Seminars Archive

Spring 2020

SPRING SEMINARS HAVE BEEN CANCELLED

SPRING SEMINARS HAVE BEEN CANCELLED

Friday, March 27, 2020

SPRING SEMINARS HAVE BEEN CANCELLED

SPRING SEMINARS HAVE BEEN CANCELLED

Wednesday, March 25, 2020

SPRING SEMINARS HAVE BEEN CANCELLED

SPRING SEMINARS HAVE BEEN CANCELLED

Friday, March 20, 2020

SPRING SEMINARS HAVE BEEN CANCELLED

SPRING SEMINARS HAVE BEEN CANCELLED

ABSTRACT

The brain is a complex organ, with billions of neurons and more than 30 distinct neurochemicals (possibly up to 100), involved in all aspects of a human life, including cognition, movement, sleep, appetite, and fear responses. For some neurological diseases/conditions, changes in neurochemical concentrations could be predictors of early onset disease or disease progression. While there are a variety of sampling techniques which can detect neurotransmitters in biofluids at low concentrations, these techniques often involve multi-step sample preparations coupled with long measurement times, and are not suited for in vivo detection. There is a need for the development of sensors for the detection of neurotransmitters that are selective, rapid, and label-free with little to no sample processing. Our group focuses on the detection of biomarkers for neurological activity in biofluids and through the skull.

Our approach is to apply surface enhanced Raman spectroscopy (SERS), a highly specific and selective vibrational spectroscopy, for the detection of neurochemicals. Raman scattering is an inherently weak phenomenon. To enhance the weak Raman scattering signal, we incorporate noble metal nanoparticles in our sensors, which when excited with a laser generate an oscillating electric field, referred to as the localized surface plasmon resonance (LSPR), at the surface of the nanoparticles. The molecules of interest are adsorbed to the nanoparticle surface, and the Raman scattered light is enhanced by the LSPR of the nanoparticles. SERS is surface selective, highly sensitive, rapid, label-free and requires little to no sample processing. We are developing SERS-based sensors for in vitro neurotransmitter sensing at physiologically relevant concentrations in biofluids. For in vivo detection, we combine SERS with spatially offset Raman spectroscopy (SORS), where Raman scattering spectra is obtained from subsurface layers of turbid media.  We demonstrate low concentration detection of neurotransmitters in the micromolar (µM) to nanomolar (nM) concentration ranges with SESORS in a brain tissue mimic through the skull.

Wednesday, March 18, 2020

A Designer's Toolkit for Constructing Complex Nanoparticle Libraries

A Designer's Toolkit for Constructing Complex Nanoparticle Libraries

Dr. Raymond Schaak | Penn State University

Professor Sen Zhang

ABSTRACT

Multi-component nanoparticles offer unique opportunities to combine different properties in a single construct, enabling both multi-functionality and the emergence of new synergistic functions. Synthesizing such multi-component nanoparticles requires simultaneous control over size, shape, composition, and structure, as well as interfaces and spatial arrangements. We have been developing two complementary strategies for synthesizing multi-component nanoparticles. The first approach involves heterogeneous seeded growth, where interfaces and asymmetry are introduced by sequentially growing new nanoparticles off of the surfaces of existing nanoparticles. Complex hybrid nanoparticles of a growing number of materials, configurations, and morphologies can now be synthesized. The second approach involves sequential partial cation exchange reactions, where interfaces and asymmetry are introduced by compositional modifications that are made within an existing nanoparticle. A growing library of complex heterostructured metal sulfide nanoparticles can now be rationally designed and then readily synthesized.

Dr. Raymond Schaak | Penn State University
Hosted by Professor Sen Zhang
Friday, March 6, 2020

Electrochemical Energy Storage through Ligand-Based Charge Manipulation

Electrochemical Energy Storage through Ligand-Based Charge Manipulation

Dr. Mitch Anstey | Davidson College

Professor Charlie Machan

ABSTRACT

Public and private investments in energy storage have created a 100 billion dollar industry, and this industry is now converging on grid-scale applications due to the urgent need for resource conservation and our ever-increasing global demand for energy. Redox flow batteries (RFBs) are one method for grid-scale energy storage, being used for peak-shaving and renewable energy incorporation into the grid. Our lab has been using molecular structure as one method to influence electrolyte performance metrics such as Coulombic efficiency, charge-recharge cycling, and voltage window. This talk will describe the work in our lab that focuses on molecular design to address these specific issues in nonaqueous redox flow battery electrolytes.

