Chemistry Commons^™

Reactivity Measurement In Estimation Of Benzoquinone And Benzoquinone Derivatives’ Allergenicity, Wilbes Mbiya, Ita Chipinda, Reuben H. Simoyi, Paul D. Siegel

Chemistry Faculty Publications and Presentations

Benzoquinone (BQ) and benzoquinone derivatives (BQD) are used in the production of dyes and cosmetics. While BQ, an extreme skin sensitizer, is an electrophile known to covalently modify proteins via Michael Addition (MA) reaction whilst halogen substituted BQD undergo nucleophilic vinylic substitution (SNV) mechanism onto amine and thiol moieties on proteins, the allergenic effects of adding substituents on BQ have not been reported. The effects of inserting substituents on the BQ ring has not been studied in animal assays. However, mandated reduction/elimination of animals used in cosmetics testing in Europe has led to an increased need for alternatives for the …

Electrochemistry-Coupled To Mass Spectrometry In Simulation Of Metabolic Oxidation Of Methimazole: Identification And Characterization Of Metabolites, Kudzanai Chipiso, Reuben H. Simoyi

Chemistry Faculty Publications and Presentations

Methimazole (MMI), an antithyroid drug, is associated with idiosyncratic toxicity. Reactive metabolites resulting from bioactivation of the drug have been implicated in these adverse drug reactions. Mimicry of enzymatic oxidation of MMI was carried out by electrochemically oxidizing MMI using a coulometric flow-through cell equipped with a porous graphite working electrode. The cell was coupled on-line to electrospray ionization mass spectrometry (EC/ESI-MS). ESI spectra were acquired in both negative and positive modes. In acidic medium, ESI spectral analysis showed that the dimer was the main product, while in neutral and basic media, methimazole sulfenic acid, methimazole sulfinic acid and methimazole …

Oxyhalogen-Sulfur Chemistry: Kinetics And Mechanism Of Oxidation Of N-Acetylthiourea By Aqueous Bromate And Acidified Bromate, Kudzanai Chipiso, Wilbes Mbiya, Thai Tran, Reuben H. Simoyi

Chemistry Faculty Publications and Presentations

The oxidation of N-acetylthiourea (ACTU) by acidic bromate has been studied by observing formation of bromine in excess bromate conditions. The reaction displays an induction period before formation of bromine. The stoichiometry of the reaction was determined to be 4:3: 4BrO 3 – +3(CH 3 CO)NH(NH 2 )C=S+3H 2 O®4Br – +3(CH 3 CO)NH(NH 2 )C=O+3SO 4 2– +6H + (A) with a complete desulfurization of ACTU to its urea analogue. In excess bromate conditions the stoichiometry was 8:5: 8BrO 3 – + 5(CH 3 CO)NH(NH 2 )C=S + H 2 O ® 4Br 2 + 5(CH 3 CO)NH(NH 2 …

The Rna World: 4,000,000,050 Years Old, Niles Lehman

Chemistry Faculty Publications and Presentations

The notion that molecular systems such as RNA can display a wide range of evolutionary processes in the absence of fully formed cellular life continues to gain support. Understanding how RNA can behave in an abiotic context is a key piece of our picture of how life developed and expanded on the Earth, and by proxy, elsewhere. We can study how RNA behaves in this regard through a combination of in vivo work (with small regulatory RNAs and larger catalytic RNAs alike), experimental work in the laboratory, and through powerful analytical and simulation studies. These efforts will not only grant …

Design Of A Vlp-Nanovehicle For Cyp450 Enzymatic Activity Delivery, Lorena Sanchez-Sanchez, Alejandro Tapia-Moreno, Karla Juarez-Moreno, Dustin P. Patterson, R. D. Cadena-Nava, T. Douglas, R. Vazquez-Duhalt

Chemistry Faculty Publications and Presentations

Background: The intracellular delivery of enzymes for therapeutic use has a promising future for the treatment of several diseases such as genetic disorders and cancer. Virus-like particles offer an interesting platform for enzymatic delivery to targeted cells because of their great cargo capacity and the enhancement of the biocatalyst stability towards several factors important in the practical application of these nanoparticles. Results: We have designed a nano-bioreactor based on the encapsulation of a cytochrome P450 (CYP) inside the capsid derived from the bacteriophage P22. An enhanced peroxigenase, CYPBM3, was selected as a model enzyme because of its potential in enzyme …

