Chemistry Commons^™

When Substituents Do Not Matter: Frontier Orbitals Explain The Unusually High And Invariant Oxidation Potential In Alkoxy-, Alkyl-, And H-Substituted Iptycenes, Maxim V. Ivanov, Denan Wang, Shriya Wadumethrige, Rajendra Rathore

Chemistry Faculty Research and Publications

Frontier molecular orbitals (FMOs) have played a critical role in predicting reactivity/selectivity of pericyclic reactions. Here we show that the structurally similar iptycene-based hydroquinone ether (HE), that is, ^MeOIpt and ^BOHE/^BHHE, molecules have drastically different ordering of bisallylic and quinoidal FMOs. They are almost degenerate in ^BOHE/^BHHE, while in ^MeOIpt, the bisallylic orbital lies far below the quinoidal HOMO. Oxidation of ^BOHE/^BHHE induces coplanarization of the methoxy group and destabilizes the bisallylic HOMO, leading to a relatively low oxidation potential. In ^MeOIpt, considerable energy …

Application Of Visible-Light Photosensitization To Form Alkyl-Radical-Derived Thin Films On Gold, Rashanique Quarels, Xianglin Zhai, Neepa Kuruppu, Jenny K. Hedlund, Ashley A. Ellsworth, Amy V. Walker, Jayne C. Garno, Justin R. Ragains

College of Science & Mathematics Departmental Research

Visible-light irradiation of phthalimide esters in the presence of the photosensitizer [Ru(bpy)3]2+ and the stoichiometric reducing agent benzyl nicotinamide results in the formation of alkyl radicals under mild conditions. This approach to radical generation has proven useful for the synthesis of small organic molecules. Herein, we demonstrate for the first time the visible-light photosensitized deposition of robust alkyl thin films on Au surfaces using phthalimide esters as the alkyl radical precursors. In particular, we combine visible-light photosensitization with particle lithography to produce nanostructured thin films, the thickness of which can be measured easily using AFM cursor profiles. Analysis with AFM …

Fatty Acid Concentration And Phase Transitions Modulate Aβ Aggregation Pathways, Pratip Rana, Dexter Dean, Edward Steen, Ashwin Vaidya, Vijayaraghavan Rangachari, Preetam Ghosh

Faculty Publications

Aggregation of amyloid β (Aβ) peptides is a significant event that underpins Alzheimer disease (AD) pathology. Aβ aggregates, especially the low-molecular weight oligomers, are the primary toxic agents in AD and hence, there is increasing interest in understanding their formation and behavior. Aggregation is a nucleation-dependent process in which the pre-nucleation events are dominated by Aβ homotypic interactions. Dynamic flux and stochasticity during pre-nucleation renders the reactions susceptible to perturbations by other molecules. In this context, we investigate the heterotypic interactions between Aβ and fatty acids (FAs) by two independent tool-sets such as …

Microstructure Of Injection Moulding Machine Mould Clamping Mechanism: Design And Motion Simulation, Z. Jin, Y. Zhang, X. Wang, J. Williams, Z. Liu, Z. Huang, D. Falkner, G. Zhou, L. Dong, J. Zhuang, Zhe Wang

Faculty and Staff Publications

With the advent of intelligence technologies, more and more machines and devices are involved in the creation of complex structures. In the intelligent manufacturing industries, mouldings including injection moulding, blow moulding, compression moulding, and others play critical roles in manufacturing highly precise parts required for building intelligent machines (such as computers, cell phones, robots etc.). The performance of the clamping mechanism directly affects the quality of the microstructure of injection products. The design of the injection moulding mould clamping mechanism is based on the microstructure characteristics of the trip of the toggle lever mechanism ratio, speed ratio, and force amplification …

Aquachlorido(2-{[6-(Dimethylamino)Pyrimidin-4- Yl]Sulfanyl}Pyrimidine-4,6-Diamine)Copper(Ii) Chloride Hydrate, Tristen E. Moyaert, Christina Paul, Weibin Chan, Amy A. Sarjeant, Louise N. Dawe