Dr. Mitch Anstey | Davidson College
Hosted by Professor Charlie Machan
Friday, February 28, 2020

Systematic Methods for Learning Complex Mechanisms from Molecular Dynamics Simulations

Systematic Methods for Learning Complex Mechanisms from Molecular Dynamics Simulations

Dr. Aaron Dinner | University of Chicago

Professor Kateri DuBay

ABSTRACT 

Computers and algorithms are now sufficiently powerful that many complex molecular processes can be simulated at atomic resolution.  Yet it remains challenging to describe dynamics when processes are stochastic and proceed by multiple pathways.  In this talk, I will illustrate these issues with simulations of insulin dimer dissociation, which serves as a paradigm for coupled (un)folding and (un)binding.  Then I will present recent work that we have done to advance methods for efficiently estimating kinetic statistics and systematically learning complex reaction mechanisms from molecular dynamics data.

Dr. Aaron Dinner | University of Chicago
Hosted by Professor Kateri DuBay
Friday, February 21, 2020

Using N-Heterocyclic Olefins (NHOs) and Frustrated Lewis Pairs (FLP) to Promote Small Molecule Activation and Nanomaterial Deposition in the Main Group

Using N-Heterocyclic Olefins (NHOs) and Frustrated Lewis Pairs (FLP) to Promote Small Molecule Activation and Nanomaterial Deposition in the Main Group

Dr. Eric Rivard | University of Alberta

Professor Robert Gilliard

ABSTRACT

This presentation will describe our recent application of Frustrated Lewis Pairs (FLPs) to gain access to inorganic methylene EH2 complexes (E = Group 14 element) and their use to deposit bulk metal films from solution.[1] This will be followed by a highlight of our studies on anionic N-heterocyclic olefin (NHO) ligands, leading to rare examples of acyclic two-coordinate silylenes (R2Si:). I will also describe the ability of our silylenes to activate strong homo- and heteroatomic bonds under mild conditions.[2]

[1] For reviews of EH2 complexes, see: E. Rivard, Chem. Soc. Rev. 2016, 45, 989-1003.

[2] a) M. M. D. Roy, E. Rivard, Acc. Chem. Res. 2017, 50, 2017-2025; b) C. Hering-Junghans, P. Andreiuk, M. J. Ferguson, R. McDonald, E. Rivard, Angew. Chem., Int. Ed. 2017, 56, 6272-6275; c) M. M. D. Roy, M. J. Ferguson, R. McDonald, Y. Zhou, E. Rivard, Chem. Sci. 2019, 10, 6476-6481.

               

Dr. Eric Rivard | University of Alberta
Hosted by Professor Robert Gilliard
Wednesday, February 19, 2020

Specific Inhibition of Heparanase by Glycopolymers for Cancer and Diabetic Therapeutics

Specific Inhibition of Heparanase by Glycopolymers for Cancer and Diabetic Therapeutics

Dr. Hien Nguyen | Wayne State University

Professor Clifford Stains

ABSTRACT

Specific Inhibition of Heparanase by Glycopolymers for Cancer and Diabetic Therapeutics

Heparanase has been illustrated to regulate aggressive tumor behavior and to play important roles in autoimmune diabetes. Heparanase cleaves polymeric heparan sulfate (HS) molecules into smaller chain length oligosaccharides, allowing for release of angiogenic growth factors promoting tumor development and autoreactive immune cells to reach the insulin-producing b cells. Interaction of heparanase with HS chains is regulated by substrate sulfation sequences, and only HS chains with specific sulfation patterns are cleaved by heparanase. Therefore, heparanase has become a potential target for anticancer and antidiabetic drug development. Several molecules have been developed to target heparanase activity, but only carbohydrate molecules have advanced to clinical trials. However, the carbohydrate-based heparanase inhibitors are heterogeneous in size and sulfation pattern leading to nonspecific binding and unforeseen adverse effects, thus halting their translation into clinical use.

Our group has recently discovered that the sulfation pattern of pendant disaccharide moiety on synthetic glycopolymers could be synthetically manipulated to achieve optimal heparanase inhibition. We have determined that glycopolymer with 12 repeating units was the most potent inhibitor of heparanase (IC50 = 0.10 ± 0.36 nM). This glycopolymer was further examined for cross-bioactivity, using a solution based competitive biolayer interferometry assay, with other HS-binding proteins (growth factors, P-selectin, and platelet factor 4) which are responsible for mediating angiogenic activity, cell metastasis, and antibody-inducedthrombocytopenia. The synthetic glycopolymer has low affinity for these HS-binding proteins in comparison to natural heparin. In addition, the glycopolymer possessed no proliferative properties towards human umbilical endothelial cells (HUVEC) and a potent antimetastatic effect against 4T1 mammary carcinoma cells. Furthermore, our recent results illustrated that treatment of cultured mouse pancreatic b cells with heparanase significantly reduced their survival. In stark contrast, the b cells treated with heparanase plus the synthetic glycopolymer exhibited a survival rate comparable to the b cells treated with the vehicle PBS. In addition, we treated insulin-secreting human pancreas islets with heparanase in the presence or absence of the glycopolymer inhibitor. Alcian blue staining of HS contents indicated that the the glycopolymer inhibitor protected the human islets from destruction of extracellular HS contents caused by elevation of heparanse. The extracellular HS contents play important roles in preserving pancreas β cell function and protecting β cells from destruction by heparanase.

