Seminars Archive

Fall 2020

Borane Lewis Acids and B-N Lewis Pairs: From Molecules to Materials

Borane Lewis Acids and B-N Lewis Pairs: From Molecules to Materials

Dr. Frieder Jaekle | Rutgers University, Newark

Professor Robert Gilliard

The incorporation of main group elements into conjugated materials is known to result in unusual properties and to enable new functions.[1] In particular, the ability of tricoordinate boron to participate in p-delocalization can have a dramatic effect on the optoelectronic properties of conjugated materials by selectively lowering the LUMO orbital levels. The electron-deficient character of boron also enables the reversible formation of Lewis pairs (LPs) by interaction of Lewis acids with Lewis bases.

In our recent work, we have explored the incorporation of boron into conjugated oligomers, macrocycles, and polymers for optoelectronic applications.[2] We have also demonstrated that base-directed electrophilic aromatic C-H borylation provides an effective means to generate luminescent B-N containing conjugated materials with unusual properties such as self-sensitized singlet oxygen generation.[3]

On the other hand, the judicious decoration of polymers with organoborane Lewis acid sites can be exploited in sensory and stimuli-responsive materials, as well as the development of supported catalysts that rely on the ability of Lewis acids to activate small molecules.[4] In addition, we have discovered that “smart” dynamic materials can be generated by embedding both Lewis acid and base sites into polymer networks.[5]

In this talk I will discuss some of these discoveries and highlight their impact in diverse application fields ranging from organic electronic materials and chemosensors to reprocessible elastomers and supported catalysts.

References:

  1. (a) Main Group Strategies towards Functional Hybrid Materials, T. Baumgartner, F. Jäkle, Eds. John Wiley & Sons Ltd, Chichester, 2018; (b) F. Vidal, F. Jäkle, Angew. Chem. Int. Ed. 2019, 58, 5846.
  2. (a) B. Meng, Y. Ren, J. Liu, F. Jäkle, L. Wan, Angew. Chem. Int. Ed. 2018, 57, 2183; (b) N. Baser-Kirazli, R. A. Lalancette, F. Jäkle, Angew. Chem. Int. Ed. 2020, 59, 8689.
  3. (a) K. Liu, R. A. Lalancette, F. Jäkle J. Am. Chem. Soc. 2019, 141, 7453; (b) M. Vanga, R. A. Lalancette, F. Jäkle Chem. Eur. J. 2019, 25, 10133.
  4. (a) F. Cheng, E. M. Bonder, F. Jäkle, J. Am. Chem. Soc. 2013, 135, 17286; (b) F. Vidal, J. McQuade, R. A. Lalancette, F. Jäkle, J. Am. Chem. Soc. 2020, 142, DOI: 10.1021/jacs.0c05454; (c) H. Lin, S. Patel, F. Jäkle, Chem. Eur. J. 2020, submitted.
  5. F. Vidal, J. Gomezcoello, R. A. Lalancette, F. Jäkle, J. Am. Chem. Soc. 2019, 141, 15963.

 

Biography

Frieder Jäkle is a Distinguished Professor in the Department of Chemistry at the Newark Campus of Rutgers University. He received his Diploma in 1994 and Ph.D. in 1997 from TU München, Germany, under the direction of Prof. Wagner. After a postdoctoral stint with Prof. Manners at the University of Toronto he joined Rutgers University in 2000. His research interests revolve around main group chemistry as applied to materials and catalysis, encompassing projects on organoborane Lewis acids, conjugated hybrid materials, luminescent materials for optoelectronic and sensory applications, stimuli-responsive and supramolecular polymers. He is the recipient of an NSF CAREER award (2004), an Alfred P. Sloan fellowship (2006), a Friedrich Wilhelm Bessel Award of the Alexander von Humboldt Foundation (2009), the ACS Akron Section Award (2012), the Boron Americas Award (2012) and the Board of Trustees Research Award at Rutgers University (2017). In 2019 he was named a Fellow of the American Chemical Society. He has served on the editorial advisory boards of several journals, including Macromolecules, ACS Macro Letters, and Organometallics.

 

Dr. Frieder Jaekle | Rutgers University, Newark
Hosted by Professor Robert Gilliard
Friday, September 18, 2020

Illuminating the Biochemical Activity Architecture of the Cell

Illuminating the Biochemical Activity Architecture of the Cell

Dr. Jin Zhang | University of California, San Diego

Professor Andreas Gahlmann

The complexity and specificity of many forms of signal transduction require spatial microcompartmentation and dynamic modulation of the activities of signaling molecules, such as protein kinases, phosphatases and second messengers. In this talk, I will focus on cAMP/PKA, PI3K/Akt/mTORC1 or Ras/ERK signaling pathways and present studies where we combined genetically encoded fluorescent biosensors, advanced imaging, targeted biochemical perturbations and mathematical modeling to probe the biochemical activity architecture of the cell.

Dr. Jin Zhang received her PhD in Chemistry from the U. Chicago.  After completing her postdoctoral work at University of California, San Diego (UCSD), she joined the faculty of Johns Hopkins University School of Medicine in 2003. She was promoted to Professor in 2013. In 2015 she moved back to UCSD and is currently a Professor of Pharmacology, Bioengineering and Chemistry & Biochemistry. Research in her lab focuses on developing enabling technologies to probe the active molecules in their native environment and characterizing how these active molecules change in diseases including cancer. Professor Zhang is a recipient of the NIH Director’s Pioneer Award (2009), the John J. Abel Award in Pharmacology from ASPET (2012), the Pfizer Award in Enzyme Chemistry from ACS (2012), and the Outstanding Investigator Award (2015) from NCI. She was elected as a Fellow of AAAS in 2014 and a Fellow of AIMBE in 2019.

