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Chemistry Faculty Research

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Articles 1 - 30 of 120

Full-Text Articles in Physical Sciences and Mathematics

Damped Oscillating Phosphoryl Transfer Reaction In The Cyanobacterial Circadian Clock, Hye In Jang, Pyonghwa Kim, Yongick Kim Mar 2023

Damped Oscillating Phosphoryl Transfer Reaction In The Cyanobacterial Circadian Clock, Hye In Jang, Pyonghwa Kim, Yongick Kim

Chemistry Faculty Research

Most organisms have circadian clocks to ensure the metabolic cycle to resonate with the rhythmic environmental changes without “damping,” or losing robustness. Cyanobacteria is the oldest and simplest form of life that is known to harbor this biological intricacy. Its KaiABC-based central oscillator proteins can be reconstituted inside a test tube, and the post-translational modification cycle occurs with 24 h periodicity. KaiC’s two major phosphorylation sites, Ser-431 and Thr-432, become phosphorylated and dephosphorylated by interacting with KaiA and KaiB, respectively. Here, we mutate Thr-432 into Ser to find the oscillatory phosphoryl transfer reaction damps. Previously, this mutant KaiC was reported …

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Thioester Synthesis By A Designed Nickel Enzyme Models Prebiotic Energy Conversion, A. C. Manesis, A. Yerbulekova, Jason M. Shearer, H. S. Shafaat Jul 2022

Thioester Synthesis By A Designed Nickel Enzyme Models Prebiotic Energy Conversion, A. C. Manesis, A. Yerbulekova, Jason M. Shearer, H. S. Shafaat

Chemistry Faculty Research

The formation of carbon-carbon bonds from prebiotic precursors such as carbon dioxide represents the foundation of all primordial life processes. In extant organisms, this reaction is carried out by the carbon monoxide dehydrogenase (CODH)/acetyl coenzyme A synthase (ACS) enzyme, which performs the cornerstone reaction in the ancient Wood-Ljungdahl metabolic pathway to synthesize the key biological metabolite, acetylCoA. Despite its significance, a fundamental understanding of this transformation is lacking, hampering efforts to harness analogous chemistry. To address these knowledge gaps, we have designed an artificial metalloenzyme within the azurin protein scaffold as a structural, functional, and mechanistic model of ACS. We …

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Evidence For A Semisolid Phase State Of Aerosols And Droplets Relevant To The Airborne And Surface Survival Of Pathogens, Erik Huynh, Anna Olinger, David Woolley, R. K. Kohli, J. M. Choczynski, J. F. Davies, K. Lin, L. C. Marr, Ryan D. Davis Jan 2022

Evidence For A Semisolid Phase State Of Aerosols And Droplets Relevant To The Airborne And Surface Survival Of Pathogens, Erik Huynh, Anna Olinger, David Woolley, R. K. Kohli, J. M. Choczynski, J. F. Davies, K. Lin, L. C. Marr, Ryan D. Davis

Chemistry Faculty Research

The phase state of respiratory aerosols and droplets has been linked to the humidity-dependent survival of pathogens such as SARS-CoV-2. To inform strategies to mitigate the spread of infectious disease, it is thus necessary to understand the humidity-dependent phase changes associated with the particles in which pathogens are suspended. Here, we study phase changes of levitated aerosols and droplets composed of model respiratory compounds (salt and protein) and growth media (organic-inorganic mixtures commonly used in studies of pathogen survival) with decreasing relative humidity (RH). Efflorescence was suppressed in many particle compositions and thus unlikely to fully account for the humidity-dependent …

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Activation Of Prp28 Atpase By Phosphorylated Npl3 At A Critical Step Of Spliceosome Remodeling, F.-L. Yeh, S.-L. Chang, G. R. Ahmed, H.-I. Liu, L. Tung, C.-S. Yeh, L. S. Lanier, Corina Maeder, C.-M. Lin, S.-C. Tsai, W.-Y. Hsiao, W.-H. Chang, T.-H. Chang Dec 2021

Activation Of Prp28 Atpase By Phosphorylated Npl3 At A Critical Step Of Spliceosome Remodeling, F.-L. Yeh, S.-L. Chang, G. R. Ahmed, H.-I. Liu, L. Tung, C.-S. Yeh, L. S. Lanier, Corina Maeder, C.-M. Lin, S.-C. Tsai, W.-Y. Hsiao, W.-H. Chang, T.-H. Chang