Dr. Hien Nguyen | Wayne State University
Hosted by Professor Clifford Stains
Friday, February 14, 2020

Examining the Dynamics of Glucose Regulation

Examining the Dynamics of Glucose Regulation

Dr. Mike Roper | Florida State University

Professor James Landers

ABSTRACT

Islets of Langerhans are the endocrine portion of the pancreas responsible for maintaining glucose homeostasis via the regulated secretion of numerous hormones, most notably insulin and glucagon. Defects in the secretion of these hormones are associated with a number of metabolic diseases, including diabetes and the metabolic syndrome. The ability to measure these glucose-regulating peptides with high time resolution and sensitivity is necessary to fully resolve the secretion dynamics of these factors and to understand how they change at various disease stages.

In this talk, a number of analytical strategies our group has developed which enable monitoring of secretion with high time resolution will be discussed. These assays include multi-color electrophoretic affinity assays, electrochromatographic separations for small molecule transmitters, and fluorescence anisotropy immunoassays. A number of these assays have been integrated into microfluidic systems to enable monitoring of secretions as a function of time. Select applications of these devices will also be discussed including how groups of islets can coordinate their secretion in vivo into pulses that are necessary for proper glucose utilization.

Dr. Mike Roper | Florida State University
Hosted by Professor James Landers
Friday, January 31, 2020

Jefferson Lecture - Re-imagining the Periodic Table: Sustainable Catalysis for the 21st Century

Jefferson Lecture - Re-imagining the Periodic Table: Sustainable Catalysis for the 21st Century

Dr. Paul Chirik | Princeton University

Graduate Student Council
Dr. Paul Chirik | Princeton University
Hosted by Graduate Student Council
Friday, January 24, 2020

Fall 2019

New Frontiers in Cosmic Carbon

New Frontiers in Cosmic Carbon

Dr. Brett McGuire | National Radio Astronomy Observatory

Professor Ilse Cleeves

Abstract.

Molecular clouds of gas and dust pervade our galaxy, and are the birthplaces of stars and planets.  The temperature, density, and radiation conditions inside these clouds make them unique chemical laboratories for studying both fundamental reactions and the evolution of the molecular complexity that seeds primitive planets.  We have recently discovered a new regime of unexpected low-temperature aromatic chemistry in these sources that has far-reaching implications on the lifecycle of carbon in the universe.  These detections are demanding new analysis techniques to extract the maximum information content from increasingly large and complex datasets both observationally and in the laboratory.  Here, I will discuss novel applications of signal processing and analysis in both arenas.  Observationally, we are using Bayesian approaches combined with matched filtering techniques, while in the laboratory, we are conducting reaction screening analyses to try to understand the content and evolution of this new carbon chemistry in space.  I will describe the results of our new observational analysis techniques, as well as outline several new methods we have developed for rapidly screening complex chemical mixtures in the laboratory using pump-probe rotational spectroscopy in a (semi-)automated fashion to enable new molecular discovery.

Dr. Brett McGuire | National Radio Astronomy Observatory
Hosted by Professor Ilse Cleeves
Friday, November 22, 2019

Approaches to the Treatment of Alzheimer’s Disease: Two Targets; Two Modalities

Approaches to the Treatment of Alzheimer’s Disease: Two Targets; Two Modalities

Professor Richard Olson | Bristol-Myers Squibb

Professor Ken Hsu

ABSTRACT

Alzheimer’s disease remains a major unmet medical need representing a huge societal burden and a difficult event in the lives of patients and families. Current treatments do not offer hope for disease altering outcomes and recent attempts to bring forward new therapies have proven largely unsuccessful. This presentation will review two programs at Bristol-Myers Squibb spanning two therapeutic targets and two drug structural classes, or modalities: Small molecules and antisense oligonucleotides (ASOs). Efforts to improve the stereospecific synthesis of an important class of ASOs will be described.

