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Articles 1 - 30 of 78
Full-Text Articles in Chemistry
Thioester Synthesis By A Designed Nickel Enzyme Models Prebiotic Energy Conversion, A. C. Manesis, A. Yerbulekova, Jason M. Shearer, H. S. Shafaat
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 …
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
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 …
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
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 …
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
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 …
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
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) …
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
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 …
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
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 …
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
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 …
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
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 …
Ph Dependent Reversible Formation Of A Binuclear Ni2 Metal-Center Within A Peptide Scaffold, Breena C. Keegan, Daniel Ocampo, Jason M. Shearer
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, …
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
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 …
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
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 …
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
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 …
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
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 …
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
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 …
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
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 …
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
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 …
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
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 …
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
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 …
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
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 …
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
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 …
Strong Metal-Support Interactions: An Extra Layer Of Complexity, Bert D. Chandler
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.
Cucurbit[7]Uril-Tetramethylrhodamine Conjugate For Direct Sensing And Cellular Imaging, Andrew T. Bockus, Lauren C. Smith, Amy G. Grice, Omar A. Ali, Carolyn C. Young, William Mobley, Ashley Leek, James Lewis Roberts, Brittany Vinciguerra, Lyle D. Isaacs, Adam R. Urbach
Cucurbit[7]Uril-Tetramethylrhodamine Conjugate For Direct Sensing And Cellular Imaging, Andrew T. Bockus, Lauren C. Smith, Amy G. Grice, Omar A. Ali, Carolyn C. Young, William Mobley, Ashley Leek, James Lewis Roberts, Brittany Vinciguerra, Lyle D. Isaacs, Adam R. Urbach
Chemistry Faculty Research
This paper describes the design and synthesis of a conjugate (Q7R) comprising the synthetic host cucurbit[7]uril (Q7) linked to the fluorescent dye tetramethylrhodamine (TMR), and the characterization of its optical and guest-binding properties as well as its cellular uptake. Q7R was synthesized in two steps from monofunctionalized azidobutyl-Q7 and NHS-activated TMR. The fluorescence of Q7R is quenched upon guest binding, and this observable was used to determine equilibrium dissociation constant (Kd) values. Unexpectedly, the Kd values for guests binding to Q7R and to unmodified Q7 were essentially identical. Therefore, Q7R can directly report binding to Q7 without …
Water-Assisted Oxygen Activation During Selective Oxidation Reactions, Hung-Vu Tran, Hieu A. Doan, Bert D. Chandler, Lars C. Grabow
Water-Assisted Oxygen Activation During Selective Oxidation Reactions, Hung-Vu Tran, Hieu A. Doan, Bert D. Chandler, Lars C. Grabow
Chemistry Faculty Research
The selective functionalization of hydrocarbons with oxygen to produce valuable commodity chemicals is inherently challenging, because of the thermodynamic stability of the complete combustion products. Emerging green synthesis routes and sustainable energy production also rely on the success of selective oxidation reactions. As one of the unselective by-products, water is always present under reaction conditions and numerous studies indicate that the catalytic activity and selectivity of selective oxidation reactions may be tuned by judiciously controlling the water content during the reaction. Some experimentally verified examples include the preferential oxidation of carbon monoxide, direct hydrogen peroxide synthesis, propene epoxidation and alcohol …
Controlling Activity And Selectivity Using Water In The Au-Catalysed Preferential Oxidation Of Co In H2, Johnny Saavedra, Todd N. Whittaker, Z. Chen, Christopher J. Pursell, R. M. Rioux, Bert D. Chandler
Controlling Activity And Selectivity Using Water In The Au-Catalysed Preferential Oxidation Of Co In H2, Johnny Saavedra, Todd N. Whittaker, Z. Chen, Christopher J. Pursell, R. M. Rioux, Bert D. Chandler
Chemistry Faculty Research
Industrial hydrogen production through methane steam reforming exceeds 50 million tons annually and accounts for 2–5% of global energy consumption. The hydrogen product, even after processing by the water–gas shift, still typically contains ∼1% CO, which must be removed for many applications. Methanation (CO + 3H2 → CH4 + H2O) is an effective solution to this problem, but consumes 5–15% of the generated hydrogen. The preferential oxidation (PROX) of CO with O2 in hydrogen represents a more-efficient solution. Supported gold nanoparticles, with their high CO-oxidation activity and notoriously low hydrogenation activity, have long been examined …
