Category: Seminars

Atomistic Resolution Dances of Membrane Proteins by NMR

Dr. Ayyalusamy Ramamoorthy, Professor
Biophysics and Department of Chemistry, University of Michigan
Date: September 25, 2015
Place: Chem-Sci Room 101
Time: 3:00 pm


Abstract

Membrane proteins are an exciting class of biomacromolecules and play important roles in a variety of biological processes that are directly linked to major diseases including cancer, aging-related diseases, and infectious diseases. A complete understanding of their function can only be accomplished using high-resolution structures and dynamics. In spite of recent developments in structural biology, membrane proteins continue to pose tremendous challenges to most biophysical techniques. A major area of research in my group is focused on the development of NMR techniques to study the dynamic structures of membrane bound proteins such as cytochrome b5, cytochrome P450 and cytochrome P450-reductase. In my talk, I will present strategies to study the structure and dynamics of these challenging systems and also on the electron transfer mechanism that enables the enzymatic function of P450. Atomic-level resolution NMR structures of amyloidogenic proteins revealing the misfolding pathway and early intermediates that play key roles in amyloid toxicity will also be presented.
References:
J. Biol. Chem. (2015) 290:12705-18; 290: 4843-55; 288:22080-95.
Chem. Soc. Rev. (2014) 43:6692-6700; J. Phys. Chem. Lett. (2014) 5:1864.

Biography

Dr. Ayyalusamy Ramamoorthy is Professor of Biophysics and Chemistry at University of Michigan, where he has been since 1996. He has applied NMR spectroscopy and other biophysical techniques to investigate high-resolution structure, dynamics, and functional properties of membrane proteins, amyloid proteins/peptides, and antimicrobial peptides. He has published more than 250 peer-reviewed papers in leading high impact journals like Science, PNAS, JACS, J. Biol. Chem., and Angew. Chem. Eng. Intl., written several review articles, edited 2 books on NMR spectroscopy, brought out several special issues as a guest editor, and organized several conferences related to NMR spectroscopy. He is a member of editorial boards of J. Biol. Chem., Plos One, Scientific Reports, Peer J, Biochimica Biophysica Acta, Journal of Magnetic Resonance, Chemistry and Physics of Lipids, Solid State Nuclear Magnetic Resonance Spectroscopy, and Magnetic Resonance in Chemistry. He has been a PI or co-PI on several NIH (and other) sponsored projects.
For more information visit http://rams.biop.lsa.umich.edu/

Engineering Bimetallic Nanostructures as Peroxidase Mimics for Disease Diagnosis

Dr. Xiaohu Xia
Assistant Professor
Department of Chemistry, Michigan Tech
September 18, 2015
Chem-Sci Room 101 3:00pm

Abstract
Peroxidase mimics (or artificial peroxidase) with dimensions at the nanoscale have received great interest as emerging artificial enzymes for biomedicine and environmental protection. While a variety of peroxidase mimics have been actively developed since 2007, limited progress has been made toward improving their catalytic efficiency. In our recent work (ACS Nano, 2015, in press, DOI: 10.1021/acsnano.5b03525), we reported a novel type of peroxidase mimic with record high efficiency. Our peroxidase mimic was engineered by depositing Ir atoms as ultrathin skins (a few atomic layers) on Pd nanocubes (i.e., Pd-Ir cubes). The Pd-Ir cubes exhibited significantly enhanced efficiency that is over 400-fold higher than that of natural peroxidase. In this talk, I will introduce the rational design, experimental synthesis, and mechanistic understanding of such a new peroxidase mimic. At the end, using human prostate specific antigen as a model example, I will highlight the application of our peroxidase mimic in ultrasensitive detection of disease biomarkers.

