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Chemistry Guest Seminars

Guest Seminars Spring 2024

Guest Seminars

Analytical & Physical Seminar

Thursday, February 29, 3:30-4:30pm, WEL 2.122tabor

Building Physics-Based and Data-Driven Methods for Efficient Polymer Design and Spectroscopy Simulations

Daniel P. Tabor

Assistant Professor

Texas A&M University

Tabor Group

Abstract:  Our research group focuses on building tools that enable inverse materials design and give new insights into the fundamental chemical physics of liquids, interfaces, and materials. For this talk, we will discuss our progress in two of our primary research thrusts. The first part of the talk will focus on our work in developing methods that are used to accelerate the design of functional materials. We focus on two types of materials: electronic polymers and intrinsically disordered proteins. Although radical-based polymers are promising energy storage materials, successful materials design requires careful molecular engineering of the polymer and electrolyte. To solve the molecular-scale part of the problem, we develop physically motivated machine learning models that predict molecular properties (e.g., hole reorganization energies) from low-cost representations, and pair these with reinforcement learning methods for inverse design applications. We will then discuss our efforts on developing representations for predicting the polymer physics of intrinsically disordered proteins at a much lower computational cost that current coarse-grained methods. One advantage of our new representation is that it avoids specifying the longest length of the chain in advance. The second part of the talk focuses on developing methods for accelerating the simulation and analysis of condensed phase spectroscopy. We present data-driven methods for computing condensed phase vibrational spectra of water directly from coarse-grained representations in a mixed quantum-classical framework. The talk will focus on model representation, development of robust physically motivated machine learning protocols, and the fidelity of the models over a range of conditions


Publications (Group Page)

Publications (Google Scholar Citations)

Organic Seminar

Friday, March 1, 1:30-2:30pm, WEL 2.122bloom

New Synthetic Tools for Peptide Medicinal Chemistry

Steven Bloom

Assistant Professor

University of Kansas

Bloom Lab

Abstract:  TBD


Publications (Group Page)

Organic Seminar

Friday, March 1, 3:30-4:30pm, WEL 2.122blakey

New Reactions, Catalysts, and Natural Products: Inspiration and Invention in Organic Synthesis

Simon Blakey

Associate Professor

Emory University

Blakey Lab

Abstract:  The development of new reactions and catalysts for the oxidative cross-coupling of C-H bonds with C-H, N-H and O-H bonds will be discussed. Strategically, these reactions allow for the synthesis of complex molecules from their constituent components, minimizing the need for functional group activation and manipulation. A novel planar chiral catalyst platform for enantioselective reactions will be presented. Illustrative examples of emergent applications will be provided, and a new traceless directing group concept for C-H annulation to form heterocycles will be presented.


Publications (Group Page)

Publications (Google Scholar)

Inorganic Seminar

Wednesday, March 27, 3:30-4:30pm, WEL 2.122roy

Next level 2D quantum materials

Xavier Roy

Associate Professor

Columbia University

Roy Group

Abstract:  Two-dimensional (2D) materials have received widespread attention in the past 15 years due to their remarkable physical, mechanical and chemical properties, and our ability to integrate them into devices. In this seminar, I will present our recent work in the development of the next generation of 2D materials. I will first discuss how magnetic order strongly couples to optical transitions in a new magnetic semiconductor developed in my laboratories, CrSBr. I will then introduce the synthesis and characterization of the first f-electron-based heavy fermion metal, CeSiI, that is also a 2D van der Waals (vdW) material. Conceptually, our synthetic design takes a traditional 3D intermetallic heavy fermion compound and slices it into atomically-thin vdW sheets by incorporating iodine into the structure. The resulting material is cleavable and effectively 2D electronically, even in bulk crystals. Finally, I will discuss the design of a two-dimensional (2D) flat band lattice model in air-stable monolayers of the van der Waals (vdW) intermetallic Pd5AlI2. In addition to being a material realization of the intriguing 2D decorated checkerboard model, this new structure demonstrates that flat bands can be designed in materials by considering both their lattice and orbital symmetries.


