UCLA

Dickerson Biochemistry Seminar Series: Prof. Sarah Keane
2023-01-20 15:30 - 16:30 (America/Los_Angeles) | 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

Physical Chemistry 228: Dr. Milena Jovanovic
2023-01-23 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Dr. Jovanovic Flyer
Title: “Delocalized Bonding in Extended Systems: From Molecules to Quantum Materials”
Abstract: A long list of words attached to extensions of two-center two-electron bonding, such as
conjugation, aromaticity, electron-deficient, and electron-rich bonding, testifies to the ubiquity of
electron delocalization and its importance in chemistry. Delocalization certainly has consequences – in
spectroscopic, ionization, and magnetic questions the most prominently – both for discrete molecules
and for polymers and extended solids. Moreover, a complex relationship between delocalized bonding
and quantum properties of extended solids has come to light in recent years. Understanding
delocalization mechanisms and how they interact with each other is crucial to designing new quantum
materials.
My talk focuses on two cases of electron delocalization in materials: σ delocalization in
permethylated polysilane and chemical bonding in kagome lattices. In the case of permethylated
polysilane, I will explain how strong conformational dependence of the polymer’s properties arises from
an interplay of two delocalization mechanisms. In the case of compounds featuring the kagome lattice, I
will derive chemical rules to predict if bonding within the lattice is possible and its relation to materials’
properties. Additionally, I will briefly reflect on the other aspects of electron delocalization, namely non-
trivial election localization in crystals and its consequences.

NSF Center for Integrated Catalysis Webinar Series: Parisa Mehrkhodavandi
2023-01-24 13:00 - 14:30
Title: Cationic indium in catalysis: Generation of functionalized copolymers from commodity monomers
Abstract: Cationic indium complexes are rare in the field of catalysis. We have developed families of cationic indium complexes supported by tridentate and tetradentate aminophenolate ligands which show reactivity towards cyclic esters, cyclic ethers, and copolymerizations with CO 2. We show that, depending on ligand design, these complexes are excellent catalysts for the coupling of functionalized epoxides and cyclic esters to form orthoesters, for the controlled ring opening polymerization of cyclic ethers, and for the copolymerization of cyclic ethers and esters. Structure-function relationships and mechanistic considerations in each of these systems will be explored.

Special Houk-Jung Organic Colloquium 247: Dr. Jose Roque
2023-01-24 16:00 - 17:00 | Young Hall 2033
Modern drug discovery has benefited from advancements in chemical reaction development. For example, C–H functionalization reactions has transformed how synthetic chemists approach the retrosynthetic analysis of bioactive compounds. Despite recent advances, the development of site-selective reactions remains a grand challenge in metal-catalyzed C–H functionalization. Typical retrosynthetic analysis results in simplified fragments by the removal of functional groups on the periphery of molecules. As a result, forward syntheses and diversification of molecules have focused on peripheral modifications. Inspired by the concept of scaffold hopping, the first part of the presentation will detail an approach to access novel chemical space by focusing on making structural edits to the core framework of molecules. The second part of the presentation will center on addressing site-selectivity and the need for more active first-row transition metal catalysts, as the low activity and limited scope of known first-row transition metal catalysts severely limit their utility. Cobalt precatalysts supported by pyridine dicarbene pincers have been developed to selectively functionalize electronically distinct C–H bonds without relying on directing groups contrasting traditional approaches. For example, the meta-selective C(sp2)–H borylation of fluoroarenes, a significant challenge due to the weak coordinating ability and the similar size of fluorine and hydrogen, has been demonstrated. Mechanistic studies on fluoroarene borylation established a kinetic preference for C–H bond activation at the meta position, while cobalt-aryl complexes resulting from ortho C–H activation are thermodynamically preferred. As a result of these mechanistic insights, the selectivity of a C–H borylation can be switched with a single catalyst by simply modifying the reaction conditions.

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Elena Meirzadeh
2023-01-25 16:00 - 17:15 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Flyer: Dr. Elena Meirzadeh Flyer
Title: From small molecules to infinite superatomic sheets
Abstract: Developing a precise understanding of structure-function relationships in molecular crystals can allow us to generate a wide range of properties from extremely simple building blocks. In the first half of my talk, I will discuss how crystal engineering and defects affect the macroscopic properties of amino acid crystals. Moreover, I will describe the molecular-level determination of the structure of defect sites, which are below the diffraction detection limit, using pyroelectric measurement coupled with dispersion-corrected density functional theory calculations and molecular dynamics simulations. In the second half of my talk, I will introduce a new two-dimensional crystalline form of carbon that we recently synthesized –– graphullerene. The constituent fullerene subunits in these crystals are arranged hexagonally in a covalently interconnected molecular sheet that can be mechanically exfoliated and characterized. I will describe how the properties of graphullerene differ from those of graphene and molecular fullerenes.