Professor Richard Olson | Bristol-Myers Squibb
Hosted by Professor Ken Hsu
Friday, November 15, 2019

Main Group Lewis Acids for Applications in Catalysis and Anion Transport

Main Group Lewis Acids for Applications in Catalysis and Anion Transport

Professor François Gabbaï | Texas A & M University

Professor Robert Gilliard

ABSTRACT

Main group Lewis acids for applications in catalysis and anion transport

Research in the Gabbaï group has been dedicated to the synthesis and study of Lewis acidic main group compounds with the development of applications in molecular recognition and catalysis as the ultimate goals.  This seminar will highlight a series of recent results obtained in pursuit of these goals.  The first part of the presentation will focus on the chemistry of antimony- and carbon-based Z-type ligands and their demonstrated ability to modulate the catalytic reactivity of adjacent metal centers.  The second part of the presentation will show how boron and antimony-based Lewis acids can be deployed in aqueous media to effectively transport a range of anions across phospholipid bilayers in artificial vesicles as well as in live cells.

Professor François Gabbaï | Texas A & M University
Hosted by Professor Robert Gilliard
Friday, November 8, 2019

Proton-Coupled Electron Transfer by Copper-Oxygen Species Relevant to Enzyme Intermediates

Proton-Coupled Electron Transfer by Copper-Oxygen Species Relevant to Enzyme Intermediates

Professor William Tolman | Washington University in St. Louis

Professor Charlie Machan

Characterization of copper intermediates in enzymes and other catalysts that attack strong C-H bonds is important for unraveling oxidation catalysis mechanisms and, ultimately, designing new, more efficient catalytic systems. New insights into the nature of such intermediates may be obtained through the design, synthesis, and characterization of copper-oxygen complexes. Two key proposed examples contain [CuO2]+ and [CuOH]2+ cores, which have been suggested as possible reactive intermediates in monocopper enzymes such as lytic polysaccharide monooxygenase. Recent progress toward the characterization of the structures and properties of complexes with these cores that feature the same supporting ligand will be described, and detailed comparisons of their kinetics in reactions with C-H and O-H bonds will be discussed. Notable differences in their PCET reaction pathways with para-substituted phenols has been discovered that shed new light on the fundamental chemistry of these important core structures.

Professor William Tolman | Washington University in St. Louis
Hosted by Professor Charlie Machan
Friday, November 1, 2019

Chemical Biology and Chemistry for Translational Lipid Biology and Beyond

Chemical Biology and Chemistry for Translational Lipid Biology and Beyond

Professor Ken Hsu | UVA Department of Chemistry

Professor Linda Columbus

ABSTRACT

Lipids represent a rich model system for understanding how nature maintains cellular architecture (membrane building blocks), bioenergetics (energy stores), and communication (secondary messengers) through fine adjustments in enzyme metabolism. Embedded within lipid structures is chemical information that define their metabolic fate and function. Elucidating structure-function relationships of lipids in biological systems has been traditionally challenging because of the massive structural diversity of lipids in nature and lack of tools to selectively probe their function in vivo. I will describe efforts from my group to use chemical biology and mass spectrometry to gain fundamental insights into diacylglycerol (DAG) biology and the translational potential of modulating DAG pathways in inflammation and immuno-oncology.

Professor Ken Hsu | UVA Department of Chemistry
Hosted by Professor Linda Columbus
Friday, October 25, 2019

Magnesium(I) Dimers: Universal Reductants for the Synthetic/Catalytic Chemist?

Magnesium(I) Dimers: Universal Reductants for the Synthetic/Catalytic Chemist?

Professor Cameron Jones | Monash University: Director, Monash Centre for Catalysis

Professor Robert Gilliard

ABSTRACT

The renaissance that has occurred in main group chemistry over the last several decades has been largely driven by the realization that very low oxidation state p-block compounds can be stable species at ambient temperature, given the right ligand environment. Increasingly, such compounds are being shown to possess "transition metal-like" reactivity patterns in small molecule activations, and associated catalytic synthetic transformations.[1] In late 2007 we extended this field to the s-block with the preparation of the first room temperature stable molecular compounds containing magnesium-magnesium covalent bonds, viz. LMgMgL (L = bulky guanidinate or b-diketiminate, e.g. 1).[2] We have subsequently shown that the unique properties these species possess lend them to use as versatile reducing agents in both organic and inorganic synthetic protocols.[3] The products of such reactions are often inaccessible using more classical reducing agents. In this lecture an overview of what has been achieved with these remarkable reagents will be given, with an emphasis placed on the preparation of unprecedented examples of low oxidation state/low coordination number metal-metal bonded complexes involving metals from the s-, p- and d-blocks, e.g. 2-4.[4] The further chemistry of these highly reactive systems will also be discussed, as will our efforts to incorporate magnesium(I) dimers into catalytic cycles.[5]

 

REFERENCES

[1] Power, P. P. Nature 2010, 463, 171.

