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Articles 1 - 17 of 17
Full-Text Articles in Chemistry
Oh Chemistry Of Non-Methane Organic Gases (Nmogs) Emitted From Laboratory And Ambient Biomass Burning Smoke: Evaluating The Influence Of Furans And Oxygenated Aromatics On Ozone And Secondary Nmog Formation, Matthew M. Coggon, Christopher Y. Lim, Abigail R. Koss, Kanako Sekimoto, Bin Yuan, Jessica B. Gilman, David H. Hagan, Vanessa Selimovic, Kyle J. Zarzana, Steven S. Brown, James M Roberts, Markus Müller, Robert Yokelson, Armin Wisthaler, Jordan E. Krechmer, Jose L. Jimenez, Christopher Cappa, Jesse H. Kroll, Joost De Gouw, Carsten Warneke
Oh Chemistry Of Non-Methane Organic Gases (Nmogs) Emitted From Laboratory And Ambient Biomass Burning Smoke: Evaluating The Influence Of Furans And Oxygenated Aromatics On Ozone And Secondary Nmog Formation, Matthew M. Coggon, Christopher Y. Lim, Abigail R. Koss, Kanako Sekimoto, Bin Yuan, Jessica B. Gilman, David H. Hagan, Vanessa Selimovic, Kyle J. Zarzana, Steven S. Brown, James M Roberts, Markus Müller, Robert Yokelson, Armin Wisthaler, Jordan E. Krechmer, Jose L. Jimenez, Christopher Cappa, Jesse H. Kroll, Joost De Gouw, Carsten Warneke
Chemistry and Biochemistry Faculty Publications
Chamber oxidation experiments conducted at the Fire Sciences Laboratory in 2016 are evaluated to identify important chemical processes contributing to the hydroxy radical (OH) chemistry of biomass burning non-methane organic gases (NMOGs). Based on the decay of primary carbon measured by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS), it is confirmed that furans and oxygenated aromatics are among the NMOGs emitted from western United States fuel types with the highest reactivities towards OH. The oxidation processes and formation of secondary NMOG masses measured by PTR-ToF-MS and iodide-clustering time-of-flight chemical ionization mass spectrometry (I-CIMS) is interpreted using a box model employing …
Isotopic Characterization Of Nitrogen Oxides (NoX), Nitrous Acid (Hono), And Nitrate (PNo3-) From Laboratory Biomass Burning During Firex, Jiajue Chai, David J. Miller, Eric Scheuer, Jack Dibb, Vanessa Selimovic, Robert Yokelson, Kyle K. Zarzana, Steven Brown, Abigail R. Koss, Carsten Warneke, Meredith Hastings
Isotopic Characterization Of Nitrogen Oxides (NoX), Nitrous Acid (Hono), And Nitrate (PNo3-) From Laboratory Biomass Burning During Firex, Jiajue Chai, David J. Miller, Eric Scheuer, Jack Dibb, Vanessa Selimovic, Robert Yokelson, Kyle K. Zarzana, Steven Brown, Abigail R. Koss, Carsten Warneke, Meredith Hastings
Chemistry and Biochemistry Faculty Publications
New techniques have recently been developed and applied to capture reactive nitrogen species, including nitrogen oxides (NOx D NOCNO2), nitrous acid (HONO), nitric acid (HNO3), and particulate nitrate (pNO3 ), for accurate measurement of their isotopic composition. Here, we report – for the first time – the isotopic composition of HONO from biomass burning (BB) emissions collected during the Fire Influence on Regional to Global Environments Experiment (FIREX, later evolved into FIREX-AQ) at the Missoula Fire Science Laboratory in the fall of 2016. We used our newly developed annular denuder system (ADS), which was verified to completely capture HONO associated …
Theoretical Studies Of Ir And Nmr Spectral Changes Induced By Sigma-Hole Hydrogen, Halogen, Chalcogen, Pnicogen, And Tetrel Bonds In A Model Protein Environment, Mariusz Michalczyk, Wiktor Zierkiewicz, Rafał Wysokiński, Steve Scheiner
Theoretical Studies Of Ir And Nmr Spectral Changes Induced By Sigma-Hole Hydrogen, Halogen, Chalcogen, Pnicogen, And Tetrel Bonds In A Model Protein Environment, Mariusz Michalczyk, Wiktor Zierkiewicz, Rafał Wysokiński, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
Various types of σ-hole bond complexes were formed with FX, HFY, H2FZ, and H3FT (X = Cl, Br, I; Y = S, Se, Te; Z = P, As, Sb; T = Si, Ge, Sn) as Lewis acid. In order to examine their interactions with a protein, N-methylacetamide (NMA), a model of the peptide linkage was used as the base. These noncovalent bonds were compared by computational means with H-bonds formed by NMA with XH molecules (X = F, Cl, Br, I). In all cases, the A–F bond, which lies opposite the base and is responsible for …
Anisotropic Singlet Fission In Single Crystalline Hexacene, Dezheng Sun, Gang-Hua Deng, Bolei Xu, Enshi Xu, Xia Li, Yajing Wu, Yuqin Qian, Yu Zhong, Colin Nuckolls, Avetik R. Harutyunyan, Hai-Lung Dai, Gugang Chen, Hanning Chen, Yi Rao
