Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Institution
- Keyword
-
- Biomass burning (12)
- NBO (6)
- Oxygenated organic compounds (5)
- AIM (4)
- Charge transfer (4)
-
- Energy decomposition (4)
- ITP (4)
- MEP (4)
- Magnetic films (4)
- Savanna fires (4)
- ITPA (3)
- Inosine (3)
- Light scattering (3)
- MP2 (3)
- Molecular electrostatic potential (3)
- Nanomagnetism (3)
- Relaxation times (3)
- Smoke (3)
- Viscosity (3)
- Ammonia (2)
- Anti-inflammatory agents (2)
- Atomic charge (2)
- Biomass fires (2)
- Coercive force (2)
- Colorectal cancer (2)
- Copper (2)
- DEE 35 (2)
- DFT (2)
- Diet therapy (2)
- Ferromagnetic resonance (2)
Articles 31 - 60 of 202
Full-Text Articles in Physical Sciences and Mathematics
Optical Stability Of 1,1′-Binaphthyl Derivatives, Nikolay V. Tkachenko, Steve Scheiner
Optical Stability Of 1,1′-Binaphthyl Derivatives, Nikolay V. Tkachenko, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
The racemization process of various 1,1′-binaphthyl derivatives is studied by quantum calculations. The preferred racemization pathway passes through a transition state belonging to the Ci symmetry group. The energy barrier for this process is independent of solvation, the electron-withdrawing/releasing power of substituents, or their ability to engage in H-bonds within the molecule. The primary factor is instead the substituent size. The barrier is thus reduced when the −OH groups of 1,1′-bi-2-naphthol are replaced by H. There is a drop in the barrier also when the substituents are moved from the 2,2′ positions to 6,6′, where they will not come …
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 …
Differential Binding Of Tetrel-Bonding Bipodal Receptors To Monatomic And Polyatomic Anions, Steve Scheiner
Differential Binding Of Tetrel-Bonding Bipodal Receptors To Monatomic And Polyatomic Anions, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
Previous work has demonstrated that a bidentate receptor containing a pair of Sn atoms can engage in very strong interactions with halide ions via tetrel bonds. The question that is addressed here concerns the possibility that a receptor of this type might be designed that would preferentially bind a polyatomic over a monatomic anion since the former might better span the distance between the two Sn atoms. The binding of Cl− was thus compared to that of HCOO−, HSO4−, and H2PO4− with a wide variety of bidentate receptors. A pair …
Carbene Triel Bonds Between Trr3 (Tr=B, Al) And N-Heterocyclic Carbenes, Zongqing Chi, Wenbo Dong, Qingzhong Li, Xin Yang, Steve Scheiner, Shufeng Liu
Carbene Triel Bonds Between Trr3 (Tr=B, Al) And N-Heterocyclic Carbenes, Zongqing Chi, Wenbo Dong, Qingzhong Li, Xin Yang, Steve Scheiner, Shufeng Liu
Chemistry and Biochemistry Faculty Publications
The carbene triel bond is predicted and characterized by theoretical calculations. The C lone pair of N‐heterocyclic carbenes (NHCs) is allowed to interact with the central triel atom of TrR3 (Tr = B and Al; R = H, F, Cl, and Br). The ensuing bond is very strong, with an interaction energy of nearly 90 kcal/mol. Replacement of the C lone pair by that of either N or Si weakens the binding. The bond is strengthened by electron‐withdrawing substituents on the triel atom, and the reverse occurs with substitution on the NHC. However, these effects do not strictly follow …
Crystallographic And Computational Characterization Of Methyl Tetrel Bonding In S-Adenosylmethionine-Dependent Methyltransferases, Raymond C. Trievel, Steve Scheiner
Crystallographic And Computational Characterization Of Methyl Tetrel Bonding In S-Adenosylmethionine-Dependent Methyltransferases, Raymond C. Trievel, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
