UCLA

Chem 278: Prof. Sheng Xu
2021-03-03 16:00 (America/Los_Angeles)
Controlled epitaxial growth and fabrication of hybrid halide perovskites
Abstract: Organic–inorganic hybrid halide perovskites have demonstrated tremendous potential for next-generation electronic and optoelectronic devices due to their remarkable carrier dynamics. Current studies are mostly focused on polycrystals, since controlled growth of high-quality single crystals is challenging. In this presentation, I will discuss strategies that enabled the first chemical epitaxial growth of single-crystal hybrid halide perovskites. Using advanced microfabrication, homo-/hetero-epitaxy, and a low-temperature solution method, single crystals can be grown with controlled locations, morphologies, orientations, and strain levels. By a lifting off approach, single-crystal thin films can be transferred from the epitaxial substrate to a general flexible substrate. This approach opens up broad opportunities for hybrid halide perovskite materials based high-performance electronic and optoelectronic devices.

Chem 218 Student Exit Seminar: Sophia King
2021-03-04 12:00
Controlling the Architecture of Nanoporous Materials to Regulate their Thermal Conductivity and Optical Transparency for Energy Efficient Windows
Transparent, low thermal conductivity coatings can be applied to windows to increase the energy efficiency of buildings. Amorphous material such as silica make good thermal insulators due to their local atomic disorder that impedes heat conduction. Moreover, pores can be added to the material to further reduce heat conduction by decreasing the material density while adding interfaces can additionally scatter heat carriers. This concept is often used in highly porous silica aerogels, which are valued for their ultra-low thermal conductivities. However, these aerogels significantly scatter light, and therefore cannot be used for applications that require high optical transparency. This talk focuses on our ongoing efforts to design silica-based coating that are insulating as well as optically transparent. First, I will describe our efforts using mesoporous thin films to expand on our fundamental understanding of heat transport in nanoporous, silica-based materials. Next, I will discuss how the knowledge gained from these thin film studies influenced our design of novel precursors and a scalable synthetic method to produce monoliths that can be used in thermal insulation applications. Finally, I will describe our efforts to use small angle X-ray scattering (SAXS) to follow structural changes in porous materials with the goal of understanding how surface chemistry and drying dynamics influence pore structure to produce materials with desired thermal conductivity and optical quality.

Break-it-to-Make-it Strategies for Chemical Synthesis Inspired by Complex Natural Products”
2021-03-04 16:00
Abstract: Natural products continue to inspire and serve as the basis of new medicines. They also provide intricate problems that expose limitations in the strategies and methods employed in chemical synthesis. Several strategies and methods that have been developed in our laboratory and applied to the syntheses of architecturally complex diterpenoid alkaloids, indole alkaloids, and several Lycopodium alkaloids, will be discussed. In addition, new ways to employ C–C bond cleavage in synthesis will be presented (i.e., break-it-to-make-it strategies).

Chem 268: Prof. Benjamin Falcon
2021-03-05 13:30
“Amyloid conformers in neurodegenerative disease”

Chem 228: Peter Dahlberg, Ph.D.
2021-03-08 16:00
“Combining cryogenic single-molecule fluorescence measurements and CryoEM: New methods with applications from biology to physical chemistry”

Chem 218 Student Exit Seminar: Wenfei Li
2021-03-10 12:00
Developing Highly Efficient Electronic Structure Theory Methods for Large Scale Simulations
Electronic structure simulations are now becoming an indispensable tool in chemistry research. The overall goal is to develop methods that give accurate results without sacrificing efficiency. In our group, we incorporate various computational techniques to drastically reduce the cost of simulations. This allows us to run large scale simulations that were not previously possible. Our major innovation is stochastic quantum chemistry, where we replaced the summation over thousands of deterministic orbitals to an average over much smaller number of stochastic orbitals, and sometimes only a few suffices. This leads to significant increase in efficiency. In this seminar, I will talk about my two projects under the stochastic quantum chemistry framework. The first project involved developing an embedding stochastic framework, where a sub-system of interest is treated using deterministic orbitals, while the rest of the system is treated using stochastic orbitals. This way, we can selectively reduce the stochastic errors associated with that sub-system. The second project involved finding an optimal DFT starting point for our stochasticGW code. Apart from that, I will also introduce our orthogonal projector augmented wave package. Compared with the norm-conserving pseudopotential approach, the PAW method will allow a lower kinetic energy cutoff, hence greatly enhances the efficiency of electronic structure theory simulations.

