Seminars Archive

Spring 2022

Dr. Sharon Glotzer | University of Michigan

Dr. Sharon Glotzer | University of Michigan

Professor Kateri DuBay
Hosted by Professor Kateri DuBay
Thursday, June 24, 2021

Spring 2021

Burger Lecture | Harnessing Chemistry to Understand the Roles of Glycans in Neuroplasticity

Burger Lecture | Harnessing Chemistry to Understand the Roles of Glycans in Neuroplasticity

Dr. Linda Hsieh-Wilson | CalTech |

Professor Ken Hsu

The field of chemical neurobiology is providing insights into the molecules and interactions involved in neuronal development, sensory perception, and memory storage. In this talk, I will describe the development of chemical tools to understand how glycosaminoglycans contribute to neuroplasticity – the ability of the brain to adapt and form new neural connections. By combining synthetic organic chemistry, biochemistry, cell biology, and neurobiology, we have shown that specific sulfation motifs within these polysaccharides regulate signaling events that underlie processes such as axon regeneration, synaptic plasticity, and the formation of neural circuits.  

Dr. Linda Hsieh-Wilson | CalTech |
Hosted by Professor Ken Hsu
Friday, April 23, 2021

ACS Poster Session

ACS Poster Session

Friday, April 16, 2021

Challenges and Opportunities in Chemical Separations with Porous Materials

Challenges and Opportunities in Chemical Separations with Porous Materials

Dr. Michael Katz | Memorial University of Newfoundland |

Diane Dickie, Ph.D., Senior Scientist

Challenges and Opportunities in Chemical Separations with Porous Materials

Porous materials such as metal-organic frameworks have been extensively studied for applications in gas-adsorption, catalysis, and chemical separation (to name a few). With particular focus on separations, one of the long-term goals in my research program is to implement porous materials in real-world applications. For the research team to be successful, it is critical to address these challenges from a top-down approach. Factoring in issues such as partial pressure, overall gas composition, and regeneration need be at the forefront of the research. With that in mind, the presentation will explore how porous materials can be designed to address the challenges associated with chemical separations.

Dr. Michael Katz | Memorial University of Newfoundland |
Hosted by Diane Dickie, Ph.D., Senior Scientist
Friday, April 9, 2021

Olfactory Receptors in Vascular Macrophages Drive Atherosclerosis by NLRP3-Dependent IL-1 Production

Olfactory Receptors in Vascular Macrophages Drive Atherosclerosis by NLRP3-Dependent IL-1 Production

Klaus Ley, M.D. | La Jolla Institute for Immunology | Division Head/Professor Center for Autoimmunity and Inflammation

Professors Jill Venton and David Cafiso

Atherosclerosis is an inflammatory disease of the arterial wall driven by macrophages and other immune cells. Olfactory receptors (OLFRs) are G-protein coupled receptors expressed primarily in olfactory epithelium and are responsible for the sense of smell. OLFRs expressed in multiple extra-nasal tissues have been implicated in diverse biological processes. Here we show that mouse vascular macrophages express many olfactory receptors including Olfr2 (also known as I7), a receptor for octanal. They also express Rtp1, Rtp2, Adcy3, Gnal and the cyclic nucleotide-gated ion channel subunits Cnga1, 2, 3, 4 and Cngb1, accessory molecules needed for Olfr signaling and trafficking. Ligation of Olfr2 and its human orthologue (OR6A2), expressed in human atherosclerotic plaque and in human monocyte-derived macrophages, activates the NLRP3 inflammasome and, in synergy with LPS, induces secretion of IL-1α and β. Knocking out Olfr2 and Nlrp3 in mouse or knocking down OR6A2 in human macrophages abolishes IL-1β secretion in response to octanal. Mouse and human blood plasma contain micromolar levels of octanal, which are positively correlated with cholesterol and triglyceride levels. Boosting octanal levels exacerbates and knocking out Olfr2 significantly reduces atherosclerosis in the aortic arch and root. Our findings suggest that inhibitors of OR6A2 are promising targets for drug development to prevent and treat atherosclerosis-based cardiovascular diseases. 

