UCLA

Physical Chemistry Seminar 228: Natalie Banerejie
2022-11-14 16:00 - 17:00 (America/Los_Angeles) | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Prof. Banerjie Flyer
Title: Organic Semiconductors in Electronics, Photovoltaics and Bioelectronics
Abstrac: Organic conjugated materials have many favourable properties that make them interesting for a variety of electronic applications. The aim of my group is to understand the fundamental processes underlying their functionality. We use ultrafast spectroscopic techniques, such as transient absorption (TA) and time-domain terahertz (TD-THz) spectroscopies, to investigate charge carriers in organic semiconductors. While femtosecond TA measurements bring insights to the nature and evolution of the photoexcited species, we use TD-THz spectroscopy to gain information about the charge transport properties on the nanoscale. After presenting an overview of our experimental techniques, I will show results about charge generation in highly efficient solar cell materials based on organic polymer:nonfullerene blends. The photophysical properties of doped organic semiconductors are then discussed, as well as their applications to bioelectronic devices such as organic electrochemical transistors (OECTs). Finally, ways to explore ultrafast spectroscopy to study such devices in operando are presented.

Chem 218 Student Exit Seminar: Bosi Peng and Rongli Liu
2022-11-15 12:00 - 13:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Emily Tsui
2022-11-16 16:00 - 17:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Flyer: Prof. Emily Tsui Flyer
Meet the Speaker: 11 a.m., YH 3096
Title: Organometallic Chemistry at Quantum Dot Surfaces
Abstract: Due to their tunable optoelectronic properties, colloidal semiconductor quantum dot nanocrystals are useful in applications like displays, photovoltaics, and photocatalysis. Chemistry at nanocrystal surfaces, including redox processes, association/dissociation, and other structural rearrangements, has an outsize effect on the nanocrystal properties, but is challenging to study with typical spectroscopic methods. We show that organometallic fragments like transition metal carbonyl complexes can act as strongly-bound X-type or Z-type ligands to the nanocrystal surfaces, and that these species can be useful spectroscopic reporters of surface chemistry. These functionalized nanocrystals therefore enable in situ measurements of surface stoichiometry and surface charge under photoexcitation and during photocatalysis.

Special Physical Chemistry Seminar by Dr. Iain McKenzie
2022-11-17 10:00 - 11:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Chem 218 Student Exit Seminar: Katie Perrotta
2022-11-17 12:00 - 13:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

CANCELED: Houk-Jung Organic Colloquium 247: Elizabeth Gilles
2022-11-17 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
PLEASE NOTE THAT THIS EVENT HAS BEEN CANCELED

Prof. Gilles Flyer
Title: Self-Immolative Polymers: Chemical Designs and Applications
Abstract: The development of degradable polymers is of significant interest across a wide range of fields from commodity plastics to medicine. Much progress has been made to date with conventional polyesters such as polylactide and polycaprolactone. However, the ability to control the degradation of these polymers in different environments is limited and they may degrade more rapidly or more slowly than desired. Many stimuli-responsive polymers have been developed over the past couple of decades, but these polymers typically require many stimuli-mediated events to achieve complete backbone degradation. Our team has been developing self-immolative polymers, a recently established class of degradable polymers, that undergo end-to-end backbone depolymerization in response to the cleavage of a single backbone bond or an end-cap from the polymer terminus, thereby providing amplification of the stimulus-mediated event. This presentation will describe the development of different classes of self-immolative polymers, as well as end-caps for these polymers, which can be triggered under different conditions. Our progress in the synthesis of these polymers, as well as their application in areas such as therapeutic delivery and medical imaging will be discussed.