Chemistry Faculty Publications

A copper(II) complex of the non-symmetric bidentate ligand 2-{[6-(di­methyl­amino)­pyrimidin-4-yl]sulfan­yl}pyrimidine-4,6-di­amine (L1) is reported. The single-crystal X-ray structure of aqua­[aqua/chlorido­(0.49/0.51)](2-{[6-(di­methyl­amino)­pyrimidin-4-yl]sulfan­yl}pyrimidine-4,6-di­amine)­copper(II) 0.49-chloride 1.51-hydrate, [CuCl_1.51(C₁₀H₁₃N₇S)(H₂O)_1.49]Cl_0.49·1.51H₂O or [(L1)Cl_1.51(H₂O)_1.49Cu]0.49Cl·1.51H₂O, exhibits distorted square-pyramidal geometry around the metal centre, with disorder in the axial position, occupied by chloride or water. The six-membered metal–chelate ring is in a boat conformation, and short inter­molecular S- - -S inter­actions are observed. In addition to its capacity for bidentate metal coordination, the ligand has …

Addressing A Common Misconception: Ammonium Acetate As Neutral Ph "Buffer" For Native Electrospray Mass Spectrometry., Lars Konermann

Chemistry Publications

Native ESI-MS involves the transfer of intact proteins and biomolecular complexes from solution into the gas phase. One potential pitfall is the occurrence of pH-induced changes that can affect the analyte while it is still surrounded by solvent. Most native ESI-MS studies employ neutral aqueous ammonium acetate solutions. It is a widely perpetuated misconception that ammonium acetate buffers the analyte solution at neutral pH. By definition, a buffer consists of a weak acid and its conjugate weak base. The buffering range covers the weak acid pK_a ± 1 pH unit. NH₄⁺ and CH₃-COO^- are …

Development And Validation Of A Novel Lc–Ms/Ms Method For Simultaneous Determination Of Abiraterone And Its Seven Steroidal Metabolites In Human Serum: Innovation In Separation Of Diastereoisomers Without Use Of A Chiral Column, Mohammad Alyamani, Zhenfei Li, Sunil K. Upadhyay, David J. Anderson, Richard J. Auchus, Nima Sharifi

Chemistry Faculty Publications

Abiraterone acetate (AA), the prodrug of abiraterone, is FDA-approved for the treatment of castration-resistant prostate cancer. Abiraterone is metabolized in patients to a more potent analogue, D4A. However, we have recently reported that this analogue is further metabolized to additional metabolites in patients treated with AA. Here, we present a liquid chromatography-tandem mass spectrometry method developed to resolve and detect abiraterone and its seven metabolites in human serum using an AB Sciex Qtrap 5500 mass analyzer coupled with a Shimadzu Nexera UPLC station. Analytes and the internal standard (abiraterone-d4) were extracted from human serum using the liquid–liquid extraction procedure. The …

Dietary Guidelines And Its Implications For Coconut Oil, Fabian M. Dayrit

Chemistry Faculty Publications

The dietary advice that is generally followed nationally and internationally closely follows the Dietary Guidelines for Americans which was first published in 1980 and which has been through eight editions. All of the editions of the Dietary Guidelines recommend a diet that is low in fat, and most editions recommend the replacement of saturated fat with polyunsaturated fat. This recommendation is based on the saturated fat-cholesterol-heart disease hypothesis that was first proposed by Ancel Keys in the 1950s. Coconut oil was labeled as unhealthy because of its high saturated fat composition. However, this label is unwarranted. Re-analysis of the work …

How To Be A Successful Organic Chemist, Alexander H. Sandtorv

PDXOpen: Open Educational Resources

How to be a successful organic chemist is meant as an introductory text for undergraduates taking organic chemistry teaching labs. The text is a clear and practical introduction to safety, chemical handling, organic chemistry techniques, and lab reports.