Tetrel bonds represent a category of non-bonding interaction wherein an electronegative atom donates a lone pair of electrons into the sigma antibonding orbital of an atom in the carbon group of the periodic table. Prior computational studies have implicated tetrel bonding in the stabilization of a preliminary state that precedes the transition state in SN2 reactions, including methyl transfer. Notably, the angles between the tetrel bond donor and acceptor atoms coincide with the prerequisite geometry for the SN2 reaction. Prompted by these findings, we surveyed crystal structures of methyltransferases in the Protein Data Bank and discovered …
Dependence Of Nmr Chemical Shifts Upon Ch Bond Lengths Of A Methyl Group Involved In A Tetrel Bond, Steve Scheiner
Dependence Of Nmr Chemical Shifts Upon Ch Bond Lengths Of A Methyl Group Involved In A Tetrel Bond, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
Four different Lewis acids that might participate in a tetrel bond with a nucleophile (SEt2Me+, NMe4+, SMe2, NMe3) are examined. The NMR chemical shifts of the methyl C and H atoms are calculated as the CH bond lengths are systematically stretched and contracted, in the absence of a base. The C shielding diminishes by roughly 2 ppm for a stretch of 0.01 Å, while that of H drops by only 0.3 ppm. The deshieldings caused purely by the bond length changes are far too small to account for the …
Primary Emissions Of Glyoxal And Methylglyoxal From Laboratory Measurements Of Open Biomass Burning, Kyle J. Zarzana, Vanessa Selimovic, Abigail R. Koss, Kanako Sekimoto, Matthew M. Coggon, Bin Yuan, William P. Dubé, Robert J. Yokelson, Carsten Warneke, Joost A. De Gouw, James M. Roberts, Steven S. Brown
Primary Emissions Of Glyoxal And Methylglyoxal From Laboratory Measurements Of Open Biomass Burning, Kyle J. Zarzana, Vanessa Selimovic, Abigail R. Koss, Kanako Sekimoto, Matthew M. Coggon, Bin Yuan, William P. Dubé, Robert J. Yokelson, Carsten Warneke, Joost A. De Gouw, James M. Roberts, Steven S. Brown
Chemistry and Biochemistry Faculty Publications
We report the emissions of glyoxal and methylglyoxal from the open burning of biomass during the NOAA-led 2016 FIREX intensive at the Fire Sciences Laboratory in Missoula, MT. Both compounds were measured using cavity-enhanced spectroscopy, which is both more sensitive and more selective than methods previously used to determine emissions of these two compounds. A total of 75 burns were conducted, using 33 different fuels in 8 different categories, providing a far more comprehensive dataset for emissions than was previously available. Measurements of methylglyoxal using our instrument suffer from spectral interferences from several other species, and the values reported here …
Speciated Online Pm1 From South Asian Combustion Sources-Part 1: Fuel-Based Emission Factors And Size Distributions, J. Douglas Goetz, Michael R. Giordano, Chelsea E. Stockwell, Ted J. Christian, Rashmi Maharjan, Sagar Adhikari, Prakash V. Bhave, Puppala S. Praveen, Arnico K. Panday, Thilina Jayarathne, Elizabeth A. Stone, Robert J. Yokelson, Peter F. Decarlo
Speciated Online Pm1 From South Asian Combustion Sources-Part 1: Fuel-Based Emission Factors And Size Distributions, J. Douglas Goetz, Michael R. Giordano, Chelsea E. Stockwell, Ted J. Christian, Rashmi Maharjan, Sagar Adhikari, Prakash V. Bhave, Puppala S. Praveen, Arnico K. Panday, Thilina Jayarathne, Elizabeth A. Stone, Robert J. Yokelson, Peter F. Decarlo
Chemistry and Biochemistry Faculty Publications