Publications (Group Page)

Publications (Google Scholar)

Organic / ChemBio Seminar

Friday, February 23, 3:30-4:30pm, WEL 2.122nowick

Unlocking the Mysteries of Alzheimer’s Disease with Macrocyclic β-Sheet Peptides

James S. Nowick

Professor

UC Irvine

Nowick Group

Abstract:  Oligomers of the β-amyloid peptide Aβ have emerged as key species involved in neurodegeneration in Alzheimer’s disease. The 40–42 amino acid peptide aggregates in the brain to form fibrils and toxic oligomers. While the fibrils and the resulting plaques are the visible hallmark of the disease, the soluble oligomers are now thought to be the damaging species responsible for neurodegeneration. Although the structures of the fibrils are becoming relatively well understood, little is known about the structures of the oligomers. By constraining peptides derived from Aβ to a β-hairpin conformation and preventing fibril formation by N-methylation, we have discovered that triangular trimers constitute a fundamental building block of amyloid oligomers. Through X-ray crystallography, we have elucidated high-resolution structures of the trimers, as well as the hexamers, dodecamers, and annular pores that the trimers form. We are now beginning to correlate the biophysical and biological properties these oligomers with those formed by full-length Aβ. We have also generated antibodies against these assemblies and identified features that react with these antibodies in the brains from transgenic mouse models for Alzheimer’s disease and individuals who have lived with Alzheimer’s disease. Through these studies, we are gaining new insights into the structures and roles of Aβ oligomers in Alzheimer’s disease.


Publications (Group Page)

Publications (Google Scholar)

Analytical & Physical / ChemBio Seminar

Thursday, February 22, 3:30-4:30pm, WEL 2.122frontiera

Raman Spectroscopic Probes of Plasmon-Molecule and Polariton Interactions

Renee R. Frontiera

Professor

University of Minnesota

Frontiera Lab

Abstract:  Photonic materials, including plasmons and polaritons, are highly promising catalysts for driving energetically unfavorable chemical reactions with sunlight, due to their large optical cross sections and ability to modify potential energy landscapes. However, the efficiencies of most plasmon-driven and polariton-driven processes are quite low, likely due to the lack of mechanistic understanding of the underlying physical processes. Here I’ll discuss our use of Raman spectroscopies to advance our fundamental understanding of these systems. First, I’ll describe our development of ultrafast surface-enhanced Raman spectroscopy (SERS) to probe the contributions of plasmon-generated hot electron transfer, heating, and vibrational energy transfer on timescales relevant to photocatalysis. Second, I will talk about our efforts in mapping out reaction coordinates in polaritonic systems, quantifying the degree of mode-specific activation. These efforts in developing a fundamental understanding of polariton and plasmon-mediated processes in molecules will ultimately aid in the rational design of cost-effective photonic materials capable of driving industrially relevant chemistries using solar radiation.


Publications (Group Page)

Publications (Google Scholar)

Welch Emerging Leaders in Chemistry Visitor Series

Thursday, February 15, 3:30-4:30pm, WEL 2.122allen

Soft Surfaces: An Insightful View of Organization

Heather C. Allen

Professor

Ohio State University

Allen Group

Abstract: Biomembrane ion transfer, lung surfactant, interfacial chemistry of materials, taste and beverage surface chemistry, ocean to marine aerosol concentration enrichments, geochemical weathering, and cloud droplet-surface electric fields provide the motivation for studies of interfacial ion pairing, binding, and surface prevalence and organization of molecules at interfaces. Ion surface activity at aqueous soft interfaces has been controversial for decades although there is growing consensus.  Here interfacial structure and the interfacial driving forces are presented using vibrational sum frequency generation spectroscopy (VSFG), second harmonic generation (SHG), Brewster angle microscopy (BAM), surface potential, surface tension, polarized Raman, and reflection absorption infrared. Some focus is on Fe(III), Al(III), Ca(II), Mg(II), saccharides, water, and solvents such as glycerol and propylene carbonate, and surface pKa of surfactant lipids and fatty acids. Binding mechanisms and ion surface activity are not necessarily correlated in that the driving forces of electrostatics and nonspecific dispersion compete with surprising outcomes.  Applied electric field data from aqueous interfaces is also explored to reveal inherent aqueous surface acidity at neutral solution-phase pH. 


