Physical Sciences and Mathematics Commons^™

Limonene Enantiomeric Ratios From Anthropogenic And Biogenic Emission Sources, Shan Gu, Wentai Luo, Avisa Charmchi, Kevin J. Mcwhirter, Todd Rosenstiel, James F. Pankow

Chemistry Faculty Publications and Presentations

Emissions from volatile chemical products (VCPs) have been identified as contributors to air quality degradation in urban areas. Limonene can be a tracer compound for VCPs containing fragrances in densely populated regions, but limonene is also emitted from conifers that are planted in urban areas. This creates challenges for using limonene to estimate VCP emissions. In this study, the −/+ enantiomeric ratios of limonene from VCP and conifer emission sources were quantified to evaluate if this measurement could be used to aid in source apportionment and emission inventory development. Samples were analyzed using a gas chromatograph equipped with a chiral …

Dna-Based Assay For Calorimetric Determination Of Protein Concentrations In Pure Or Mixed Solutions, Matthew W. Eskew, Patrick Reardon, Albert S. Benight

Chemistry Faculty Publications and Presentations

It was recently reported that values of the transition heat capacities, as measured by differential scanning calorimetry, for two globular proteins and a short DNA hairpin in NaCl buffer are essentially equivalent, at equal concentrations (mg/mL). To validate the broad applicability of this phenomenon, additional evidence for this equivalence is presented that reveals it does not depend on DNA sequence, buffer salt, or transition temperature (Tm). Based on the equivalence of transition heat capacities, a calorimetric method was devised to determine protein concentrations in pure and complex solutions. The scheme uses direct comparisons between the thermodynamic stability of a short …

The Α-Crystallin Chaperones Undergo A Quasi-Ordered Co-Aggregation Process In Response To Saturating Client Interaction, Kirsten Lampi, Adam P. Miller, Susan E. O'Neill, Steve L. Reichow

Chemistry Faculty Publications and Presentations

Small heat shock proteins (sHSPs) are ATP-independent chaperones vital to cellular proteostasis, preventing protein aggregation events linked to various human diseases including cataract. The α-crystallins, αA-crystallin (αAc) and αB-crystallin (αBc), represent archetypal sHSPs that exhibit complex polydispersed oligomeric assemblies and rapid subunit exchange dynamics. Yet, our understanding of how this plasticity contributes to chaperone function remains poorly understood. This study investigates structural changes in αAc and αBc during client sequestration under varying degree of chaperone saturation. Using biochemical and biophysical analyses combined with single-particle electron microscopy (EM), we examined αAc and αBc in their apo-states and at various stages of …

Using Flipped Classroom Modules To Facilitate Higher Order Learning In Undergraduate Organic Chemistry, Lauren R. Holloway, Tabitha Miller, Bryce Da Camara, Paul M. Bogie, Briana L. Hickey, Jack Barbera, Angie L. Lopez, Multiple Additional Authors

Chemistry Faculty Publications and Presentations

In an ongoing effort to incorporate active learning and promote higher order learning outcomes in undergraduate organic chemistry, a hybrid (“flipped”) classroom structure has been used to facilitate a series of collaborative activities in the first two courses of the lower division organic chemistry sequence. An observational study of seven classes over a five-year period reveals there is a strong correlation between performance on the in-class activities and performance on the final exam across all classes; however, a significant number of students in these courses continue to struggle on both the in-class activities and final exam. The Activity Engagement Survey …

An Efficient And Chemoselective Method To Generate Arynes, Bryan Metze, Riley A. Roberts, Aleksandra Nilova, David R. Stuart

Chemistry Faculty Publications and Presentations

Arynes hold immense potential as reactive intermediates in organic synthesis as they engage in a diverse range of mechanistically distinct chemical reactions. However, the poor functional group compatibility of generating arynes or their precursors has stymied their widespread use. Here, we show that generating arynes by deprotonation of an arene and elimination of an “onium” leaving group is mild, efficient and broad in scope. This is achieved by using aryl(TMP)iodonium salts (TMP = 2,4,6-trimethoxyphenyl) as the aryne precursor and potassium phosphate as the base, and a range of arynophiles are compatible. Additionally, we have performed the first quantitative analysis of …

The Discovery Of Diverse Picophytoplankton Populations In The Columbia And Willamette Rivers Using Flow Cytometry, Kylee Brevick

