����vlog�ٷ����

Abstract: Sulfur is a constituent atom in two naturally occurring amino acids, namely, methionine and cysteine. It has been well established that in many proteins and enzymes the non-covalent interactions involving sulfur atom in these two amino acids play important role in lending them their intrinsic structures and also in enzymatic catalysis. These interactions have been interchangeably categorized as either as generic non-covalent interactions or specifically hydrogen bonding interactions. However, in many instances their structural properties do not necessarily confirm to those of the conventional hydrogen bonds. We have been investigating the spectroscopic and electronic structure properties of sulfur centered non-covalent contacts using a variety of laser spectroscopic techniques in gas phase and have been able to show that they satisfy all the criteria of hydrogen bonding interaction. We have also determined the dissociation energies of OH---S hydrogen bonded complexes using a combination of the ZEKE photoelectron spectroscopy and photo-fragmentation spectroscopy. In this talk I will present some of these results.

Spectroscopy of Cold Trapped Ions – Fundamentals and Chemical Applications

Christopher J. Johnson, Stony Brook University

In the last 10 years, advances in ion sources for mass spectrometry, laser spectroscopy of gaseous ions, and temperature controlled ion traps have been combined to make it possible to record electronic and vibrational spectra of essentially any chemical system that can be analyzed by mass spectrometry.  This has led to fundamental advances in cluster chemistry and spectroscopy as well as applications in catalytic mechanisms, biomolecular structure and solvation, and atmospheric chemistry, to name a few.  I will discuss the development of these spectroscopic methods and the current state-of-the-art.  Examples of the application of this technology to address questions in vibrational spectroscopy of systems with large-amplitude motion and the mechanism of atmospheric new particle formation will be presented.  Finally, I will give a look ahead at planned advances in speed, sensitivity, and complexity of systems amenable for study using these techniques.

Virus Based Nanotechnology and Nanotechnology Based on Viruses

Abstract:  Nature long ago solved problems plaguing contemporary chemists with polydispersity and controlled synthesis at the nanoscale. The biological production and proliferation of viruses—each viral particle identical to the last—is unsurpassed in terms of both output and quality control relative to anything humans can accomplish today at such a scale. Our research program reengineers viruses for a palate of purposes, from drug delivery to materials fabrication to a test-bed for new bioconjugation reactions. I will be presenting several projects in our group that illustrate the power of chemical virology from an organic/materials chemist’s perspective with applications in medicinal science as well as material science.

Bio: Dr Jeremiah Gassensmith earned his B. Sc. (Hons in ����vlog�ٷ����) degree under the tutelage of Professor Joseph Gajewski at Indiana University and his Ph.D. from Professor Bradley D Smith at the University of Notre Dame, where he studied the synthesis of sterically shielded near-infrared luminescent dyes. After his PhD, he traveled to Northwestern University to learn under Professor Sir J. Fraser Stoddart. At Northwestern, he investigated a diverse array of topics, including gas sequestration by cyclodextrin based metal-organic frameworks. He joined the faculty at the University of Texas at Dallas in August 2013. He’s the author of 30 scientific articles, has a book chapter, and two US patents. Check out his website () or his twitter account (@gassensmith)!

Light-driven P450 enzymes

 

Lionel Cheruzel¹ , lionel.cheruzel@sjsu.edu

¹ ����vlog�ٷ����, San Jose State University, San Jose, California, United States

Cytochrome P450s are unique heme thiolate enzymes that catalyze the regio and stereoselective functionalization of unactivated C-H bonds in a wide range of substrates, using molecular dioxygen, two protons, and two electrons provided by a reductase domain. As an alternative approach to deliver the necessary electrons and perform P450 reactions upon visible light excitation, we have developed hybrid P450 enzymes contain a Ru(II)-diimine photosensitizer covalently attached to strategically positioned non-native cysteine residues of P450 heme domains. High photocatalytic activity (i.e. high total turnover numbers and initial reaction rates) could be achieved in the hydroxylation of natural long-chain fatty acid substrates. The crystal structure of an efficient hybrid enzyme reveals that the photosensitizer is ideally positioned to deliver electrons to the active site utilizing the natural electron transfer pathway. A combination of rational and directed evolution approaches has been used to develop the next generation of hybrid enzymes showing enhanced photocatalytic activity towards a wide range of non-natural substrates.

Statistics of Battery Failure

Steve Harris

Lawrence Berkeley Lab

The battery community, implicitly or explicitly, usually takes failure to be deterministic rather than statistical.  This means that there should be a function (model) which predicts a single value for life as a function of critical parameters such as C-rate, temperature, electrode properties, etc.  Variability is rarely explicitly discussed, but when it is, it is further assumed that any variability in life is Gaussian and that with sufficiently close control of the appropriate parameters, the variability can be always be reduced.  In this talk I will make the case that battery failure is intrinsically statistical, which means that there is no single function (model) that predicts the lifetime of a battery, just as there is no model that can predict lifetime of a person or a gear.  On the other hand, as I will show with standard statistical methods, it is possible to predict the time-evolution of the distribution of lifetimes with considerable accuracy using capacity vs cycle data.  Furthermore, the analysis offers a way to qualitatively classify the type of degradation that the cells are undergoing.

Professor Emeritus Jame Flesher from the ����vlog�ٷ����'s Deparetment of Pharmacology will present his seminar titled Structure, Function, and Carcinogenicity of Oxidized Metabolites of Methylated and non-Methylated Polynuclear Hydrocarbons.