Chem 278: Prof. Long Luo
2021-03-10 16:00
Electrifying Inorganic and Organic Synthesis
Abstract: Electrochemical synthesis is a powerful tool for formulating functional materials and moleculesbecause it offers an additional level of control over the synthesis relative to its chemical counterpart by fine-tuning mass transfer, potential, or current. Electrochemical synthesis also allows the convenient analysis of chemical reaction thermodynamics and kinetics using the current signal generated during the electrochemical synthesis. In this talk, two recent advancements in electrochemical synthesis will be presented: (1) Electrochemical gelation of nanoparticles and (2) Alternating current electrolysis for organic synthesis.

Chem 218 Student Exit Seminar: David Reilley
2021-03-11 12:00
Chemical Change in Protein Molecular Dynamics: Developing Computational Tools for Metal Binding and pH Sensitivity
Molecular dynamics (MD) is a powerful tool to study atomic scale changes in proteins underpinning biological pathways. However, simulations traditionally sample a fixed chemical state and struggle to achieve quantitatively accurate energies, making comparisons of different chemical ensembles challenging. Hybrid quantum mechanical-classical approaches (QM/MM) can provide accurate energies for small regions of interest, such as the active site, but cannot readily capture all chemical transformations relevant to protein function. This talk will focus on developments and applications of hybrid methods to study the metal binding preferences and pH sensitivity of proteins. We will first discuss how we used QM/DMD combined with a competitive metal affinity method, a semi-empirical thermodynamic cycle, to obtain relative binding affinities for a wide range of metals to human serum transferrin (hTF), an iron transport protein. Our results clarified a mechanism for promiscuous metal binding in hTF and the role the protein may play in transport of non-physiological and potentially cytotoxic metals. We will then discuss the development of a titration feature for constant pH simulations with DMD (titr-DMD). Our method features stochastic protonation and deprotonation of amino acids while treating solvent implicitly, which makes it computationally efficient compared to other techniques. We successfully benchmarked titr-DMD on experimentally verified pH-dependent conformational changes. Our work demonstrates the utility of molecular dynamics, and QM/DMD in particular, to study chemical changes in proteins with good accuracy and speed.

CIC Careers in Green Chemistry Seminar Series
2021-03-11 13:00
The Center for Integrated Catalysis is hosting a new seminar series called the “Careers in Green Chemistry.” With these webinars, we aim to bring speakers from a wide variety of careers, linked through green chemistry, to come talk about their current job as well as the career path that led them to that position. We are pleased to invite all students, postdocs, and faculty.

CANCELLED - Chem 268: Prof. Hernan Garcia
2021-03-12 15:30
“Dissecting Transcriptional Dynamics in Development One Burst at a Time”

Chem 218 Student Exit Seminar: Arundhati Deshmukh
2021-03-18 12:00
“Tuning the Excitonic Properties of 2-Dimensional Molecular Aggregates across the Visible and Shortwave Infrared”
Molecular aggregates are non-covalent self-assemblies of chromophores wherein transition dipole moments of individual molecules couple coherently over long distances, forming delocalized excitons. This imparts exciting photophysical properties such as extreme blue or red shifts (seen in H- or J-aggregates respectively), narrow linewidths and high molar absorptivities. We modulate the transition dipole couplings within an aggregate via molecular packing, topology, and disorder in order to tune and explore new photophysical behaviors. In this talk, I will discuss the unusual situation that arises from 2D transition dipole coupling in sheet-like aggregates. In addition to traditional H- and J-aggregation, we find a new case of ‘I-aggregation’ which shows intermediate characteristics of H- and J-aggregates. I will also describe how we use thermodynamics of self-assembly to control the aggregate packing and thereby, tune excitonic properties. Using a three-component equilibrium model, I will lay down general principles for selectively stabilizing H- or J-aggregates, allowing us to construct a library of 2D J-aggregates with absorptions spanning the visible and shortwave infrared (SWIR) regions. Finally, I will show how subtle differences in chromophore structures within this library modulate the aggregate packing and eventually lead to distinct excitonic band pictures, that can be experimentally probed using temperature dependent spectroscopy. Overall, this work establishes molecular aggregation as a tunable avenue for accessing unusual photophysical properties and thus, opens up organic chromophores to new functionalities including SWIR imaging, plexitonics, and telecommunications.