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Α-Conotoxin Decontamination Protocol Evaluation: What Works And What Doesn’T, Matthew W. Turner, John R. Cort, Owen M. Mcdougal

Chemistry and Biochemistry Faculty Publications and Presentations

Nine publically available biosafety protocols for safely handling conotoxin peptides were tested to evaluate their decontamination efficacy. Circular dichroism (CD) spectroscopy and mass spectrometry (MS) were used to assess the effect of each chemical treatment on the secondary and primary structure of α-CTx MII (L10V, E11A). Of the nine decontamination methods tested, treatment with 1% (m/v) solution of the enzymatic detergent Contrex™ EZ resulted in a 76.8% decrease in α-helical content as assessed by the mean residue ellipticity at 222 nm, and partial peptide digestion was demonstrated using high performance liquid chromatography mass spectrometry (HPLC-MS). Additionally, …

Synthesis And Antitumor Activity Of N-Triazol-5-Yl-Oxazolidin-4-One Derivatives., R. Luo, S. Guo, Shilong Zheng, Guangdi Wang, X. Bao, L. He

Faculty and Staff Publications

Fifteen novel N-triazol-5-yl-oxazolidin-4-ones were synthesized through a few of steps from the benzaldehydes. It was found that N-iodosuccinimide (NIS) can promote intramolecular amination reaction which is the key step of the syntheses, which will be used as new method for the intramolecular formation of nitrogen-containing heterocycles. Part of the compounds were evaluated for their anticancer activity. Among them, compounds 6a, 6b and 6c showed moderate antiprolifiration activity toward human breast cancer cells MDA-MB-231 cell lines, while the mild activity of 6a, 6b and 6d against human cervical cancer HeLa cell lines was confirmed in vitro assay.

Optical Studies Of The Solution Phase Reduction And Stabilization Of Indigo Tetrasulfonate In Polyelectrolyte Complexes, Becca Hoene, Dion Rivera

All Faculty Scholarship for the College of the Sciences

Ultraviolet-visible (UV-vis) and fluorescence spectroscopy have been used to characterize the polyelectrolyte complexes (PECs) formed when potassium indigo tetrasulfonate (ITS) interacts with poly diallydimethylammonium chloride (PDADMAC) through columbic attraction in the presence of the reducing agent sodium bisulfite, NaHSO3. The PDADMAC facilitates both the reduction of the ITS and the stabilization of the reduced state of the ITS in an atmospheric oxygen environment. Dilutions of the dye solution show that the PEC is stable to dilutions of at least 1 to 1000. UV–vis studies indicate that the reduced ITS (ITSred) forms what is likely a J-aggregate in the presence of …

Synthesis And Evaluation Of Tetrahydroprotoberberines As Dopamine Receptor Ligands, Satishkumar V. Gadhiya

Dissertations, Theses, and Capstone Projects

Dopamine (DA) receptors belong to the G-protein coupled receptors (GPCRs) family, divided in to two groups based on their high homology transmembrane domains; D1-like DA receptors (D1, D5) and D2-like DA receptors (D2-D4). DA receptor specific ligands have been exploited as a means for studying the prognosis and curing several CNS disorders. Though several efforts have been devoted to discover selective and potent DA receptor ligands, complete selectivity within the DA receptor subtypes remains a challenge.

Tetrahydroprotoberberines (THPBs) are a group of naturally occurring tetracyclic alkaloids that belong to the tetrahydroisoquinoline family. A wide range of biological activities are associated …

Computational Investigation Of The Pore Formation Mechanism Of Beta-Hairpin Antimicrobial Peptides, Richard Lipkin

Dissertations, Theses, and Capstone Projects

β-hairpin antimicrobial peptides (AMPs) are small, usually cationic peptides that provide innate biological defenses against multiple agents. They have been proposed as the basis for novel antibiotics, but their pore formation has not been directly observed on a molecular level. We review previous computational studies of peptide-induced membrane pore formation and report several new molecular dynamics simulations of β-hairpin AMPs to elucidate their pore formation mechanism. We simulated β-barrels of various AMPs in anionic implicit membranes, finding that most of the AMPs’ β-barrels were not as stable as those of protegrin. We also performed an optimization study of protegrin β-barrels …

Heterojunction Engineering For Next Generation Hybrid Ii-Vi Materials, Thor Garcia