Publications (Group Page)

Publications (Google Scholar)

ORCID: https://orcid.org/0000-0003-3120-6784

Analytical & Physical / ChemBio Seminar

Thursday, February 8, 3:30-4:30pm, WEL 2.122stephanopoulos

Hybrid, functional nanomaterials that integrate proteins/peptides and DNA

Nicholas Stephanopoulos

Associate Professor

Arizona State University

Stephanopoulos Lab

Abstract:  The ability to design materials that mimic the complexity and functionality of biological systems is a long standing goal of nanotechnology, with applications in medicine, energy, and fundamental science. Biological molecules such as proteins, peptides, and DNA possess a rich palette of self-assembly motifs and chemical functional diversity, and are attractive building blocks for the synthesis of such nanomaterials. In this talk, we will describe research in creating hybrid materials that incorporate proteins and peptides with DNA nanotechnology to create cages, nanofibers, and synthetic antibodies with a high degree of programmability and nanoscale resolution. Key to these endeavors will be (bio)molecular design, organic chemistry for linking components in a site-specific fashion, and the tuning of multiple self-assembly "modes" to create hybrid structures. We will also outline some exciting future directions, like DNA “nano-assemblers” for building asymmetric protein nanostructures. Although the talk will focus on the fundamental chemistry and self-assembly of these systems, we will also discuss potential applications in areas such as targeted cargo delivery, biomaterials for regenerative medicine, and synthesis of virus- and antibody-mimetic nanostructures.


Publications (Group Page)

Publications (Google Scholar)

Chemical Biology/Organic/Inorganic Seminar

Monday, February 5, 3:30-4:30pm, WEL 2.122korendovych

Design and Directed Evolution of Protein Catalysts

Ivan Korendovych

Associate Professor

Baylor University

Korendovych Lab

Abstract: Catalytic Amyloids. We showed that small peptides designed from the first principles can self-assemble to form efficient catalysts for various reactions (hydrolytic, oxygen activation, carbene transfer, etc.) with activity on par with those of the best small molecule and peptide catalysts reported to date. These results provide the first demonstration of substantial catalytic activity in simple peptide amyloids, and from a more practical perspective, open the door to the design of highly stable, robust, and easily varied enzyme-like catalysts. Moreover, by mixing different peptides we were able to observe synergistic interactions that increased activity even further. Unlike enzymes, catalytic amyloids are extremely robust and can be used under harsh conditions.  NMR-guided approach to directed evolution. Directed evolution has emerged as a powerful tool for improving protein properties and imparting completely new functionalities onto existing proteins. Nonetheless, it is inherently limited by the astronomical number of possible amino acid sequences to screen. We have demonstrated that mutagenic host spots in proteins can be identified using NMR chemical shift perturbation. In a proof-of-concept study we converted a non-enzymatic protein myoglobin into FerrElCat a highly efficient lyase for Kemp elimination, an unnatural reaction, using only three mutations. FerrElCat shows catalytic efficiency of 1.5x107 M-1s-1 that is at least 60-fold higher than the best artificial enzyme ever reported and is only 1-2 orders away from the diffusion limit. Given the ease such drastic increase in efficiency in just one round of directed evolution we are confident that our approach will be broadly applicable.