ON THE PROTECTIVE PROPERTIES OF GLYCINE BASED OSMOLYTES IN A THIOL REDUCING ENVIRONMENT

Michigan Technological University
Department of Chemistry
John Hausman
Advisor: Dr. Ashutosh Tiwari
Master’s Defense
Monday August 10, 2015
9:30 am, Chem-Sci 101

ON THE PROTECTIVE PROPERTIES OF GLYCINE BASED OSMOLYTES IN A THIOL REDUCING ENVIRONMENT

The protective properties of osmolytes have been studied intently for decades. Originally used to aid in the crystallization of proteins in x-ray diffraction studies, these cosolvents have been shown to reverse protein denaturation and aggregation. Osmolytes aid extremophiles in surviving harsh environments by preferentially excluding themselves from the surface of the protein, thus directing water molecules to the protein’s surface. Their use is increasing and affects the everyday consumer as these osmolytes are naturally found in many health foods and also in many daily use products such as shampoo. Consumers also supplement their diets with thiol-based antioxidants such as glutathione as part of healthier life style. However, thiol-based antioxidants in high concentration have been known to cause un-intended health issues that relate to its disulfide reducing property. The disulfide-reducing agent can cleave the proteins’ disulfide-bonds and promote misfolding and aggregation. In this thesis, we investigated the influence of commonly consumed glycine-based osmolytes on providing stability to proteins against a disulfide-reducing agent. We chose glycine, sarcosine (N-methyl glycine), di-methyl glycine (DMG), and betaine (N,N,N-trimethylglycine) with increasing number of methyl groups. An added benefit to studying this class of osmolytes is to also investigate the impact N-methyl substitution has on the osmolytes’ protective properties. We studied the effect of these osmolytes on protein aggregation using spectroscopic techniques such as UV-visible absorbance, intrinsic fluorescence and extrinsic fluorescence measurements. In addition, we carried out non-reducing SDS-PAGE to check for higher order aggregates and characterized morphology of these aggregates using scanning electron microscopy. Overall, our results show that of all the osmolytes used, glycine was the best stabilizer followed by sarcosine. Betaine and dimethylglycine did not provide effective protection against disulfide-reducing influence.

Gold Nanorod-based Theranostics for Specific Cancer Imaging and Therapy

Jianheng Bi
Original Research Proposal
Michigan Technological University
Department of Chemistry
Advisor- Dr. Haiying Liu
Tuesday August 4, 2015
9:00 am
Chem-Sci 101

ABSTRACT
This proposal describes the preparation, characterization and application of gold nanorod-based theranostics for specific cancer imaging and therapy. Cancer theranostics will be constructed by modifying the gold nanorods with near-infrared dyes and cancer-imaging peptides via silica layers and poly(ethylene glycol) tethered spacers. The thickness of the silica layers will be carefully controlled to significantly enhance the fluorescence intensity of near-infrared dyes via a surface plasma of gold nanrods while specific targeting and imaging will be achieved through strong specific multivalent interactions of cancer-homing peptide residues with cancer cells and tissues. Once specific targeting to cancer cells or tissues are achieved, thermotherapy and photodynamic therapy will be conducted to kill cancer cells and tissues via thermal heat from gold nanorods and singlet oxygen generated by photodynamic agent under near-infrared pulse laser.

Title: Soil Organic Matter Matters: Why is there so much carbon underground?

Chemistry Seminar
Dr. Katherine Heckman, Research Biologist
USDA Forest Service, Northern Research Station

Friday July 24, 2015
Chem Sci Room 101
3:00 pm

Title: Soil Organic Matter Matters: Why is there so much carbon underground?
Abstract:

Soils contain roughly twice as much carbon as the atmosphere, and 1.5 times as much as the atmosphere and aboveground vegetation combined. Yet the mechanisms regulating the stability of this massive carbon pool remain the largest uncertainty in terrestrial carbon models. To provide context, a brief review of the soil carbon cycle and mechanisms of soil carbon stabilization will be given, followed by the results of a recent investigation into how mineral crystallinity influences soil carbon stability.