Combustion of biomass, garbage, and fossil fuels in South Asia has led to poor air quality in the region and has uncertain climate forcing impacts. Online measurements of submicron aerosol (PM1) emissions were conducted as part of the Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) to investigate and report emission factors (EFs) and vacuum aerodynamic diameter (dva) size distributions from prevalent but poorly characterized combustion sources. The online aerosol instrumentation included a qmini aerosol mass spectrometer (mAMS) and a dual-spot eight-channel aethalometer (AE33). The mAMS measured non-refractory PM1 mass, composition, and size. The AE33-measured black carbon (BC) mass and …
High-And Low-Temperature Pyrolysis Profiles Describe Volatile Organic Compound Emissions From Western Us Wildfire Fuels, Kanako Sekimoto, Abigail R. Koss, Jessica B. Gilman, Vanessa Selimovic, Matthew M. Coggon, Kyle J. Zarzana, Bin Yuan, Brian M. Lerner, Steven S. Brown, Carsten Warneke, Robert J. Yokelson, James M. Roberts, Joost De Gouw
High-And Low-Temperature Pyrolysis Profiles Describe Volatile Organic Compound Emissions From Western Us Wildfire Fuels, Kanako Sekimoto, Abigail R. Koss, Jessica B. Gilman, Vanessa Selimovic, Matthew M. Coggon, Kyle J. Zarzana, Bin Yuan, Brian M. Lerner, Steven S. Brown, Carsten Warneke, Robert J. Yokelson, James M. Roberts, Joost De Gouw
Chemistry and Biochemistry Faculty Publications
Biomass burning is a large source of volatile organic compounds (VOCs) and many other trace species to the atmosphere, which can act as precursors to secondary pollutants such as ozone and fine particles. Measurements performed with a proton-transfer-reaction time-of-flight mass spectrometer during the FIREX 2016 laboratory intensive were analyzed with positive matrix factorization (PMF), in order to understand the instantaneous variability in VOC emissions from biomass burning, and to simplify the description of these types of emissions. Despite the complexity and variability of emissions, we found that a solution including just two emission profiles, which are mass spectral representations of …
Comparison Between Tetrel Bonded Complexes Stabilized By Σ And Π Hole Interactions, Wiktor Zierkiewicz, Mariusz Michalczyk, Steve Scheiner
Comparison Between Tetrel Bonded Complexes Stabilized By Σ And Π Hole Interactions, Wiktor Zierkiewicz, Mariusz Michalczyk, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
The σ-hole tetrel bonds formed by a tetravalent molecule are compared with those involving a π-hole above the tetrel atom in a trivalent bonding situation. The former are modeled by TH4, TH3F, and TH2F2 (T = Si, Ge, Sn) and the latter by TH2=CH2, THF=CH2, and TF2=CH2, all paired with NH3 as Lewis base. The latter π-bonded complexes are considerably more strongly bound, despite the near equivalence of the σ and π-hole intensities. The larger binding energies of the π-dimers are attributed to greater electrostatic attraction and orbital interaction. Each progressive replacement of H by F increases the strength of …
Characterization Of A Catalyst-Based Conversion Technique To Measure Total Particulate Nitrogen And Organic Carbon And Comparison To A Particle Mass Measurement Instrument, Chelsea E. Stockwell, Agnieszka Kupc, Bartlomiej Witkowski, Ranajit K. Talukdar, Yong Liu, Vanessa Selimovic, Kyle J. Zarzana, Kanako Sekimoto, Carsten Warneke, Rebecca A. Washenfelder, Robert J. Yokelson, Ann M. Middlebrook, James M. Roberts
Characterization Of A Catalyst-Based Conversion Technique To Measure Total Particulate Nitrogen And Organic Carbon And Comparison To A Particle Mass Measurement Instrument, Chelsea E. Stockwell, Agnieszka Kupc, Bartlomiej Witkowski, Ranajit K. Talukdar, Yong Liu, Vanessa Selimovic, Kyle J. Zarzana, Kanako Sekimoto, Carsten Warneke, Rebecca A. Washenfelder, Robert J. Yokelson, Ann M. Middlebrook, James M. Roberts
Chemistry and Biochemistry Faculty Publications