Chemistry Faculty Research

Splicing, a key step in the eukaryotic gene-expression pathway, converts precursor messenger RNA (pre-mRNA) into mRNA by excising introns and ligating exons. This task is accomplished by the spliceosome, a macromolecular machine that must undergo sequential conformational changes to establish its active site. Each of these major changes requires a dedicated DExD/H-box ATPase, but how these enzymes are activated remain obscure. Here we show that Prp28, a yeast DEAD-box ATPase, transiently interacts with the conserved 5' splice-site (5'SS) GU dinucleotide and makes splicing-dependent contacts with the U1 snRNP protein U1C, and U4/U6.U5 tri-snRNP proteins, Prp8, Brr2, and Snu114. We further …

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Scaffold-Based [Fe]-Hydrogenase Model: H2 Activation Initiates Fe(0)-Hydride Extrusion And Non-Biomimetic Hydride Transfer, S. A. Kerns, J. Seo, V. M. Lynch, Jason M. Shearer, S. T. Goralski, E. R. Sullivan, M. J. Rose Oct 2021

Scaffold-Based [Fe]-Hydrogenase Model: H2 Activation Initiates Fe(0)-Hydride Extrusion And Non-Biomimetic Hydride Transfer, S. A. Kerns, J. Seo, V. M. Lynch, Jason M. Shearer, S. T. Goralski, E. R. Sullivan, M. J. Rose

Chemistry Faculty Research

We report the synthesis and reactivity of a model of [Fe]-hydrogenase derived from an anthracene-based scaffold that includes the endogenous, organometallic acyl(methylene) donor. In comparison to other non-scaffolded acyl-containing complexes, the complex described herein retains molecularly well-defined chemistry upon addition of multiple equivalents of exogenous base. Clean deprotonation of the acyl(methylene) C-H bond with a phenolate base results in the formation of a dimeric motif that contains a new Fe-C(methine) bond resulting from coordination of the deprotonated methylene unit to an adjacent iron center. This effective second carbanion in the ligand framework was demonstrated to drive heterolytic H2 activation …

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The Circadian Clock—A Molecular Tool For Survival In Cyanobacteria, Pyonghwa Kim, Manpreet Kaur, Hye-In Jang, Yongick Kim Dec 2020

The Circadian Clock—A Molecular Tool For Survival In Cyanobacteria, Pyonghwa Kim, Manpreet Kaur, Hye-In Jang, Yongick Kim

Chemistry Faculty Research

Cyanobacteria are photosynthetic organisms that are known to be responsible for oxygenating Earth’s early atmosphere. Having evolved to ensure optimal survival in the periodic light/dark cycle on this planet, their genetic codes are packed with various tools, including a sophisticated biological timekeeping system. Among the cyanobacteria is Synechococcus elongatus PCC 7942, the simplest clock-harboring organism with a powerful genetic tool that enabled the identification of its intricate timekeeping mechanism. The three central oscillator proteins—KaiA, KaiB, and KaiC—drive the 24 h cyclic gene expression rhythm of cyanobacteria, and the “ticking” of the oscillator can be reconstituted inside a test tube just …

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Ion-Molecule Interactions Enable Unexpected Phase Transitions In Organic-Inorganic Aerosol, David S. Richards, Kristin L. Trobaugh, Josefina Hajek-Herrera, C. L. Price, C. S. Sheldon, J. F. Davies, Ryan D. Davis Nov 2020

Ion-Molecule Interactions Enable Unexpected Phase Transitions In Organic-Inorganic Aerosol, David S. Richards, Kristin L. Trobaugh, Josefina Hajek-Herrera, C. L. Price, C. S. Sheldon, J. F. Davies, Ryan D. Davis

Chemistry Faculty Research

Atmospheric aerosol particles are commonly complex, aqueous organic-inorganic mixtures, and accurately predicting the properties of these particles is essential for air quality and climate projections. The prevailing assumption is that aqueous organic-inorganic aerosols exist predominately with liquid properties and that the hygroscopic inorganic fraction lowers aerosol viscosity relative to the organic fraction alone. Here, in contrast to those assumptions, we demonstrate that increasing inorganic fraction can increase aerosol viscosity (relative to predictions) and enable a humidity-dependent gel phase transition through cooperative ion-molecule interactions that give rise to long-range networks of atmospherically relevant low-mass oxygenated organic molecules (180 to 310 Da) …

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Pharmacologic Ire1/Xbp1s Activation Confers Targeted Er Proteostasis Reprogramming, J. M. D. Grandjean, A. Madhavan, L. Cech, B. O. Seguinot, R. J. Paxman, E. Smith, L. Scampavia, E. T. Powers, Christina B. Cooley, L. Plate, T. P. Spicer, J. W. Kelly, R. L. Wiseman Oct 2020

Pharmacologic Ire1/Xbp1s Activation Confers Targeted Er Proteostasis Reprogramming, J. M. D. Grandjean, A. Madhavan, L. Cech, B. O. Seguinot, R. J. Paxman, E. Smith, L. Scampavia, E. T. Powers, Christina B. Cooley, L. Plate, T. P. Spicer, J. W. Kelly, R. L. Wiseman