Bio:
Kate Heckman earned her PhD in Soil Science at the University of Arizona in 2010, and since then has been working for the USDA Forest Service. In addition to doing basic research involving soil, Kate also runs the Radiocarbon Collaborative, a research initiative focused on making radiocarbon analyses more accessible to earth systems researchers. Kate will be moving up to Houghton this fall where she will continue her research in the Forestry Sciences Laboratory at Michigan Tech.

T Synthesis of Isobractatin and Neobractatin

Shanshan Hou
Original Research Proposal
Michigan Technological University
Department of Chemistry
Advisor- Dr. Lanrong Bi
Tuesday April 21, 2015
9:00 am
Chem-Sci 106

T Synthesis of Isobractatin and Neobractatin

Abstract
The new Garcinia derivatives, neobractatin and isobractatin, will be synthesized. These compounds are caged-prenylxanthones which are isolated from Chinese native Garcinia bracteata. They displayed strong inhibition of cancer cells, which could significantly induce cell apoptosis and inhibit autophagy. However, the compounds which are extracted from the Chinese native Garcinia species have very low yield. Total synthesis of these derivatives will provide adequate quantities for biological studies. In addition, the new synthetic methodologies could not only produce the target compounds but also give rise to their isomers which could be potential anti-tumor candidates and used for future research.

Interfaced Heterogeneous Nanodimers

Chemistry Seminar
Dr. Yugang Sun
Center for Nanoscale Materials, Argonne National Laboratory
Friday, April 17, 2015 3:00pm Chem-Sci 101

Interfaced Heterogeneous Nanodimers
Abstract:
Synthesis of interfaced nanoparticle dimers made of asymmetric compositions (i.e., interfaced heterodimers) is challenging because it is difficult to manipulate the nanoparticles’ surface properties to control the assembly and/or growth of different nanoparticles. In this presentation, the general principle will be first introduced for the formation of interfaced heterogeneous dimers made of different inorganic nanodomains that exhibit either crystalline or amorphous structures. Although many different combinations are possible, the heterodimers containing plasmonic components (e.g., gold and silver nanodomains) will be focused in this presentation to highlight a number of synthetic methods and unique properties observed in heterodimers. For example, a seed-mediated, surface-confined epitaxial overgrowth strategy is capable of synthesizing high-quality interfaced Au-Ag heterodimers with varying sizes. Au and Ag share a common face-centered cubic lattice and have nearly identical lattice constants, which facilitates epitaxial overgrowth and allows direct contact between the Au and Ag domains. The interfaced Ag nanodomains can be chemical transformed to hollow nanoshells of other materials through a galvanic replacement reaction, resulting in the formation of interfaced dimers made of solid Au nanoparticles and hollow nanoshells. Due to the direct contact between the two components in each interfaced dimer, strong coupling between them are expected to induce new properties that cannot be observed from any individual components.

Biography:

Dr. Yugang Sun is a Scientist at the Center for Nanoscale Materials, Argonne National laboratory. He received his B.S. and PhD degrees from University of Science and Technology of China in 1996 and 2011, respectively. He worked as a Postdoc at University of Washington at Seattle (with Prof. Younan Xia) from 2001 to 2003. During 2004-2004, he had been working with Prof. John Rogers at University of Illinois at Urbana-Champaign as a postdoctoral fellow. In August 2008, he was appointed as an Assistant Scientist at Argonne National laboratory. He was promoted to Scientist in January 2010.

Dr. Sun’s research interests focus on developing novel approaches for the synthesis of a wide range of nanostructures including metal nanoparticles with well-controlled morphologies, single-crystal semiconductor nanostructures with mechanical flexibility, and metal/semiconductor nanocomposites with multiple functionalities. As of now, he has published more than 130 research papers, with an h-index = 47 and citation times > 23,400. He was honored as one of the “Top 100 Materials Scientists with highest impact score (2000-2010), Rank #5” by Thomson Reuters.