Distinguished Lecture Series: Daniel G. Nocera
2023-01-26 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Flyer TBA
Title TBA
Abstract TBA

Special Inorganic Chemistry Seminar Series: Agnes Thorarinsdottir
2023-01-27 13:00 - 14:15 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Flyer: Dr. Agnes Thorarinsdottir flyer
Title: New Approaches to Magnetic Resonance Imaging and Energy Catalysis Through Chemical Design
Abstract: Synthetic chemistry is a powerful tool for realizing molecules and materials with novel functions for addressing grand challenges in biomedical, environmental, and energy science. This presentation will discuss two avenues by which specific molecular and materials functions may be implemented by chemical design to create chemical systems with advanced properties.
Part 1: Variation of properties such as temperature, pH, and redox status in the tissue microenvironment is closely associated with a number of biological processes and diseases. Magnetic resonance imaging (MRI) probes that can alter their magnetic properties in response to specific changes in their surrounding environment provide new opportunities for overcoming the current limitations of traditional MRI contrast agents, namely relatively low sensitivity and poor specificity. This presentation will describe the employment of spin-crossover iron complexes for monitoring temperature using 19F NMR chemical shift and dinuclear cobalt complexes for the ratiometric quantitation of solution pH in a noninvasive manner.
Part 2: Global adoption of sustainable energy technologies and chemical industries relies heavily on the efficiency by which small gas molecules such as CO2, N2, O2, and H2 can be converted to fuels, chemicals, and electricity. Electrocatalysis of such gas molecules driven by renewable energy sources offers a promising route, however, performing such reactions in aqueous environments has been limited by the low solubilities of gases in water. This presentation will describe a strategy of harnessing the high gas capacities of microporous water—aqueous porous liquids comprising microporous nanocrystals—for engendering current enhancement in the electroreduction of O2 in water.

Special Biochem Seminar - Jie Zhou
2023-01-30 11:00 - 12:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Title: Identify and Target Proteolytic Neoepitopes in Cancer

Organic Student Seminar 248: Georgia Scherer
2023-01-30 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: Dolores Bozovic
2023-01-30 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Prof. Bozovic Flyer
Title: Physics of the Auditory System
Abstract: Hair cells of the auditory system constitute a remarkable biological sensor that exhibits nanometer-scale sensitivity of mechanical detection. Our experiments explore the active nonlinear processes behind the detection of very weak signals. We demonstrate the presence of chaos in the innate motility of active bundles, and explore both theoretically and experimentally its role in enhancing the sensitivity of detection. We further show that these cells utilize weakly chaotic dynamics to combine sensitive response with high temporal resolution. The presence of chaos in individual hair bundles also aids in the synchronization between coupled hair cells, and gives rise to new dynamical states. Finally, we explore the neural mechanisms that reduce and control the responsiveness of the cell. Specifically, we show that the efferent neurons serve as a gain control system, which can strongly affect the very compliance of the mechanosensory cells.

Special Houk-Jung Organic Colloquium 247: Soumitra Athavale
2023-01-31 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Tales in Molecular Evolution: From Chiral Symmetry Breaking to New-to-Nature Biocatalysis

The evolutionary journey of chemistry on our planet, from small molecules to genetic polymers, presents fascinating opportunities for the organic chemist. At one end, mysterious early steps evoke grand questions at the foundations of chemistry, while at the other, biology’s extraordinary machinery lies primed for creative manipulation.
An illustration of the former is the riddle of the origin of biological homochirality, inspiring the general query, ‘can asymmetric synthesis transpire without any chiral intervention’? The Soai reaction – diisopropylzinc alkylation of pyrimidine carbaldehydes – remains a singular, celebrated example where this is possible and has received widespread attention from diverse chemical fields. I will present structural, experimental, and computational investigations which reveal the first comprehensive mechanistic picture of this iconic transformation.
For the latter case, I will showcase how the principles of directed evolution can be applied to develop new enzymes for promoting processes never seen in nature. The engineering of heme proteins enables enantioselective catalysis of challenging nitrene C–H insertion reactions for accessing nitrogen containing compounds from feedstock chemicals. This example of ‘new-to-nature biocatalysis’ is emblematic of a modern age of protein biochemistry that promises to revolutionize the use of enzymes for molecular construction.