Phase Considerations In The Gas/Particle Partitioning Of Organic Amines In The Atmosphere, James F. Pankow

Chemistry Faculty Publications and Presentations

Amines in the atmosphere are of interest because of their likely role in new particle formation, and because of anthropogenic emissions of amines at post-combustion carbon capture (PCCC) facilities. A conceptual framework for considering the partitioning of a monobasic amine (Am = unprotonated "free-base form) from the gas phase to atmospheric particulate matter (PM) is presented for cases when the PM may be composed of multiple liquid phases. Three types of liquid phases are considered as being individually or simultaneously possible for absorptive uptake of atmospheric amines: w) a mostly water phase; α ) a mostly (by mass) organic phase …

Formaldehyde From E-Cigarettes - It's Not As Simple As Some Suggest, James F. Pankow, Robert M. Strongin, David H. Peyton

Chemistry Faculty Publications and Presentations

The Authors address critics of a previously published letter to the Editor in The New England Journal of Medicine, pertaining to hidden formaldehyde in E-Cigarette aerosols and the need for future testing of their safety.

Molecular View Modeling Of Atmospheric Organic Particulate Matter: Incorporating Molecular Structure And Co-Condensation Of Water, James F. Pankow, Marguerite Colasurdo Marks, Kelley C. Barsanti, Abdullah Mahmud, William E. Asher, Jingyi Li, Qi Ying, Shantanu H. Jathar, Michael J. Kleeman

Chemistry Faculty Publications and Presentations

Most urban and regional models used to predict levels of organic particulate matter (OPM) are based on fundamental equations for gas/particle partitioning, but make the highly simplifying, anonymized-view (AV) assumptions that OPM levels are not affected by either: a) the molecular. characteristics of the condensing organic compounds (other than simple volatility); or b) co-condensation of water as driven by non-zero relative humidity (RH) values. The simplifying assumptions have allowed parameterized chamber results for formation of secondary organic aerosol (SOA) (e.g., “two-product” (2p) coefficients) to be incorporated in chemical transport models. However, a return towards a less simplistic (and more computationally …

Synthesis And Structure−Activity Relationships Of Tambjamines And B‑Ring Functionalized Prodiginines As Potent Antimalarials, Papireddy Kancharla, Jane Xu Kelly, Kevin A. Reynolds

Chemistry Faculty Publications and Presentations

Synthesis and antimalarial activity of 94 novel bipyrrole tambjamines (TAs) and a library of B-ring functionalized tripyrrole prodiginines (PGs) against a panel of Plasmodium falciparum strains are described. The activity and structure–activity relationships demonstrate that the ring-C of PGs can be replaced by an alkylamine, providing for TAs with retained/enhanced potency. Furthermore, ring-B of PGs/TAs can be substituted with short alkyl substitutions at either 4-position (replacement of OMe) or 3- and 4-positions without impacting potency. Eight representative TAs and two PGs have been evaluated for antimalarial activity against multidrug-resistant P. yoelii in mice in the dose range of 5–100 mg/kg …

Nmr-Based Structural Analysis Of Threonylcarbamoyl-Amp Synthase And Its Substrate Interactions, Kimberly A. Harris, Benjamin G. Bobay, Kathryn L. Sarachan, Alexis F. Sims, Yann Bilbille, Christopher Deutsch, Dirk Iwata-Reuyl, Paul F. Agris

Chemistry Faculty Publications and Presentations

The hypermodified nucleoside N(6)-threonylcarbamoyladenosine (t(6)A37) is present in many distinct tRNA species and has been found in organisms in all domains of life. This post-transcriptional modification enhances translation fidelity by stabilizing the anticodon/codon interaction in the ribosomal decoding site. The biosynthetic pathway of t(6)A37 is complex and not well understood. In bacteria, the following four proteins have been discovered to be both required and sufficient for t(6)A37 modification: TsaC, TsaD, TsaB, and TsaE. Of these, TsaC and TsaD are members of universally conserved protein families. Although TsaC has been shown to catalyze the formation of L-threonylcarbamoyl-AMP, a key intermediate in …