The chemical composition of aerosol particles is a key aspect in determining their impact on the environment. For example, nitrogen-containing particles impact atmospheric chemistry, air quality, and ecological N deposition. Instruments that measure total reactive nitrogen (Nr Combining double low line all nitrogen compounds except for N2 and N2O) focus on gas-phase nitrogen and very few studies directly discuss the instrument capacity to measure the mass of Nr-containing particles. Here, we investigate the mass quantification of particle-bound nitrogen using a custom Nr system that involves total conversion to nitric oxide (NO) across platinum and molybdenum catalysts followed by NOĝ'O3 chemiluminescence …
Organic Compound Emissions From A Landfarm Used For Oil And Gas Solid Waste Disposal, Seth N. Lyman, Marc L. Mansfield
Organic Compound Emissions From A Landfarm Used For Oil And Gas Solid Waste Disposal, Seth N. Lyman, Marc L. Mansfield
Chemistry and Biochemistry Faculty Publications
Solid or sludgy hydrocarbon waste is a byproduct of oil and gas exploration and production. One commonly-used method of disposing of this waste is landfarming. Landfarming involves spreading hydrocarbon waste on soils, tilling it into the soil, and allowing it to biodegrade. We used a dynamic flux chamber to measure fluxes of methane, a suite of 54 non-methane hydrocarbons, and light alcohols from an active and a remediated landfarm in eastern Utah, U.S.A. Fluxes from the remediated landfarm were not different from a PTFE sheet or from undisturbed soils in the region. Fluxes of methane, total non-methane hydrocarbons, and alcohols …
Structure Of Frequency-Interacting Rna Helicase From Neurospora Crassa Reveals High Flexibility In A Domain Critical For Circadian Rhythm And Rna Surveillance, Yalemi Morales, Keith J. Olsen, Jacqueline M. Bulcher, Sean J. Johnson
Structure Of Frequency-Interacting Rna Helicase From Neurospora Crassa Reveals High Flexibility In A Domain Critical For Circadian Rhythm And Rna Surveillance, Yalemi Morales, Keith J. Olsen, Jacqueline M. Bulcher, Sean J. Johnson
Chemistry and Biochemistry Faculty Publications
The FRH (frequency-interacting RNA helicase) protein is the Neurospora crassa homolog of yeast Mtr4, an essential RNA helicase that plays a central role in RNA metabolism as an activator of the nuclear RNA exosome. FRH is also a required component of the circadian clock, mediating protein interactions that result in the rhythmic repression of gene expression. Here we show that FRH unwinds RNA substrates in vitro with a kinetic profile similar to Mtr4, indicating that while FRH has acquired additional functionality, its core helicase function remains intact. In contrast with the earlier FRH structures, a new crystal form of FRH …
Magnetic Properties Of Acenes And Their O-Quinone Derivatives: Computer Simulation, A. A. Starikova, A. G. Starikov, R. M. Minyaev, Alexander I. Boldyrev, V. I. Minkin
Magnetic Properties Of Acenes And Their O-Quinone Derivatives: Computer Simulation, A. A. Starikova, A. G. Starikov, R. M. Minyaev, Alexander I. Boldyrev, V. I. Minkin
Chemistry and Biochemistry Faculty Publications
Quantum chemical study (DFT UB3LYP/6-311++G(d,p)) of the structure and properties of acenes functionalized with two o-benzoquinone groups and their complexes with sodium cations has been performed. An increase in the number of fused rings has been shown to result in the stabilization of biradicaloid state of acenes and the switching of the character of exchange interactions between redox-active moieties from antiferromagnetic to ferromagnetic. The obtained results allow one to consider o-quinone acene derivatives as a basis for designing magnetoactive compounds.