Chemistry Faculty Research

Activation of the IRE1/XBP1s signaling arm of the unfolded protein response (UPR) is a promising strategy to correct defects in endoplasmic reticulum (ER) proteostasis implicated in diverse diseases. However, no pharmacologic activators of this pathway identified to date are suitable for ER proteostasis remodeling through selective activation of IRE1/XBP1s signaling. Here, we use high-throughput screening to identify non-toxic compounds that induce ER proteostasis remodeling through IRE1/XBP1s activation. We employ transcriptional profiling to stringently confirm that our prioritized compounds selectively activate IRE1/XBP1s signaling without activating other cellular stress-responsive signaling pathways. Furthermore, we demonstrate that our compounds improve ER proteostasis of destabilized …

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Structure And Unprecedented Reactivity Of A Mononuclear Nonheme Cobalt(Iii) Iodosylbenzene Complex, J. Yang, M. S. Seo, K. H. Kim, Y. M. Lee, S. Fukuzumi, Jason M. Shearer, W. Nam Aug 2020

Structure And Unprecedented Reactivity Of A Mononuclear Nonheme Cobalt(Iii) Iodosylbenzene Complex, J. Yang, M. S. Seo, K. H. Kim, Y. M. Lee, S. Fukuzumi, Jason M. Shearer, W. Nam

Chemistry Faculty Research

A mononuclear nonheme cobalt(III) iodosylbenzene complex, [CoIII(TQA)(OIPh)(OH)]2+ (1), is synthesized and characterized structurally and spectroscopically. While 1 is a sluggish oxidant in oxidation reactions, it becomes a competent oxidant in oxygen atom transfer reactions, such as olefin epoxidation, in the presence of a small amount of proton. More interestingly, 1 shows a nucleophilic reactivity in aldehyde deformylation reaction, demonstrating that 1 has an amphoteric reactivity. Another interesting observation is that 1 can be used as an oxygen atom donor in the generation of high-valent metal-oxo complexes. To our knowledge, we present the first crystal structure …

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Efficient Eco-Friendly Syntheses Of Dithiocarbazates And Thiosemicarbazones, Nur Halilatul Sadiqin O. Ali, Malai Haniti S. A. Hamid, Nurul Amirah 'Aqilah Mohamad' Asri Putra, Hajar Azirah Adol, Aminul Huq Mirza, Anwar Usman, Tasneem A. Siddiquee, Md. Rejaul Hoq, Mohammad R. Karim Apr 2020

Efficient Eco-Friendly Syntheses Of Dithiocarbazates And Thiosemicarbazones, Nur Halilatul Sadiqin O. Ali, Malai Haniti S. A. Hamid, Nurul Amirah 'Aqilah Mohamad' Asri Putra, Hajar Azirah Adol, Aminul Huq Mirza, Anwar Usman, Tasneem A. Siddiquee, Md. Rejaul Hoq, Mohammad R. Karim

Chemistry Faculty Research

Eight Schiff bases have been synthesized by conventional and three different eco-friendly methods, whereby two aromatic carbonyl compounds viz. 2-thiophenecarboxaldehyde and salicylaldehyde were reacted with S-methyl, S-benzyl, and S-n-octyl-dithiocarbazates and thiosemicarbazide. In order to evaluate the efficiency of the synthesis methods, the time to complete the reaction and the yield of the Schiff base synthezised by eco-friendly methods, such as solvent-free grinding, water as a solvent, and lemon juice as catalyst, were compared with those synthesized by the conventional method. The chemical structures of all the synthesized Schiff bases, where two of them are …

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Comparative Analysis Of Water Quality Disparities In The United States In Relation To Heavy Metals And Biological Contaminants, Kaleh Karim, Sujata Guha, Ryan Beni Mar 2020

Comparative Analysis Of Water Quality Disparities In The United States In Relation To Heavy Metals And Biological Contaminants, Kaleh Karim, Sujata Guha, Ryan Beni

Chemistry Faculty Research

Drinking water quality can be compromised by heavy metals, such as copper and lead. If consumed raw, water can pose a health burden to the general population. In this study, the roles of heavy metals and biological contaminants have been explored in determining the quality of drinking water available to consumers of various socioeconomic backgrounds in the United States. In an effort to gain an understanding of possible social disparities in drinking water, a quantitative analysis was conducted to examine whether vulnerable populations are disproportionately impacted by drinking water contaminants. Our data indicated that states with middle-average household incomes were …