Klaus Ley, M.D. | La Jolla Institute for Immunology | Division Head/Professor Center for Autoimmunity and Inflammation
Hosted by Professors Jill Venton and David Cafiso
Friday, April 2, 2021

Dr. Robert Kennedy | University of Michigan

Dr. Robert Kennedy | University of Michigan

Professors Rebecca Pompano and Jill Venton

The Nanoliter Lab: Droplet Microfluidics for Screening and Sensing

Manipulating samples as droplets within microfluidic devices has emerged as an interesting approach for chemical analysis and screening. In segmented flow, one embodiment of this technology, nanoliter samples are manipulated in microfluidic channels as plugs separated by an immiscible fluid, such as air or fluorinated oil. These plugs serve as miniature test-tubes in which reactions can be performed at high throughput. Microfluidic tools have been developed to split, dilute, extract, and filter such plugs at rates >10 samples/s. We have developed methods to analyze plug content by electrophoresis and mass spectrometry (MS). A natural application of this technology is for high throughput screening. By coupling droplet manipulation with MS detection, it is possible to greatly reduce reagent consumption and eliminate the need for fluorescent labels or coupled reactions. The technology and application to screens of deacetylase reactions and protein-protein interactions will be presented. A more involved screening allows for monitoring reactions of enzyme variants to identify new biocatalysts. Droplet technology can also be used for chemical monitoring or sensing applications. In this approach samples emerging from a miniaturized sampling device are segmented for later analysis. We have used this method to monitor neurotransmitter dynamics in the brain. The technology and application to studies of neurotransmission in a Huntington’s disease models will be demonstrated. 

Hosted by Professors Rebecca Pompano and Jill Venton
Friday, March 26, 2021

2021 Hecht Lecture

2021 Hecht Lecture

Dr. Frank Bennett | Ionis Pharmaceuticals

Dr. Sidney Hecht

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.

Dr. Frank Bennett | Ionis Pharmaceuticals
Hosted by Dr. Sidney Hecht
Wednesday, March 24, 2021

Graduate Visitation Weekend 3/18 - 3/19

Graduate Visitation Weekend 3/18 - 3/19

Friday, March 19, 2021

Membrane Partitioning by and for Cell Wall Synthesis

Membrane Partitioning by and for Cell Wall Synthesis

Dr. Sloan Siegrist | University of Massachusetts |

Professor Marcos Pires

Membrane Partitioning by and for Cell Wall Synthesis

Diffuse, sidewall patterning of cell wall peptidoglycan synthesis by the actin homolog MreB enables model organisms like Escherichia coli and Bacillus subtilis to maintain rod shape. Mycobacteria are also rods but grow from their poles and lack MreB. It is unclear how mycobacteria establish and propagate rod morphology. My lab has investigated the roles of the essential, cytoskeletal-like protein DivIVA (Wag31) and of inner membrane partitioning in polar growth and envelope assembly. Our work with the model organism M. smegmatis suggests that the membrane-cell wall axis is a self-organizing system in which DivIVA-directed cell wall synthesis organizes the inner membrane, and an organized inner membrane in turn makes cell wall synthesis more efficient and precise. These findings complement what has been reported for eukaryotic cell membranes, which can be partitioned by pinning to cytoplasmic structures such as the actin cytoskeleton and to external structures like extracellular matrix and cellulose. They are also congruent with the literature on model lipid bilayers, which can be phase separated by adhesive forces.