Anisotropic Singlet Fission In Single Crystalline Hexacene, Dezheng Sun, Gang-Hua Deng, Bolei Xu, Enshi Xu, Xia Li, Yajing Wu, Yuqin Qian, Yu Zhong, Colin Nuckolls, Avetik R. Harutyunyan, Hai-Lung Dai, Gugang Chen, Hanning Chen, Yi Rao
Chemistry and Biochemistry Faculty Publications
Singlet fission is known to improve solar energy utilization by circumventing the Shockley-Queisser limit. The two essential steps of singlet fission are the formation of a correlated triplet pair and its subsequent quantum decoherence. However, the mechanisms of the triplet pair formation and decoherence still remain elusive. Here we examined both essential steps in single crystalline hexacene and discovered remarkable anisotropy of the overall singlet fission rate along different crystal axes. Since the triplet pair formation emerges on the same timescale along both crystal axes, the quantum decoherence is likely responsible for the directional anisotropy. The distinct quantum decoherence rates …
Spectroscopic Description Of The E1 State Of Mo Nitrogenase Based On Mo And Fe X‑Ray Absorption And MöSsbauer Studies, Casey Van Stappen, Roman Davydov, Zhi-Yong Yang, Ruixi Fan, Yisong Guo, Eckhard Bill, Lance C. Seefeldt, Brian M. Hoffman, Serena Debeer
Spectroscopic Description Of The E1 State Of Mo Nitrogenase Based On Mo And Fe X‑Ray Absorption And MöSsbauer Studies, Casey Van Stappen, Roman Davydov, Zhi-Yong Yang, Ruixi Fan, Yisong Guo, Eckhard Bill, Lance C. Seefeldt, Brian M. Hoffman, Serena Debeer
Chemistry and Biochemistry Faculty Publications
Mo nitrogenase (N2ase) utilizes a two-component protein system, the catalytic MoFe and its electron-transfer partner FeP, to reduce atmospheric dinitrogen (N2) to ammonia (NH3). The FeMo cofactor contained in the MoFe protein serves as the catalytic center for this reaction and has long inspired model chemistry oriented toward activating N2. This field of chemistry has relied heavily on the detailed characterization of how Mo N2ase accomplishes this feat. Understanding the reaction mechanism of Mo N2ase itself has presented one of the most challenging problems in bioinorganic chemistry because of the ephemeral nature of its …
Nepal Ambient Monitoring And Source Testing Experiment (Namaste): Emissions Of Particulate Matter And Sulfur Dioxide From Vehicles And Brick Kilns And Their Impacts On Air Quality In The Kathmandu Valley, Nepal, Min Zhong, Eri Saikawa, Alexander Avramov, Chen Chen, Boya Sun, Wenlu Ye, William C. Keene, Robert J. Yokelson, Thilina Jayarathne, Elizabeth A. Stone, Maheswar Rupakheti, Arnico K. Panday
Nepal Ambient Monitoring And Source Testing Experiment (Namaste): Emissions Of Particulate Matter And Sulfur Dioxide From Vehicles And Brick Kilns And Their Impacts On Air Quality In The Kathmandu Valley, Nepal, Min Zhong, Eri Saikawa, Alexander Avramov, Chen Chen, Boya Sun, Wenlu Ye, William C. Keene, Robert J. Yokelson, Thilina Jayarathne, Elizabeth A. Stone, Maheswar Rupakheti, Arnico K. Panday
Chemistry and Biochemistry Faculty Publications
Air pollution is one of the most pressing environmental issues in the Kathmandu Valley, where the capital city of Nepal is located. We estimated emissions from two of the major source types in the valley (vehicles and brick kilns) and analyzed the corresponding impacts on regional air quality. First, we estimated the on-road vehicle emissions in the valley using the International Vehicle Emissions (IVE) model with local emissions factors and the latest available data for vehicle registration. We also identified the locations of the brick kilns in the Kathmandu Valley and developed an emissions inventory for these kilns using emissions …
Consumption Of Black Raspberries Altered The Composition Of The Fecal Microbiome In Mice Fed A Western Type Diet (Or04-01-19), Abby D. Benninghoff, Sumira Phatak, Korry Hintze
Consumption Of Black Raspberries Altered The Composition Of The Fecal Microbiome In Mice Fed A Western Type Diet (Or04-01-19), Abby D. Benninghoff, Sumira Phatak, Korry Hintze
Chemistry and Biochemistry Faculty Publications
Dietary strategies to reduce colonic inflammation and promote gut homeostasis may markedly reduce the risk of colitis-associated colorectal cancer. Previously, we showed that dietary supplementation with black raspberries significantly suppressed colitis and colon tumorigenesis promoted by the consumption a Western type diet in mice. In this study, our goal was to assess the impact of consumption of the TWD with and without black raspberry supplementation on the composition of the fecal microbiome over the course of disease development.