Dft Analysis Into The Intermediates Of Nickel Pyridenthiolate Catalysed Proton Reduction, Carolyn N. Virca, Theresa M. Mccormick

Chemistry Faculty Publications and Presentations

Nickel pyridine 2-thiolate (Ni(PyS)₃ −) has shown good stability and activity as a H₂ generation catalyst for use in solar energy storage. The experimentally proposed catalytic pathway is explored using DFT calculations. Free energy changes along the reaction coordinate, spin states, localization of charge and geometry of the intermediates were explored. Calculations were performed using Gaussian 09 with a B3P86/ 6-31+G(d) basis set and a CPCM water solvation model. Of particular interest were our findings that the first reduction occurs at the nickel rather than through non-innocent ligands and that water coordination is not favourable although protonation of …

Hydrophobic Surfactant Proteins Strongly Induce Negative Curvature, Mariya Chavarha, Ryan W. Loney, Shankar B. Rananavare, Stephen B. Hall

Chemistry Faculty Publications and Presentations

The hydrophobic surfactant proteins SP-B and SP-C greatly accelerate the adsorption of vesicles containing the surfactant lipids to form a film that lowers the surface tension of the air/water interface in the lungs. Pulmonary surfactant enters the interface by a process analogous to the fusion of two vesicles. As with fusion, several factors affect adsorption according to how they alter the curvature of lipid leaflets, suggesting that adsorption proceeds via a rate-limiting structure with negative curvature, in which the hydrophilic face of the phospholipid leaflets is concave. In the studies reported here, we tested whether the surfactant proteins might promote …

Flavour Chemicals In Electronic Cigarette Fluids, Peyton A. Tierney, Clarissa D. Karpinski, Jessica E. Brown, Wentai Luo, James F. Pankow

Chemistry Faculty Publications and Presentations

Background: Most e-cigarette liquids contain flavour chemicals. Flavour chemicals certified as safe for ingestion by the Flavor Extracts Manufacturers Association may not be safe for use in e-cigarettes. This study identified and measured flavour chemicals in 30 e-cigarette fluids.

Methods: Two brands of single-use e-cigarettes were selected and their fluids in multiple flavour types analysed by gas chromatography/mass spectrometry. For the same flavour types, and for selected confectionary flavours (eg, bubble gum and cotton candy), also analysed were convenience samples of e-cigarette fluids in refill bottles from local ‘vape’ shops and online retailers.

Results: In many liquids, total flavour chemicals …

Aerosol Optical Hygroscopicity Measurements During The 2010 Cares Campaign, Dean B. Atkinson, James Gregory Radney, Janel Lum, Katheryn R. Kolesar, Daniel J. Cziczo, Mikhail Pekour, Qi Zhang, Ari Setyan, Alla Zelenyuk, Christopher D. Cappa

Chemistry Faculty Publications and Presentations

Measurements of the effect of water uptake on particulate light extinction or scattering made at two locations during the 2010 CARES study around Sacramento, CA are reported. The observed influence of water uptake, characterized through the dimensionless optical hygroscopicity parameter γ, is compared with calculations constrained by observed particle size distributions and size-dependent particle composition. A closure assessment has been carried out that allowed for determination of the average hygroscopic growth factors (GF) at 85% relative humidity and the dimensionless hygroscopicity parameter κ for oxygenated organic aerosol (OA) and for supermicron particles, yielding κ = 0.1–0.15 and 0.9–1.0, respectively. The …

Analysis Of The Surface Density And Reactivity Of Perfluorophenylazide And The Impact On Ligand Immobilization, Gilad Zorn, David G. Castner, Anuradha Tyagi, Xin Wang, Hui Wang, Mingdi Yan

Chemistry Faculty Publications and Presentations

Perfluorophenylazide (PFPA) chemistry is a novel method for tailoring the surface properties of solid surfaces and nanoparticles. It is general and versatile, and has proven to be an efficient way to immobilize graphene, proteins, carbohydrates, and synthetic polymers. The main thrust of this work is to provide a detailed investigation on the chemical composition and surface density of the PFPA tailored surface. Specifically, gold surfaces were treated with PFPA-derivatized (11-mercaptoundecyl) tetra(ethylene glycol) (PFPA-MUTEG) mixed with 2-[2-(2-mercaptoethoxy)ethoxy]ethanol (MDEG) at varying solution mole ratios. Complementary analytical techniques were employed to characterize the resulting films including Fourier transform infrared spectroscopy to detect fingerprints …