Chemistry Undergraduate Departmental Honors Theses

As important primary producers, picophytoplankton determine the flow of carbon and energy in aquatic ecosystems. Picocyanobacteria are one picophytoplankton group known to be dominant in oceans and lakes, but they are still poorly understood in river systems. This project examined picophytoplankton communities in two distinct river systems: the Columbia and Willamette Rivers in Portland, Oregon. I aimed to characterize and quantify the picophytoplankton populations in the context of the environmental conditions of the two rivers. I used flow cytometry to detect cells based on their relative size and pigment fluorescence. I sampled nearly weekly for ten months to capture population …

Cognitive Engagement During Group Learning Activities In Chemistry Courses: An Analysis Of Student Discourse, Safaa Youssef El-Mansy

Dissertations and Theses

As educators, our goal is to help our students be successful, but in order to accomplish this, we need to understand what factors contribute to student success. One factor, small-group active learning, has been correlated to improved academic outcomes; however, the magnitude of this improvement can vary across different courses, different types of group work, and even across courses that use the same group work structure. Therefore, it is important to understand what aspects of group work contribute to its effectiveness. The work presented in this dissertation investigated one specific aspect: students’ cognitive engagement. This was done by analyzing the …

Calorimetric Analysis Using Dna Thermal Stability To Determine Protein Concentration, Matthew W. Eskew, Patrick Reardon, Albert S. Benight

Chemistry Faculty Publications and Presentations

It was recently reported for two globular proteins and a short DNA hairpin in NaCl buffer that values of the transition heat capacities, Cp,DNA and Cp,PRO for equal concentrations (mg/mL) of DNA and proteins, are essentially equivalent (differ by less than 1%). Additional evidence for this equivalence is presented that reveals this phenomenon does not depend on DNA sequence, buffer salt, or Tm. Sequences of two DNA hairpins were designed to confer a near 20°C difference in their Tm’s. For the molecules, in NaCl and CsCl buffer the evaluated Cp,PRO and C …

Cfa-Treated Mice Induce Hyperalgesia In Healthy Mice Via An Olfactory Mechanism, Yangmiao Zhang, Wentai Luo, Maryt M. Heinricher, Andrey E. Ryabinin

Chemistry Faculty Publications and Presentations

Background

Social interactions with subjects experiencing pain can increase nociceptive sensitivity in observers, even without direct physical contact. In previous experiments, extended indirect exposure to soiled bedding from mice with alcohol withdrawal-related hyperalgesia enhanced nociception in their conspecifics. This finding suggested that olfactory cues could be sufficient for nociceptive hypersensitivity in otherwise untreated animals (also known as “bystanders”).

Aim

The current study addressed this possibility using an inflammation-based hyperalgesia model and long- and short-term exposure paradigms in C57BL/6J mice.

Materials & Method

Adult male and female mice received intraplantar injection of complete Freund's adjuvant (CFA) and were used as stimulus …

Electrochemical Hydrogen Gas Production And Carbon Dioxide Sequestration Via In Situ Formation Of Nickel (Ii) Tris-(Pyridinethiolate) Derivatives, Dayalis S.V. Brown

Dissertations and Theses

In the research presented, we use electrochemical techniques, such as cyclic voltammetry and controlled potential electrolysis, to study in situ formation of hydrogen evolution catalysts which also reduce carbon dioxide. Using pyridinethiol-based ligands and a nickel (II) precursor, both homo- and heteroleptic complexes were investigated as catalysts to produce alternative fuels while mitigating greenhouse gas emissions. Existing synthetic procedures to obtain these Ni(II) catalysts lead to low yields of the complexes and difficulties in crystallizing samples for further analysis, limiting sample size and restricting the number of studies. While current research is heavily focused on photochemically-driven experiments, given that solar …

Studies On Bonding, Syntheses, And Applications Of Diarylhalonium Compounds, Shubhendu Karandikar

Dissertations and Theses

Organic compounds containing functionalized benzenoid rings have found tremendous applications in pharmaceuticals, agrochemicals, commodity chemicals, and beyond. As a result, development of methods for the synthesis of functionalized benzenoid rings has gained much attention from the synthetic community. Although many transition-metal mediated methods to functionalize benzenoid rings are known, there has been an upsurge of activity in developing protocols for decoration of benzenoid cores promoted by p-block elements. This excitement stems from the sustainability of earth-abundant elements and unique reactivity patterns observed within the p-block. Among these, transformations promoted by hypervalent halogen compounds, and especially, the diarylhalonium salts are very …