Dietary Intervention With Black Raspberries To Reduce Colitis Symptoms In Mice Fed Either Standard Ain93g Diet Or The Total Western Diet (P05-021-19), Daphne Michelle Rodriguez Jimenez, Michaela Brubaker, Elizabeth Park, Canyon Neal, Korry Hintze, Abby D. Benninghoff
Dietary Intervention With Black Raspberries To Reduce Colitis Symptoms In Mice Fed Either Standard Ain93g Diet Or The Total Western Diet (P05-021-19), Daphne Michelle Rodriguez Jimenez, Michaela Brubaker, Elizabeth Park, Canyon Neal, Korry Hintze, Abby D. Benninghoff
Chemistry and Biochemistry Faculty Publications
Approximately 1.4 million people suffer from inflammatory bowel disease, which is a major risk factor for developing colitis associated colorectal cancer (CAC). Dietary interventions with the goal to reduce colon inflammation and encourage gut microbiome homeostasis may be a strategy to reduce the risk of CAC. The antioxidants and anti-inflammatory compounds present in black raspberries (BRB) have demonstrated protective effects in the colon epithelium and may alter the composition of the gut microbiome. Previously, we showed that dietary supplementation with black raspberries significantly suppressed colitis and colon tumorigenesis promoted by the consumption of a Western type diet in mice. The …
Interactions Of (My) 6 (M = Zn, Cd; Y = O, S, Se) Quantum Dots With N-Bases, Mariusz Michalczyk, Wiktor Zierkiewicz, Steve Scheiner
Interactions Of (My) 6 (M = Zn, Cd; Y = O, S, Se) Quantum Dots With N-Bases, Mariusz Michalczyk, Wiktor Zierkiewicz, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
(MY)6 clusters, with M = Zn and Cd and Y = O, S, Se, form double-layer drum-like structures containing M–Y covalent bonds. The positive regions near the M atoms attract the N atom of both NH3 and NMe3 so as to form a noncovalent M···N bond. This bond is quite strong, with interaction energies exceeding 35 kcal/mol. The bond strength diminishes with reduced electronegativity of the Y atom (O > S > Se) and is stronger for M = Zn than for Cd. Trimethylation of the base enhances the bond strength. The interaction is dominated by the electrostatic component …
Production Of Secondary Organic Aerosol During Aging Of Biomass Burning Smoke From Fresh Fuels And Its Relationship To Voc Precursors, A. T. Ahern, E. S. Robinson, D. S. Tkacik, R. Saleh, L. E. Hatch, K. C. Barsanti, C. E. Stockwell, R. J. Yokelson, A. A. Presto, A. L. Robinson, R. C. Sullivan, N. M. Donahue
Production Of Secondary Organic Aerosol During Aging Of Biomass Burning Smoke From Fresh Fuels And Its Relationship To Voc Precursors, A. T. Ahern, E. S. Robinson, D. S. Tkacik, R. Saleh, L. E. Hatch, K. C. Barsanti, C. E. Stockwell, R. J. Yokelson, A. A. Presto, A. L. Robinson, R. C. Sullivan, N. M. Donahue
Chemistry and Biochemistry Faculty Publications
After smoke from burning biomass is emitted into the atmosphere, chemical and physical processes change the composition and amount of organic aerosol present in the aged, diluted plume. During the fourth Fire Lab at Missoula Experiment, we performed smog-chamber experiments to investigate formation of secondary organic aerosol (SOA) and multiphase oxidation of primary organic aerosol (POA). We simulated atmospheric aging of diluted smoke from a variety of biomass fuels while measuring particle composition using high-resolution aerosol mass spectrometry. We quantified SOA formation using a tracer ion for low-volatility POA as a reference standard (akin to a naturally occurring internal standard). …
In Situ Measurements Of Trace Gases, Pm, And Aerosol Optical Properties During The 2017 Nw Us Wildfire Smoke Event, Vanessa Selimovic, Robert J. Yokelson, Gavin R. Mcmeeking, Sarah Coefield
In Situ Measurements Of Trace Gases, Pm, And Aerosol Optical Properties During The 2017 Nw Us Wildfire Smoke Event, Vanessa Selimovic, Robert J. Yokelson, Gavin R. Mcmeeking, Sarah Coefield
Chemistry and Biochemistry Faculty Publications