Dissertations, Theses, and Capstone Projects

Molecular Beam Epitaxy(MBE) is a versatile thin film growth technique with monolayer control of crystallization. The flexibility and precision afforded by the technique allows for unique control of interfaces and electronic structure of the films grown. This facilitates the realization of novel devices and structures within a research environment normally only achieved though complex industrial processes. In the past, the control of each interface in MBE has been explored to great benefit. In this work, we study the control of these interfaces so as to increase the performance of novel devices material systems. This dissertation focuses on two main areas …

Mukaiyama Addition Of (Trimethylsilyl) Acetonitrile To Dimethyl Acetals Mediated By Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Alice Y.-K. Lee, John R. Goodin, Courtney J. Botelho, William M. Stith

Chemistry Faculty Publications

(Trimethylsilyl) acetonitrile reacts smoothly with dimethyl acetals in the presence of stoichiometric trimethylsilyl trifluoromethanesulfonate (TMSOTf) to yield β-methoxynitriles. The ideal substrates for this reaction are acetals derived from aromatic aldehydes. Elimination to the corresponding α,β-unsaturated nitriles is observed as the major product in the case of electron-rich acetals. A mechanistic hypothesis that includes isomerization of the silylnitrile to a nucleophilic N-silyl ketene imine is presented.

Gold Nanoparticle Colorants As Traditional Ceramic Glaze Alternatives, Raef H. Lambertson, Christie A. Lacy, Samuel D. Gillespie, Michael C. Leopold

Chemistry Faculty Publications

Historically, Roman stained glass has been a standard for high‐temperature color stability since biblical times but was not properly characterized as emission from nanoparticle plasmon resonance until the 1990s. The methods under which it was created have been lost, but some efforts have recently been made to recreate these properties using gold nanoparticle inks on glassy surfaces. This body of work employs gold nanoparticle systems ranging from 0.015% to 0.100% (wt/wt), suspended in a clear glaze body. The glazes are fired with traditional ceramic methods—in both gas reduction and electric oxidation kilns—in which nanoparticles are retained and can be imaged …

Lyapunov Exponents And The Belousov-Zhabotinsky Oscillator: An Interactive Computational Approach, Matthew W. Eskew, Reuben H. Simoyi

Chemistry Faculty Publications and Presentations

The Belousov-Zhabotinsky (BZ) chemical oscillator is the most studied oscillator. It has been modelled on the basis of single-step mechanisms which have been continuously refined since the seminal manuscript by Field, Koros and Noyes in 1972. This manuscript reports on a unique way of modelling the global dynamics of the oscillator by assuming that the BZ oscillator has shown chaotic behaviour. The unique mathematical definition of chaos is very stringent, and, in this manuscript, we attempt to trace this unique exotic behaviour by the use of ‘onto’ maps of the interval onto itself which are known to exhaustively show a …

Formaldehyde Hemiacetal Sampling, Recovery, And Quantification From Electronic Cigarette Aerosols, James C. Salamanca, Ian Munhenzva, Jorge O. Escodedo, R. Paul Jensen, Angela Shaw, Robert Campbell, Wentai Luo, David H. Peyton, Robert Strongin

Chemistry Faculty Publications and Presentations

The electronic cigarette solvents propylene glycol and glycerol are known to produce toxic byproducts such as formaldehyde, acetaldehyde and acrolein. However, the aerosol toxin yield depends upon a variety of chemical and physical variables. The formaldehyde hemiacetals derived from these solvents were reported as major electronic cigarette aerosol components by us in 2015. In the study described herein, the formaldehyde hemiacetals were found at higher levels than those of free formaldehyde via an orthogonal sample collection protocol. In addition, the common aldehyde collection methods for electronic cigarettes, such as impingers and sorbent tubes containing DNPH, significantly underestimate the levels of …

Niclosamide Induces Protein Ubiquitination And Inhibits Multiple Pro-Survival Signaling Pathways In The Human Glioblastoma U-87 Mg Cell Line, Benxu Cheng, Liza Doreen Morales, Yonghong Zhang, Shizue Mito, Andrew Tsin