Abstract:

The Unified Theory of PAH Carcinogenicity accommodates the activities of methylated and non-methylated polycyclic aromatic hydrocarbons (PAHs) and states that substitution of methyl groups on meso-methyl substituted PAHs with hydroxy, acetoxy, chloride, bromide or sulfuric acid ester groups imparts potent cancer producing properties. It incorporates specific predictions from past researchers on the mechanism of carcinogenesis by methyl-substituted hydrocarbons, including (1) requirement for metabolism to an ArCH2X type structure where X is a good leaving group and (2) biological substitution of a meso-methyl group at the most reactive center in non-methylated hydrocarbons. The Theory incorporates strong inferences of Fieser: (1) The mechanism of carcinogenesis involves a specific metabolic substitution of a hydrocarbon at its most reactive center and (2) Metabolic elimination of a carcinogen is a detoxifying process competitive with that of carcinogenesis and occurring by a different mechanism. According to this outlook, chemical or biochemical substitution of a methyl group at the reactive meso-position of non-methylated hydrocarbons is the first step in the mechanism of carcinogenesis for most, if not all, PAHs and the most potent metabolites of PAHs are to be found among the meso methyl-substituted hydrocarbons. Some PAHs and their known or potential metabolites and closely related compounds have been tested in rats for production of sarcomas at the site of subcutaneous injection and the results strongly support the specific predictions of the Unified Theory.

Abstract: Nanoscale carbon materials including tubes, sheets, and dots have interesting and, in many cases, unique optical, electronic, and thermal properties. We have been exploring these nanomaterials for various technologies, from bulk-separated metallic/semiconducting single-walled carbon nanotubes for electrical/electronic devices to carbon nanosheets for thermal and mechanical composites and carbon-based photoluminescent nanoparticles (?carbon dots?) as effective imaging-sensing agents and photocatalysts. In this talk, some interesting and representative recent results from our research will be highlighted.

Nanotechnology-Enabled Water Treatment:

A Vision to Enable Decentralized Water Treatment

Pedro J.J. Alvarez

Dept. of Civil & Environmental Engineering, Rice University, Houston, TX. 77005, USA

Through control over material size, morphology and chemical structure, nanotechnology offers novel materials that are nearly “all surface” and that can be more reactive per atom than bulk materials. Such engineered nanomaterials (ENMs) can offer superior catalytic, adsorptive, optical, electrical and/or antimicrobial properties that enable new technology platforms for next-generation water treatment. This presentation will address emerging opportunities for nanotechnology to meet a growing need for safer and more efficient decentralized water treatment and reuse. Because water is by far the largest waste stream of the energy industry, emphasis will be placed on technological innovation to enable produced water reuse in remote (off-grid) oil and gas fields or offshore platforms, to minimize freshwater withdrawals and disposal challenges. Examples of applicable nano-enabled technologies include fouling-resistant membranes with embedded ENMs that allow for self-cleaning and repair; capacitive deionization with highly conductive and selective electrodes to remove multivalent ions that precipitate or cause scaling; rapid magnetic separation using superparamagnetic nanoparticles; solar-thermal processes enabled by nanophotonics to desalinate with membrane distillation; disinfection and advanced oxidation using nanocatalysts; and nanostructured surfaces that discourage microbial adhesion and protect infrastructure against biofouling and corrosion. These enabling technologies can be used to develop compact modular water treatment systems that are easy to deploy and that can treat challenging waters to protect human lives and support sustainable economic development. 

Short Bio

Pedro J.J. Alvarez is the George R. Brown Professor of Civil and Environmental Engineering at Rice University, where he also serves as Director of the NSF ERC on Nanotechnology-Enabled Water Treatment (NEWT). His research interests include environmental implications and applications of nanotechnology, bioremediation, fate and transport of toxic chemicals, water footprint of biofuels, water treatment and reuse, and antibiotic resistance control. Pedro received the B. Eng. Degree in Civil Engineering from McGill University and MS and Ph.D. degrees in Environmental Engineering from the University of Michigan. He is the 2012 Clarke Prize laureate and also won the 2014 AAEES Grand Prize for Excellence in Environmental Engineering and Science. Past honors include President of AEESP, the AEESP Frontiers in Research Award, the WEF McKee Medal for Groundwater Protection, the SERDP cleanup project of the year award, and various best paper awards with his students. Pedro currently serves on the advisory board of NSF Engineering Directorate and as Associate Editor of Environmental Science and Technology. He also serves on the Advisory Board of the Engineering Director of the National Science Foundation (NSF).

Abstract: Our group’s research focuses on directional interactions in ordered assemblies of organic semiconductors. Using tools of single-molecule spectroscopy, our approach is based on isolated crystalline nanowires where the nanowire itself plays a material role analogous to a single molecule, and optical polarization (in either absorption or emission) can be referenced to specific crystallographic directions. Of particular interest are timescales for mixing transverse and longitudinal polarizations which encode information on the (directional) interaction of different intermolecular coupling modes in the assembly. In this talk, I’ll summarize some recent work on isolated crystalline nanowires of an interesting small-molecule semiconductor called 7,8,15,16-tetraazaterrylene (TAT, for short) which display several unusual and exciting properties with applications to organic opto-electronics.