In mid-August through mid-September of 2017 a major wildfire smoke and haze episode strongly impacted most of the NW US and SW Canada. During this period our ground-based site in Missoula, Montana, experienced heavy smoke impacts for ∼ 500h (up to 471μ-3 hourly average PM2.5). We measured wildfire trace gases, PM2.5 (particulate matter ≤2.5μm in diameter), and black carbon and submicron aerosol scattering and absorption at 870 and 401nm. This may be the most extensive real-time data for these wildfire smoke properties to date. Our range of trace gas ratios for δNH3 δCO and δC2H4 δCO confirmed that the smoke …
Molecular Rotation In 3 Dimensions At An Air/Water Interface Using Femtosecond Time Resolved Sum Frequency Generation, Yi Rao, Yuqin Qian, Gang-Hua Deng, Ashlie Kinross, Nicholas J. Turro, Kenneth B. Eisenthal
Molecular Rotation In 3 Dimensions At An Air/Water Interface Using Femtosecond Time Resolved Sum Frequency Generation, Yi Rao, Yuqin Qian, Gang-Hua Deng, Ashlie Kinross, Nicholas J. Turro, Kenneth B. Eisenthal
Chemistry and Biochemistry Faculty Publications
This paper presents the first study of the rotations of rigid molecules in 3 dimensions at the air/water interface, using the femtosecond time resolved sum frequency generation (SFG) technique. For the purpose of this research, the aromatic dye molecule C153 was chosen as an example of a molecule having two functional groups that are SFG active, one being the hydrophilic −−C==O group and the other the hydrophobic −−CF3 group. From polarized SFG measurements, the orientations of the two chromophores with respect to the surface normal were obtained. On combining these results with the known relative orientation of the two …
Transition State Interactions In A Promiscuous Enzyme: Sulfate And Phosphate Monoester Hydrolysis By Pseudomonas Aeruginosa Arylsulfatase, Bert Van Loo, Ryan Berry, Usa Boonyuen, Mark F. Mohamed, Marko Golicnik, Alvan C. Hengge, Florian Hollfelder
Transition State Interactions In A Promiscuous Enzyme: Sulfate And Phosphate Monoester Hydrolysis By Pseudomonas Aeruginosa Arylsulfatase, Bert Van Loo, Ryan Berry, Usa Boonyuen, Mark F. Mohamed, Marko Golicnik, Alvan C. Hengge, Florian Hollfelder
Chemistry and Biochemistry Faculty Publications
Pseudomonas aeruginosa arylsulfatase (PAS) hydrolyses sulfate and, promiscuously, phosphate monoesters. Enzyme-catalyzed sulfate transfer is crucial to a wide variety of biological processes, but detailed studies of the mechanistic contributions to its catalysis are lacking. We present linear free energy relationships (LFERs) and kinetic isotope effects (KIEs) of PAS and active site mutants that suggest a key role for leaving group (LG) stabilization. In LFERs PASWT has a much less negative Brønsted coefficient (ßleaving group obs-Enz=-0.33) than the uncatalyzed reaction (ßleaving group obs=-1.81). This situation is diminished when cationic active site groups are exchanged for alanine. …
Catalytic Mechanism For The Conversion Of Salicylate Into Catechol By The Flavin-Dependent Monooxygenase Salicylate Hydroxylase, Débora M. A. Costa, Stefanya V. Gómez, Simara S. De Araújo, Mozart S. Pereira, Rosemeire B. Alves, Denize C. Favaro, Alvan C. Hengge, Ronaldo A. P. Nagem, Tiago A. S. Brandão
Catalytic Mechanism For The Conversion Of Salicylate Into Catechol By The Flavin-Dependent Monooxygenase Salicylate Hydroxylase, Débora M. A. Costa, Stefanya V. Gómez, Simara S. De Araújo, Mozart S. Pereira, Rosemeire B. Alves, Denize C. Favaro, Alvan C. Hengge, Ronaldo A. P. Nagem, Tiago A. S. Brandão
Chemistry and Biochemistry Faculty Publications