NSF Center for Integrated Catalysis Webinar Series
2021-03-19 13:00
“Invention of Catalysts for Synthesis of New Plastics”
Abstract: This presentation will begin with a brief discussion of the properties of polyethylene and the synthesis of various forms of polyethylene via early metal catalysts and via free radical processes. Following this short discussion, I will discuss our thought processes in developing late metal olefin polymerization catalysts and focus particularly on the chemistry of Ni(II) and Pd(II) diimine-derived catalysts. The talk will finish with a discussion of issues surrounding copolymerization of ethylene and polar vinyl monomers and a mechanistic dissection of the copolymerization of ethylene with vinyl trialkoxysilanes using both Pd(II) and Ni(II) diimine catalysts.

Chem 278: Prof. Wenliang Huang
2021-03-31 16:00
“f-Block metal-arene interactions: from inverse sandwiches to redox chemistry”
Abstract: Recent years have witnessed the breakthrough of identifying unusual oxidation states of f-block elements in molecular compounds such as divalent rare earth metals and actinides, as well as tetravalent terbium and praseodymium. By taking advantage of the symmetry and energy match between the f/d orbitals of low-valent f-block ions and π* orbitals of arenes, we synthesized a series of metal arene complexes featuring an inverse-sandwich structure. We found that δ bonds are responsible for the unusual stability of the tetranionic arene anions in such compounds. Moreover, f-block ions show a significant covalent character, and the extent of covalent interaction increases according to the order: rare earth metals < thorium < uranium. Inspired by these metal-arene δ bonding interactions, as well as the traditional π-donor character of arene ligands, we designed a tripodal-type tris(amide) ligand system featuring an arene anchor. We anticipated that the amphiphilic nature of the arene backbone may support both low and high valent f-block metal centers. This strategy allowed us to stabilize multiple oxidation states of f-block metals with a single ligand and opened up new avenues in the redox chemistry of these ions.

Chem 268: Prof. Hernan Garcia
2021-04-02 15:30

OCDS Seminar: Prof. Karin Chumbimuni-Torres
2021-04-05 16:00
“Electrochemical biosensors for viruses and bacteria: new approaches and challenges”

Chem 278: Prof. Charles W. Machan
2021-04-07 16:00
“Earth-Abundant Molecular Catalyst System for the Reduction of Dioxygen and Carbon Dioxide”
Abstract: The steady increase in anthropogenic carbon dioxide (CO2) emissions and corresponding atmospheric concentrations continues to generate interest in using CO2 as a liquid fuel and commodity chemical precursor. The conversion of CO2 has the dual benefit of addressing its associated negative environmental effects and the diminishing supply of petrochemical feedstocks. At the heart of efficient reductive transformations are proton-coupled electron transfer (PCET) reactions, where electrons and protons move in a concerted way to mitigate kinetic and thermodynamic penalties. Mechanistic understanding of these reactions can inform the design of optimized catalyst structures with improved activity and selectivity for specific products. Another cathodic reaction, the electrocatalytic reduction of dioxygen (O2), has relevance to the development of more efficient fuel cells and can be similarly optimized through fundamental knowledge of the underlying PCET reactions. Molecular systems are well-positioned to provide a better understanding of these reactions because of the relative fidelity with which they can be characterized, as well as the possibility for systematic testing of structure-function relationships through iterative molecular design. In addition to developing new Fe-, Mn-, and Cr-based molecular electrocatalysts for these reactions, we are exploring the use of redox mediators and flow-based electrochemical reactors to understand how these reactions can be scaled relative to comparable heterogeneous systems.

Chem 228: Prof. Chanmin Su
2021-04-12 16:00
“Scanning probe microscopy for physical and chemical property characterizations at the nanoscale”

NSF Center for Integrated Catalysis Webinar Series
2021-04-13 13:00
The NSF Center for Integrated Catalysis is delighted to announce that it will be hosting a monthly webinar series. The next webinar of this series will be held on Tuesday, April 13th, 2021 at 1:00 PM. We are pleased to invite all students, postdocs, faculty, and staff.

Perfluorocarbon nanomaterials as theranostic delivery vehicles
2021-04-13 16:00
Abstract: Perfluorocarbon nanoemulsions, droplets of fluorous solvent stabilized by a polymeric amphiphile dispersed in water, are an intriguing platform for drug delivery. The fluorous phase is biocompatible, has a high dissolved oxygen content, and is both lipophobic and hydrophobic, preventing the leaching of payloads. Here, we describe the use of perfluorocarbon nanoemulsions as a drug delivery platform in which the payload can be easily modified. First, we utilize the high oxygen solubility of perfluorocarbons to perform photodynamic therapy, a treatment modality that requires oxygen, photosensitizer, and light to produce cytotoxic reactive oxygen species. Next, we deliver pDNA solubilized by noncovalent fluorous tags, resulting in the transfection of cells. Lastly, a panel of polymeric amphiphiles were studied to determine design properties such as size, stability, payload release, cellular uptake and protein corona. With these design principles PFC nanoemulsions can be tailored to a desired application.