Organic Student Seminar 248: Emma Greene
2022-11-21 15:00 - 15:50 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Physical Chemistry Seminar 228: Vojtech Vleck
2022-11-21 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Prof. Vlcek Flyer
Title: Excitation Dynamics Driving the Electronic Structure of Molecules and Solids
Abstract: Capturing the dynamics of electronic excitations in realistic systems containing more than a few electrons is one of the outstanding theoretical challenges. Dynamical quantum correlations mediate interactions and couplings between multiple excited states in materials and represent an important driver of their optoelectronic characteristics. A predictive ab-initio theory is thus critical for understanding, predicting, and designing novel compounds with tailored (quantum) properties. I will discuss how to tackle the first-principles description of excitation dynamics in systems with thousands of electrons and study individual excited states, including their non-trivial interactions. I will exemplify these approaches in practical applications to quantum materials, e.g., exploring the correlated phenomena for localized moire states in twisted bilayer graphene and defect centers in diamond. Our theoretical framework uses real-time methods combined with ab-initio dynamical downfolding. Together with efficient low-scaling numerical techniques, it is generally applicable to (quantum) material science and chemistry problems and constitutes an ideal platform for simulating complex nanoscale systems, such as molecular assemblies or materials interfaces.

Organic Student Seminar 248: Gabriella Cooper
2022-11-28 15:00 - 15:50 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Megan Fieser
2022-11-30 16:00 - 17:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Flyer: Prof. Megan Fieser Flyer
Meet the Speaker: 11 a.m., YH 3096
Title: Development of Catalytic Strategies for Advances in Polymer Sustainability
Abstract: As we strive to support our busy and demanding lifestyles, our dependence on disposable plastics has led to a global environmental crisis. The high stability of plastics to an array of conditions that was once highlighted as a value for commercialization has now become a serious flaw. Addressing this crisis is going to require collective efforts to recycle or upcycle the commercial products already produced at large scale and to develop more degradable or recyclable replacements. The Fieser group strives to achieve these ends through two research thrusts. In our polymerization thrust, rare earth metal catalysts are being developed for the synthesis of degradable plastics through the perfectly alternating copolymerization of epoxides and cyclic anhydrides and the block copolymerization of 1,3-dienes with cyclic esters. Using a host of complementary techniques, we demonstrate the development of efficient synthetic methods, thorough characterization of physical properties of the resulting polymers, and proof-of-concepts for future recycling processes. In our depolymerization thrust, we are exploring environmentally-friendly catalytic methods for the dechlorination of polyvinyl chloride, with an emphasis on establishing control over product selectivity. Using both inorganic and organic catalyst systems, we show facile tunability of the organic polymer product for potential assimilation to varying applications. Recent advances from both research thrusts will be discussed.

Chem 218 Student Exit Seminar: Mengzhen Chen
2022-12-01 12:00 - 13:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Houk-Jung Organic Colloquium 247: Sidney Wilkerson-Hill
2022-12-01 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Seminar Sponsored by Organization for Cultural Diversity in Science
Prof Wilkerson Hill Flyer
Title: Orphaned Cyclopropanes
Abstract: Cyclopropanes are strained carbocycles that have fascinated chemists for decades with many established methods for their construction. Unfortunately, many methods struggle to build cyclopropanes containing only alkyl functionality, which limits access to antiviral medicines (e.g., nirmatrelvir), pyrethroid insecticides and sesquiterpenoid natural products. These cyclopropanes have been “orphaned” or left behind by state-of-the-art cycloaddition methods and are typically characterized as arising from the transfer of a unstabilized carbene unit. The goals of the Hill group are to develop new methods to obtain orphaned cyclopropanes and to use these strategies to address the coming “insectocalypse”. To this end, we have developed three cyclopropanation methods that break with traditional paradigms and enable the rational design and facile access to orphaned cyclopropanes. Our most recent approach leverages the high reactivity of lithiosulfones to transfer dialkyl carbene groups to styrenes.