Mxin Differentially Regulates Monomeric And Oligomeric Species Of The Shigella Type Three Secretion System Atpase Spa47, Heather B. Case, Nicholas E. Dickenson
Mxin Differentially Regulates Monomeric And Oligomeric Species Of The Shigella Type Three Secretion System Atpase Spa47, Heather B. Case, Nicholas E. Dickenson
Chemistry and Biochemistry Faculty Publications
Shigella rely entirely on the action of a single type three secretion system (T3SS) to support cellular invasion of colonic epithelial cells and to circumvent host immune responses. The ATPase Spa47 resides at the base of the Shigella needle-like type three secretion apparatus (T3SA), supporting protein secretion through the apparatus and providing a likely means for native virulence regulation by Shigella and a much needed target for non-antibiotic therapeutics to treat Shigella infections. Here, we show that MxiN is a differential regulator of Spa47 and that its regulatory impact is determined by the oligomeric state of the Spa47 ATPase, with …
Non-Methane Organic Gas Emissions From Biomass Burning: Identification, Quantification, And Emission Factors From Ptr-Tof During The Firex 2016 Laboratory Experiment, Abigail R. Koss, Kanako Sekimoto, Jessica B. Gilman, Vanessa Selimovic, Matthew M. Coggon, Kyle J. Zarzana, Bin Yuan, Brian M. Lerner, Steven S. Brown, Jose L. Jimenez, Jordan Krechmer, James M. Roberts, Carsten Warneke, Robert J. Yokelson, Joost De Gouw
Non-Methane Organic Gas Emissions From Biomass Burning: Identification, Quantification, And Emission Factors From Ptr-Tof During The Firex 2016 Laboratory Experiment, Abigail R. Koss, Kanako Sekimoto, Jessica B. Gilman, Vanessa Selimovic, Matthew M. Coggon, Kyle J. Zarzana, Bin Yuan, Brian M. Lerner, Steven S. Brown, Jose L. Jimenez, Jordan Krechmer, James M. Roberts, Carsten Warneke, Robert J. Yokelson, Joost De Gouw
Chemistry and Biochemistry Faculty Publications
Volatile and intermediate-volatility non-methane organic gases (NMOGs) released from biomass burning were measured during laboratory-simulated wildfires by proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF). We identified NMOG contributors to more than 150 PTR ion masses using gas chromatography (GC) pre-separation with electron ionization, H3O+ chemical ionization, and NO+ chemical ionization, an extensive literature review, and time series correlation, providing higher certainty for ion identifications than has been previously available. Our interpretation of the PTR-ToF mass spectrum accounts for nearly 90ĝ€-% of NMOG mass detected by PTR-ToF across all fuel types. The relative contributions of different NMOGs to individual exact ion masses are …
Aerosol Optical Properties And Trace Gas Emissions By Pax And Op-Ftir For Laboratory-Simulated Western Us Wildfires During Firex, Vanessa Selimovic, Robert J. Yokelson, Carsten Warneke, James M. Roberts, Joost De Gouw, James Reardon, David W.T. Griffith
Aerosol Optical Properties And Trace Gas Emissions By Pax And Op-Ftir For Laboratory-Simulated Western Us Wildfires During Firex, Vanessa Selimovic, Robert J. Yokelson, Carsten Warneke, James M. Roberts, Joost De Gouw, James Reardon, David W.T. Griffith
Chemistry and Biochemistry Faculty Publications
Western wildfires have a major impact on air quality in the US. In the fall of 2016, 107 test fires were burned in the large-scale combustion facility at the US Forest Service Missoula Fire Sciences Laboratory as part of the Fire Influence on Regional and Global Environments Experiment (FIREX). Canopy, litter, duff, dead wood, and other fuel components were burned in combinations that represented realistic fuel complexes for several important western US coniferous and chaparral ecosystems including ponderosa pine, Douglas fir, Engelmann spruce, lodgepole pine, subalpine fir, chamise, and manzanita. In addition, dung, Indonesian peat, and individual coniferous ecosystem fuel …