2020-2021 Sigman Symposium
2021-04-15 10:00
The UCLA Molecular Biology Institute (MBI) will hold the 2020-2021 Sigman Symposium in honor of Professor David Sigman (1939-2001), who was an internationally renowned UCLA professor of chemistry and biological chemistry who illuminated the molecular mechanisms by which enzymes catalyze biological reactions and was one of the founding members of the MBI.
2020-2021 Sigman Award Honoree:
Professor Catherine DrennanDepartments of Chemistry and BiologyMassachusetts Institute of Technology andthe Howard Hughes Medical Institute
Kenote Address: “Shake, Rattle, & Roll:Capturing Snapshots of Ribonucleotide Reductase in Action”
Symposium Schedule – Thursday, April 15, 2021 – 10 am to 1:30 pm

Tribute to David Sigman: Prof. Steven Clarke
Guest Speaker: Prof. Douglas Rees (Caltech):“The Ns and Outs of Nitrogen Fixation”
Keynote introduction/award presentation: Prof. Keriann Backus
Keynote address: Prof. Catherine Drennan
Poster Session and Poster Prize Announcement

PosteSession: The poster session will feature immersion in an 8-bit world complete with “walking” around to interact with poster presenters and attendees, games, and more while providing an opportunity to share your science with our awardee, members of the UCLA community, and have a chance to win one of our poster prizes! Poster prizes will include Best Poster Prizes (up to four $250 prizes) and Honorable mention prizes (up to four $100 prizes) and will be selected with an audience voting component. All UCLA students and postdocs studying in any area of biology or chemistry are eligible to submit. To present a poster please fill out the google form with your poster title by Friday, April 2, 2021 and submit a png, jpeg, or gif image file of your poster to SigmanSymposium2021@gmail.com by Tuesday April 6, 2021. Poster prize winners will be announced after the poster session in a gather.town award ceremony.
For more information about the Sigman Symposium or poster session please visit the MBI website or email SigmanSymposium2021@gmail.com.

Electrophotocatalysis with a trisaminocyclopropenium ion
2021-04-15 12:00
Abstract: This lecture will describe some recent developments in the area of electrophotocatalysis, with a particular focus on a trisaminocyclopropenium (TAC) ion catalyst developed by our group.

Chem 268: Dylan Valencia
2021-04-16 15:30
Quinlan Group
“Biochemical Characterization of Mammalian Formin FHOD3 in Cardiomyocytes”

Chem 228: Prof. Hirofumi Tanaka
2021-04-19 16:00
“Reservoir computing device composed by chemical dynamics”

Trehalose glycopolymer as an excipient for insulin stabilization: safety, mechanism, optimization, and fluid properties
2021-04-20 16:00
Abstract: Biopharmaceutics are widely used to treat serious diseases, but the architectural and chemical complexity that makes proteins good therapeutics renders them susceptible to degradation and aggregation during manufacturing, transportation, and storage. Loss of intact biopharmaceutics causes patient under-dosing as well as adverse reactions. With the growth of biopharmaceuticals coming to market, the need increases for benign excipients to stabilize proteins against environmental stresses without posing a safety concern. A class of glycopolymers bearing a pendant trehalose, a natural sugar, were developed by our group and demonstrated the ability to stabilize a range of biopharmaceuticals. However, this research area had not yet explored the trehalose polymer for safety, mechanism of stabilization, physical properties, or potential optimization. This talk focuses on the ongoing efforts to expand our knowledge base in applying the methacrylate trehalose polymer as an excipient to formulate biopharmaceuticals. In particular, I will highlight the glycopolymer’s benign immunogenic, excretion, and biodistribution behaviors as well as how proteins are unaffected in vivo by the polymer. Next, because the mechanism by which proteins are stabilized as well as the conformation in which they are stabilized affects their onset of activity, I will show how the glycopolymer stabilizes insulin. Due to the importance of patient comfort and compliance, I will finally present my research into the fluid properties of the glycopolymer, optimization of insulin formulations, and optimized formulations properties. Altogether, this work shows specifically how insulin is stabilized by the methacrylate trehalose polymer and, more broadly, that the glycopolymer can be broadly applied as an excipient to stabilize therapeutic macromolecules safely and without significantly changing the in vivo response or physical properties.