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Dual-Balance Electrodynamic Trap As A Microanalytical Tool For Identifying Gel Transitions And Viscous Properties Of Levitated Aerosol Particles, David S. Richards, Kristin L. Trobaugh, Josefina Hajek-Herrera, Ryan D. Davis Jan 2020

Dual-Balance Electrodynamic Trap As A Microanalytical Tool For Identifying Gel Transitions And Viscous Properties Of Levitated Aerosol Particles, David S. Richards, Kristin L. Trobaugh, Josefina Hajek-Herrera, Ryan D. Davis

Chemistry Faculty Research

The formation of gelatinous networks within an aerosol particle significantly alters the physicochemical properties of the aerosol material. Existing techniques for studying gel transitions rely on bulk rheometry, which is limited by contact with the sample, or microrheological techniques such as holographic optical tweezers, which rely on expensive equipment and high-powered lasers that can degrade light-absorbing aerosol. Here, we present a new technique to probe the microrheological characteristics of aerosol particles and explore gel formation under atmospheric conditions in a contactless environment without the need for high-power light sources. In a dual-balance quadrupole electrodynamic balance, levitated droplets of opposite polarity …

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A Critical Analysis Of Electrospray Techniques For The Determination Of Accelerated Rates And Mechanisms Of Chemical Reactions In Droplets, G. Rovelli, M. I. Jacobs, M. D. Willis, Rebecca J. Rapf, A. M. Prophet, K. R. Wilson Jan 2020

A Critical Analysis Of Electrospray Techniques For The Determination Of Accelerated Rates And Mechanisms Of Chemical Reactions In Droplets, G. Rovelli, M. I. Jacobs, M. D. Willis, Rebecca J. Rapf, A. M. Prophet, K. R. Wilson

Chemistry Faculty Research

Electrospray and Electrosonic Spray Ionization Mass Spectrometry (ESI-MS and ESSI-MS) have been widely used to report evidence that many chemical reactions in micro- and nano-droplets are dramatically accelerated by factors of ∼102 to 106 relative to macroscale bulk solutions. Despite electrospray's relative simplicity to both generate and detect reaction products in charged droplets using mass spectrometry, substantial complexity exists in how the electrospray process itself impacts the interpretation of the mechanism of these observed accelerated rates. ESI and ESSI are both coupled multi-phase processes, in which analytes in small charged droplets are transferred and detected as gas-phase ions with a …

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Ph Dependent Reversible Formation Of A Binuclear Ni2 Metal-Center Within A Peptide Scaffold, Breena C. Keegan, Daniel Ocampo, Jason M. Shearer Jul 2019

Ph Dependent Reversible Formation Of A Binuclear Ni2 Metal-Center Within A Peptide Scaffold, Breena C. Keegan, Daniel Ocampo, Jason M. Shearer

Chemistry Faculty Research

A disulfide-bridged peptide containing two Ni2+ binding sites based on the nickel superoxide dismutase protein, {Ni2(SODmds)} has been prepared. At physiological pH (7.4), it was found that the metal sites are mononuclear with a square planar NOS2 coordination environment with the two sulfur-based ligands derived from cysteinate residues, the nitrogen ligand derived from the amide backbone, and a water ligand. Furthermore, S K-edge X-ray absorption spectroscopy indicated that the two cysteinate sulfur atoms ligated to nickel are each protonated. Elevation of the pH to 9.6 results in the deprotonation of the cysteinate sulfur atoms, …

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On The Limited Role Of Electronic Support Effects In Selective Alkyne Hydrogenation: A Kinetic Study Of Au/MoX Catalysts Prepared From Oleylamine-Capped Colloidal Nanoparticles, James E. Bruno, K. B. Sravan Kumar, Nicolas S. Dwarica, Alexander Hüther, Zhifeng Chen, Clemente S. Guzman Iv, Emily R. Hand, William C. Moore, Robert M. Rioux, Lars C. Grabow, Bert D. Chandler Mar 2019

On The Limited Role Of Electronic Support Effects In Selective Alkyne Hydrogenation: A Kinetic Study Of Au/MoX Catalysts Prepared From Oleylamine-Capped Colloidal Nanoparticles, James E. Bruno, K. B. Sravan Kumar, Nicolas S. Dwarica, Alexander Hüther, Zhifeng Chen, Clemente S. Guzman Iv, Emily R. Hand, William C. Moore, Robert M. Rioux, Lars C. Grabow, Bert D. Chandler

Chemistry Faculty Research

We report a quantitative kinetic evaluation and study of support effects for partial alkyne hydrogenation using oleylaminecapped Au colloids as catalyst precursors. The amine capping agents can be removed under reducing conditions, generating supported Au nanoparticles of ~2.5 nm in diameter. The catalysts showed high alkene selectivity (>90%) at all conversions during alkyne partial hydrogenation. Catalytic activity, observed rate constants, and apparent activation energies (25– 40 kJ/mol) were similar for all Au catalysts, indicating support effects are relatively small. Alkyne adsorption, probed with FTIR and DFT, showed adsorption on the support was associated with hydrogen-bonding interactions. DFT calculations indicate …