Dr. Sloan Siegrist | University of Massachusetts |
Hosted by Professor Marcos Pires
Friday, March 12, 2021

Dr. Dan Mindiola | University of Pennsylvania

Dr. Dan Mindiola | University of Pennsylvania

Professor Robert Gilliard

Metal-Ligand Multiple Bonds: Catalytic Dehydrogenation of Volatile Alkanes, Methane Olefination, and Super Bases

Abstract. Converting natural resources such as methane and ethane, the main components of natural and shale gas, into more value-added materials under mild conditions and using base metals, is one of the main objectives in my research program. I will start by presenting the reactivity of a transient titanium alkylidyne (PNP)Ti≡CtBu (pincer PNP = N[2-P(CHMe2)2-4-methylphenyl]2), specifically how this species forms and engages in intermolecular C-H activation and functionalization reactions.  Such a system can dehydrogenate methane, and react with C2-C8 alkanes selectively by activating at the a- and b-positions. In the case of linear alkanes C4-C8, we only observe formation of the terminal olefin adduct.  A new catalytic cycle for transfer dehydrogenation of alkanes will be also introduced in addition to unique platforms to form kinetically stable Ti=CH2 moieties (titanium methylidene) that are relevant to our proposed catalytic cycle. I will also discuss a new transformation involving the room temperature conversion of methane to an olefin using a titanium alkylidene in cooperation with a redox-active ligand and how it compares to an electrophilic iridium system that can convert methane to ethylene with the aid of a phosphorus ylide reagent. The last component, if time permitted, will present the synthesis and reactivity of group 4 transition metal nitrides and how one can tune the basicity of the nitride ligand by shifting down the group. 

Hosted by Professor Robert Gilliard
Friday, March 5, 2021

Manipulating Main Group Elements with Transition Metal Isocyanides

Manipulating Main Group Elements with Transition Metal Isocyanides

Dr. Joshua Figueroa | University of California, San Diego |

Professor Robert Gilliard

Manipulating Main Group Elements with Transition Metal Isocyanides

 

Abstract: Transition metal complexes supported by encumbering m-terphenyl isocyanides are adept platforms for the stabilization of unusual molecular species. It has recently been reported that an iron complex featuring two m-terphenyl isocyanide ligands can support a terminal boron monfluoride (BF) ligand. This simple 10e molecule is isoelectronic to carbon monoxide, but possesses vastly different electronic structure properties. In this presentation, the electronic features of metal-coordinated BF are discussed. In addition, the reactivity properties coordinated BF are detailed, with an emphasis on reactions where BF is the primary chemical protagonist. Highlighted are a series of reactions between the BF complex and nucleophilic substrates. In certain cases, nucleophiles are shown to displace fluoride from BF to generate new boron-containing ligands. These reactions are compared and contrasted with transformations where fluoride remains bound to the boron atom. Also presented are reactions between transition metal isocyanide anions and other substrates that generate uncommon metal-bound main group species.

Dr. Joshua Figueroa | University of California, San Diego |
Hosted by Professor Robert Gilliard
Friday, February 26, 2021

Chemical Engineering Approaches for Catalytic Reduction of CO2

Chemical Engineering Approaches for Catalytic Reduction of CO2

Dr. Jingguang Chen | Columbia University

Professor Sen Zhang

Rising atmospheric concentration of CO2 is forecasted to have potentially disastrous effects on the environment from its role in global warming and ocean acidification.  Converting CO2 into valuable chemicals and fuels is one of the most practical routes for reducing CO2 emissions while fossil fuels continue to dominate the energy sector.  In the past few years our group has investigated the catalytic reduction of CO2 using a combination of kinetic studies, in situ characterization and density functional theory calculations.  In this talk we will present several examples on (1) CO2 conversion by thermocatalysis, (2) CO2 reduction by electrocatalysis, and (3) simultaneous upgrading of CO2 and shale gas. We will use these examples to highlight the importance of using fundamental chemical engineering principles to guide the selection of reaction conditions and catalyst compositions.