Publications (Group Page)

Publications (Google Scholar)

Organic Seminar

Friday, February 2, 3:30-4:30pm, WEL 2.122johnson

(De)constructing Macromolecules

Jeremiah A. Johnson

Professor

MIT

Johnson Group

Abstract:  Polymers are arguably the most important materials on Earth. Despite a century of study, however, much remains unknown about how the molecular-scale features of polymers translate to their bulk properties, preventing predictive design of next-generation, sustainable materials. This talk will highlight our efforts to leverage efficient synthetic methods and strategies to construct and deconstruct macromolecules, thereby unveiling previously hidden features of macromolecular structure and enabling new polymeric material functions.


Publications (Group Page)

Publications (Google Scholar)

Organic / ChemBio Seminar

Thursday, February 1, 3:30-4:30pm, WEL 2.122hines

Exploring the influence of membrane fluidity on antibacterial susceptibilities using multi-dimensional lipidomic methods

Kelly M. Hines

Assistant Professor

University of Georgia

Hines Lab

Abstract:  Staphylococcus aureus varies its membrane fluidity in response to environmental stresses by changing the ratio of branched-chain fatty acids (BCFAs) to straight-chain fatty acids (SCFAs) in its membrane lipids. Altered membrane fluidity has been associated with an increased tolerance of membrane-targeting antibiotics, including daptomycin. The routine assessment of microbial membrane fluidity relies on the measurement of total BCFA-versus-SCFA determination by GC-MS. Although GC-MS is capable of resolving BCFA and SCFA isomers, the requirement of free fatty acids eliminates the possibility to evaluate the preferences of lipid subclasses for BCFAs vs. SCFAs. We recently demonstrated a RPLC method that can separate lipid isomers having branched-branched, branched-straight, or straight-straight fatty acyl tail combinations. Using this approach and stable isotope labeling, we examined the distribution of FA isomers in the lipids of a S. aureus strain with daptomycin resistance. A strain of S. aureus N315 with high-level daptomycin resistance was found to have substantially more BCFAs in its membrane lipids compared to the isogenic parent N315, which correlated with increased membrane fluidity. Despite the preference for BCFAs is the resistant strain, we found that both organisms could utilize SCFAs when provided in the culture broths. This supplementation reversed the resistant strain’s membrane fluidity towards that of the parent strain. These results indicate that daptomycin resistance can be facilitated in-part by increased membrane fluidity, and support the concept of targeted remodeling of the S. aureus membrane to mediate antibiotic resistance.


Publications (Group Page)

Publications (Google Scholar)

ORCID: https://orcid.org/0000-0001-9125-5268

Organic Seminar

Friday, January 26, 3:30-4:30pm, WEL 2.122minami

Supramolecular sensor devices based on organic transistors

Tsuyoshi Minami

Associate Professor

University of Tokyo

Minami Lab

Abstract:  Supramolecular materials have the potential to be applied to analytical tools owing to their fascinating functions. However, their materials have not been satisfactorily used in practical sensing situations. Herein, the presenter proposes an approach for the development of supramolecular sensor devices based on organic field-effect transistors (OFETs). OFETs are electronic devices showing switching characteristics by applying voltage, of which the device characteristics depend on assembled organic semiconductive molecules. Therefore, OFETs can be referred to as supramolecular devices. Owing to their beneficial device properties, OFETs functionalized with appropriate recognition materials contribute to sensitive detection over conventional electrochemical sensing methods. Biological materials such as enzymes and antibodies have been employed owing to their favorable specificities to analytes based on the lock-and-key recognition principle. However, detectable analyte structures are limited by a library of these biological materials. Therefore, synthetic receptors based on molecular recognition chemistry are promising approaches in the design of recognition sites. In this study, molecularly imprinted polymers (MIPs) were applied to recognition materials for selective detection. MIPs provide three-dimensional recognition networks against specific analytes because a pre-organized structure made of a template (i.e., analyte) and functional monomers can be optimized by quantum chemical calculation methods. Such optimized MIP structures contribute to selective detection even in the presence of interferents. In contrast, the inherent cross-reactivity of supramolecular receptors can be applied to simultaneous detection by using pattern recognition methods. This presentation will discuss the usability of this approach for the realization of supramolecular sensor devices based on fusion technologies of organic electronics, molecular recognition chemistry, and polymer chemistry.