Hidden Formaldehyde In E-Cigarette Aerosols, R. Paul Jensen, Wentai Luo, James F. Pankow, Robert M. Strongin, David H. Peyton

Chemistry Faculty Publications and Presentations

This letter reports a chemical analysis of vapor from electronic cigarettes that shows high levels of formaldehyde, a known carcinogen. The authors project that the associated incremental lifetime risk of cancer could be higher than that from long-term smoking.

Controlled Deposition Of Tin Oxide And Silver Nanoparticles Using Microcontact Printing, Joo C. Chan, Nicole Hannah-Moore, Shankar B. Rananavare

Chemistry Faculty Publications and Presentations

This report describes extensive studies of deposition processes involving tin oxide (SnO_x) nanoparticles on smooth glass surfaces. We demonstrate the use of smooth films of these nanoparticles as a platform for spatially-selective electroless deposition of silver by soft lithographic stamping. The edge and height roughness of the depositing metallic films are 100 nm and 20 nm, respectively, controlled by the intrinsic size of the nanoparticles. Mixtures of alcohols as capping agents provide further control over the size and shape of nanoparticles clusters. The distribution of cluster heights obtained by atomic force microscopy (AFM) is modeled through a modified …

Phthalimide-Based Π-Conjugated Small Molecules With Tailored Electronic Energy Levels For Use As Acceptors In Organic Solar Cells, Arthur D. Hendsbee, Seth M. Mcafee, Jon-Paul Sun, Theresa M. Mccormick, Ian G. Hill, Gregory C. Welch

Chemistry Faculty Publications and Presentations

The design, synthesis, and characterization of seven phthalimide-based organic π-conjugated small molecules are reported. The new materials are based on a phthalimide–thiophene–CORE–thiophene–phthalimide architecture. The CORE units utilized were phthalimide (M2), diketopyrrolopyrrole (M3), isoindigo (M4), naphthalene diimide (M5), perylene diimide (M6), and difluorobenzothiadiazole (M7); they were specifically selected to progressively increase the electron affinity of the resulting compound. A small molecule with no core (M1) was synthesized for comparison. Each material was synthesized through optimized direct heteroarylation cross-coupling procedures using bench top solvents in air. Combinations of …

Empirical Demonstration Of Environmental Sensing In Catalytic Rna: Evolution Of Interpretive Behavior At The Origins Of Life, Niles Lehman, Tess Bernhard, Brian C. Larson, Andrew J.N. Robinson, Christopher C.B. Southgate

Chemistry Faculty Publications and Presentations

Background: The origins of life on the Earth required chemical entities to interact with their environments in ways that could respond to natural selection. The concept of interpretation, where biotic entities use signs in their environment as proxy for the existence of other items of selective value in their environment, has been proposed on theoretical grounds to be relevant to the origins and early evolution of life. However this concept has not been demonstrated empirically.

Results: Here, we present data that certain catalytic RNA sequences have properties that would enable interpretation of divalent cation levels in their environment. …

Human Whole-Blood (1)H2o Longitudinal Relaxation With Normal And High-Relaxivity Contrast Reagents: Influence Of Trans-Cell-Membrane Water Exchange, Gregory J. Wilson, Mark Woods, Charles S. Springer Jr., Sarah Bastawrous, Puneet Bhargava, Jeffrey H. Maki

Chemistry Faculty Publications and Presentations

PURPOSE: Accurate characterization of contrast reagent (CR) longitudinal relaxivity in whole blood is required to predict arterial signal intensity in contrast-enhanced MR angiography (CE-MRA). This study measured the longitudinal relaxation rate constants (R₁ ) over a concentration range for non-protein-binding and protein-binding CRs in ex vivo whole blood and plasma at 1.5 and 3.0 Tesla (T) under physiologic arterial conditions.