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Fluorogenic Atom Transfer Radical Polymerization In Aqueous Media As A Strategy For Detection, Zachary T. Allen, Jemima R. Sackey-Addo, Madeline P. Hopps, Danyal Tahseen, Joseph T. Anderson, Tyler A. Graf, Christina B. Cooley Jan 2019

Fluorogenic Atom Transfer Radical Polymerization In Aqueous Media As A Strategy For Detection, Zachary T. Allen, Jemima R. Sackey-Addo, Madeline P. Hopps, Danyal Tahseen, Joseph T. Anderson, Tyler A. Graf, Christina B. Cooley

Chemistry Faculty Research

The development of novel approaches to signal amplification in aqueous media could enable new diagnostic platforms for the detection of water-soluble analytes, including biomolecules. This paper describes a fluorogenic polymerization approach to amplify initiator signal by the detection of visible fluorescence upon polymerization in real-time. Fluorogenic monomers were synthesized and co-polymerized by atom transfer radical polymerization (ATRP) in water to reveal increasing polymer fluorescence as a function of both reaction time and initiator concentration. Optimization of the fluorogenic ATRP reaction conditions allowed for the quantitative detection of a small-molecule initiator as a model analyte over a broad linear concentration range …

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A Biochemical Nickel(I) State Supports Nucleophilic Alkyl Addition: A Roadmap For Methyl Reactivity In Acetyl Coenzyme A Synthase, A. C. Manesis, B. W. Musselman, Breena C. Keegan, Jason M. Shearer, N. Lehnert, H. S. Shafaat Jan 2019

A Biochemical Nickel(I) State Supports Nucleophilic Alkyl Addition: A Roadmap For Methyl Reactivity In Acetyl Coenzyme A Synthase, A. C. Manesis, B. W. Musselman, Breena C. Keegan, Jason M. Shearer, N. Lehnert, H. S. Shafaat

Chemistry Faculty Research

Nickel-containing enzymes such as methyl coenzyme M reductase (MCR) and carbon monoxide dehydrogenase/acetyl coenzyme A synthase (CODH/ACS) play a critical role in global energy conversion reactions, with significant contributions to carbon-centered processes. These enzymes are implied to cycle through a series of nickel-based organometallic intermediates during catalysis, though identification of these intermediates remains challenging. In this work, we have developed and characterized a nickel-containing metalloprotein that models the methyl-bound organometallic intermediates proposed in the native enzymes. Using a nickel(I)-substituted azurin mutant, we demonstrate that alkyl binding occurs via nucleophilic addition of methyl iodide as a methyl donor. The paramagnetic Ni …

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Reduction Of Co2 By A Masked Two-Coordinate Cobalt(I) Complex And Characterization Of A Proposed Oxodicobalt(Ii) Intermediate, L. Roy, M. H. Al-Afyouni, D. E. Derosha, B. Mondal, I. M. Dimucci, K. M. Lancaster, Jason M. Shearer, E. Bill, W. W. Brennessel, F. Neese, S. Ye, P. L. Holland Jan 2019

Reduction Of Co2 By A Masked Two-Coordinate Cobalt(I) Complex And Characterization Of A Proposed Oxodicobalt(Ii) Intermediate, L. Roy, M. H. Al-Afyouni, D. E. Derosha, B. Mondal, I. M. Dimucci, K. M. Lancaster, Jason M. Shearer, E. Bill, W. W. Brennessel, F. Neese, S. Ye, P. L. Holland

Chemistry Faculty Research

Fixation and chemical reduction of CO2 are important for utilization of this abundant resource, and understanding the detailed mechanism of C-O cleavage is needed for rational development of CO2 reduction methods. Here, we describe a detailed analysis of the mechanism of the reaction of a masked two-coordinate cobalt(i) complex, LtBuCo (where LtBu = 2,2,6,6-tetramethyl-3,5-bis[(2,6-diisopropylphenyl)imino]hept-4-yl), with CO2, which yields two products of C-O cleavage, the cobalt(i) monocarbonyl complex LtBuCo(CO) and the dicobalt(ii) carbonate complex (LtBuCo)2(μ-CO3). Kinetic studies and computations show that the …

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H2 Oxidation Over Supported Au Nanoparticle Catalysts: Evidence For Heterolytic H2 Activation At The Metal-Support Interface, Todd N. Whittaker, K. B. Sravan Kumar, Christine Peterson, Meagan N. Pollock, L. C. Grabow, Bert D. Chandler Dec 2018

