques can be combined to create highly versatile silk-conducting polymer (silk-CP) composites with enhanced conductivity and electrochemical stability. Interpenetrating silk-CP composites were first generated via in situ deposition of polypyrrole during chemical polymerization of pyrrole. These composites were sufficiently conductive to serve as working electrodes for electropolymerization, allowing an additional layer of CP to be deposited on the surface. This two-step technique expanded the range of available polymers …

Copper Indium Disulfide Nanocrystal Luminescent Solar Concentrators, Ryan I. (Ryan Isaac) Sumner

WWU Graduate School Collection

The sun is the most prominent renewable energy resource. Technologies such as photovoltaics (PVs) have yet to emerge as a cost effective alternative to non-renewable energy resources such as fossil fuels. Luminescent solar concentrators (LSC) possess the ability to lower the cost of solar energy by the reduction of the photovoltaic cell area and yet increase photovoltaic conversion efficiency. LSC’s offer an attractive approach to concentrating both specular and diffuse light, which eliminates expensive solar tracking methods. Luminophores for LSC applications are often dominated by reabsorption losses and absorb a small part of the solar spectrum, which prevents LSC’s from …

Toward Accurate And Efficient Computational Screening Of The Electronic Structure And Band Gaps Of Semiconductors, Linda Grabill

WWU Graduate School Collection

With increasing population, growing energy demands, and environmental concerns the search for greener energy resources has intensified in recent decades. For example, in the ongoing effort to harness solar energy, researchers have worked to identify and optimize the efficiency of semiconductors beyond traditional silicon photovoltaic materials.

In the development of new materials, synthetic chemists and materials scientists often look to computational chemistry to guide and understand experiments. In the case of semiconductors for solar energy conversion, this includes calculations of electronic band structure and band gap. The most precise computational approaches, such as density functional theory (DFT) are both time …

Progress Toward Structural Studies Of A Circularly Permuted Human Hemoglobins Containing T-State Stabilizing Mutations, Rachel J. (Rachel Joy) Hubbard

WWU Graduate School Collection

Our research is focused on the production of a hemoglobin based oxygen carrier (HBOC) which can be used as a therapeutic in the event of acute blood loss. The administration of cell-free hemoglobin is associated with severe adverse effects due to dissociation of the tetrameric α₂β₂ complex into αβ heterodimers. Our approach to the design of an effective HBOC, is based on a recombinant circularly permuted human hemoglobin in which all of the subunits are linked in a single-chain fashion. This design would prevent the dissociation of the tetramer and allow for the biosynthesis of polymeric hemoglobins of defined mass. …

Ring-Closing Metathesis Reactions Of Acyloxysulfones: Synthesis Of Γ-Alkylidene Butenolides, Iris T. Phan

WWU Graduate School Collection

As we set out to investigate ring-closing methatesis reactions of acyloxysulfones, we discovered that treatment with triethylamine resulted in its quantitative conversion into the γ-alkylidene butenolides. γ-Alkylidene Butenolides are common to a number of biologically important natural products, and have been of great interest. To date, there has been no metathesis-based synthesis of γ-alkylidene butenolides making our approach the first. Development of the metathesis-based approach has allowed us to synthesize a variety of γ-alkylidene butenolides from the RCM products in high yields (69-100%). The elimination is proposed to proceed via an E1cb mechanism leading to (Z)-γ-alkylidene butenolides as …

Synthesis & Reactivity Of Iron (Ii) Pyridinediimine Complexes For The Reduction Of Nitrite, Yubin Kwon

WWU Graduate School Collection

The activation of small molecules has been studied by the scientific field for many decades as it plays a key role in nature such as photosynthesis and respiration. Many of these reactions are catalyzed by metalloenzymes in nature where the transfer of electrons and protons are coupled for the reaction to move forward. Noncovalent interactions in the secondary coordination sphere of metalloenzymes play an important role in determining the activity and selectivity. Hydrogen bonds are the most common noncovalent interactions that metalloenzymes utilize to control the reactivity in the secondary coordination sphere. Therefore, it is important to develop compounds and …

Development Of A Samarium Based Allylic Benzoate Elimination/Isomerization: Application To A Total Synthesis Of Honokiol, Alicia M. Wright

WWU Graduate School Collection

We have developed a new samarium diiodide-mediated elimination/isomerization reaction of benzoyl esters, capable of delivering olefinic products with high yield and selectivity depending on substrate structure and the additives used. The ability to selectively synthesize terminal, non-conjugated alkene substituents inspired us to use these optimized conditions in order to complete the total synthesis of the natural product, honokiol. Honokiol is a biaryl natural product isolated from magnolia trees that displays desirable oncological properties as evidenced by several biological studies in recent years. We found that our initially proposed pathway for completing the synthesis of honokiol was not a feasible route …

Exploring The Biofuel Potential Of Isochrysis Sp., John R. Williams Ii

WWU Graduate School Collection

A select few strains of marine microalgae, such as Isochrysis sp., produce high-melting (∼70 °C) lipids known as long-chain alkenones that detrimentally affect biodiesel fuel quality. A method has been developed for the production of an alkenone-free Isochrysis biodiesel. This material was prepared on sufficient scale to allow for extensive analysis according to ASTM standards. Results revealed that while cold flow improved by removal of these high-melting components, a cloud point was still unattainable due to the fuels dark pigment. Further effort in relating the presence of alkenones and the resulting cloud point of the biodiesel, led to decolorization of …

The Deoxygenation And Hydrogenation Properties Of Noble Metal-Based Bimetallic Phosphide Catalysts, Paul M. Cochran

WWU Graduate School Collection

With increasing concern regarding the environmental impacts of fossil fuels, and the difficulty of extracting petroleum feedstocks, alternative liquid fuels are becoming more desirable. Bio-oil, which is oil derived from biomass, is a renewable source of liquid fuels. However, the high oxygen and water content of bio-oil results in high corrosivity and low energy density, making it unusable in the current liquid fuel infrastructure. The process of removing heteroatom impurities from oil is known as hydrotreating. Current hydrotreating catalysts are optimized for refinement of petroleum, and are not suitable for bio-oil deoxygenation. Transition metal phosphides (such as Ru₂P) …

Comprehensive Solution Structure Analysis Of Dna Duplexes Containing Chemical Base Alterations, Joanna Hoppins

WWU Graduate School Collection

Most types of chemical modifications of DNA bases are endogenous processes which are sensitive to the intracellular conditions. For example, the enzymatically catalyzed methylation of canonical cytosine to 5-methylcytosine (5metC) is a key form of epigenetic regulation of gene expression patterns. This modification is catalyzed and controlled by DNA methyltransferases (DNMTs). Perturbed rates of enzymatic DNA methylation leads to hyper- or hypo-methylation, both of which are a common initiating step in several forms of cancer. In addition to epigenetics, DNA bases can be chemically altered, or damaged, in response to reactive oxygen species (ROS). The oxidation of DNA by ROS …