7-Deazaguanines In Dna: Functional And Structural Elucidation Of A Dna Modification System, Samanthi Herath Gedara, Andrew Gustafson, Dirk Iwata-Reuyl, Multiple Additional Authors

Chemistry Faculty Publications and Presentations

The modified nucleosides 2′-deoxy-7-cyano- and 2′-deoxy-7-amido-7-deazaguanosine (dPreQ₀ and dADG, respectively) recently discovered in DNA are the products of the bacterial queuosine tRNA modification pathway and the dpd gene cluster, the latter of which encodes proteins that comprise the elaborate Dpd restriction–modification system present in diverse bacteria. Recent genetic studies implicated the dpdA, dpdB and dpdC genes as encoding proteins necessary for DNA modification, with dpdD–dpdK contributing to the restriction phenotype. Here we report the in vitro reconstitution of the Dpd modification machinery from Salmonella enterica serovar Montevideo, the elucidation of the roles of each protein and the X-ray …

Nanoscale Hafnium Metal-Organic Frameworks Enhance Radiotherapeutic Effects By Upregulation Of Type I Interferon And Tlr7 Expression, Eunseo Choi, Madeleine R. Landry, Nathan Pennock, Katherine Weinfurter, Multiple Additional Authors

Chemistry Faculty Publications and Presentations

Recent preclinical and clinical studies have highlighted the improved outcomes of combination radiotherapy and immunotherapy. Concurrently, the development of high-Z metallic nanoparticles as radiation dose enhancers has been explored to widen the therapeutic window of radiotherapy and potentially enhance immune activation. In this study, we evaluate folate-modified hafnium-based metal-organic frameworks (HfMOF-PEG-FA) in combination with imiquimod, a TLR7 agonist, as a well-defined interferon regulatory factor (IRF) stimulator for local antitumor immunotherapy. The enhancement of radiation dose deposition by HfMOF-PEG-FA and subsequent generation of reactive oxygen species (ROS) deregulates cell proliferation and increases apoptosis. HfMOF-PEG-FA loaded with imiquimod (HfMOF-PEG-FA@IMQ) increases DNA double-strand …

Chemical Elements, Flavor Chemicals, And Nicotine In Unused And Used Electronic Cigarettes Aged 5–10 Years And Effects Of Ph, Monique Williams, Wentai Luo, Kevin J. Mcwhirter, Omeka Ikegbu, Prue Talbot

Chemistry Faculty Publications and Presentations

The concentrations of elements/metals, nicotine, flavor chemicals and acids were compared in the e-liquids of unused and used first-generation electronic cigarettes (ECs) that were stored for 5–10 years. Metal analysis was performed using inductively coupled plasma optical emission spectroscopy; nicotine and flavor chemical analyses were performed using gas chromatography/mass spectroscopy. Of the 22 elements analyzed, 10 (aluminum, chromium, copper, iron, lead, nickel, selenium, silicon, tin, zinc) were often found in the e-liquids. Five elements had the highest average concentrations: copper (1161.6 mg/L), zinc (295.8 mg/L), tin (287.6 mg/L), nickel (71.1 mg/L), and lead (50.3 mg/L). Nicotine concentrations were always lower …

A First-Tier Framework For Assessing Toxicological Risk From Vaporized Cannabis Concentrates, Shawna Vreeke, David M. Faulkner, Robert Strongin, Echoleah Rufer

Chemistry Faculty Publications and Presentations

Vaporization is an increasingly prevalent means to consume cannabis, but there is little guidance for manufacturers or regulators to evaluate additive safety. This paper presents a first-tier framework for regulators and cannabis manufacturers without significant toxicological expertise to conduct risk assessments and prioritize additives in cannabis concentrates for acceptance, elimination, or further evaluation. Cannabinoids and contaminants (e.g., solvents, pesticides, etc.) are excluded from this framework because of the complexity involved in their assessment; theirs would not be a first-tier toxicological assessment. Further, several U.S. state regulators have provided guidance for major cannabinoids and contaminants. Toxicological risk assessment of cannabis concentrate …