Electron Transfer To Nitrogenase In Different Genomic And Metabolic Backgrounds, Saroj Poudel, Daniel R. Colman, Kathryn R. Fixen, Rhesa N. Ledbetter, Yanning Zheng, Natasha Pence, Lance C. Seefeldt, John W. Peters, Caroline S. Harwood, Eric S. Boyd
Electron Transfer To Nitrogenase In Different Genomic And Metabolic Backgrounds, Saroj Poudel, Daniel R. Colman, Kathryn R. Fixen, Rhesa N. Ledbetter, Yanning Zheng, Natasha Pence, Lance C. Seefeldt, John W. Peters, Caroline S. Harwood, Eric S. Boyd
Chemistry and Biochemistry Faculty Publications
Nitrogenase catalyzes the reduction of dinitrogen (N2) using low-potential electrons from ferredoxin (Fd) or flavodoxin (Fld) through an ATP-dependent process. Since its emergence in an anaerobic chemoautotroph, this oxygen (O2)-sensitive enzyme complex has evolved to operate in a variety of genomic and metabolic backgrounds, including those of aerobes, anaerobes, chemotrophs, and phototrophs. However, whether pathways of electron delivery to nitrogenase are influenced by these different metabolic backgrounds is not well understood. Here, we report the distribution of homologs of Fds, Flds, and Fd-/Fld-reducing enzymes in 359 genomes of putative N2 fixers (diazotrophs). Six distinct lineages …
Implications Of Monomer Deformation For Tetrel And Pnicogen Bonds, Wiktor Zierkiewicz, Mariusz Michalczyk, Steve Scheiner
Implications Of Monomer Deformation For Tetrel And Pnicogen Bonds, Wiktor Zierkiewicz, Mariusz Michalczyk, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
A series of TF4 and ZF5 molecules (T = Si, Ge, Sn and Z = P, As, Sb) were allowed to engage in tetrel and pnicogen bonds, respectively, with NH3, pyrazine, and HCN. The interaction energies are quite large, approaching 50 kcal mol-1 in some cases. The formation of each complex is accompanied by substantial geometrical deformation of the Lewis acid to accommodate the approaching base. The energy associated with this monomer rearrangement is the largest for the smaller central atoms Si and P, where it exceeds 20 kcal mol-1. The total reaction …
Chemical Characterization Of Fine Particulate Matter Emitted By Peat Fires In Central Kalimantan, Indonesia, During The 2015 El Niño, Thilina Jayarathne, Chelsea E. Stockwell, Ashley A. Gilbert, Kaitlyn Daugherty, Mark A. Cochrane, Kevin C. Ryan, Erianto I. Putra, Bambang H. Saharjo, Ati D. Nurhayati, Israr Albar, Robert J. Yokelson, Elizabeth A. Stone
Chemical Characterization Of Fine Particulate Matter Emitted By Peat Fires In Central Kalimantan, Indonesia, During The 2015 El Niño, Thilina Jayarathne, Chelsea E. Stockwell, Ashley A. Gilbert, Kaitlyn Daugherty, Mark A. Cochrane, Kevin C. Ryan, Erianto I. Putra, Bambang H. Saharjo, Ati D. Nurhayati, Israr Albar, Robert J. Yokelson, Elizabeth A. Stone
Chemistry and Biochemistry Faculty Publications
Fine particulate matter (PM2:5) was collected in situ from peat smoke during the 2015 El Niño peat fire episode in Central Kalimantan, Indonesia. Twenty-one PM samples were collected from 18 peat fire plumes that were primarily smoldering with modified combustion efficiency (MCE) values of 0.725-0.833. PM emissions were determined and chemically characterized for elemental carbon (EC), organic carbon (OC), water-soluble OC, water-soluble ions, metals, and organic species. Fuel-based PM2:5 mass emission factors (EFs) ranged from 6.0 to 29.6 g kg1 with an average of 17:36:0 g kg1. EC was detected only in 15 plumes and comprised 1% of PM mass. …