Inaugural Dickerson Lecture Biochemistry Seminar Series: Robert M. Stroud
2022-12-01 16:00 - 17:30 | Boyer 159, 611 Charles E Young Dr E, Los Angeles, CA 90095, Los Angeles, CA, 90095, United States
Flyer: Dickerson Lecture Flyer – Robert M. Stroud
Title: “Caught in the Act! – Building the Wall!”
Abstract: From the atomic structure of the first protein, Myoglobin in which Richard Dickerson played the key role(1), proteins were necessarily purified from large animals. Now complex machines can be ‘tagged’ and purified endogenously from cells growing under normal conditions(2), revealing their endogenous partnerships, natural substrates, and reactions as if trapped ‘in action’. The mycolic acid layer of the Mycobacterium tuberculosis cell wall is essential for viability and virulence, and the enzymes responsible for its synthesis are therefore targets for antimycobacterial drug development. Polyketide synthase 13 (Pks13) performs the key essential final condensation of mycolic acids. Structures determined by cryogenic electron microscopy of dimeric multi-enzyme Pks13 purified from mycobacteria, are captured with native endogenous long-chain fatty acid substrates. Structures define the ketosynthase (KS), linker domains, and acyltransferase (AT) domains at 1.8 Å resolution, and show two alternate locations of the N-terminal acyl carrier protein that delivers substrate from a fatty acid synthase to the KS domain. Other domains, visible only at low resolution, are flexible relative to the KS-AT core. These structures, together with cross linking and integrative modeling suggest intermediate states on the pathway to mycolic acid synthesis(3).

Special Materials Chemistry Seminar by Prof. Jennifer Dionne
2022-12-06 13:00 - 14:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Mahdi Abu-Omar
2022-12-07 16:00 - 17:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Flyer: Prof. Mahdi Abu-Omar Flyer
Meet the Speaker: 11 a.m., YH 3096
Title: Bifunctional catalysis for upcycling of polyethylene to alkylaromatics
Abstract: The current scale of plastics production (nearing 400 million tons per year) and the accompanying waste disposal problems represent a largely untapped opportunity for chemical upcycling. Tandem catalytic conversion by platinum supported on γ-alumina converts various polyethylene grades in high yields to liquid alkyl aromatics in the absence of added solvent or molecular hydrogen. These molecules can be used as biodegradable detergents. Coupling exothermic hydrogenolysis with endothermic aromatization renders the overall process thermodynamically accessible despite moderate reaction temperature. The UCSB upcycling process demonstrates how waste polyolefins can be a viable feedstock for the generation of useful and value-added molecules.

Chem 218 Student Exit Seminar: Chenxiang Wang
2022-12-08 12:00 - 13:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Special Biochem Seminar - Steve Bonilla
2023-01-05 11:00 - 12:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Title: Dissecting Dynamic RNA 3D Landscapes by Cryo-EM

Physical Chemistry Seminar 228: Dr. Victoria Barber
2023-01-05 11:00 - 12:00 | via Zoom
Dr. Barber Flyer 1.5.23

Houk-Jung Organic Colloquium 247: Dr. Saki Ichikawa
2023-01-05 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Dr. Ichikawa Flyer
Title: Natural Recognition Motifs for the E3 Ligase Adapter Cereblon
Abstract: Understanding the biology of drug target proteins is essential to enhance drug discovery efforts and mechanistic studies. The clinical drugs thalidomide and its derivatives, known as immunomodulatory drugs (IMiDs), are recognized by a conserved binding domain on the E3 ligase adapter cereblon (CRBN), resulting in lifesaving anti-cancer treatments or horrific teratogenicity. However, despite the growing use of CRBN in the lab and clinic, the mechanisms CRBN uses to recognize protein substrates have escaped definition to date. E3 ligase complexes select proteins for degradation by recognizing degrons, specific amino acid sequences sufficient to promote ubiquitination and degradation when embedded in a protein substrate. We hypothesized that degrons for the thalidomide-binding domain of CRBN could be installed on its substrates via post-translational modifications. Here, I will discuss our chemical approaches to discovering a degron for the thalidomide-binding domain of CRBN and its implications for the physiological function and therapeutic engagement of CRBN.
Bio: Saki Ichikawa is currently a postdoctoral fellow in the laboratory of Professor Christina M. Woo at Harvard University, where she investigates natural substrate recognition mechanisms of the E3 ligase adapter cereblon (CRBN). She obtained a BS in Chemistry from the University of Tokyo (2014), where she conducted undergraduate research in the laboratory of Professor Eiichi Nakamura. In 2019, Saki received her Ph.D. in Chemistry from the Massachusetts Institute of Technology (MIT) under the guidance of Professor Stephen L. Buchwald. While at MIT, she focused on the development of copper-catalyzed asymmetric hydroamination reactions. By integrating chemical biology, organic chemistry, and chemical proteomics, Saki aims to address significant questions in the chemistry and biology of protein modifications.