H2 Oxidation Over Supported Au Nanoparticle Catalysts: Evidence For Heterolytic H2 Activation At The Metal-Support Interface, Todd N. Whittaker, K. B. Sravan Kumar, Christine Peterson, Meagan N. Pollock, L. C. Grabow, Bert D. Chandler

Chemistry Faculty Research

Water adsorbed at the metal-support interface (MSI) plays an important role in multiple reactions. Due to its importance in CO preferential oxidation (PrOx), we examined H2 oxidation kinetics in the presence of water over Au/TiO2 and Au/Al2O3 catalysts, reaching the following mechanistic conclusions: (i) O2 activation follows a similar mechanism to that proposed in CO oxidation catalysis; (ii) weakly adsorbed H2O is a strong reaction inhibitor; (iii) fast H2 activation occurs at the MSI, and (iv) H2 activation kinetics are inconsistent with traditional dissociative H2 chemisorption on metals. Density …

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Characterization And Effect Of Metal Ions On The Formation Of The Thermus Thermophilus Sco Mixed Disulfide Intermediate, Liezelle C. Lopez, Nikita Mukhitov, Lindsey D. Handley, Cristina S. Hamme, Cristina R. Hofman, Lindsay Euers, Jennifer R. Mckinney, Amani D. Piers, Ellen Wadler, Laura M. Hunsicker-Wang Nov 2018

Characterization And Effect Of Metal Ions On The Formation Of The Thermus Thermophilus Sco Mixed Disulfide Intermediate, Liezelle C. Lopez, Nikita Mukhitov, Lindsey D. Handley, Cristina S. Hamme, Cristina R. Hofman, Lindsay Euers, Jennifer R. Mckinney, Amani D. Piers, Ellen Wadler, Laura M. Hunsicker-Wang

Chemistry Faculty Research

The Sco protein from Thermus thermophilus has previously been shown to perform a disulfide bond reduction in the CuA protein from T. thermophilus, which is a soluble protein engineered from subunit II of cytochrome ba 3 oxidase that lacks the transmembrane helix. The native cysteines on TtSco and TtCuA were mutated to serine residues to probe the reactivities of the individual cysteines. Conjugation of TNB to the remaining cysteine in TtCuA and subsequent release upon incubation with the complementary TtSco protein demonstrated the formation of the mixed disulfide intermediate. The cysteine of …

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Molecular Recognition Of Methionine-Terminated Peptides By Cucurbit[8]Uril, Zoheb Hirani, Hailey F. Taylor, E. F. Babcock, Andrew T. Bockus, C. D. Varnado Jr., Christopher W. Bielawski, Adam R. Urbach Sep 2018

Molecular Recognition Of Methionine-Terminated Peptides By Cucurbit[8]Uril, Zoheb Hirani, Hailey F. Taylor, E. F. Babcock, Andrew T. Bockus, C. D. Varnado Jr., Christopher W. Bielawski, Adam R. Urbach

Chemistry Faculty Research

This Article describes the molecular recognition of peptides containing an N-terminal methionine (Met) by the synthetic receptor cucurbit[8]-uril (Q8) in aqueous solution and with submicromolar affinity. Prior work established that Q8 binds with high affinity to peptides containing aromatic amino acids, either by simultaneous binding of two aromatic residues, one from each of two different peptides, or by simultaneous binding of an aromatic residue and its immediate neighbor on the same peptide. The additional binding interface of two neighboring residues suggested the possibility of targeting nonaromatic peptides, which have thus far bound only weakly to synthetic receptors. A peptide library …

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Functional And Biochemical Characterization Of Dib1'S Role In Pre-Messenger Rna Splicing, Christian C. Schreib, Emily K. Bowman, Cody A. Hernandez, Amber L. Lucas, Camile H. S. Potts, Corina Maeder May 2018

Functional And Biochemical Characterization Of Dib1'S Role In Pre-Messenger Rna Splicing, Christian C. Schreib, Emily K. Bowman, Cody A. Hernandez, Amber L. Lucas, Camile H. S. Potts, Corina Maeder

Chemistry Faculty Research

The spliceosome is a dynamic macromolecular machine that undergoes a series of conformational rearrangements as it transitions between the several states required for accurate splicing. The transition from the B to Bact is a key part of spliceosome assembly and is defined by the departure of several proteins, including essential U5 component Dib1. Recent structural studies suggest that Dib1 has a role in preventing premature spliceosome activation, as it is positioned adjacent to the U6 snRNA ACAGAGA and the U5 loop I, but its mechanism is unknown. Our data indicate that Dib1 is a robust protein that tolerates incorporation of …