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

Glioblastoma is the most common and lethal malignant primary brain tumor for which the development of efficacious chemotherapeutic agents remains an urgent need. The anti-helminthic drug niclosamide, which has long been in use to treat tapeworm infections, has recently attracted renewed interest due to its apparent anticancer effects in a variety of in vitro and in vivo cancer models. However, the mechanism(s) of action remains to be elucidated. In the present study, we found that niclosamide induced cell toxicity in human glioblastoma cells corresponding with increased protein ubiquitination, ER stress and autophagy. In addition, niclosamide treatment led to down-regulation of …

Stereospecific Electrophilic Fluorination Of Alkylcarbastannatrane Reagents, Xinghua Ma

Dissertations, Theses, and Capstone Projects

The introduction of fluorine atoms into organic molecules significantly changes their physical, chemical, and biological properties. Fluorinated organic compounds are used as pharmaceuticals, agrochemicals, materials, and tracers for positron emission tomography (PET). For example, the site-specific fluorination of drugs can block sites of phase I metabolism by cytochrome P450 enzymes as well as improve target-binding affinities. In view of the unique features of fluorine-containing compounds, there has been increasing interest in the development of novel methods for the synthesis of fluorinated molecules, especially the site-specific monofluorination of complex molecules. Herein, we present the enantiospecific conversion of chiral secondary alkylcarbastannatranes into …

Molecular Dynamics Simulations On Gas-Phase Proteins With Mobile Protons: Inclusion Of All-Atom Charge Solvation., Lars Konermann

Chemistry Publications

Molecular dynamics (MD) simulations have become a key tool for examining the properties of electrosprayed protein ions. Traditional force fields employ static charges on titratable sites, whereas in reality, protons are highly mobile in gas-phase proteins. Earlier studies tackled this problem by adjusting charge patterns during MD runs. Within those algorithms, proton redistribution was subject to energy minimization, taking into account electrostatic and proton affinity contributions. However, those earlier approaches described (de)protonated moieties as point charges, neglecting charge solvation, which is highly prevalent in the gas phase. Here, we describe a mobile proton algorithm that considers the electrostatic contributions from …

Special Issue: 15th National Symposium On Organic Electrochemistry And Electrochemical Industry, Xinsheng Zhang, Chengchu Zeng

Journal of Electrochemistry

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Density Functional Investigation On Cathode/Electrolyte Interface In Solid-State Lithium Batteries, Xuelong Wang, Ruijuan Xiao, Yong Xiang, Hong Li, Liquan Chen

Journal of Electrochemistry

The rapidly expanding application of lithium ion batteries stimulates research interest on energy storage devices with higher energy density, better safety and faster charge/discharge speed. All-solid-state lithium batteries have been considered as promising candidates because of their fewer side reactions and better safety compared with conventional lithium-ion batteries with organic liquid electrolytes. Looking for well-matched electrode/electrolyte interfaces is one of the keys to ensuring good comprehensive performance of solid-state lithium batteries. In this report, with the aid of first-principles simulations, the local structure and lithium ions transportation properties of electrolyte surfaces and cathode/electrolyte interfaces are investigated. The β-Li₃PS …

Electrostatic Interactions Of Water In External Electric Field: Molecular Dynamics Simulations, Qiang Zhu, Zigui Kan, Jing Ma

Journal of Electrochemistry

A series of molecular dynamics simulations with or without external electric field have been carried out for a bulk water with periodic boundary condition. The difference in radial distribution function of interatomic O…O distance is subtle, with and without external electric field, except for the orientation of dipole moments of water molecules. Without the applied external electric field, distribution of the orientation angle of dipole moments is rather broad. The induced local electric field is analyzed as a function of altitude in direction of electric field. The variation of the local induced electric field is increased as the increase of …

Influence Of Typical Anions In Seawater Environments On Corrosion Behaviors Of 5083 Aluminum Alloy, Yang-Fan Tu, Li-Ming Feng, Zhi-Gang Fang, Hai-Tao Liu, Ming-Hua Jing, Yong Guan

Journal of Electrochemistry

The interaction effects of typical anions, namely, Cl^-, HCO₃^- and SO₄^2-, presented in seawater environments on corrosion resistance behaviors of AA5083 aluminum alloy have been studied. The corrosion resistances of the 5083 aluminum alloy in different simulated seawater environments were tested by factorial analysis method. The polarization curves, the corrosion potentials, corrosion current densities and the breakdown potentials were examined in different concentrations of Cl^-, HCO₃^- and SO₄^2-.The corrosion behavior was analyzed by electrochemical impedance spectroscopy (EIS). The results showed that both Cl^-,  and …