Zintl and Polar Intermetallic Compounds

Chemistry Department Seminar Faculty Candidate
Dr. Fei Wang

Polymer and Material Chemistry, Lund University Sweden
Monday April 6, 2015
4:00 PM, MUB~ Alumni Lounge A

Abstract:
Zintl and polar intermetallic compounds are compounds between electropositive metals (e.g. alkali, alkaline earth, and rare earth) and electronegative metals/metalloids (e.g. late transition and post transition elements). Just like their constituent elements, these compounds are also metals/metalloids. Meanwhile, partial charge transfer is expected from the electropositive metals to the electronegative metals/metalloids, the latter of which are formal “anions” and covalent interactions can occur among them. Therefore, Zintl and polar intermetallic compounds possess simultaneously metallic, ionic, and covalent characteristics. I will demonstrate what will happen when metallicity, covalency, and ionicity coincide and interplay with each other.
Besides, the bonding between the “anionic” electronegative metals/metalloids is also intriguing. The well-know electron counting rules, such as the octet rule and the Wade-Mingo’s rules, fail frequently in rationalizing the bonding in Zintl and polar intermetallic compounds. I will present a few examples to illustrate the cause, with emphasis on the involvement of d-orbitals and the relativistic effects in bonding.

Biography:
I obtained my master’s degree from Zhejiang University in China in 2005. There I worked on morphology controlled syntheses of inorganic compounds under the direction of Prof. Linhai Yue. After that, I joined Prof. Gordon J. Miller’s research group in Iowa State University, where I developed the majority of my expertise in solid state chemistry, including high temperature synthesis, X-ray crystallography, and first-principle computations. In 2011, I received my PhD degree in inorganic chemistry and moved to Stuttgart, Germany, working as a postdoc in Prof. Martin Jansen’s department in Max Planck Institute for Solid State Research. My project is on the syntheses, structures, and rationalization of thallium cluster compounds featuring significant relativistic spin-orbit coupling. Currently, I am in Prof. Sven Lidin’s group at Lund University in Sweden, working on my second postdoc position which started in 2013 and is supported by the Wenner-Gren Scholarship. Here, my expertise has been further broadened with incommensurate crystallography and thermoelectric materials.

Sustainable Clean Energy Based on Solid State Ionic Materials and Devices

Chemistry Department Seminar Faculty Candidate
Dr. Jianhua Tong
Colorado Center for Advanced Ceramics,
Metallurgical & Materials Engineering, Colorado School of Mines
Thursday March 19, 2015
MUB ~ Alumni Lounge A
1:00 pm

Abstract
It is estimated that global energy consumption will be doubled by 2035 due to growth in global population and continued industrialization of developing countries. Solar energy is a renewable clean energy source and can satisfy the rising energy demand eventually from long-term point of view. However, fossil energy, a non-renewable carbon-based energy source, still dominates the energy supplies in near future. Therefore, the efficient conversions of fossil energy and the efficient storage of solar energy are also very important from both scientific and industrial point of view. Among the energy materials, the leading actors for energy conversion and storage, solid state ionic materials have found a great number of applications such as catalytic membrane reactors, fuel cells, electrolysis cells, heterogeneous catalysts, photovoltaics, thermal electronic devices, materials for solar thermal chemical fuels production, and catalysts for oxygen reduction reaction and oxygen evolution reaction etc.
In the first part of the talk, I would like to briefly highlight my significant research contributions to sustainable clean energy based on solid state ionic materials and devices. In the second part of the talk, I would like to intensively focus on my recent discovery of perovskite-type oxides as promising materials for solar thermochemical (STC) fuels production through two-step redox cycles.

Bio:
Dr. Jianhua Tong is working as an Associate Research Professor in Colorado Center for Advanced Ceramics at the Colorado School of Mines (US). He received his PhD degree in Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Subsequently, he worked as NEDO project researcher in Research Institute of Innovative Technology for the Earth (Japan), JSPS fellow in National Institute of Advanced Industrial Science and Technology (Japan), and postdoctoral scholar in California Institute of Technology (US) for several years. He has made some important contributions to the materials and devices for sustainable clean energy by focusing on fuel cells, catalytic membrane reactors, pure hydrogen production, pure oxygen production, natural gas conversion, mixed conducting oxides, proton conducting ceramics, and solar thermochemical fuels etc. He published >60 peer-reviewed papers, filed >15 patents, and got citations >2500 and H-index >24.

