ANYL Sem Abstracts
This page contains the abstracts for upcoming and past Analytical & Environmental Chemistry Seminars at CU. Please post newer seminars at the top, but do not erase the abstracts from old seminars.
Contents
MONDAY, October 12, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
New Insights Into the Mechanism of 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase
Gregory Schill
Class II 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate limiting enzyme of the mevalonate pathway, represents an attractive potential target for the development of antibiotics the against multiple drug-resistant strains of Gram-positive cocci. However, recent steady-state spectrofluorimetric studies suggest that the mechanism of catalysis does not go through a mevaldehyde intermediate as accepted in the literature. The objective of this study was to investigate HMG-CoA reductase catalysis prior to steady-state conditions to determine if this incongruence was the result of a fast equilibrium. Stopped-flow kinetic assays, with dead times of 8 ms, were conducted to probe for the elusive mevaldehyde intermediate. Results found that a fast equilibrium can not account for the absence of mevaldehyde, suggesting a revision of the current literature-accepted mechanism of catalysis to one where coenzyme A plays a more integral role.
A NEGATIVE ION PHOTOELECTRON SPECTROSCOPIC STUDY OF Mo2-.
Sunil Baidar
Abstract
The homonuclear diatomic metal ion Mo2- was studied using negative ion photoelectron spectroscopy. This bare, homonuclear group 6 transition metal dimer allows the study of multiple metal-metal bonding free of ligand effects. The photoelectron spectra, obtained at 488 nm with an instrumental resolution of about 6 meV (50 cm-1), provide measurements of the electron affinities, vibrational frequencies for both the anion and the neutral states, and bond length changes upon electron detachment. The Mo2- spectra displays a transition to the multiply-bonded 1Σg+(dπ)4(dδ)4(dσ)2(sσ)2 ground state of the neutral molecule. In the anion, the extra electron occupies the vacant antibonding sσ* orbital, giving a 2Σu+ ground state.
MONDAY, October 5, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
Aerosols of the Past: Lessons from Saturn’s Moon Titan
Margaret Tolbert
Dept. Chem & Biochem., and CIRES, CU-Boulder
Abstract
An organic haze layer in the upper atmosphere of Titan plays a crucial role in the atmospheric composition and climate of that moon. Photochemistry in the atmosphere of the early Earth shortly after the time of planetary formation may have led to a similar haze. However, due to differences in atmospheric chemistry, the aerosols formed on the early Earth may have had distinct chemical and optical properties from those suspected to make up the hazes on Titan. We have conducted laboratory experiments simulating photochemical haze production on Titan and early Earth. The resulting aerosols are analyzed using an Aerosol Mass Spectrometer (AMS) to obtain compositional information and extinction cavity ring down (CRD) spectroscopy to determine the optical properties of the particles. The hazes on the two worlds will be compared and the implications of haze on the climate and habitability of ancient Earth will be discussed.
What have we learned about organic aerosol sources and processing? What’s next?
Jose-Luis Jimenez
Dept. Chem & Biochem., and CIRES, CU-Boulder
Abstract
Aerosols play major roles in climate forcing and the hydrological cycle, and also on human health effects, visibility degradation, and deposition of acids, toxics, and nutrients to ecosystems. Organic aerosols (OA) account for a large fraction (~50%) of ambient submicron aerosol mass, but their sources and transformation processes are still poorly understood. I will summarize recent findings about the sources, processing and budget of OA arising from multiple field and lab studies, as well as comparisons to 1D and 3D models. OA from all sources evolves in the atmosphere by becoming more oxygenated and hygroscopic and less volatile, and partially losing the chemical signature of the original source and gaining a common signature of atmospheric oxidation. Secondary OA (SOA) formation in urban areas is greatly underestimated by traditional models, in contrast with biogenic SOA formed under pristine conditions which is reasonably predicted. New models close the gap and even exceed the observed SOA in urban areas, but it is not clear whether this is for the right reasons. Further progress necessitates more complete high-quality measurements at one location as well as new measurement & analysis techniques, and we are preparing for two such campaigns in Los Angeles, CA in 2010 and Manitou Springs, CO in 2011.