Salicylate hydroxylase (NahG) is a flavin-dependent monooxygenase that catalyzes the decarboxylative hydroxylation of salicylate into catechol in the naphthalene degradation pathway in Pseudomonas putida G7. We explored the mechanism of action of this enzyme in detail using a combination of structural and biophysical methods. NahG shares many structural and mechanistic features with other versatile flavin-dependent monooxygenases, with potential biocatalytic applications. The crystal structure at 2.0 Å resolution for the apo form of NahG adds a new snapshot preceding the FAD binding in flavin-dependent monooxygenases. The kcat/Km for the salicylate reaction catalyzed by the holo form is …
Speciated And Total Emission Factors Of Particulate Organics From Burning Western Us Wildland Fuels And Their Dependence On Combustion Efficiency, Coty N. Jen, Lindsay E. Hatch, Vanessa Selimovic, Robert J. Yokelson, Robert Weber, Arantza E. Fernandez, Nathan M. Kreisberg, Kelley C. Barsanti, Allen H. Goldstein
Speciated And Total Emission Factors Of Particulate Organics From Burning Western Us Wildland Fuels And Their Dependence On Combustion Efficiency, Coty N. Jen, Lindsay E. Hatch, Vanessa Selimovic, Robert J. Yokelson, Robert Weber, Arantza E. Fernandez, Nathan M. Kreisberg, Kelley C. Barsanti, Allen H. Goldstein
Chemistry and Biochemistry Faculty Publications
Western US wildlands experience frequent and large-scale wildfires which are predicted to increase in the future. As a result, wildfire smoke emissions are expected to play an increasing role in atmospheric chemistry while negatively impacting regional air quality and human health. Understanding the impacts of smoke on the environment is informed by identifying and quantifying the chemical compounds that are emitted during wildfires and by providing empirical relationships that describe how the amount and composition of the emissions change based upon different fire conditions and fuels. This study examined particulate organic compounds emitted from burning common western US wildland fuels …
Dual Geometry Schemes In Tetrel Bonds: Complexes Between Tf4(T = Si, Ge, Sn) And Pyridine Derivatives, Wiktor Zierkiewicz, Mariusz Michalczyk, Rafał Wysokiński, Steve Scheiner
Dual Geometry Schemes In Tetrel Bonds: Complexes Between Tf4(T = Si, Ge, Sn) And Pyridine Derivatives, Wiktor Zierkiewicz, Mariusz Michalczyk, Rafał Wysokiński, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
When an N-base approaches the tetrel atom of TF4(T = Si, Ge, Sn) the latter moleculedeforms from a tetrahedral structure in the monomer to a trigonal bipyramid. The base can situateitself at either an axial or equatorial position, leading to two different equilibrium geometries.The interaction energies are considerably larger for the equatorial structures, up around 50 kcal/mol,which also have a shorter R(T··N) separation. On the other hand, the energy needed to deform thetetrahedral monomer into the equatorial structure is much higher than the equivalent deformationenergy in the axial dimer. When these two opposite trends are combined, it is the axial …
Development Of Ultrafast Broadband Electronic Sum Frequency Generation For Charge Dynamics At Surfaces And Interfaces, Gang-Hua Deng, Yuqin Qian, Yi Rao
Development Of Ultrafast Broadband Electronic Sum Frequency Generation For Charge Dynamics At Surfaces And Interfaces, Gang-Hua Deng, Yuqin Qian, Yi Rao
Chemistry and Biochemistry Faculty Publications
Understandings of population and relaxation of charges at surfaces and interfaces are essential to improve charge collection efficiency for energy conversion, catalysis, and photosynthesis. Existing time-resolved surface and interface tools are limited to either under ultrahigh vacuum or in a narrow wavelength region with the loss of spectral information. There lacks an efficient time-resolved surface/interface-specific electronic spectroscopy under ambient conditions for the ultra fast surface/interface dynamics. Here we developed a novel technique for surface/interface-specific broadband electronic sum frequency generation (ESFG). The broadband ESFG was based on a stable two-stage BiB3O6 crystal-based optical parametric amplifier, which generates a …