Publications (Group Page)

Publications (Google Scholar)

ORCID: https://orcid.org/0000-0001-8331-378X

Faculty Recruiting Seminar

Monday, January 22, 3:30-4:30pm, WEL 2.122boyle

Unlocking reactive intermediates for methodology development

Benjamin T. Boyle

Postdoctoral Fellow

Princeton University

Ph.D, Colorado State, 2021 (McNally)

Dave Macmillan Group

Abstract:  Reactive intermediates are the backbone of synthetic chemistry. Developing new strategies to transform building blocks into reactive species and tapping into the potential reactivity of underexplored intermediates are critical for advances in desirable bond formations. This seminar will discuss my work in the exploration of reactive intermediates through both stochiometric and catalytic methods for the development of new synthetic strategies. Pyridines and nitrogen-containing heteroaromatics are important and ubiquitous scaffolds in medicinal chemistry; however, these electron-deficient heteroaromatics remain challenging to functionalize. I will discuss my research in bridging the methodological gap in pyridine derivatization, with a particular focus on selective C–H bond functionalization through underexplored and unconventional reactive intermediates. Building upon this, my seminar will explore a new strategy leveraging metallaphotoredox to achieve highly enabling reactive intermediates beyond radicals. With an eye for versatile bond forming strategies, I will discuss a new area in visible-light mediated bond formations from abundant feedstock chemicals such as alcohols, carboxylic acids, and amino acids.


Publications (ResearchGate)

Organic / ChemBio Seminar

Friday, January 19, 3:30-4:30pm, WEL 2.122lairson

Chemistry-Enabled Biological Discovery

Luke Lairson

Associate Professor

Scripps

Lairson Lab

Abstract:  The Lairson laboratory uses chemical biology-based approaches, involving cell-based phenotypic screening coupled to target identification and mechanism of action studies, to investigate cell fate- and cell state-determining processes that play causative roles in human disease biology. Research is primarily focused on applying this approach to study remyelination and cGAS-STING pathway signal transduction, as well as to target glioblastoma cancer stem cells in a cell type-selective manner. Remyelination-inducing agents have significant potential utility in the treatment of demyelinating diseases, including progressive forms of multiple sclerosis. Using a cell-based imaging assay involving primary optic nerve-derived progenitor cells, a drug class was identified that induces oligodendrocyte differentiation and enhances remyelination in rodent models. A representative member from this drug class was subsequently demonstrated to meet a remyelination-based endpoint in a phase 2 clinical trial conducted by investigators at UCSF. Current efforts in this area, involving pairwise combinatorial drug screening, have built on these findings and resulted in new mechanistic hypotheses for future clinical investigation. cGAS-STING signal transduction plays an essential role in innate responses to infection or pathogenic sources of self-DNA. Pharmacological activators or inhibitors of this pathway have diverse potential applications in diseases ranging from cancer to inflammation. Using a pathway-targeted cell-based screening approach, small molecules with demonstrated in vivo activity have been identified that function not only by acting as direct agonists of STING adaptor function, but also as pathway-specific modulators that function via newly identified targets. Finally, glioblastoma cancer stem cells (GBM CSCs) have been demonstrated to be responsible for tumor initiation, metastasis, therapy resistance and recurrence following surgical resection. Cell-based screening involving primary GBM CSCs resulted in the identification of a chemical series that induces cell death in GBM CSCs in a cell type-selective manner. Cell type selectivity was determined to be derived at least in part from the ability of the series to act as a prodrug that becomes preferentially activated in the target cell population to yield a cytotoxic agent. Very recently, it has been demonstrated that this prodrug strategy can be applied to significantly enhance the selectivity profile of a clinical stage drug, which yielded a GBM-selective cytotoxic derivative with low nM potency and demonstrated in vivo activity in an orthotopic tumor xenograft model.