MONDAY, September 28, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
Water and photon mediated chemistry relevant to atmospheric aerosol formation
Veronica Vaida
Dept. Chem & Biochem., and CIRES, CU-Boulder
Abstract
Research in the Vaida group explores the interface between physical chemistry and atmospheric science using tools of spectroscopy, photochemistry and photoreaction dynamics. This presentation will exemplify discuss water catalyzed photochemical reactions of oxidized organic species (acids, alcohols, aldehydes and ketones) relevant to atmospheric chemistry. Our approach utilizes electronic and vibrational spectroscopy to explore chemical reactions. Theoretical modeling in collaboration with the skodje group elucidates the roles of cluster conformation and dynamical effects in the photochemical processes. The specific example of methyl glyoxal, and pyruvic and glyoxilic acids and of their hydrates will be presented. The discussion will point to the role of water and photon mediated chemistry of organic molecules to the generation and processing of secondary organic aerosols and, more generally, to climate.
Instrument development for use in field and laboratory experiments in the ATMOSpeclab
Rainer Volkamer
Dept. Chem & Biochem., and CIRES, CU-Boulder
Abstract
The Atmospheric Trace Molecule Spectroscopy Laboratory (ATMOSpeclab) was established in 2007 at CU Boulder to develop and apply optical spectroscopic instruments to measure atmospheric composition of reactive trace gases in polluted urban, and pristine natural atmospheric environments. Specific atmospheric chemistry projects in the ATMOSpeclab will be discussed, and include: - Impact of halogen chemistry on Mercury deposition in the coastal environment - Airborne MAX-DOAS from research aircraft - Ship based MAX-DOAS in the Southern Hemisphere Pacific Ocean - Laboratory studies of SOA formation from glyoxal in simulation chambers - Development of a detailed model to represent SOA formation via the aerosol aqueous phase
MONDAY, September 21, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
CU Inhalable Dry Powder Vaccines have Provided Protection Against Infection
R. Sievers, S. Cape, J. Burger, D. McAdams, J. Manion, L. Rebits, S. Winston, B. Quinn, J. Searles, D. Krank, P. Bhagwat, P. Pathak, A. Genosar, R. Dhere, V. Vaidya, R. Muley, D. Griffin, W-H Lin, and P. Rota
Abstract
Protection against infection with measles virus has been demonstrated in animal models immunized 14 months earlier by inhalation of CU-invented dry powder vaccine microparticles. Needle-free aerosol delivery of dry powder vaccines may provide an effective and low-cost means of immunization. Powder manufacturing with gentle, rapid drying by Carbon Dioxide Assisted Nebulization with a Bubble Dryer (CAN-BD) appears to be an attractive alternative to freeze drying of sensitive biologicals like live attenuated Edmonston-Zagreb measles virus vaccine. Stability of measles virus in glassy, dry, respirable microparticles made by CAN-BD with less than 1% water sealed in unidose aluminum foil has been demonstrated. The dry powder aggregate, upon dispersion from an active dry powder inhaler, deposits in the moist respiratory tract where the microparticles rapidly dissolve within minutes. Antibiotics are also being studied and delivered as microparticles against infectious diseases.
Funded by FNIH Grant 1077.
Improving the Performance of Li Ion Batteries Using Atomic Layer Deposition
Steven M. George
Depts. of Chemistry and Chemical Engineering University of Colorado, Boulder, CO 80309 Steven.George@Colorado.Edu
Abstract
Lithium ion batteries (LIBs) are emerging as the dominant power source for portable electronics. Improvement in their capacity lifetime during charge-discharge cycles must be achieved before LIBs can be used for plug-in-hybrid and electric vehicles. LiCoO2 and graphite are common cathode and anode materials, respectively, for LIBs. The capacity loss of LIBs is linked to electrode deterioration caused by interfacial reactions with the electrolyte, dissolution of the metal oxide cathodes and structural instabilities caused by volume expansion during lithium intercalation. Atomic layer deposition (ALD) is based on the strategy of sequential, self-limiting surface reactions to deposit inorganic materials. ALD can deposit thin, conformal films on cathode and anode materials in LIBs to provide chemical protection, restrict dissolution and stabilize structural changes. Our recent work has demonstrated that ultrathin Al2O3 ALD films can improve the capacity stability of LiCoO2 cathodes and graphite anodes. Additional work is developing new protective coatings that will serve as an artificial solid-electrolyte interphase (SEI) for further stability improvement.