[2] Green, S. P.; Jones, C.; Stasch, A. Science 2007, 305, 1136.

[3] Jones, C. Nature Rev. Chem. 2017, 1, 0059.

[4] Bonyhady, S.J.; Collis, D.; Holzmann, N.; Edwards, A.J.; Piltz, R.O.; Frenking, G.; Stasch, A.; Jones, C. Nature Comm., 2018, 9, 3079.

[5] (a) Boutland, A. J.; Carroll, A.; Lamsfus, C. A.; Stasch, A.; Maron, L.; Jones, C. J. Am. Chem. Soc. 2017, 139, 18190; (b) Yuvaraj, K.; Douair, I.; Paparo, A.; Maron, L.; Jones, C. J. Am. Chem. Soc., 2019, 141, 8764.

Professor Cameron Jones | Monash University: Director, Monash Centre for Catalysis
Hosted by Professor Robert Gilliard
Wednesday, October 23, 2019

Annual Burger Lecture: Removing Organic Pollutants from Water Using Polymers Derived from Corn

Annual Burger Lecture: Removing Organic Pollutants from Water Using Polymers Derived from Corn

Dr. William Dichtel | Northwestern University

Professor Cassandra Fraser

Organic micropollutants, such as pesticides and pharmaceuticals, have raised concerns about negative effects on ecosystems and human health. These compounds are introduced into water resources by human activities, and current wastewater treatment processes do not remove them. Activated carbons are the most widespread adsorbents used to remove organic pollutants from water, but they have several deficiencies, including poor removal of relatively hydrophilic micropollutants, inferior performance in the presence of naturally occurring organic matter, and energy intensive regeneration processes. I will describe polymers based on β-cyclodextrin, an inexpensive, sustainably produced derivative of glucose, that binds these emerging contaminants from water. We also recently modified our original polymer design to target perfluorinated alkyl substances such as PFOA and PFOS, which are environmentally persistent and associated with negative effects at trace concentrations.

Figure: A porous polymer containing cyclodextrins (blue cups) binds organic pollutants from water.

 
Dr. William Dichtel | Northwestern University
Hosted by Professor Cassandra Fraser
Friday, October 18, 2019

Graham Lecture: Increasing Access to Global Healthcare through Process Intensification

Graham Lecture: Increasing Access to Global Healthcare through Process Intensification

Dr. Frank Gupton | Virginia Commonwealth University

Professor Brooks Pate

Abstract:   Access to global public healthcare is impacted by many technical, economic, and social factors. It is widely recognized that the resources required to deliver and improve global public health are currently constrained.  A powerful way to increase access is to lower the cost of products and services that have already proven to be effective.  Currently, the cost of producing a wide range of pharmaceutical products is higher than it needs to be. The mission of Medicines for All (M4All) is to transform active pharmaceutical ingredient (API) processes in order to reduce medication cost and improve patient access.  To fulfil this objective, M4ALL has developed a set of core principles for API process development, which are derived from fundamental elements of process intensification that are commonly known but often neglected. These principles have been applied to several global health drugs yielding dramatic improvements in chemical efficiency. The development of novel and highly efficient heterogeneous catalysts for cross-coupling reactions that support this effort will also be presented.

Dr. Frank Gupton | Virginia Commonwealth University
Hosted by Professor Brooks Pate
Thursday, October 10, 2019

The Unique Chemistry of Dying Stars: Organics, Metals, and Fullerenes

The Unique Chemistry of Dying Stars: Organics, Metals, and Fullerenes

Dr. Lucy Ziurys | University of Arizona

Professor Robin Garrod

ABSTRACT

The past 40 years of astrochemistry has showed that unusual molecules readily form in extreme interstellar environments. One of these interesting settings is the material lost from stars in their final stages. Here gas-phase material is ejected from the hot stellar photosphere, often at high velocities, and rapidly cools to create molecules and dust grains under competing thermodynamic and kinetic conditions. Using a combined program of high-resolution laboratory spectroscopy and astronomical observations, we have been investigating the chemistry of stellar ejecta. Measurements of rotational spectra of small, metal-bearing molecules using millimeter-wave and Fourier transform microwave methods have been conducted, such as simple oxides and dicarbides. Molecular-line observations have shown that some of these exotic species are present in circumstellar material, defying thermodynamic predictions, including such highly refractory molecules as VO and FeCN. At the very late stages of stellar evolution, the planetary nebula phase, a wide variety of carbon-containing molecules appear to be present, ranging from CCH and c-C3H2 to C60, despite the presence of very high ultraviolet radiation fields. The chemical formation of this wide variety of chemical compounds will be discussed, including a novel mechanism for fullerene production in circumstellar environments.