Publications (Group Page)

Publications (Google Scholar)

ORCID: https://orcid.org/0000-0001-6701-996X

Faculty Recruiting Seminar

Thursday, January 18 3:30-4:30pm, WEL 2.122gould

Radical Chemistry: From Single-Molecule Magnets to Photoredox Catalysis

Colin A. Gould

Postdoctoral Fellow

Princeton University

Ph.D, UC Berkeley 2020 (Jeffrey Long)

Dave Macmillan Group

Abstract:  Molecules with unpaired electrons display intriguing electronic/magnetic properties and unique reactivity, phenomena that are widely studied across diverse chemical disciplines. In this seminar, I will discuss my research on radical chemistry in two distinct areas: single-molecule magnets and photoredox catalysis.  First, I will describe the synthesis and characterization of lanthanide complexes that contain radical ligands or single-electron metal–metal bonding interactions. I will highlight the isolation of a triplet benzene diradical—typically a high-energy excited state species—through ligand design and magnetic exchange. I will also discuss how metal–metal bonding within a dilanthanide complex gives rise to the largest coercive magnetic fields yet observed for any molecule or molecule-based material.  Next, I will describe a “radical sorting” method for C(sp3)–C(sp3) cross-coupling that is enabled by dual photoredox and iron catalysis. I will discuss both the mechanistic investigation of this transformation and synthetic applications, including the conversion of tertiary alcohols—abundant, structurally-diverse feedstocks—to quaternary carbons, a motif that is challenging to access via conventional synthetic methods.


ORCID: https://orcid.org/0000-0001-9539-1582

Analytical & Physical Seminar

Thursday, January 11, 3:30-4:30pm, WEL 2.122hamid

Diagnosis of Infectious Diseases by Ion Mobility Mass Spectrometry

Ahmed M. Hamid

Assistant Professor

Auburn University

Hamid Lab

Abstract:  There is a projection of 10 million deaths per year by 2050 due to antimicrobial resistance, highlighting the need for rapid detection and accurate identification of microorganisms. Therefore, developing fast robust diagnosis techniques will increase the recovery rates of patients suffering from various infections and will lead to significantly reduced antibiotic resistance. The membrane of bacteria contains varying lipid compositions that can be utilized as diagnostic biomarkers for disease. However, full characterization of lipids remains analytically challenging due to their enormous structural diversity and complexity (e.g., varying acyl chain positions and/or double bond geometries). This presentation will demonstrate the advantages of interfacing liquid chromatography and structurally-based ion mobility with tandem mass spectrometry in the resolution of isomeric lipids. Moreover, this presentation will demonstrate our recent developments of ambient ionization techniques when coupled to high-resolution ion mobility spectrometry; we used the paper spray technique coupled with ion mobility separation and tandem mass spectrometry (PS-IM-MS/MS) to rapidly discriminate and identify five Bacillus species in 2 minutes of analysis time after only 4 hours of incubation time. Bacterial cells were harvested by filtering their liquid cultures and ionized directly by PS. Numerical multivariate statistics (principal component analysis, followed by linear discriminant analysis) allowed species-level discrimination with a prediction rate of 99.7% and 100% utilizing the negative and positive ion information of PS-IM-MS/MS, respectively. Next, we examined the capability of our methods to achieve strain-level differentiation of seven E. coli strains. Using numerical data fusion of negative and positive ion PS-IM-MS/MS data increased the classification rates of PS-IM-MS/MS to 80.5%. Upon using LC-IM-MS/MS, a prediction rate of 96.1% and 100% utilizing the negative and positive ion information, respectively could be achieved.


Publications (Group Page)

Publications (Google Scholar Citations)

ORCID: https://orcid.org/0000-0002-1443-979X

Welcome

Seminar tabs are listed in the order of upcoming dates, followed by past seminars (most recent first).

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