MONDAY, September 14, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
Renewable and Sustainable Energy Institute (RASEI): What does this mean for the Dept. of Chemistry and Biochemistry (and other departments and institutes)?
Carl A. Koval, Co-Director
Abstract
In June 2009, the University of Colorado’s Board of Regents approved the formation of a new campus institute: RASEI (pronounced ‘racy”). This formation of this institute grew out of the former CU-Boulder Energy Initiative (EI), which was created in early 2006. In addition, administrators at CU-Boulder and the National Renewable Energy Laboratory (NREL) in Golden signed a MOU to operate RASEI as a joint institute. In this presentation, I will focus on:
• the transition of the EI to RASEI, from initiative to institute;
• opportunities for faculty to be involved in RASEI governance and programs;
• opportunities for students to be involved RASEI’s research, teaching, commercialization and outreach activities.
For more information about RASEI, go to http://rasei.colorado.edu.
Research at the Interface of Nanoscale Materials and Biology
Daniel L. Feldheim
Dept. Chem & Biochem., CU-Boulder
Abstract
Between the size scale of individual biomacromolecules and cellular organelles lies a size regime―the few nm to 100 nm range―that is not readily probed using existing technologies. Thus, while a vast inventory of RNA and protein sequences and structures are being catalogued, a quantitative cellular context for these structures is lagging. Yet to understand this context would be to know how collections of individual macromolecules assemble into the dynamic machines that form a living cell. Once these interactions are revealed, a new picture of the cell and its disease states is sure to emerge.
With achievable 2 nm resolution and perfect preservation of cellular structure, electron tomography (ET) now represents the highest resolution technique for examining biomolecules in their native cellular context. Indeed, cell biologists now dream of generating 3D images containing the entire proteome of a living cell. This dream remains out of reach, not because ET cannot visualize individual proteins, but because it is simply not possible currently to know which protein is which in a tomographic cellular reconstruction.
This presentation will describe methods being developed in our lab for creating electron dense nanoparticle tags for identifying cellular biomolecules by ET. These methods rely on the discovery of materials ribozymes and enzymes―RNA and protein/peptide sequences that can catalyze the formation of inorganic nanoparticles and control nanoparticle growth. The isolation and structure-function relationships of a number of materials ribozymes and enzymes will be shown.
In addition to visualizing biomolecule interactions in cells, we are working on ways to mimic and disrupt such interactions for disease treatment. We view this largely as a materials problem as well, and have been learning how to design metal nanoclusters to effectively interact with cellular biomolecules. A few lessons learned in our studies of cell and nuclear targeting and the prevention of viral infection will be described.
THURSDAY, September 10, 2009
4:00 p.m. CIRES Auditorium (note change of location) University of Colorado, Boulder
What controls the diurnal variability of carbon dioxide and reactive species? (a.k.a. "Boundary Layers for Chemists")
Jordi Vilà-Guerau de Arellano Meteorology and Air Quality Section Wageningen University (The Netherlands) e-mail: jordi.vila@wur.nl http://www.met.wau.nl/medewerkers/vila/index.html
Abstract
We examine the main physical and chemical processes that determine the diurnal variability of atmospheric compounds in the boundary layer. In addition to surface processes, turbulent mixing and reactivity, we put special emphasis on investigating the role of the exchange of heat, water and chemical species between the free troposphere and the atmospheric boundary layer, namely the entrainment process. This process enhances the dilution of compounds and introduces free tropospheric air masses with different characteristics into the atmospheric boundary layer.
In the seminar, I will discuss several cases where entrainment plays a major role in the evolution of atmospheric compounds. By analyzing observational evidence or performing numerical experiments by the large eddy simulation technique and a conceptual (mixed-layer theory) model, we are able to find the contribution of entrainment to the diurnal variability of carbon dioxide or isoprene. Particular emphasis is placed on the need to maintain a balance in dynamic processes and the specific characteristic of each atmospheric compound.