Dr. Lucy Ziurys | University of Arizona
Hosted by Professor Robin Garrod
Friday, October 4, 2019

Why does O-GlcNAc Transferase Matter?

Why does O-GlcNAc Transferase Matter?

Professor Suzanne Walker | Harvard University

Professor Ken Hsu

ABSTRACT

O-GlcNAc transferase (OGT) is essential for viability of all mammalian cells but no one knows why. OGT has two catalytic activities that take place in the same active site. In one, OGT attaches N-acetyl glucosamine to serine and threonine side chains of at least a thousand nuclear and cytoplasmic proteins. In the other, OGT cleaves a transcriptional co-activator involved in cell-cycle regulation. Because OGT is found in several stable protein-complexes, it is also proposed to act as a scaffolding protein. How do you dissect the cellular functions of an essential protein that has multiple biochemical activities and a thousand different substrates? I will argue that you need to start by understanding the chemistry –  mechanisms of catalysis and substrate recognition – so you can develop variants with some activities and not others. I will describe how we have done so and how we have used our knowledge to answer a fundamental question: What is the essential biochemical function of OGT for cell survival? I will also describe how we have developed and used a specific small molecule inhibitor of OGT to uncover an unexpected role in controlling RNA splicing.  

Professor Suzanne Walker | Harvard University
Hosted by Professor Ken Hsu
Friday, September 27, 2019

Ethylene Trimerization Using Chromium Pyridyl Amine Complexes: A Computational Study

Ethylene Trimerization Using Chromium Pyridyl Amine Complexes: A Computational Study

Professor Glen Alliger | ExxonMobil

Professor Charlie Machan

ABSTRACT

Selective trimerization of ethylene to produce 1-hexene is a commercially practiced process that yields valuable comonomer for linear low density polyethylene production. Several years ago, ExxonMobil chemists developed a family of chromium catalysts useful for ethylene trimerization, but a mechanistic understanding of the catalysis remained elusive. This talk presents a mechanistic proposal to explain the catalytic selectivity, supported by a computational exploration of proposed cycle. Results will be discussed in terms of geometric requirements for reaction and the fundamental steps involved in catalysis.

Professor Glen Alliger | ExxonMobil
Hosted by Professor Charlie Machan
Friday, September 20, 2019

Engineering Adaptive (bio) Materials from Functional Polymers and Peptide Stereocomplexes

Engineering Adaptive (bio) Materials from Functional Polymers and Peptide Stereocomplexes

Dr. Rachel Letteri | University of Virginia (Department of Chemical Engineering)

Professor Rebecca Pompano

ABSTRACT

Advancing highly tunable synthetic materials to operate in an increasingly cooperative fashion with biological systems and the environment provides a compelling opportunity to expand the repertoire and enhance the performance of critically needed technologies.  To this end, we are developing new building blocks for polymer biomaterials so as to access to a breadth of thermomechanical properties and promote productive interactions with biological systems.  The first part of this talk will describe our research on mirror image peptide complexes, or ‘stereocomplexes’, as tunable, transient junctions in synthetic polymer biomaterials.  Varying the primary structure of the peptides and solvent conditions were found to markedly impact the secondary structure, which in turn determined the macroscale properties of polymer-peptide conjugates.  These junctions are envisioned as molecular ‘VELCRO®’ strips and are anticipated to impart a myriad of adaptive properties, including self-healing and shear thinning, useful for 3D printing-based manufacturing processes and targeting biological proteins, among other applications.  Another approach to engineer adaptive materials involves controlling degradation rates, and the second part of this talk will describe the synthesis, thermomechanical characterization, and degradation profiles of poly(β-amino ester) networks.  By adjusting monomer composition, networks were obtained with degradation times scales that spanned hours to months.  Synthetically accessible and highly tunable, this polymer platform offers enormous opportunities, from sacrificial template materials for biomanufacturing to commodity materials that degrade after their useful lifetime.  Ultimately, by intertwining concepts from small molecule and peptide chemistry with polymer science and engineering, we aim to advance polymer and peptide building blocks, and thereby contribute to next generation materials and technologies for healthcare and beyond.