Exploring environmentally relevant aqueous interfaces and reactions on solid surfaces

Chemistry Department Seminar Faculty Candidate
Dr. Kathryn A. Perrine

Department of Chemistry, University of California Irvine
Monday March 16, 2015
Chem-Sci 101
4:00 pm

Abstract:

Ions and solutes impact chemistry at the aqueous liquid/vapor interface, particularly in environmental chemistry where aerosols can carry pollutants into the atmosphere and react to form harmful byproducts. Liquid Jet X-ray Photoelectron Spectroscopy technique probes the surface and bulk of aqueous solutions. Low photoelectron kinetic energies are used to probe the surface layers of solutions and higher photoelectron kinetic energies probe deeper into the bulk of aqueous solutions. Binary acetonitrile-water mixtures are shown to be inhomogeneous and that the surface forms a saturated dipole layer near 0.2 mole fraction. These studies are contrasted to ternary solutions that have added ions from salts that affect the interface of organic solutes. Potassium iodide was added to aqueous acetonitrile and propionitrile solutions to observe the effects of ions on the surface nitrile distributions. Results from other salt solutions suggest specific cation effects are unexpected and apparent at the aqueous interface. These studies help elucidate the role ions play at the interface of aqueous organic solutions.

Solid interfaces can also have an impact on reactions in catalysis and in the environment. Supported metal oxide structures that are commonly found in urban and rural environments can produce various byproducts with pollutants through core-hole activation in the presence of UV and visible light. In order to understand how the interface is impacted on heterogeneous surfaces, thermal desorption studies of water on different heterogeneous structured TiO2 materials were investigated. Results suggest as the size of the metal oxide decreases, its physical properties change its chemistry and reactivity. Monolayer and second layer activation energies of water were determined on different graphite supported TiO2 structures, ranging from supported nanoparticles to thin films. These studies compare the reactivity of small molecules, representative of those in the air/water environment, and will help explain gas/solid reactions on heterogeneous supported metal oxide materials for catalysis and environmental applications.

Biosketch:
Dr. Kathryn A. Perrine found a passion for surface science as an undergraduate student at the University of South Carolina, where she worked on characterizing the decomposition of metal encapsulated dendrimers for supported metal catalysis applications. She then attended graduate school and earned her PhD at the University of Delaware, where she studied semiconductor surface science. Her work there focused on understanding how Cu nanostructures grow on different functionalized silicon surfaces from chemical vapor deposition of copper metal-organic precursors. She also collaborated with researchers at the Materials Science Department to examine how organic molecules react on silicon for future use in organic electronics. There she won the competitive University of Delaware Professional Development Award for her research accomplishments. She also completed a full year in teaching in higher education by completing the Higher Education Teaching Certification.

She later went on to do postdoctoral work at the University of California, Irvine mainly focused on Liquid-Jet X-ray Photoelectron Spectroscopy (LJ-XPS). She collaborated with researchers at the BESSY II light source at the Helmholtz Center for Materials and Energy on aqueous and acidic systems. She helped build a separate LJ-XPS system at Beam line 11.0.2 end station at the Advanced Light Source at Lawrence Berkeley National Laboratory to continue aqueous liquid jet studies in a higher pressure environment. She collaborated with others in the Hemminger group to investigate other projects, including hydrocarbon decomposition on supported Pt nanoparticles and understanding the reactivity of supported TiO2 materials for heterogeneous catalysis applications. There she was a member of the Postdoctoral association and received the UCI postdoctoral service award for developing a seminar series for postdoctoral teaching. She currently works as a visiting postdoctoral scholar at the Joint Center for Photosynthesis at the California Institute of Technology on heterogeneous catalysts for electrochemical solar energy conversion.