Enlarging The Stokes Shift By Weakening The Π-Conjugation Of Cyanines For High Signal-To-Noise Ratiometric Imaging, Yongkang Yue, Tingting Zhao, Zhou Xu, Weijie Chi, Xiaojun Chai, Jiahong Ai, Jiawei Zhang, Fangjun Huo, Robert M. Strongin, Caixia Yin

Chemistry Faculty Publications and Presentations

The signal-to-noise ratio (SNR) is one of the key features of a fluorescent probe and one that often defines its potential utility for in vivo labeling and analyte detection applications. Here, it is reported that introducing a pyridine group into traditional cyanine-7 dyes in an asymmetric manner provides a series of tunable NIR fluorescent dyes (Cy-Mu-7) characterized by enhanced Stokes shifts (≈230 nm) compared to the parent cyanine 7 dye (nm). The observed Stokes shift increase is ascribed to symmetry breaking of the Cy-Mu-7 core and a reduction in the extent of conjugation. The fluorescence signals of the Cy-Mu-7 dyes …

Investigating Small-Group Cognitive Engagement In General Chemistry Learning Activities Using Qualitative Content Analysis And The Icap Framework, Safaa Y. El-Mansy, Jack Barbera, Alissa J. Hartig

Chemistry Faculty Publications and Presentations

The level of students’ engagement during active learning activities conducted in small groups is important to understanding the effectiveness of these activities. The Interactive–Constructive–Active–Passive (ICAP) framework is a way to determine the cognitive engagement of these groups by analyzing the conversations that occur while student groups work on an activity. This study used qualitative content analysis and ICAP to investigate cognitive engagement during group activities in a General Chemistry course at the question level, a finer grain size than previously studied. The analysis determined the expected engagement based on question design and the observed engagement based on group conversations. Comparisons …

Chemical Interactions And Cytotoxicity Of Terpene And Diluent Vaping Ingredients, Yanira Baldovinos, Alexandra Archer, James C. Salamanca, Robert M. Strongin, Christie Sayes

Chemistry Faculty Publications and Presentations

Vaping devices have risen in popularity since their inception in 2007. The practice involves using a variety of commercially available devices. Internal heating systems in devices aerosolize e-liquid formulations of complex mixtures including an active ingredient (e.g., THC, CBD, and nicotine), diluents (or cutting agents), solvents, and flavoring agents (e.g., terpenes and aldehydes). The vaping toxicology literature consists of cytotoxicity studies of individual chemicals and commercial formulas. Because of the variation of e-liquid composition, there is a limited understanding of the toxicity of ingredient combinations. This study analyzed the cytotoxic effects after exposure to individual and binary mixtures of a …

Computational Investigation Into Heteroleptic Photoredox Catalysts Based On Nickel(Ii) Tris-Pyridinethiolate For Water Splitting Reactions, Avik Bhattacharjee, Dayalis S.V. Brown, Trent E. Ethridge, Kristine M. Halvorsen, Alejandra C. Acevedo Montano, Theresa M. Mccormick

Chemistry Faculty Publications and Presentations

This work demonstrates a strategy to fine-tune the efficiency of a photoredox water splitting Ni(II) tris-pyridinethiolate catalyst through heteroleptic ligand design using computational investigation of the catalytic mechanism. Density functional theory (DFT) calculations, supported by topology analyses using quantum theory of atoms in molecules (QTAIM), show that the introduction of electron donating (ED) −CH3 and electron withdrawing (EW) −CF₃ groups on the thiopyridyl (PyS–) ligands of the same complex can tune the pK_a and E0, simultaneously. Computational modeling of two heteroleptic nickel(II) tris-pyridinethiolate complexes with 2:1 and 1:2 ED and EW −CH₃ and −CF_{3 …}

Nmr Analyses Of Flavored E-Cigarette Liquids Before And After Aerosolization, Paul Joseph Kerber

Dissertations and Theses

Electronic cigarettes (e-cigarettes) are the most commonly used tobacco products among adolescents with ~11 and ~3% of high school and middle school students reporting past 30 day use in 2021 according to the Centers for Disease Control and Prevention (CDC), respectively. Furthermore, greater than ~80% of high school and middle school e-cigarette consumers use flavored e-liquids. Consumers can be exposed to variable toxicant levels upon e-liquid aerosolization, depending on the composition of the e-liquid, type of e-cigarette, e-cigarette settings, and other customizations.