Dr. Rachel Letteri | University of Virginia (Department of Chemical Engineering)
Hosted by Professor Rebecca Pompano
Friday, September 13, 2019

SYNTHETIC COLLOQUIUM | Symmetry Making and Breaking in Seeded Growth of Metal Nanocrystals

SYNTHETIC COLLOQUIUM | Symmetry Making and Breaking in Seeded Growth of Metal Nanocrystals

Dr. Sara Skrabalak | Indiana University, Bloomington

Professor Sen Zhang

Crystal growth theory predicts that heterogeneous nucleation will occur preferentially at defect sites, such as the vertices rather than the faces of shape-controlled seeds. Platonic metal solids are generally assumed to have vertices with nearly identical chemical potentials, and also nearly identical faces, leading to the useful generality that heterogeneous nucleation preserves the symmetry of the original seeds in the final product. This presentation will discuss how this generality can be used to access stellated metal nanocrystals with high and tunable symmetries for applications in plasmonics. This presentation will also discuss the limits of this generality in the extreme of low supersaturation. A strategy for favoring localized deposition that differentiates between both different vertices and different edges or faces, i.e., regioselective deposition, will be demonstrated. Such regioselective heterogeneous nucleation was achieved at low supersaturation by a kinetic preference for high-energy defect-rich sites over lower-energy sites. This outcome was enhanced by using capping agents to passivate facet sites where deposition was not desired. Collectively, the results presented provide a model for breaking the symmetry of seeded growth and for achieving regioselective deposition.

Dr. Sara Skrabalak | Indiana University, Bloomington
Hosted by Professor Sen Zhang
Wednesday, September 11, 2019

Graphene-based Materials for Applications in Heterogeneous Catalysis, Water Treatment and Solar Water Desalination

Graphene-based Materials for Applications in Heterogeneous Catalysis, Water Treatment and Solar Water Desalination

Dr. Samy El Shall | Virginia Commonwealth University

Professor Eric Herbst

This talk will address the development of three classes of graphene-based materials as (1) support for metal nanoparticle catalysts in heterogeneous catalysis, (2) sorbent materials for the removal of heavy metal ions from polluted water, and (3) photothermal energy converter materials for efficient solar water desalination.

In heterogeneous catalysis, we will discuss the superior catalytic activity of Pd nanoparticles supported on reduced graphene oxide (RGO) nanosheets for carbon-carbon cross-coupling reactions. Second, the enhanced catalytic activity for the Fe-based nanoparticle catalysts supported on graphene in the Fischer-Tropsch Synthesis of liquid transportation fuels will be presented. Finally, the superior catalytic activity and selectivity of Pd nanoparticles supported on a sandwich-type nanocomposite consisting of Metal-Organic Frameworks (MOFs) wrapped with thin RGO nanosheets for the biomass-refining of liquids derived from lignocelluloisc sources will be presented.

For the removal of heavy metals from water, we will discuss the development of chemically modified graphene-based adsorbents containing highly efficient chelating groups such as diamine, imino and thiourea for the effective extraction of the toxic metal ions mercury (II), lead (II) and arsenic (V) from wastewater.

For photothermal energy conversion, we will discuss the development of a new generation of highly efficient, flexible, low weight, highly porous and cost effective Plasmonic Graphene Polyurethane (PGPU) nanocomposite materials for solar steam generation through the efficient evaporation of water surface pools. The PGPU nanocomposites contain metallic nanoparticles that exhibit very strong solar absorption. The polyurethane (PU) foam provides a hydrophilic surface with abundant microporous structure, excellent thermal insulation properties, and facile and scalable synthesis. The high solar thermal evaporation efficiency, excellent stability and long-time durability make the PGPU nanocomposites excellent candidates for solar-steam-generation applications and seawater desalination.

Dr. Samy El Shall | Virginia Commonwealth University
Hosted by Professor Eric Herbst
Friday, September 6, 2019

Escaping Flatland: Synthetic Innovation for the Future of Drug Discovery

Escaping Flatland: Synthetic Innovation for the Future of Drug Discovery

Professor Mike Hilinski | Department of Chemistry Kickoff Seminar

ABSTRACT

The majority of FDA-approved drugs are small organic molecules, generally defined as having a molecular weight below 900 g/mol. The speed and reliability with which one can synthesize complex bioactive small molecules is a major limiting factor in the race to discover new drugs. As a consequence of this, a historical overreliance on a small number of highly robust synthetic methods has limited the diversity of chemical structures generally pursued as drug leads. A long-term goal of our research program is to develop new synthetic methods that fill significant current gaps in the organic chemist’s toolbox, in order to work towards eliminating synthetic considerations as a barrier to the discovery of new therapeutics. Two major areas of research will be presented: (1) The development of new strategies and new modes of catalysis for the direct, site-selective functionalization of C–H bonds, and (2) The development of new methods for the synthesis and selective modification of nitrogen-containing heterocycles, which are present in the majority of FDA-approved small molecule drugs.