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Factors Affecting The Association Of Single- And Double-Stranded Rnas With Montmorillonite Nanoclays, A. Gujjari, B. V. Rodriguez, J. Pescador, Corina Maeder, G. W. Beall, L. K. Lewis Apr 2018

Factors Affecting The Association Of Single- And Double-Stranded Rnas With Montmorillonite Nanoclays, A. Gujjari, B. V. Rodriguez, J. Pescador, Corina Maeder, G. W. Beall, L. K. Lewis

Chemistry Faculty Research

Montmorillonite (MMT) nanoclays exist as single and stacked sheet-like structures with large surface areas that can form stable associations with many naturally occurring biomolecules, including nucleic acids. They have been utilized successfully as vehicles for delivery of both drugs and genes into cells. Most previous studies have focused on interactions of MMT with DNA. In the current study, we have investigated the binding of small RNAs similar to those used for RNA interference (RNAi) therapy to two major forms of the clay, Na-MMT and Ca-MMT. Association of both forms of MMT with several double-stranded RNAs (dsRNAs), including 25mers, 54mers and …

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Investigation On The Reactivity Of Tetranuclear Group 7/8 Mixed-Metal Clusters Toward Triphenylphosphine, Md. Rassel Moni, Md. Jadu Mia, Shishir Ghosh, Derek A. Tocher, Shaikh M. Mobin, Tasneem A. Siddiquee, Shariff E. Kabir Mar 2018

Investigation On The Reactivity Of Tetranuclear Group 7/8 Mixed-Metal Clusters Toward Triphenylphosphine, Md. Rassel Moni, Md. Jadu Mia, Shishir Ghosh, Derek A. Tocher, Shaikh M. Mobin, Tasneem A. Siddiquee, Shariff E. Kabir

Chemistry Faculty Research

Reactions of the tetranuclear mixed-metal clusters ReM3(CO)13(µ3-thpymS) (1, M = Os; 2, M = Ru; thpymSH = tetrahydropyrimidine-2-thiol) with PPh3 are examined. At room temperature reaction between 1 and PPh3 in the presence Me3NO leads to the formation of mono- and bis-phosphine substituted clusters ReOs3(CO)12(PPh3)(µ3-thpymS) (3) and ReOs3(CO)11(PPh3)2(µ3-thpymS) (4). Cluster 3 also reacts with PPh3 under similar conditions to give 4. In contrast, a similar reaction between 2 and PPh3 furnishes only the mono-phosphine substituted clusters ReRu3(CO)12(PPh3)(µ3-thpymS) (3). All the new clusters have been characterized by analytical and spectroscopic data together with single crystal X-ray diffraction for 1, 3 and …

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Evaluating Differences In The Active-Site Electronics Of Supported Au Nanoparticle Catalysts Using Hammett And Dft Studies, G. Kumar, Luke Tibbitts, Jaclyn Newell, Basu Panthi, Ahana Mukhopadhyay, Robert M. Rioux, Christopher J. Pursell, M. Janik, Bert D. Chandler Mar 2018

Evaluating Differences In The Active-Site Electronics Of Supported Au Nanoparticle Catalysts Using Hammett And Dft Studies, G. Kumar, Luke Tibbitts, Jaclyn Newell, Basu Panthi, Ahana Mukhopadhyay, Robert M. Rioux, Christopher J. Pursell, M. Janik, Bert D. Chandler

Chemistry Faculty Research

Supported metal catalysts, which are composed of metal nanoparticles dispersed on metal oxides or other high-surface-area materials, are ubiquitous in industrially catalysed reactions. Identifying and characterizing the catalytic active sites on these materials still remains a substantial challenge, even though it is required to guide rational design of practical heterogeneous catalysts. Metal-support interactions have an enormous impact on the chemistry of the catalytic active site and can determine the optimum support for a reaction; however, few direct probes of these interactions are available. Here we show how benzyl alcohol oxidation Hammett studies can be used to characterize differences in the …

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Polysaccharide-Mediated Synthesis Of Melanins From Serotonin And Other 5-Hydroxy Indoles, Koen Vercruysse, Astiney Clark, Noor Alattas, Dylan Brooks, Nafisa Hamza, Margaret Whalen Jan 2018

Polysaccharide-Mediated Synthesis Of Melanins From Serotonin And Other 5-Hydroxy Indoles, Koen Vercruysse, Astiney Clark, Noor Alattas, Dylan Brooks, Nafisa Hamza, Margaret Whalen