Dr. Jingguang Chen | Columbia University
Hosted by Professor Sen Zhang
Wednesday, February 24, 2021

Elucidating Proton-Coupled Electron Transfer Mechanisms Underpinning the Catalytic Generation of Renewable Fuels

Elucidating Proton-Coupled Electron Transfer Mechanisms Underpinning the Catalytic Generation of Renewable Fuels

Dr. Jillian Dempsey | University of North Carolina

Professor Brent Gunnoe

Elucidating Proton-Coupled Electron Transfer Mechanisms Underpinning the Catalytic Generation of Renewable Fuels

The conversion of energy-poor feedstocks like water and carbon dioxide into energy-rich fuels involves multi-electron, multi-proton transformations. In order to develop catalysts that can mediate fuel production with optimum energy efficiency, this complex proton-electron reactivity must be carefully considered. Using a combination of electrochemical methods and time-resolved spectroscopy, we have revealed new details of how molecular catalysts mediate the reduction of protons to dihydrogen and the experimental parameters that dictate catalyst kinetics and mechanism. Through these studies, we are revealing opportunities to promote, control and modulate the proton-coupled electron transfer reaction pathways of catalysts.

Dr. Jillian Dempsey | University of North Carolina
Hosted by Professor Brent Gunnoe
Friday, February 19, 2021

Prebiotic Astrochemistry in the "THz-Gap"

Prebiotic Astrochemistry in the "THz-Gap"

Dr. Susanna L. Widicus Weaver | University of Wisconsin-Madison

Professor Eric Herbst

Prebiotic Astrochemistry in the "THz-Gap"

Small reactive organic molecules are key intermediates in interstellar chemistry, leading to the formation of biologically-relevant species as stars and planets form.   These molecules are identified in space via their pure rotational spectral fingerprints in the far-IR or terahertz (THz) regime.  Despite their fundamental roles in the formation of life, many of these molecules have not been spectroscopically characterized in the laboratory, and therefore cannot be studied via observational astronomy.  The reason for this lack of fundamental laboratory information is the challenge of spectroscopy in the THz regime combined with the challenge of studying unstable molecules.  Our laboratory research involves characterization of astrophysically-relevant unstable species, including small radicals that are the products of photolysis reactions, organic ions formed via plasma discharges, and small reactive organics that form via O(1D) insertion reactions.  Our observational astronomy research seeks to examine the chemical mechanisms at play in a range of interstellar environments and to identify chemical tracers that can be used as clocks for the star-formation process.  In this seminar, I will present recent results from our laboratory and observational studies that examine prebiotic chemistry in the interstellar medium.  I will discuss these results in the broader context of my integrative research program that encompasses laboratory spectroscopy, observational astronomy, and astrochemical modeling.

Dr. Susanna L. Widicus Weaver | University of Wisconsin-Madison
Hosted by Professor Eric Herbst
Friday, February 12, 2021

No Seminar: Candidacy Exams

No Seminar: Candidacy Exams

Friday, February 5, 2021

Studying Cell Signaling in Complex Environments Using Open Microfluidics

Studying Cell Signaling in Complex Environments Using Open Microfluidics

Dr. Ashleigh Theberge | University of Washington

Professor Rebecca Pompano

Studying Cell Signaling in Complex Environments Using Open Microfluidics

Small molecule and protein signals provide a rich vocabulary for cellular communication. To better understand signaling processes in both normal and disease states, we have developed new open microfluidic platforms that accommodate the culture of multiple cell types in microfabricated compartments while allowing soluble factor signaling between cell types. Our microscale culture systems allow a 10- to 500-fold reduction in volume compared to conventional assays, enabling experiments with limited cells from patient samples. Furthermore, our devices are open, pipette accessible, interface with high resolution microscopy, and can be manufactured at scale by injection molding, increasing translation to collaborators in biological and clinical labs without chemistry and engineering expertise. Finally, this talk will highlight recent results using open microfluidic principles to develop novel strategies to 3D print hydrogels for biological and materials science applications.