Dr. Jin Zhang | University of California, San Diego
Hosted by Professor Andreas Gahlmann
Friday, September 11, 2020

Expanding the Chemical Toolbox for Acoustic-based Imaging of Cancer

Expanding the Chemical Toolbox for Acoustic-based Imaging of Cancer

Dr. Jefferson Chan | University of Illinois, Urbana-Champaign

Professor Clifford Stains

Many disease states are characterized by molecular level changes that occur before detectable symptoms have begun to manifest. In order to maximize treatment outcomes it is essential to accurately detect such alterations at an early stage. Chemical probes designed to selectively image such molecular processes have the potential to not only aid in disease diagnosis but can also provide unique insights into disease progression. As an important step toward these goals we have developed a palette of activatable probes for photoacoustic imaging and apply these to visualize changes in the tumor microenvironment. Briefly, photoacoustic imaging is a state-of-the-art technique that generates ultrasound signals from light, which can be detected and converted into high-resolution 3D images. Since sound scattering is three orders of magnitude less than light in tissue, photoacoustic imaging can be employed to image up to 8 cm in depth while achieving micron resolution. To image deeper regions of the body in real-time, we have recently developed the first activatable ‘smart bubbles’ for ultrasound imaging. Like our photoacoustic probes, smart bubbles respond selectively to a disease property to provide signal enhancements via enhancement of their echogenic properties. In this seminar, we will discuss the strategies employed to construct both photoacoustic and ultrasound probes, as well as highlight notable examples from our laboratory.      

 

Brief Bio:

Professor Chan received his BSc degree in chemistry from the University of British Columbia in 2006 and his PhD from Simon Fraser University (Prof. Andrew Bennet) in 2011. For his graduate research, he received the Boehringer Ingelheim (Canada) Doctoral Research Award for the top Canadian thesis in the areas of organic and bioorganic chemistry. From 2011-2014 he was a Human Frontiers Science Program Postdoctoral Fellow at the University of California, Berkeley (Prof. Christopher Chang). In the fall of 2014 he joined the faculty at the University of Illinois, Urbana-Champaign.

Dr. Jefferson Chan | University of Illinois, Urbana-Champaign
Hosted by Professor Clifford Stains
Friday, September 4, 2020

Lighting up inflammation outside the body using chemistry and microfluidics

Lighting up inflammation outside the body using chemistry and microfluidics

Dr. Rebecca Pompano | Assistant Professor, University of Virginia, Department of Chemistry

Professor Jill Venton

Life is sustained through a delicate balancing act of the immune system, a complex network of molecular and cellular interactions from which health or disease can emerge.  Despite a long catalogue of the cells and signaling proteins in this system, traditional experimental approaches have struggled to explain how they are organized in organs such as the lymph node to dynamically protect against infection, cancer, and autoimmunity.  The overarching goal of my laboratory is to develop bioanalytical methods to visualize where, when, and how cells interact during immunity and inflammation, to inform the development of immunotherapies. In this talk, I will describe the development of (1) hybrids of microfluidics with live immune tissues, to study local dynamics in the lymph node and multi-organ immunity, and (2) novel, spatially resolved analyses of the activity of cells and proteins in living tissue.  I also will give a preview of the future, with our work towards better understanding the organization of the lymph node by building one from cells, matrix elements, and proteins.  

Dr. Rebecca Pompano | Assistant Professor, University of Virginia, Department of Chemistry
Hosted by Professor Jill Venton
Friday, August 28, 2020

Spring 2020

SPRING SEMINARS HAVE BEEN CANCELLED

SPRING SEMINARS HAVE BEEN CANCELLED

Friday, April 24, 2020

SPRING SEMINARS HAVE BEEN CANCELLED

SPRING SEMINARS HAVE BEEN CANCELLED

Friday, April 17, 2020

SPRING SEMINARS HAVE BEEN CANCELLED

SPRING SEMINARS HAVE BEEN CANCELLED

Friday, April 17, 2020

SPRING SEMINARS HAVE BEEN CANCELLED

SPRING SEMINARS HAVE BEEN CANCELLED

Wednesday, April 15, 2020

SPRING SEMINARS HAVE BEEN CANCELLED

SPRING SEMINARS HAVE BEEN CANCELLED

ABSTRACT

Antisense Oligonucleotide Therapeutics for Neurological Diseases

Antisense oligonucleotides (ASOs) are synthetic, chemical modified nucleic acid analogs designed to bind to RNA by Watson-Crick base paring and upon binding, modulate the function of the targeted RNA. There are a variety of mechanisms by which ASOs can modulate RNA function dependent on the chemical design of the ASO, the type of RNA and where on the RNA the ASO is designed to bind. Both protein coding, as well as non-coding RNAs, can be targets of ASO based drugs, significantly broadening therapeutic targets for drug discovery compared to small molecules and protein-based therapeutics. The recent approval of nusinersen (Spinraza™) as a treatment for spinal muscular atrophy (SMA) and inotersen (Tegsedi) for polyneuropathy of hereditary transthyretin-mediated amyloidosis (hATTR)  validates the utility of antisense drugs for the treatment of neurological  diseases. A summary of the progress, lessons learned and future challenges applying antisense technology for neurological diseases will be provided.

Friday, April 10, 2020

VISITATION WEEKEND HAS BEEN CANCELLED

VISITATION WEEKEND HAS BEEN CANCELLED

Friday, April 3, 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

Pages