Houk-Jung Organic Colloquium 247: Zachary Wickens
2023-02-02 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Prof. Wickens Flyer
Selective Synthesis via Light and Electricity
Abstract: We are investigating how organic radical ions–typically thought of as fleeting intermediates–can be tamed and exploited as a new family of organocatalysts and small molecule reagents. We identified selective generation of such species as a key hurdle stymying exploration these electronically-destabilized systems. To address this problem, we have leveraged electrochemistry to develop new synthetic transformations driven by organic radical ions. Electrochemistry offers not only an environmentally benign approach to promote redox events but also substantially simplifies the study of these unusual systems by enabling the exclusion of byproducts from oxidation or reductive generation of the key radical ion promoters.
This seminar will describe two new platforms for synthetic reaction development based on electrogenerated persistent organic radical ions. In the first system, we describe the development of a new family of radical anion photoredox catalysts over a volt more reducing than conventional photocatalyst systems. These potent catalysts have enabled abundant but classes of arene substrates to now act as general aryl radical precursors for diverse radical coupling reactions. In the second system, we will discuss a new approach to oxidatively functionalize alkenes via a metastable dielectrophilic intermediate derived from reaction with thianthrene radical cation. This strategy has enabled new synthetic methods to construct high value aliphatic amine products by coupling amines and feedstock hydrocarbons.

Biochemistry Seminar Series - Prof. Zhipeng Lu
2023-02-03 15:30 - 16:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Flyer: Zhipeng Lu Flyer
Title: What does RNA look like in cells? Structures, interactions and modifications.
Abstract: RNA in living cells are in constant motion, form dynamic structures, and interact with many molecules, including other RNAs. Direct determination of RNA structures and interactions in vivo is essential to understanding their functions, and developing new RNA-based and RNA-targeting therapeutics, but has been challenging in the past. We developed a number of novel chemical and computational tools to capture the 2D and 3D RNA structurome and interactome in cells, providing a comprehensive view of RNA conformations that underlie their roles in gene regulation and human diseases. In particular, our recent applications of these methods revealed new mechanisms in lncRNA functions and RNA modifications.

Norma Stoddart Prize - Grad Student Q&A with Sir Fraser Stoddart
2023-02-06 09:00 - 10:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
9:00 AM – 10:00 AM
Grad Student Q&A with Nobel Laureate Sir Fraser Stoddart
Norma Stoddart Prize Flyer – Dr. Marco Messina

Norma Stoddart Prize - Around the World in 80 Years by Sir Fraser Stoddart
2023-02-06 10:00 - 23:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
10:00 – 11:00 AM
Around the World in 80 Years, a presentation by Sir Fraser Stoddart
Norma Stoddart Prize Flyer – Dr. Marco Messina

Norma Stoddart Prize - Marco Messina
2023-02-06 13:00 - 14:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Title: Tandem Activity-Based and Labeling Approaches to Monitor Transient Analytes in Biological Systems
Norma Stoddart Prize Flyer – Dr. Marco Messina

Organic Student Seminar 248: Daniel Min
2023-02-06 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: David Ginger
2023-02-06 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Prof Ginger Flyer
Title: Probing Ion Injection and Transport in Conjugated Polymers: From Bioelectronic Brains to Energy Storage
Abstract: Ion injection and transport in conjugated polymers affects the performance of devices ranging from organic electrochemical transistors (OECT) for bioelectronic signal transduction, and from aqueous polymer batteries to next generation neuromorphic computing architectures. The performance of conjugated polymers in these applications is due to the ability of the polymer to accommodate ionic countercharge throughout the device volume during redox processes. For instance, in OECTs, the resulting volumetric capacitance allows for very large modulations of the charge density in the transistor channel and large transconductance values. Using OECTs as a testbed, we explore measurements on different polymers with different counterions. At the nanoscale, we use electrochemical strain microscopy (ESM) to probe local swelling resulting from ion uptake, and photoinduced force microscopy (PiFM) to probe the IR fingerprints of ion injection which we correlate with ensemble measurements such as electrochemical quartz crystal microbalance (eQCM), spectroelectrochemistry, and in operando synchrotron structure measurements. We correlate these methods to gain insight into how local polymer structure governs ion uptake and transport and how the chemical nature of the counterion and associated structural changes impact electronic charge transport. We show that the counterion polarizability strongly affects both ion injection kinetics, as well as the mechanism of charge compensation (contrasting counterion expulsion vs. and counterion injection). In the process we observe non-Fickian ion “diffusion” in a conjugated polymer which show can be explained as a propagating phase change front. We discuss microscopic insights into these processes and propose new material design rules.