Nepal Ambient Monitoring And Source Testing Experiment (Namaste): Emissions Of Particulate Matter From Wood-And Dung-Fueled Cooking Fires, Garbage And Crop Residue Burning, Brick Kilns, And Other Sources, Thilina Jayarathne, Chelsea E. Stockwell, Prakash V. Bhave, Puppala S. Praveen, Chathurika M. Rathnayake, Robiul Md Islam, Arnico K. Panday, Sagar Adhikari, Rashmi Maharjan, J. Douglas Goetz, Peter F. Decarlo, Eri Saikawa, Robert J. Yokelson, Elizabeth A. Stone
Nepal Ambient Monitoring And Source Testing Experiment (Namaste): Emissions Of Particulate Matter From Wood-And Dung-Fueled Cooking Fires, Garbage And Crop Residue Burning, Brick Kilns, And Other Sources, Thilina Jayarathne, Chelsea E. Stockwell, Prakash V. Bhave, Puppala S. Praveen, Chathurika M. Rathnayake, Robiul Md Islam, Arnico K. Panday, Sagar Adhikari, Rashmi Maharjan, J. Douglas Goetz, Peter F. Decarlo, Eri Saikawa, Robert J. Yokelson, Elizabeth A. Stone
Chemistry and Biochemistry Faculty Publications
The Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) characterized widespread and under-sampled combustion sources common to South Asia, including brick kilns, garbage burning, diesel and gasoline generators, diesel groundwater pumps, idling motorcycles, traditional and modern cooking stoves and fires, crop residue burning, and heating fire. Fuel-based emission factors (EFs; with units of pollutant mass emitted per kilogram of fuel combusted) were determined for fine particulate matter (PM2.5), organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals, and organic species. For the forced-draft zigzag brick kiln, EFPM2.5 ranged from 12 to 19gkg-1 with major contributions from OC (7%), sulfate …
Investigating Biomass Burning Aerosol Morphology Using A Laser Imaging Nephelometer, Katherine M. Manfred, Rebecca A. Washenfelder, Nicholas L. Wagner, Gabriela Adler, Frank Erdesz, Caroline C. Womack, Kara D. Lamb, Joshua P. Schwarz, Alessandro Franchin, Vanessa Selimovic, Robert J. Yokelson, Daniel M. Murphy
Investigating Biomass Burning Aerosol Morphology Using A Laser Imaging Nephelometer, Katherine M. Manfred, Rebecca A. Washenfelder, Nicholas L. Wagner, Gabriela Adler, Frank Erdesz, Caroline C. Womack, Kara D. Lamb, Joshua P. Schwarz, Alessandro Franchin, Vanessa Selimovic, Robert J. Yokelson, Daniel M. Murphy
Chemistry and Biochemistry Faculty Publications
Particle morphology is an important parameter affecting aerosol optical properties that are relevant to climate and air quality, yet it is poorly constrained due to sparse in situ measurements. Biomass burning is a large source of aerosol that generates particles with different morphologies. Quantifying the optical contributions of non-spherical aerosol populations is critical for accurate radiative transfer models, and for correctly interpreting remote sensing data. We deployed a laser imaging nephelometer at the Missoula Fire Sciences Laboratory to sample biomass burning aerosol from controlled fires during the FIREX intensive laboratory study. The laser imaging nephelometer measures the unpolarized scattering phase …
Pi Tetrel Bonds, And Their Influence On Hydrogen Bonds And Proton Transfers, Yuanxin Wei, Qingzhong Li, Steve Scheiner
Pi Tetrel Bonds, And Their Influence On Hydrogen Bonds And Proton Transfers, Yuanxin Wei, Qingzhong Li, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
The positive region that lies above the plane of F2TO (T=C and Si) interacts with malondialdehyde (MDA), which contains an intramolecular H‐bond. The T atom of F2TO can lie either in the MDA molecular plane, forming a T⋅⋅⋅O tetrel bond, or F2TO can stack directly above MDA in a parallel arrangement. The former structure is more stable than the latter, and in either case, F2SiO engages in a much stronger interaction than does F2CO, reaching nearly 200 kJ mol−1. The π‐tetrel bond strengthens/weakens the MDA H‐bond when the bond is formed to the hydroxyl/carbonyl group of MDA, and causes an …