Chem 278: Prof. Jinyao Tang
2021-04-21 16:00
“Synthetic Nanorobot – from Individual Microswimmer to Active Swarm”
Abstract: Over 60 years ago, Prof. Richard Feynman envisioned that, in principle, machines could be made so tiny, we can use them to construct matters from atomic/molecular scale; nanorobots can perform surgeries and deliver drugs at cellar level. Sixty years later, the scientific community finds an inconvenient truth: many scientific challenges remain to be solved before nanodoctor can really enter clinics. In this talk, I will start with the realization of the synthetic microswimmers with optical navigation capability to discuss how light can be used to manipulate designed semiconductor microparticles at high precision. I will then showcase how simple theoretical consideration in surface kinetics can help make microswimmer particles more biocompatible and operational in the biological environment. At last, I will envision an intelligent, active swarm system based on complex chemical interaction networks which may be used as a true nanosurgeon in the future.

Chem 218 Student Exit Seminar: Fang-Chu Lin
2021-04-22 12:00
“Superparamagnetic Core/Shell Mesoporous Silica Nanoparticle for Magnetic Heating-Induced Anticancer Drug Delivery”
ABSTRACT: Superparamagnetic iron oxide nanoparticles (SPION) generate heat in the presence of an alternating magnetic field (AMF) and are used in clinics to treat cancers. Mesoporous silica nanoparticles (SPION@MSN) embedded with SPION possess the advantageous features of both the SPION core and the shell, i.e., localized magnetic heating and a high payload of various cargo molecules such as anticancer drugs, respectively. This talk focuses on the development of SPION@MSNs as a heat-activated drug delivery platform in which the precise drug release can be directly controlled by using AMF. To expand our knowledge base in this application, we first study the local heating mechanism of a SPION in suspension and in MSN. We carried out this investigation by using fluorescence depolarization based on detecting the mobility-dependent polarization anisotropy of two luminescence emission bands corresponded to the luminescent SPION core and the shell of the SPION@MSN. Utilizing the magnetic heating, we then designed a magnetically activated and enzyme-responsive SPION@MSN vehicle with extra-large pores to deliver and release anticancer peptides on-demand. We demonstrate that a SPION core can act as a nano-heater to stimulate a cascade drug release and high tumor-targeting/inhibiting efficiency can be achieved. Altogether, these works show the full potential of AMF-controlled core/shell nanoparticle vehicles for a more selected and precise dosage control.

Understanding the chemistry of volcanic RNA to treat cancer & COVID-19
2021-04-22 16:00
Abstract: N4-acetylcytidine is an ancient RNA modification catalyzed by an enzyme essential for human life. However, its distribution, dynamics, and function remain mysterious. In this seminar I will introduce my group’s work developing chemical tools to investigate RNA acetylation, why this led us to study an organism that thrives in solfatara (volcanic craters), and how we are using these fundamental studies to enable new therapeutic approaches.

Chem 268: Brendan Mahoney and Sudeepa Rajan
2021-04-23 15:30
Brendan Mahoney, Ph.D.
Clubb Group
“Leveraging a new fluorescent fusion sensor reveals that bacterial chaperones associate with one another to rapidly transfer heme”
~and~
Sudeepa Rajan, Ph.D.
Reisler Group
“Disassembly of fascin bundled actin filaments via their oxidation by Mical”

Chem 228: Prof. Andrew Pelling
2021-04-26 16:00
“Growing Cells on Apples, LEGOs and Bread. Why Developing Unconventional Biomaterials Matters.”

The Revolution Will Be Compartmentalized: Activity-Based and Cellular DNA-Encoded Library Technology
2021-04-27 16:00
Abstract: The NIH Molecular Libraries Program was founded to translate the discoveries of the Human Genome Project into therapeutics through a network of high-throughput screening (HTS) centers. A decade of discovery produced hundreds of probes—highly selective small molecules that modulate cellular function—but centralized HTS bears the same cost and infrastructure burdens of millennial DNA sequencing centers, restricting access to the technology and therefore the rate of probe discovery. We are building a distributable drug discovery platform analogous to next-generation DNA sequencing based on ultra-miniaturized solid-phase DNA-encoded libraries and microfluidic instrumentation for scalable, automated screening. I will overview chemical synthesis and microfluidic screening technology development efforts and describe their application to hit finding for two clinically relevant targets implicated in fibrosis and cancer. Looking toward the future, we are exploring approaches that directly translate genomic sequence into bioactive chemical probes, with the ultimate goal of fulfilling the originally promised pay dirt of the Human Genome Project.