Chemistry Faculty Research

Aim: As a continuation of our research on the melanin formation from catecholamines, we studied the polysaccharide-mediated oxidation of serotonin and other 5-hydroxy indoles into melanin-like materials. As for the catecholamines, we observed that many polysaccharides promote the oxidation of such compounds, particularly in the presence of Cu2+. Methodology: The reactions were monitored using reverse phase-HPLC and size-exclusion chromatography techniques. Melanin-like materials were purified through dialysis and characterized using UV-Vis and Fourier transform IR spectroscopic techniques. Results: One such material, synthesized from chondroitin sulfate type A and serotonin in the presence of Cu2+ was found to affect …

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Chalcogen Impact On Covalency Within Molecular [Cu3(Μ3-E)]3+ Clusters (E = O, S, Se): A Synthetic, Spectroscopic, And Computational Study, B. J. Cook, G. N. Di Francesco, R. B. Ferreira, J. T. Lukens, K. E. Silberstein, B. C. Keegan, V. J. Catalano, K. M. Lancaster, Jason M. Shearer, L. J. Murray Jan 2018

Chalcogen Impact On Covalency Within Molecular [Cu3(Μ3-E)]3+ Clusters (E = O, S, Se): A Synthetic, Spectroscopic, And Computational Study, B. J. Cook, G. N. Di Francesco, R. B. Ferreira, J. T. Lukens, K. E. Silberstein, B. C. Keegan, V. J. Catalano, K. M. Lancaster, Jason M. Shearer, L. J. Murray

Chemistry Faculty Research

Reaction of the tricopper(I)-dinitrogen tris(β-diketiminate) cyclophane, Cu3(N2)L, with O-atom-transfer reagents or elemental Se affords the oxido-bridged tricopper complex Cu3(μ3-O)L (2) or the corresponding Cu3(μ3-Se)L (4), respectively. For 2 and 4, incorporation of the bridging chalcogen donor was supported by electrospray ionization mass spectrometry and K-edge X-ray absorption spectroscopy (XAS) data. Cu L2,3-edge X-ray absorption data quantify 49.5% Cu 3d character in the lowest unoccupied molecular orbital of 2, with Cu 3d participation decreasing to 33.0% in 4 and 40.8% in the related sulfide cluster Cu3 …

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Gum Arabic Promotes Oxidation And Ester Hydrolysis, Koen P. Vercruysse, Lauren E. Tyler, Jade Readus Oct 2017

Gum Arabic Promotes Oxidation And Ester Hydrolysis, Koen P. Vercruysse, Lauren E. Tyler, Jade Readus

Chemistry Faculty Research

We studied the interactions between gum Arabic and select catecholic compounds like caffeic acid, chlorogenic acid and catechol. We observed that GA is capable of promoting the auto-oxidation of the above-mentioned compounds into darkly colored pigments without the addition of redox-sensitive cations. Gum Arabic appeared to be unique among polysaccharide-based materials as many other types of polysaccharides promote the oxidation of the above-mentioned compounds only in the presence of redox cations like Fe2+ or Cu2+. RP-HPLC and SEC chromatographic techniques were employed to monitor the reactions and to observe the formation of high molecular mass, pigmented materials from gum Arabic …

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Identification Of Hydrated And Dehydrated Lipids And Protein Secondary Structures In Seeds Of Cotton (Gossypium Hirsutum) Line, Diwas Kumar Silwal, Nsoki Phambu, Bharat Pokharel, Ahmad Naseer Aziz Aug 2017

Identification Of Hydrated And Dehydrated Lipids And Protein Secondary Structures In Seeds Of Cotton (Gossypium Hirsutum) Line, Diwas Kumar Silwal, Nsoki Phambu, Bharat Pokharel, Ahmad Naseer Aziz

Chemistry Faculty Research

Cottonseeds from two parents (TM-1 and 3-79) and their 17 progeny (chromosomal substitution) lines were analyzed for various secondary structures of proteins and moisture content of lipids, separately in hulls and kernels. Fourier transform infrared spectroscopy (FTIR) was used on mature seeds from Upland cotton (G. hirsutum) progeny lines and parents. Based on secondary structures of proteins and hydration levels of lipids, differences were observed among the cottonseeds. The two progeny lines – CS-B12sh and CS-B22sh retained lipid moisture content and protein secondary structures similar to both parents, while CS-B06, CS-B15sh and CS-B16 remained distinct from either parent. On the …

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Strong Metal-Support Interactions: An Extra Layer Of Complexity, Bert D. Chandler Feb 2017

Strong Metal-Support Interactions: An Extra Layer Of Complexity, Bert D. Chandler

Chemistry Faculty Research

Strong interactions between oxide supports and catalytic metal particles can lead to inhibitive oxide layers forming over the active metal catalyst. Now, adsorbate-induced metal–support interactions have been shown to lead to a porous overlayer in the Rh/TiO2 system that tunes catalyst activity, improving its selectivity for the partial reduction of CO2.

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