METHODS: Relaxivities of gadoteridol, gadobutrol, gadobenate, and gadofosveset were measured for [CR] from 0 to 18 mM [mmol(CR)/L(blood)]: the latter being the upper limit of what may be expected in CE-MRA.

RESULTS: In plasma, the ¹H2 O R …

Reducing The Effects Of Shot Noise Using Nanoparticles, Moshood K. Morakinyo, Shankar B. Rananavare

Chemistry Faculty Publications and Presentations

We present a hybrid nano-lithographic approach to minimizes the effects of line edge roughness and shot noise in nano-hole patterning by reflowing photoresist polymers around the nanoparticles deposited using self-assembly and simple etch chemistries. The method extends the transistor contact holes patterning limits to below 20 nm.

Inhalable Constituents Of Thirdhand Tobacco Smoke: Chemical Characterization And Health Impact Considerations, Mohamad Sleiman, Jennifer M. Logue, Wentai Luo, James F. Pankow, Lara A. Gundel, Hugo Destaillats

Chemistry Faculty Publications and Presentations

Tobacco smoke residues lingering in the indoor environment, also termed thirdhand smoke (THS), can be a source of long-term exposure to harmful pollutants. THS composition is affected by chemical transformations and by air–surface partitioning over time scales of minutes to months. This study identified and quantified airborne THS pollutants available for respiratory exposure, identified potential environmental tracers, and estimated health impacts to nonsmokers. In a ventilated 18 m3 laboratory chamber, six cigarettes were machine-smoked, and levels of particulate matter (PM2.5) and 58 volatile organic compounds (VOCs) were monitored during an aging period of 18 h. Results were compared with field …

The Atmosphere Can Be A Source Of Certain Water Soluble Volatile Organic Compounds In Urban Streams, Scott J. Kenner, David A. Bender, James F. Pankow, John S. Zogorski

Chemistry Faculty Publications and Presentations

Surface water and air volatile organic compound (VOC) data from 10 U. S. Geological Survey monitoring sites were used to evaluate the potential for direct transport of VOCs from the atmosphere to urban streams. Analytical results of 87 VOC compounds were screened by evaluating the occurrence and detection levels in both water and air, and equilibrium concentrations in water (C-w(s)) based on the measured air concentrations. Four compounds (acetone, methyl tertiary butyl ether, toluene, and m- & p-xylene) were detected in more than 20% of water samples, in more than 10% of air samples, and more than 10% of detections …

Promiscuous And Adaptable Enzymes Fill “Holes” In The Tetrahydrofolate Pathway In Chlamydia Species, Nancy E. Adams, Jennifer J. Thiaville, James Proestos, Ana L. Juárez-Vázquez, Andrea J. Mccoy, Francisco Barona-Gómez, Dirk Iwata-Reuyl, Valérie De Crécy-Lagard, Anthony T. Maurelli

Chemistry Faculty Publications and Presentations

Folates are tripartite molecules comprising pterin, para-aminobenzoate (PABA), and glutamate moieties, which are essential cofactors involved in DNA and amino acid synthesis. The obligately intracellular Chlamydia species have lost several biosynthetic pathways for essential nutrients which they can obtain from their host but have retained the capacity to synthesize folate. In most bacteria, synthesis of the pterin moiety of folate requires the FolEQBK enzymes, while synthesis of the PABA moiety is carried out by the PabABC enzymes. Bioinformatic analyses reveal that while members of Chlamydia are missing the genes for FolE (GTP cyclohydrolase) and FolQ, which catalyze the initial …

Candy Flavorings In Tobacco, Jessica E. Brown, Wentai Luo, Lorne M. Isabelle, James F. Pankow

Chemistry Faculty Publications and Presentations

Professor James F. Pankow reveals striking similarities between the patterns in the flavoring chemicals used in flavored tobacco products and those in popular candy and Kool-Aid products. The authors analyzed 12 artificially flavored candy and fruit drink products and compared them to 15 widely-available flavored tobacco products. They found significant overlap in the chemical signatures of the flavor chemicals. Several of the tobacco products contained flavor chemicals at much higher concentrations than in the non-tobacco products.