NSF Center for Integrated Catalysis Webinar Series: Frank A. Leibfarth
2023-02-07 13:00 - 14:30
Title: Stereoselective Cationic Polymerization of Prochiral Monomers
Abstract: The stereochemistry of vinyl polymers, known as polymer tacticity, is intimately linked to their resultant material properties. Despite the well-developed stereoselective methods for the polymerization of propylene and other nonpolar -olefins, general approaches to the stereoselective polymerization of polar vinyl monomers are not well developed. In this lecture, we will discuss the design of chiral counterions that systematically tune the reactivity and chain-end stereochemical environment during cationic polymerization. This approach overrides conventional chain-end stereochemical bias to achieve catalyst-controlled stereoselective polymerization of prochiral vinyl monomers through a cationic mechanism. We demonstrate that chiral counterion catalysis is a general conceptual approach that can be leveraged for the stereoselective polymerization of both vinyl ethers and N-vinyl carbazoles. The properties of the isotactic polymers will also be described, with a focus on how unique function can be derived from stereocontrol.

Houk-Jung Organic Colloquium 247: Nicholas Ball
2023-02-09 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Prof Ball Flyer
Unlocking Fluorine: Activation of Sulfur(VI) Fluorides for New Sulfur-Fluorine Exchange (SuFEx) Reactions
Abstract: Sulfur-fluoride exchange (SuFEx) chemistry is emerging as a promising synthetic tool in chemical biology, material science, and synthetic chemistry. In synthesis, sulfur (VI) fluorides show unique promise as synthons in organic chemistry due their stability versus other sulfur (VI) halogen analogues. Key to the adoption of SuFEx chemistry is the development of efficient modes to synthesize and react sulfur (VI) fluorides. Research initiatives employing group 2, and transition-metal chemistry toward the synthesis of sulfonyl fluorides will be described. New SuFEx methods that react a broad set of S (VI) fluorides with carbon, oxygen, and nitrogen-based nucleophiles towards structurally diverse S(VI) compounds will also be presented.
A focus will be on a new SuFEx reaction to synthesize nitrogen-based sulfonylated compounds from a variety of S(VI) fluorides mediated via a Lewis acidic calcium salt will be described. Under a unified set of reaction conditions, sulfonyl fluorides, fluorosulfates, and sulfamoyl fluorides can be coupled with a variety of amines to synthesis a wide array of aryl and alkyl sulfonamides, sulfamides, and sulfamates in good to excellent yield. Computational and NMR kinetic studies that aim to elucidate the mechanism of Ca-activation will be discussed. Lessons learned from the mechanistic studies have led to preliminary data suggesting Ca-catalysis is possible.

Biochemistry Seminar Series - Prof. Linlin Zhao
2023-02-10 15:30 - 16:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Title: Exploiting Abasic Site Chemistry to Decipher Mitochondrial Genome Biology
Abstract: Human mitochondrial DNA (mtDNA) encodes 37 essential genes and plays a critical role in mitochondrial and cellular functions. Compared to nuclear DNA (nDNA), mtDNA is more susceptible to chemical modifications by endogenous and exogenous factors partly due to its proximity to the oxidative phosphorylation system and the lack of certain DNA repair pathways. Our research aims to understand the chemical and molecular mechanisms by which DNA modifications are processed in the mitochondrial genome and their implications in human diseases. In this seminar, I will discuss our recent efforts to probe the role of mitochondrial transcription factor A (TFAM) in damaged mtDNA degradation. We focus on a prevalent type of DNA modification, i.e., abasic (AP) sites, formed by the loss of nucleobases during natural depurination or depyrimidination and DNA repair. We used biochemical and cellular assays to demonstrate that TFAM accelerates DNA scission at AP sites. The reaction produces chemically reactive entities at the DNA terminus and leads to secondary products, such as TFAM-DNA cross-links and glutathionylated DNA single-strand breaks, which could serve as triggers for mtDNA degradation and the recruitment of additional proteins. We have also identified the cross-linking amino acids of TFAM using mass spectrometry. Together, our research demonstrates the involvement of TFAM in processing AP DNA damage in mitochondria. Last but not least, I will discuss how we exploit the chemistry of AP sites to develop specific chemical probes to label and enrich AP-DNA. We have successfully used the workflow to map AP sites and DNA alkylation modifications using next-generation sequencing in cultured human cells.
Linlin Zhao Flyer