Dr. Ashleigh Theberge | University of Washington
Hosted by Professor Rebecca Pompano
Friday, January 22, 2021

Fall 2020

Harnessing RNA Regulation to Direct Protein Evolution and Control Mammalian Gene Expression

Harnessing RNA Regulation to Direct Protein Evolution and Control Mammalian Gene Expression

Dr. Bryan Dickinson | University of Chicago

Professor Clifford Stains

Harnessing RNA Regulation to Direct Protein Evolution and Control Mammalian Gene Expression

 

I will present two recent technologies our group has developed that harness RNA regulation – one for basic science purposes and one for therapeutic development. First, I will describe new methods that use our RNA polymerase-based biosensors to harness evolution in order to probe the emergence of “selectivity” between biomolecular interfaces, in particular, protein-protein interactions (PPIs). Using a combination of high-throughput biochemical methods, ancestral reconstruction, and a new rapid evolution technology, we developed a model system involving the BCL-2 family of apoptotic regulatory proteins to probe fundamental evolutionary questions about PPIs and how selectivity (or not) emerges between them. In the second half of the talk, I will discuss therapeutic opportunities involving RNA regulation and “epitranscriptomics”. While RNA regulation offers exciting opportunities to create genetic therapies that are reversible and tunable, most current approaches rely on large, microbially-derived systems that pose clinical challenges. We developed the CRISPR/Cas-inspired RNA targeting system (CIRTS), a new protein engineering strategy for constructing programmable RNA regulatory systems entirely from human protein parts. The small size and human-derived nature of CIRTS provides a less-perturbative method for fundamental studies as well as a potential strategy to avoid immune issues when applied to epitranscriptomic therapies.

Dr. Bryan Dickinson | University of Chicago
Hosted by Professor Clifford Stains
Friday, November 13, 2020

Inspiration from Fluorination:  Chemical Epigenetics Approaches to Probe Molecular Recognition Events in Transcription

Inspiration from Fluorination:  Chemical Epigenetics Approaches to Probe Molecular Recognition Events in Transcription

Dr. William Pomerantz | University of Minnesota

Professor Marcos Pires

Inspiration from Fluorination:  Chemical Epigenetics Approaches to Probe Molecular Recognition Events in Transcription

 

Protein-protein interaction inhibitor discovery has proven difficult due to the large surface area and dynamic interfaces of proteins.  To facilitate the early lead discovery rate, I will first describe a rapid protein-based 19F NMR method for detecting protein-ligand interactions by screening low complexity molecules (fragments), drug-like molecules, and peptidomimetics. We have tested the sensitivity, accuracy, and speed of this method through screening libraries of small molecule fragments.  The advantages of using 3D-fragments for discovery of more selective hits for bromodomain-containing proteins will be specifically highlighted. In the second part of the talk, I will describe improvements in our method for the field of epigenetics targeting bromodomain and extra-terminal (BET) family proteins. These studies have led to a selective inhibitor for the first bromodomain of BRD4. Structure-based design has identified several new design rules for maintaining selectivity and potency.  Cellular efficacy in cancer and inflammatory model systems using this novel BRD4 inhibitor will be briefly described.  Finally, development of a new heterocyclic scaffold for the second bromodomain of BRD4 will be highlighted. The speed, ease of interpretation, and low concentration of protein needed for binding experiments affords a new method to discover and characterize both native and new ligands for bromodomains and may find utility in the study of additional epigenetic “reader” domains.

Dr. William Pomerantz | University of Minnesota
Hosted by Professor Marcos Pires
Friday, November 6, 2020

Incorporating Metal-Ligand and Metal-Metal Cooperativity into First Row Transition Metal Complexes with Applications in Catalysis

Incorporating Metal-Ligand and Metal-Metal Cooperativity into First Row Transition Metal Complexes with Applications in Catalysis

Dr. Christine Thomas | Ohio State University

Professor Charlie Machan

Incorporating Metal-Ligand and Metal-Metal Cooperativity into First Row Transition Metal Complexes with Applications in Catalysis

 