The Impact Of Surface Ligands And Synthesis Method On The Toxicity Of Glutathione-Coated Gold Nanoparticles, Bryan Harper, Federico Sinche, Meenambika Gowrishankar, Grant Marquart, Marilyn R. Mackiewicz, Stacey L. Harper

Chemistry Faculty Publications and Presentations

Gold nanoparticles (AuNPs) are increasingly used in biomedical applications, hence understanding the processes that affect their biocompatibility and stability are of significant interest. In this study, we assessed the stability of peptide-capped AuNPs and used the embryonic zebrafish (Danio rerio) as a vertebrate system to investigate the impact of synthesis method and purity on their biocompatibility. Using glutathione (GSH) as a stabilizer, Au-GSH nanoparticles with identical core sizes were terminally modified with Tryptophan (Trp), Histidine (His) or Methionine (Met) amino acids and purified by either dialysis or ultracentrifugation. Au-GSH-(Trp)2 purified by dialysis elicited significant morbidity and mortality at …

A Facile Route To Tailoring Peptide-Stabilized Gold Nanoparticles Using Glutathione As A Synthon, Rosina Ho Wu, Tan P. Nguyen, Grant W. Marquart, Thomas J. Miesen, Theresa Mau, Marilyn R. Mackiewicz

Chemistry Faculty Publications and Presentations

The preparation of gold nanoparticles (AuNPs) of high purity and stability remains a major challenge for biological applications. This paper reports a simple synthetic strategy to prepare water-soluble peptide-stabilized AuNPs. Reduced glutathione, a natural tripeptide, was used as a synthon for the growth of two peptide chains directly on the AuNP surface. Both nonpolar (tryptophan and methionine) and polar basic (histidine and dansylated arginine) amino acids were conjugated to the GSH-capped AuNPs. Ultracentrifugation concentrators with polyethersulfone (PES) membranes were used to purify precursor materials in each stage of the multi-step synthesis to minimize side reactions. Thin layer chromatography, transmission electron …

Serial Transfer Can Aid The Evolution Of Autocatalytic Sets, Wim Hordijk, Nilesh Vaidya, Niles Lehman

Chemistry Faculty Publications and Presentations

Background: The concept of an autocatalytic set of molecules has been posited theoretically and demonstrated empirically with catalytic RNA molecules. For this concept to have significance in a realistic origins-of-life scenario, it will be important to demonstrate the evolvability of such sets. Here, we employ a Gillespie algorithm to improve and expand on previous simulations of an empirical system of self-assembling RNA fragments that has the ability to spontaneously form autocatalytic networks. We specifically examine the role of serial transfer as a plausible means to allow time-dependent changes in set composition, and compare the results to equilibrium, or "batch" scenarios. …

Photocatalytic Hydrogen Production From A Noble Metal Free System Based On A Water Soluble Porphyrin Derivative And A Cobaloxime Catalyst, Theodore Lazarides, Milan Delor, Igor V. Sazanovich, Theresa M. Mccormick, Irene Georgakaki, Georgios Charalambidis, Julia A. Weinstein, Athanassios G. Coutsolelos

Chemistry Faculty Publications and Presentations

A combination of noble-metal free components, a water soluble porphyrin photosensitizer zincmeso-tetrakis(1-methylpyridinium-4-yl)porphyrin chloride [ZnTMPyP⁴⁺]Cl₄ (1) with cobaloxime complex [Co^III(dmgH)₂(py)Cl] (2) as a catalyst, creates an efficient system for photochemical hydrogen production acting under visible light with 280 TONs. This is the first example of a water soluble porphyrin acting as a photosensitizer for cobaloxime catalysed H₂ production.

The Confluence Of Structure And Dynamics In Lanthanide(Iii) Chelates: How Dynamics Help Define Structure In Solution, Benjamin Charles Webber, Mark Woods

Chemistry Faculty Publications and Presentations

Coordination exchange processes tend to dominate the solution state behaviour of lanthanide chelates and generally prohibit the study of small conformational changes. In this article we take advantage of coordinatively rigid Eu³⁺ chelates to examine the small conformational changes that occur in these chelates as water dissociatively exchanges in and out of the inner coordination sphere. The results show that the time-averaged conformation of the chelate alters as the water exchange rate increases. This conformational change reflects a change in the hydration state (q/r_LnH⁶) of the chelate. The hydration state has recently come …