Organic Student Seminar 248: Brady Dehnert
2023-02-13 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: Anton Van der Ven
2023-02-13 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Prof Van der Ven Flyer
Title: From Electronic Structure to Battery Thermodynamics and Kinetics
Abstract: Most electrochemical processes can be modeled with powerful phenomenological theories that describe ion transport, interface reactions and mechanical responses. Phenomenological descriptions, however, rely on materials specific coefficients and free energies, which are quantities that are often difficult to measure in isolation. An alternative to an experimental approach is to predict these quantities from first principles. Since electrochemical processes are thermally activated, temperature and entropy play an important role. The prediction of materials properties, therefore, requires a statistical mechanics approach. In this talk I will describe a generalized framework with which to connect the electronic structure of crystalline solids to their equilibrium and kinetic properties at the macroscopic scale. I will illustrate how the application of first-principles statistical mechanics can generate crucial ingredients for phenomenological models of electrochemical processes, including composition dependent free energies and open circuit voltage profiles, ionic transport coefficients and chemo-mechanical response functions. The capability to predict thermodynamic and kinetic properties of electrode materials is allowing us to explore and design new battery chemistries and concepts. Electrode materials for Li, Na and Mg ion batteries undergo a series of phase transformations as a result of large changes in concentration during each charge and discharge cycle. While the mechanisms of these phase transformations remain poorly characterized, they can to an extent be understood with first-principles multi-scale approaches.

Chem 218 Student Exit Seminar: Ashley Shin
2023-02-16 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: Wei Liu
2023-02-16 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Prof Liu Flyer
Copper-Catalyzed Coupling Reactions: Mechanism, Catalysis, and Applications in Life Sciences
Abstract: Owing to their many attractive characteristics, copper catalysts represent appealing alternatives to precious metal catalysts, although various limitations remain in copper-catalyzed cross-coupling reactions. Recently, we and others recognized that copper catalysis presents a powerful strategy to functionalize sp3 hybridized carbon radicals for the construction of carbon-carbon and carbon-heteroatom bonds. In this talk, I will discuss our group’s recent efforts in understanding the mechanism of copper catalysis and developing new copper-catalyzed cross-coupling reactions.

Biochemistry Seminar Series - Prof. Jonathan Abraham
2023-02-17 15:30 - 16:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Title: Mechanisms of immune evasion by the SARS-CoV-2 spike protein
Jonathan Abraham Flyer

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Seth Cohen
2023-02-22 16:00 - 17:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Flyer: Prof. Seth Cohen Flyer
Title: Exploring MOF-Polymer Hybrid Materials
Abstract: Hybrid materials of metal-organic frameworks (MOFs) and polymers have gained interest as processible composites that might be suitable for a wide range of applications. A number of approaches have been pursued to create MOF-polymer composites, including mixed-matrix membranes (MMMs) prepared with MOFs, polymer-decorated MOF particles, and MOFs constructed from polymer buidling blocks referred to as polyMOFs. The design, synthesis, and unusual properties of these MOF-polymer composite materials will be presented and discussed.

Special Physical Chemistry Seminar 228: Jörg Enderlein
2023-02-23 11:00 - 12:00 | Young Hall 2033
Enderlein Flyer Updated
Title: Metal and Graphene Induced Energy Transfer
Abstract: Metal-Induced Energy Transfer (MIET) Imaging is a recently developed method [1] that allows for nanometer resolution along the optical axis. It is based on the fact that, when placing a fluorescent molecule close to a metal, its fluorescence properties change dramatically, due to electromagnetic coupling of its excited state to surface plasmons in the metal. This is very similar to Förster Resonance Energy Transfer (FRET) where the fluorescence properties of a donor are changed by the proximity of an acceptor that can resonantly absorb energy emitted by the donor. In particular, one observes a strongly modified lifetime of its excited state. This coupling between an excited emitter and a metal film is strongly dependent on the emitter’s distance from the metal. We have used this effect for mapping the basal membrane of live cells with an axial accuracy of ~3 nm. The method is easy to implement and does not require any change to a conventional fluorescence lifetime microscope; it can be applied to any biological system of interest, and is compatible with most other super-resolution microscopy techniques that enhance the lateral resolution of imaging [2-4]. Moreover, it is even applicable to localizing individual molecules [5-6], thus offering the prospect of three-dimensional single-molecule localization microscopy with nanometer isotropic resolution for structural biology [7]. I will also present latest developments of MIET where we use a single layer of graphene instead of a metal film that allows for increasing the spatial resolution down to a few Ångströms [8-10].

Chem 218 Student Exit Seminar: Anthony Sica
2023-02-23 12:00 - 13:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