The formation and cleavage of chemical bonds in catalytic reactions relies on accessible two-electron redox processes that are often challenging for base metals such as first row and early transition metals. Metal-ligand and metal-metal cooperativity provide a potential solution to this challenge by enabling heterolytic bond cleavage processes and/or facilitating redox processes. Both strategies will be discussed, showcasing the many ways that metal-ligand and bimetallic cooperativity can operate and the methods by which cooperativity can be built into catalyst design. A tridentate pincer ligand featuring a reactive N-heterocyclic phosphido fragment is found to be both redox active and an active participant in bond activation across the metal-phosphide bond, with catalytic applications in alkene hydroboration. A tetradentate bis(amido)bis(phosphide) ligand has been coordinated to iron and it has been shown that the resulting complex can activate two σ bonds across the two iron-amide bonds in the molecule without requiring a change in the formal metal oxidation state. In the context of metal-metal cooperativity, phosphinoamide-linked early/late heterobimetallic frameworks have been shown to support metal-metal multiple bonds and facilitate redox processes across a broad range of metal-metal combinations and the resulting complexes have been shown to activate small molecules and catalyze organic transformations.

Dr. Christine Thomas | Ohio State University
Hosted by Professor Charlie Machan
Wednesday, October 28, 2020

Sensing through the Skull: Developing Surface-Enhanced Spatially-Offset Raman Spectroscopy (SESORS) for in vivo Neurochemical Detection

Sensing through the Skull: Developing Surface-Enhanced Spatially-Offset Raman Spectroscopy (SESORS) for in vivo Neurochemical Detection

Dr. Bhavya Sharma | University of Tennessee, Knoxville

Professor Jill Venton

Sensing through the Skull: Developing Surface-Enhanced Spatially-Offset Raman Spectroscopy (SESORS) for in vivo Neurochemical Detection

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. We focus 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. We incorporate the electric field generated at the surface of noble metal nanoparticles in our sensors to enhance the weak Raman scattering signal. 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 detection of physiologically relevant concentrations of neurotransmitters in the micromolar (µM) to nanomolar (nM) concentration ranges with SESORS in a brain tissue mimic through the skull.

Dr. Bhavya Sharma | University of Tennessee, Knoxville
Hosted by Professor Jill Venton
Friday, October 23, 2020

Graham Lecture | Repurposing the Blue Print of Life for Materials Design | 7:00 PM | Chemistry Zoom Meeting

Graham Lecture | Repurposing the Blue Print of Life for Materials Design | 7:00 PM | Chemistry Zoom Meeting

Dr. Chad Mirkin | George B. Rathmann Professor of Chemistry, Northwestern University

Professor Charles Machan

 The materials-by-design approach to the development of functional materials requires new synthetic strategies that allow for material composition and structure to be independently controlled and tuned on demand. Although it is exceedingly difficult to control the complex interactions between atomic and molecular species in such a manner, interactions between nanoscale components can be encoded, independent of the nanoparticle structure and composition, through the ligands attached to their surface. DNA represents a powerful, programmable tool for bottom-up material design. We have shown that DNA and other nucleic acids can be used as highly programmable surface ligands (“bonds”) to control the spacing and symmetry of nanoparticle building blocks (“atoms”) in structurally sophisticated materials, analogous to a genetic code for materials assembly. The sequence and length tunability of nucleic acid bonds has allowed us to define a powerful set of design rules for the construction of nanoparticle superlattices with more than 50 unique lattice symmetries, spanning over one order of magnitude of interparticle distances, with several well-defined crystal habits. Furthermore, this control has enabled exploration of sophisticated symmetry breaking processes, including the body-centered tetragonal lattice as well as the clathrate lattice, the most structurally complex nanoparticle-based material to date (>20 particles per unit cell). The nucleic acid bond can also be programmed to respond to external biomolecular and chemical stimuli, allowing structure and properties to be dynamically tailored. Notably, this unique genetic approach to materials design affords functional nanoparticle architectures that can be used to catalyze chemical reactions, manipulate light-matter interactions, and improve our fundamental understanding of crystallization processes.