Special Biochemistry Seminar - Michael Lawson
2023-01-09 11:00 - 12:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Michael Lawson Seminar
Title: Defining the Pathways of Eukaryotic Translational Quality Control
Abstract: My research examines how protein synthesis concludes on normal and defective mRNAs. Understanding how these processes are choregraphed is crucial for human health; for example, 11% of all heritable human diseases are caused by premature stop codons. As a postdoctoral fellow, I defined the molecular events that liberate polypeptides from ribosomes as translation concludes on normal mRNAs. Using an in vitro reconstituted yeast translation system and single-molecule assays, I tracked the interplay of eukaryotic release factors (eRF1 and eRF3) with ribosomes halted at stop codons. I discovered that eRF1 and eRF3 act together to quickly recognize stop codons and elicit termination via a tightly regulated process that resembles how ribosomes select proper tRNAs in translation elongation, which explains how translation termination is fast yet also specific for stop codons. Since the release factors are well conserved throughout eukaryotes, these mechanisms are likely a fundamental feature of eukaryotic protein synthesis. My work also revealed that diverse effectors inhibit translation termination to promote stop codon readthrough, suggesting a new route to treat diseases caused by premature stop codons which includes cystic fibrosis and hereditary cancers. In the future, I will use single-molecule and structural approaches to watch translation unfold on defective mRNAs to understand the molecular events used to evaluate mRNAs and prevent the repeated synthesis of toxic proteins.

Organic Student Seminar 248: Aaron Chavarria
2023-01-09 15:00 - 15:50 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Physical Chemistry 228: Dr. Youn Jue (Eunice) Bae
2023-01-09 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Dr. Bae Flyer

Special Houk-Jung Organic Colloquium 247: Dr. Masha Elkin
2023-01-12 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Abstract: The synthesis of natural products is motivated by their potent biological effects, enigmatic biosynthetic origins, and complex molecular structures. Computational tools such as density functional theory and machine learning can provide mechanistic insights and predict reactivity in silico to inform synthetic campaigns. In addition, computational tools and predictive analytics can guide the development and application of transition-metal catalysis. Several examples of computational approaches to challenges in synthesis and catalysis are presented: selectivity rationalization during the synthesis of berkeleyone A, machine learning to guide the synthesis of clovane terpenoids, hybrid modeling to predict the site of late-stage functionalization of pharmaceutical intermediates, and machine learning to develop new catalysts for olefin hydroformylation. These advances enable more efficient use of synthetic resources and offer modern solutions to pressing challenges in synthesis and catalysis.

Special Biochem Seminar -Jinfan Wang
2023-01-17 11:00 - 12:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Title: How does protein synthesis start in eukaryotes?