Effects Of Temperature On The Nucleation And Growth Mechanism Of Pbo2 Electrodeposition, Lei Wang, Juan-Qin Xue, Li-Hua Yu, Chang-Bin Tang, Qiang Bi

Journal of Electrochemistry

In order to investigate the effects of temperature on the nucleation and growth of lead dioxide (PbO₂), the in situ electrochemical depositions of PbO₂ were carried out on the glassy carbon electrode at different temperatures, namely, 25℃,35℃, 45℃, 55℃, and 65℃.The cyclic voltammetric curves, the time-current and the time-potential curves,SEM images and XRD patterns of the PbO₂ coatings deposited at different temperatures were obtained. The results showed that the PbO₂ underwent nucleation and grew at different temperatures. The 3D continuous nucleation mode of PbO₂ electrodeposition remained unchanged with the increase of temperature. However, the …

Effects Of Surface Modification Modes On Proton-Over-Vanadium Ion Selectivity Of Nafion®Membrane For Application In Vanadium Redox Flow Battery, Qing-Long Tan, Hai-Ning Wang, Shan-Fu Lu, Da-Wei Liang, Chun-Xiao Wu, Yan Xiang

Journal of Electrochemistry

The effect of surface modification modes on proton-over-vanadium ion selectivity was studied by spin-coating chitosan-Phosphotungstic Acid (PWA) as a single or double layer on Nafion membrane surface. To suppress the vanadium ions permeation through the Nafion? membrane in a vanadium redox flow battery (VRFB), the single surface-modified Nafion membrane (Nafion/chitosan-PWA)S and double surface-modified Nafion membrane (Nafion/chitosan-PWA)D demonstrated a 89.9% and 92.7% reduction of vanadium ion permeability in comparison with pristine Nafion, respectively. The (Nafion/chitosan-PWA)D exhibited betterhigher selectivity between proton and vanadium ions than the (Nafion/chitosan-PWA)S at the same layer thickness. Furthermore, the columbic efficiency for the VRFB single cell based …

Tetrabutylammonium Hexafluorophosphate As Flame Retardant Additive For Lithium Ion Batteries, Qing Zhao, Qian Zhang, Jing-Min Fan, Ming-Sen Zheng, Quan-Feng Dong

Journal of Electrochemistry

Safety issues have been attracted more and more attentions due to the wide applications of lithium ion batteries. Introducing flame retardant additives are one of the effective strategies to improve the safety of lithium-ion batteries. In this paper, the tetrabutylammonium hexafluorophosphate (TBAPF₆) as a flame retardant additive was added to the electrolyte as a flame retardant additive to enhance the safety of lithium ion batteries. The self-extinguishing time (SET) and ionic conductivities of the electrolytes with different TBAPF₆ contents were investigated. It is found that TBAPF6 dramatically reduced the flammability of the electrolyte while slightly decreasing ionic …

Electrochemical Performance Of Sodium Difluoro(Oxalato)Borate As The Additive Of Non-Aqueous Electrolytes For Sodium-Ion Batteries, Ding Zhang, Qin Zhu, Ying Wang, Cheng-Long Zhao, Shi-Bin Liu, Shou-Dong Xu

Journal of Electrochemistry

Sodium ion battery has attracted worldwide and intensive attention recently, while the adoption of electrolyte additives has been considered as one effective strategy to promote the cell performance. Within this work sodium difluoro(oxalato)borate (NaDFOB) was prepared and adopted as an additive for the general non-aqueous electrolyte formula of 1 mol·L-1 NaClO4/EC/PC (Vol: Vol=1:1), and the effects of the additive concentration on ionic conductivity and oxidization decomposition voltage were investigated in detail. In addition, the cell performance evaluated by NaNi0.5Mn0.5O2 as the cathode was also studied. It reveals that the addition of NaDFOB into the NaClO4/EC/PC electrolyte resulted in the significantly …