 

Dr. Chad Mirkin | George B. Rathmann Professor of Chemistry, Northwestern University
Hosted by Professor Charles Machan
Thursday, October 15, 2020

Polymer Modified Carbon Fiber Microelectrodes and Multielectrode Arrays for Multiplexing Neurochemical Measurements

Polymer Modified Carbon Fiber Microelectrodes and Multielectrode Arrays for Multiplexing Neurochemical Measurements

Dr. Alexander Zestos | Assistant Professor of Chemistry, American University

Professor Jill Venton

Polymer Modified Carbon Fiber Microelectrodes and Multielectrode Arrays for Multiplexing Neurochemical Measurements

We have developed novel methods to detect neurotransmitters and their metabolites. Traditionally, carbon-fiber microelectrodes (CFMEs) have been utilized to detect dopamine, serotonin, and other important neurotransmitters. However, this method is limited due to a low sensitivity to detect physiologically relevant concentrations of these neurotransmitters. Polymer modified microelectrodes will be utilized to detect fast changes of neurotransmitters. Furthermore, novel electrode coatings and waveforms will also be utilized to detect several neurotransmitter metabolites such as 3,4-dihydroxy-benzeneacetaldehyde (DOPAL), 3-methoxytyramine (3-MT), and 3,4 dihydroxyphenylacetic acid (DOPAC). There is no current assay to detect metabolites of dopamine utilizing voltammetry. Through waveform modifications and polymer electrode coatings, we develop a novel method for dopamine metabolite detection utilizing fast scan cyclic voltammetry (FSCV), which will help differentiate the cyclic voltammograms of dopamine and dopamine metabolites through the shapes and positions of their respective cyclic voltammograms. Preliminary measurements have been made in zebrafish retina ex vivo. We have also developed multielectrode arrays (MEAs) for neurotransmitter detection with FSCV in multiple brain regions simultaneously. Parylene and silicon insulated CFME arrays measured neurochemicals in multiple brain regions simultaneously when coupled with multichannel potentiostats. Moreover, we have utilized techniques such as plasma enhanced chemical vapor deposition to deposit conductive carbon nanospikes onto the surface of existing metal multielectrode arrays to give them dual functionality as neurotransmitter sensors with FSCV in addition to being used primarily for electrical stimulation and recording. Other assays have shown the utility of electrodepositing carbon nanotubes and polymers such as PEDOT to coat metal arrays with carbon to give them dual sensing capabilities.

Dr. Alexander Zestos | Assistant Professor of Chemistry, American University
Hosted by Professor Jill Venton
Friday, October 9, 2020

Dye-Sensitization for the Production of Electrical Power and Chemical Fuels from Sunlight

Dye-Sensitization for the Production of Electrical Power and Chemical Fuels from Sunlight

Dr. Jerry Meyer | University of North Carolina

Professor Charlie Machan

 

Dye-Sensitization for the Production of Electrical Power and Chemical Fuels from Sunlight

Gerald J. Meyer

Department of Chemistry,
University of North Carolina at Chapel Hill, Chapel Hill, NC, USA 27599-3290

E-mail: gjmeyer@email.unc.edu

Dye-sensitized solar cells have received considerable attention since the advent of mesoporous metal oxide thin films first described by Grätzel and O’Regan [1]. We have a fundamental interest in light driven interfacial electron transfer in these materials that is motivated by applications in electrical power generation and in solar fuels production [1,2]. Background on dye-sensitization and solar energy conversion will be provided that gives context for our most recent advances that suggest new directions for future research. An example includes the identification of a kinetic pathway for electron transfer from TiO2 to transition metal complexes with two redox active groups. [2,3] The distance between the two groups were held near parity yet electron transfer through an aromatic bridge that separated them was critically dependent on the degree of conjugation [3,4]. Electron transfer to acceptors positioned at variable distances from a conductive oxide surface revealed that the intrinsic barriers were dramatically decreased within the electric double layer [5]. Mechanistic study of core/shell oxide materials provided new insights into electron transport that were correlated with water oxidation efficiency [6]. Finally, an alternative approach to solar fuel production with small band gap semiconductors and tandem catalyst hybrids will be presented. This approach forms the basis of a new Department of Energy supported Solar Hub entitled the Center for Hybrid Approaches in Solar Energy to Liquid Fuels (CHASE) [7].       