E-liquids are typically composed of a carrier solvent (propylene glycol (PG) and glycerol (GL)), flavorants, and nicotine. PG …

Improved Photodecarboxylation Properties In Zinc Photocages Constructed Using M‐Nitrophenylacetic Acid Variants, Austin K. Shigemoto, Avik Bhattacharjee, Erin E. Hickey, Hallee Jade Boyd, Theresa M. Mccormick, Shawn C. Burdette

Chemistry Faculty Publications and Presentations

The methoxy- and fluoro-derivatives of meta-nitrophenylacetic acid (mNPA) chromophores undergo photodecarboxylation with comparable quantum yields to unsubstituted mNPA, but uncage at red-shifted excitation wavelengths. This observation prompted us to investigate DPAdeCageOMe (2-[bis(pyridin-2-ylmethyl)amino]-2-(4-methoxy-3-nitrophenyl)acetic acid) and DPAdeCageF (2-[bis(pyridin-2-ylmethyl)amino]-2-(4-fluoro-3-nitrophenyl)acetic acid) as Zn2+ photocages. DPAdeCageOMe has a high quantum yield and exhibits other photophysical properties comparable to XDPAdeCage ({bis[(2-pyridyl)methyl]amino}(9-oxo-2-xanthenyl) acetic acid), the best perforiming Zn2+ photocage reported to date. Since the synthesis of DPAdeCageOMe is more straightforward than XDPACage, the new photocage will be a highly competitive tool for biological applications.

Exploring Structure-Function Relationship In Small-Molecular Catalysts Using Computational And Experimental Methodologies, Avik Bhattacharjee

Dissertations and Theses

Molecular modeling is a useful tool in the field of catalyst design for various processes. The use of Density Functional Theory (DFT) is routine in almost every discipline of chemistry. This allows for a deeper understanding of a molecular system even in situations where implementation of an experimental technique is unfeasible. However, without the right choice of theory and insufficient description, the model becomes susceptible to produce ambiguous results. This often leads to poor correlation with experimental findings hence an incomplete understanding of the system under study. Hence, to acquire a thorough knowledge of the intricacies involved in a system, …

A Multi‑Analytical Approach To Identify Red Colorants On Woodblock Prints Attributed To Suzuki Harunobu, Lyndsay Nichole Kissell, Trine K. Quady, Dario Durastanti, Samantha Springer, Jeannie Kenmotsu, Tami Lasseter Clare

Chemistry Faculty Publications and Presentations

Red organic dye identification is an important topic for conservation of Japanese ukiyo-e prints. Of particular interest are the works of Suzuki Harunobu, who was working at the inception of full-color printmaking. These prints were made on thin kōzo paper and woodblock printed with semi-transparent to opaque regions of dye(s) and/ or pigment(s) mixed with binder. This study used imaging analysis, X-ray fluorescence (XRF), Raman, and surfaceenhanced Raman spectroscopies (SERS) to identify the red dyes and pigments on Harunobu prints in the collection of the Portland Art Museum. Through image analysis (visible, UV, and IR illuminations), 23 prints were categorized …

Detection And Quantification Of Arsenic Pollution With A Moss Bio-Indicator And Icp-Ms, Erin R. Bowey

University Honors Theses

Heavy metal pollution is a recognized concern with an established source of anthropogenic activity, which is ever-increasing. While work has been done to make the monitoring of some metals more accessible, resourceful, and efficient with the use of epiphytic moss as a bio-indicator, this method has not been optimized for the detection of arsenic. Previously used analytical instrumentation has not proven sensitive enough to reliably detect arsenic, creating a gap in the monitoring process. However, inductively coupled plasma mass spectrometry (ICP-MS) is proposed as the solution to fill this gap. Its potential for low limits of detection and quantification express …

Investigating Student Engagement In General Chemistry Active Learning Activities Using The Activity Engagement Survey (Aces), Nicole Naibert, Jack Barbera