Identification Of Rnase-Resistant Rnas In Saccharomyces Cerevisiae Extracts: Separation From Chromosomal Dna By Selective Precipitation, Blanca V. Rodriguez, Eric T. Malczewskyj, Joshua M. Cabiya, L Kevin Lewis, Corina Maeder
Identification Of Rnase-Resistant Rnas In Saccharomyces Cerevisiae Extracts: Separation From Chromosomal Dna By Selective Precipitation, Blanca V. Rodriguez, Eric T. Malczewskyj, Joshua M. Cabiya, L Kevin Lewis, Corina Maeder
Chemistry Faculty Research
High-quality chromosomal DNA is a requirement for many biochemical and molecular biological techniques. To isolate cellular DNA, standard protocols typically lyse cells and separate nucleic acids from other biological molecules using a combination of chemical and physical methods. After a standard chemical-based protocol to isolate chromosomal DNA from Saccharomyces cerevisiae and then treatment with RNase A to degrade RNA, two RNase-resistant bands persisted when analyzed using gel electrophoresis. Interestingly, such resistant bands did not appear in preparations of Escherichia coli bacterial DNA after RNase treatment. Several enzymatic, chemical, and physical methods were employed in an effort to remove the resistant …
Small Molecule Proteostasis Regulators That Reprogram The Er To Reduce Extracellular Protein Aggregation, L. Plate, Christina B. Cooley, J. J. Chen, R. J. Paxman, C. M. Gallagher, F. Madoux, J. C. Genereux, W. Dobbs, D. Garza, T. P. Spicer, L. Scampavia, S. J. Brown, H. Rosen, E. T. Powers, P. Hodder, R. L. Wiseman, J. W. Kelly
Small Molecule Proteostasis Regulators That Reprogram The Er To Reduce Extracellular Protein Aggregation, L. Plate, Christina B. Cooley, J. J. Chen, R. J. Paxman, C. M. Gallagher, F. Madoux, J. C. Genereux, W. Dobbs, D. Garza, T. P. Spicer, L. Scampavia, S. J. Brown, H. Rosen, E. T. Powers, P. Hodder, R. L. Wiseman, J. W. Kelly
Chemistry Faculty Research
Imbalances in endoplasmic reticulum (ER) proteostasis are associated with etiologically-diverse degenerative diseases linked to excessive extracellular protein misfolding and aggregation. Reprogramming of the ER proteostasis environment through genetic activation of the Unfolded Protein Response (UPR)-associated transcription factor ATF6 attenuates secretion and extracellular aggregation of amyloidogenic proteins. Here, we employed a screening approach that included complementary arm-specific UPR reporters and medium-throughput transcriptional profiling to identify non-toxic small molecules that phenocopy the ATF6-mediated reprogramming of the ER proteostasis environment. The ER reprogramming afforded by our molecules requires activation of endogenous ATF6 and occurs independent of global ER stress. Furthermore, our molecules phenocopy …
Sequence-Specific, Nanomolar Peptide Binding Via Cucurbit[8]Uril-Induced Folding And Inclusion Of Neighboring Side Chains, Lauren C. Smith, David G. Leach, Brittney E. Blaylock, Omar A. Ali, Adam R. Urbach
Sequence-Specific, Nanomolar Peptide Binding Via Cucurbit[8]Uril-Induced Folding And Inclusion Of Neighboring Side Chains, Lauren C. Smith, David G. Leach, Brittney E. Blaylock, Omar A. Ali, Adam R. Urbach
Chemistry Faculty Research
This paper describes the molecular recognition of the tripeptide Tyr-Leu-Ala by the synthetic receptor cucurbit[8]uril (Q8) in aqueous buffer with nanomolar affinity and exceptional specificity. This combination of characteristics, which also applies to antibodies, is desirable for applications in biochemistry and biotechnology but has eluded supramolecular chemists for decades. Building on prior knowledge that Q8 binds to peptides with N-terminal aromatic residues, a library screen of 105 peptides was designed to test the effects of residues adjacent to N-terminal Trp, Phe, or Tyr. The screen used tetramethylbenzobis(imidazolium) (MBBI) as a fluorescent indicator and resulted in the unexpected discovery that MBBI …
Impact Of Size, Secondary Structure, And Counterions On The Binding Of Small Ribonucleic Acids To Layered Double Hydroxide Nanoparticles, B. V. Rodriguez, J. Pescador, N. Pollok, G. W. Beall, Corina Maeder, L. K. Lewis
Impact Of Size, Secondary Structure, And Counterions On The Binding Of Small Ribonucleic Acids To Layered Double Hydroxide Nanoparticles, B. V. Rodriguez, J. Pescador, N. Pollok, G. W. Beall, Corina Maeder, L. K. Lewis
Chemistry Faculty Research
Use of ribonucleic acid (RNA) interference to regulate protein expression has become an important research topic and gene therapy tool, and therefore, finding suitable vehicles for delivery of small RNAs into cells is of crucial importance. Layered double metal hydroxides such as hydrotalcite (HT) have shown great promise as nonviral vectors for transport of deoxyribose nucleic acid (DNA), proteins, and drugs into cells, but the adsorption of RNAs to these materials has been little explored. In this study, the binding of small RNAs with different lengths and levels of secondary structure to HT nanoparticles has been analyzed and compared to …
The Critical Role Of Water At The Gold-Titania Interface In Catalytic Co Oxidation, Johnny Saavedra, H. Doan, Christopher J. Pursell, L. C. Grabow, Bert D. Chandler
The Critical Role Of Water At The Gold-Titania Interface In Catalytic Co Oxidation, Johnny Saavedra, H. Doan, Christopher J. Pursell, L. C. Grabow, Bert D. Chandler
Chemistry Faculty Research
We provide direct evidence of a water-mediated reaction mechanism for room-temperature CO oxidation over Au/TiO2 catalysts. A hydrogen/deuterium kinetic isotope effect of nearly 2 implicates O-H(D) bond breaking in the rate-determining step. Kinetics and in situ infrared spectroscopy experiments showed that the coverage of weakly adsorbed water on TiO2 largely determines catalyst activity by changing the number of active sites. Density functional theory calculations indicated that proton transfer at the metal-support interface facilitates O2 binding and activation; the resulting Au-OOH species readily reacts with adsorbed Au-CO, yielding Au-COOH. Au-COOH decomposition involves proton transfer to water and was suggested to be …