Special Houk-Jung Organic Colloquium 247: Dr. Alistair Sterling
2023-01-17 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Strain is a foundational concept in organic chemistry. Its presence can transform an inert molecule into one with exciting properties, or steer a reaction toward a single product with exquisite control. Understanding—and importantly, predicting—the delicate balance between strain and reactivity will enable the full potential of strain to be harnessed for drug discovery, materials chemistry, bioconjugation and beyond. In this talk, efforts to uncover the fundamental principles that govern strain release chemistry will be discussed, using the highly-strained hydrocarbon [1.1.1]propellane to develop the concept of bond delocalization,1 before demonstrating how this idea can be generalized to predict the behaviour of all small-ring carbocycles.2 The implications of this interplay between strain, bonding and reactivity will be explored through reaction development built upon halogen bonding and photoredox catalysis,3,4 offering guidelines to develop reactions that capitalize on strain release reactivity.5
[1] Sterling, A. J., Dürr, A. B., Smith, R. C., Anderson, E. A., Duarte, F., Chem. Sci. 2020, 11, 4895–4903.
[2] Sterling, A. J., Smith, R. C., Anderson, E. A., Duarte, F., ChemRxiv 2021 (https://doi.org/10.26434/chemrxiv-2021-n0xm9).
[3] Livesly, S., Sterling, A. J., Robertson, C. C., Goundry, W., Morris, J. A., Duarte, F., Aïssa, C., Angew. Chem. Int. Ed. 2022, 61, e202111291.
[4] Wong, M. L. J., Sterling, A. J., Mousseau, J. J., Duarte, F., Anderson, E. A., Nat. Commun. 2021, 12, 1644.
[5] Frank, N., Nugent, J., Shire, B. R., Pickford, H. D., Rabe, P., Sterling, A. J., Zarganes-Tzitzikas, T., Grimes, T., Thompson, A. L., Smith, R. C., Schofield, C. J., Brennan, P. E., Duarte, F., Anderson, E. A., Nature 2022, 611, 721–726.

Special Biochem Seminar - Alex Guseman
2023-01-19 11:00 - 12:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Title: Targeting Spike Glycans to Inhibit Viral Entry

Houk-Jung Organic Colloquium 247: Tehshik Yoon
2023-01-19 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Prof. Yoon Flyer
Stereocontrol in Photochemical Synthesis
Abstract: Photochemistry is intriguing as a synthetic tool because the absorption of light by an organic molecule results in the formation of exceptionally energetic reactive intermediates that can react in ways that are inaccessible to ground-state molecules. However, this high reactivity is also a challenge for stereoselective synthesis: control over the stereochemistry of photochemical reactions, particularly using enantioselective catalysts, has been a long-standing challenging synthetic problem with few general solutions. We recently developed a strategy that utilizes privileged chiral Brønsted acid scaffolds to control both the absolute and relative stereochemistry of complex [2+2] photocycloadditions. These reactions have enabled a general, concise, and stereocontrolled strategy for the synthesis of the truxinate and truxillate natural products.

Biochemistry Seminar Series - Prof. Sarah Keane
2023-01-20 15:30 - 16:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Title: TBD
Abstract: TBD

Dickerson Biochemistry Seminar Series: Prof. Sarah Keane
2023-01-20 15:30 - 16:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Flyer: Sarah Keane Flyer
Title: Structure of pre-miR-31 reveals an active role in Dicer processing
Abstract: As an essential post-transcriptional regulator of gene expression, microRNA (miR) levels must be strictly maintained. The biogenesis of many, but not all, miRs is mediated by trans-acting protein partners through a variety of mechanisms, including remodeling of the RNA structure. The intrinsic structural properties of RNAs can provide an additional layer of regulation. miR-31 functions as an oncogene in numerous cancers and interestingly, its biogenesis is not known to be regulated by protein binding partners. We determined the solution structure of the precursor element of miR-31 (pre-miR-31) to investigate the role of distinct structural elements in regulating Dicer processing. We found that the presence or absence of mismatches within the helical stem do not strongly influence Dicer processing of the pre-miR. However, both the apical loop size and structure at the Dicing site are key elements for discrimination by Dicer. Interestingly, our NMR-derived structure reveals the presence of a triplet of base pairs that link the Dicer cleavage site and the apical loop. Mutational analysis in this region suggests that the stability of the junction region strongly influence both Dicer binding and processing. Our results enrich our understanding of the active role that RNA structure plays in regulating Dicer processing.

Organic Student Seminar 248: Madeline Ruos
2023-01-23 15:00 - 15:50 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