Chemistry Faculty Publications and Presentations

Investigating student engagement in active learning activities could provide valuable insight into variations of student learning outcomes when active learning is included in a course. This study sought to explore students’ engagement in relation to active learning activities incorporated in a general chemistry lecture course using the Activity Engagement Survey (AcES). The AcES can be used to simultaneously assess students’ overall engagement, as well as dimensions above and beyond overall engagement including their combined behavioral/cognitive engagement, emotional engagement, and social engagement. As students’ engagement may be influenced by aspects related to the learning environment and context, differences in engagement were …

The Hyperporphyrin Concept: A Contemporary Perspective, Carl C. Wamser, Abhik Ghosh

Chemistry Faculty Publications and Presentations

The Gouterman four-orbital model conceptualizes porphyrin UV–visible spectra as dominated by four frontier molecular orbitals─two nearly degenerate HOMOs and two exactly degenerate LUMOS under D4h symmetry. These are well separated from all the other molecular orbitals, and normal spectra involve transitions among these MOs. Unusual spectra occur when additional orbitals appear in this energy range, typically as a consequence of the central coordinated atom. For example, metals with empty d orbitals in a suitable energy range may lead to charge transfer from porphyrin (ligand) to metal, that is, so-called LMCT transitions. Metals with filled p or d orbitals may …

Development Of The Chemistry Mindset Instrument (Chemi) For Use With Introductory Undergraduate Chemistry Students, Deborah L. Santos, Jack Barbera, Suazette R. Mooring

Chemistry Faculty Publications and Presentations

Chemistry education research has increasingly considered the role of affect when investigating chemistry learning environments over the past decade. Despite its popularity in educational spheres, mindset has been understudied from a chemistry-specific perspective. Mindset encompasses one's beliefs about the ability to change intelligence with effort and has been shown to be a domain-specific construct. For this reason, students’ mindset would be most relevant in chemistry if it were measured as a chemistry-specific construct. To date, no instrument has been developed for use in chemistry learning contexts. Here we present evidence supporting the development process and final product of a mindset …

Synthesis Of Diaryl And Alkyl-Aryl Ethers Via Diaryl Iodonium Reagents, Rory Tennessee Gallagher

Dissertations and Theses

Substituted benzenoid rings are a prevalent motif in many industries including high tech, agrochemicals, and pharmaceuticals. As a result, the arylation of chemical compounds is a highly sought-after chemical transformation. There are many literature methods to achieve this chemical transformation, nucleophilic aromatic substitution and transition metal catalysis are both widely used and studied. Diaryliodonium salt mediated chemistry is an attractive alternative to these methods as it does not require the expensive toxic metals and designer ligands of transition metal catalysis and is not restricted to electron deficient aryl rings with specific substitution patterns like nucleophilic aromatic substitution.

Many diaryliodonium salt …

Orbital Analysis Of Bonding In Diarylhalonium Salts And Relevance To Periodic Trends In Structure And Reactivity, Shubhendu S. Karandikar, Avik Bhattacharjee, Bryan Metze, Nicole Javaly, Edward J. Valente, Theresa M. Mccormick, David R. Stuart

Chemistry Faculty Publications and Presentations

Diarylhalonium compounds provide new opportunities as reagents and catalysts in the field of organic synthesis. The three center, four electron (3c–4e) bond is a center piece of their reactivity, but structural variation among the diarylhaloniums, and in comparison with other λ3-iodanes, indicates that the model needs refinement for broader applicability. We use a combination of Density Functional Theory (DFT), Natural Bond Orbital (NBO) Theory, and X-ray structure data to correlate bonding and structure for a λ3-iodane and a series of diarylchloronium, bromonium, and iodonium salts, and their isoelectronic diarylchalcogen counterparts. This analysis reveals that the s-orbital on the central halogen …

Simple Arenes As Aryne Synthetic Equivalents Via Sulfonium Salt Intermediates, Riley A. Roberts

Student Research Symposium

Arynes are ephemeral molecules that are yet to be fully exploited in synthetic strategy because they are often challenging to access. These reactive intermediates participate in a myriad of reactions that conventional chemistry is incapable of, making them extremely useful for the synthesis of important molecules like pharmaceuticals and agrochemicals. While classical approaches for synthesizing arynes employ cheap starting material, extremely harsh reagents are necessary to generate the aryne. In contrast, methods that do not require harsh reaction conditions do require starting material that is exceedingly difficult to synthesize. To access arynes quickly and efficiently, the work described herein aims …