Professor Mike Hilinski | Department of Chemistry Kickoff Seminar
Friday, August 30, 2019

Spring 2019

Energy Conversion and Storage: Novel Materials and Operando Methods

Energy Conversion and Storage: Novel Materials and Operando Methods

Professor Héctor D. Abruña | Cornell University

Professor Sen Zhang
Professor Héctor D. Abruña | Cornell University
Hosted by Professor Sen Zhang
Friday, April 19, 2019

Two-Dimensional Carbides and Nitrides (MXenes) Challenge Graphene (Location: Monroe Hall Rm 110)

Two-Dimensional Carbides and Nitrides (MXenes) Challenge Graphene (Location: Monroe Hall Rm 110)

Dr. Yury Gogotsi | Drexel University

Professor Sen Zhang

ABSTRACT

Two-dimensional (2D) materials with a thickness of a few nanometers or less can be used as single sheets, or as building blocks, due to their unique properties and ability to assemble into a variety of structures. Graphene is the best-known example, but several other elemental 2D materials (silicene, borophene, etc.) have been discovered. Numerous compounds, ranging from clays to boron nitride (BN) and transition metal dichalcogenides, have been produced as 2D sheets. By combining various 2D materials, unique combinations of properties can be achieved which are not available in any bulk material. The family of 2D transition metal carbides and nitrides (MXenes) has been expanding rapidly since the discovery of Ti3C2 in 2011 [1]. Approximately 30 different MXenes have been synthesized, and the structure and properties of numerous other MXenes have been predicted using density functional theory (DFT) calculations [2]. Moreover, the availability of solid solutions on M and X sites, control of surface terminations, and the discovery of ordered double-M MXenes (e.g., Mo2TiC2) offer the potential for synthesis of dozens of new distinct structures.

This presentation will describe the synthesis of MXenes by selective etching of layered ceramic precursors, including various MAX phases. Delamination into single-layer 2D flakes and assembly into films and 3D structures, as well as their properties will be discussed. Synthesis-Structure-Properties relations of MXenes will be addressed on the example of Ti3C2.

The versatile chemistry of the MXene family renders their properties tunable for a large variety of applications [3]. Oxygen or hydroxyl- terminated Menes, such as Ti3C2O2, have been shown to have redox capable transition metals layers on the surface and offer a combination of high electronic conductivity with hydrophilicity, as well as fast ionic transport [4].  This, among many other advantageous properties, makes the material family promising candidates for energy storage and related electrochemical applications [5], but applications in plasmonics, electrocatalysis, biosensors, water purification/ desalination and other fields are equally exciting. In particular, capacitive deionization and membrane desalination and purification will be addressed.

 

Dr. Yury Gogotsi | Drexel University
Hosted by Professor Sen Zhang
Wednesday, April 17, 2019

Understanding Cardiac Calcium Signaling from Molecules to Systems

Understanding Cardiac Calcium Signaling from Molecules to Systems

Professor Peter Kekenes-Huskey | University of Kentucky

Professor Kateri DuBay

Abstract.

Calcium is critical to a wide range of physiological processes, including neurological function, immune responses, and muscle contraction in the heart. Calcium-dependent signaling pathways driving these functions enlist a variety of proteins and channels that must rapidly and selectively bind calcium against thousand-fold higher cation concentrations. Frequently these pathways further rely on co-localization of these proteins within specialized subcellular structures to function properly. Our lab has developed multi-scale simulation tools to understand calcium homeostasis and its dysregulation at the molecular through systems levels. Applications include molecular simulations to predict protein-protein interactions, reaction-diffusion simulations that leverage high-resolution microscopy data and computer vision techniques to characterize morphological differences in cells important to their function. In this seminar, I will describe these tools and their applications to a calcium-dependent signaling pathway driven by calmodulin and calcineurin activation, which is important in cardiac development and hypertrophy.

Professor Peter Kekenes-Huskey | University of Kentucky
Hosted by Professor Kateri DuBay
Friday, April 5, 2019

Hecht Lecture: Redesign of Vancomycin for Resistant Bacteria

Hecht Lecture: Redesign of Vancomycin for Resistant Bacteria

Professor Dale Boger | Scripps Research Institute; La Jolla, CA

Professor Sid Hecht

ABSTRACT

A summary of studies on the total synthesis and evaluation of the vancomycin family of glycopeptide antibiotics, their ligand binding pocket redesign to address the underlying molecular basis of resistance, and their subsequent peripheral tailoring to address the emerging public health problem of vancomycin resistance will be presented.

 

 

 

Professor Dale Boger | Scripps Research Institute; La Jolla, CA
Hosted by Professor Sid Hecht
Friday, March 29, 2019

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