References:

[1] “A Low- Cost, High Efficiency Solar Cell Based on the Dye- Sensitized Colloidal TiO2 Films” O’Regan, B.; Grätzel, M. Nature 1991, 353, 737.

[2] “Perspectives in Dye Sensitization of Nanocrystalline Mesoporous Thin Films” Hu, K.; Sampaio, R.N.; Schneider, J.; Troian-Gautier, L.; Meyer, G.J. J. Am. Chem. Soc. 2020, in press.

[3] “A Kinetic Pathway for Interfacial Electron Transfer from a Semiconductor to a Molecule” Hu. K.; Blair, A.D.; Piechota, E.J.; Schauer, P.A.; Sampaio, R.N.; Parlane, F.; Meyer, G.J.; Berlinguette, C.P. Nature Chem. 2016, 8, 853-859.

[4] “Kinetics Teach That Equilibrium Constants Shift Toward Unity with Increased Electronic Coupling” Sampaio, R.N.; Piechota, E.J.; Troian-Gautier, L.; Maurer, A.B.; Berlinguette, C.P., Meyer, G.J. Proc. Nat. Acad. Sci. USA 2018, 115, 7248-7253.

[5] “Kinetic Evidence that the Solvent Barrier for Electron Transfer is Absent in the Electric Double Layer” Bangle, R.E.; Schneider, J.; Conroy, D.T.; Aramburu-Troselj, B.M.; Meyer, G.J. J. Am. Chem. Soc. 2020142, 14940-14946. 

[6] “Electron Localization and Transport in SnO2/TiO2 Mesoporous Thin Films: Evidence for a SnO2/SnxTi1- xO2/TiO2 Structure” James, E.M.; Bennett, M.T.; Bangle, R.E.; Meyer, G.J. Langmuir 2019, 39, 12694-12703.

[7] https://uncnews.unc.edu/2020/07/31/department-of-energy-funds-milestone-north-carolina-led-initiative-to-advance-solar-energy-research/

 

Dr. Jerry Meyer | University of North Carolina
Hosted by Professor Charlie Machan
Friday, October 2, 2020

A Modular Approach to Materials Design

A Modular Approach to Materials Design

Dr. Dmitri Talapin | University of Chicago

Dr. Sen Zhang

Dmitri V. Talapin

Department of Chemistry and James Franck Institute

University of Chicago, Chicago IL 60637, USA

 

Inorganic nanomaterials enabled impressive developments, both in the fundamental understanding of nucleation, growth and surface chemistry of inorganic solids, and in our ability to make functional materials for real-world applications. Nanocrystals and nanocrystal assemblies offer a versatile platform for designing two- and three-dimensional solids with tailored electronic, optical, magnetic, and catalytic properties. Unlike atomic and molecular crystals where atoms, lattice geometry, and interatomic distances are fixed entities, the arrays of nanocrystals represent solids made of “designer atoms” with continuously tunable properties.

I will discuss our recent developments in synthesis of inorganic nanostructures, from new semiconductor quantum dots to two-dimensional transition metal carbides, also known as MXenes. We are developing chemical approaches to electronically couple individual nanostructures into extended materials. These “modular” materials are explored as active components for electronic, light-emitting, thermoelectric and photovoltaic devices.

Dr. Dmitri Talapin | University of Chicago
Hosted by Dr. Sen Zhang
Friday, September 25, 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

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