a fluidic race to the bottom thwarted by diffusion
Bets, anyone?12:00 pre-race chitchat
12:15 they're off!
Steven Banik, Stanford University
Hijacking the Lysosome for Targeted Protein DegradationMultifunctional molecules have redefined how both small molecules, such as catalysts, and large biomolecules, such as cellular enzymes and receptors, can be exploited for gain-of-function processes. In the former, examples of iodoarene and hydrogen bond donor catalysts highlight how multiple functionalities can act cooperatively for asymmetric fluorination reactions and the generation of reactive cationic intermediates from stable precursors. In the latter, targeted protein degradation has emerged as a powerful strategy to address the canonically difficult-to-drug proteome enabled by multifunctional molecules. However, current technologies are limited to targets with cytosolically-accessible and ligandable domains. As the primary molecular interactors with other cells, secreted and plasma membrane proteins play direct roles in oncogenesis, immune modulation, and aging-related diseases. I will discuss how the development of conjugates capable of binding both a cell surface lysosome targeting receptor and the extracellular domain of a target protein enables degradation of secreted and transmembrane proteins from the cell surface. These lysosome targeting chimeras (LYTACs) consist of a target-binding moiety (e.g. small molecules, antibodies) fused to agonist ligands for the cation-independent mannose-6-phosphate receptor (CI-M6PR), and degrade disease-relevant proteins such as apolipoprotein E4, EGFR, and PD-L1. Mechanistic analysis of LYTAC selectivity using functional genomics revealed new cellular machinery responsible for CI-M6PR recycling, and analysis of selectivity using quantitative proteomics enabled target interactome analysis. Further in vivo work suggests unique opportunities for targeted protein degradation approaches using LYTACs. The strategy outlined here provides a blueprint for expansion of a variety of tailored multifunctional molecules to allow for selective extracellular and transmembrane protein trafficking to lysosomes.
Gregory Tarnopolsky, Harvard University
Origin of flat bands in Twisted Bilayer GrapheneOrigin of flat bands in Twisted Bilayer Graphene, Gregory Tarnopolsky, Harvard University
Several years ago, in a continuum model of the Twisted Bilayer Graphene, a dramatic flattening of electronic low energy bands was observed numerically at a magic angle of 1.1 degrees. This theoretical discovery is believed to provide a foundation for the various interacting phenomena which were recently observed experimentally near this magic angle, including unconventional superconductivity and correlated insulators.
In this talk I will present a variant of the continuum model where the bands are exactly flat at a series of magic angles, the biggest of which is 1.1 degrees. I will exhibit an analytic derivation of this and show that the wave functions of the exactly flat band are reminiscent of the Lowest Landau Level ones. I will also discuss application of this for a construction of the Laughlin wave function in Twisted Bilayer Graphene.
Brandi Cossairt, University of Washington
Interfacial Chemistry of Colloidal Nanocrystals to Direct Energy ConversionWe are interested in developing colloidal nanocrystals for wide-ranging applications in energy conversion. Our approach leverages the extraordinary properties of nanoscale systems by applying the design principles of molecular inorganic chemistry. This talk will focus on two key research themes. First, we will explore interfacial chemistry concepts to control the inner-sphere reactivity of colloidal electrocatalysts for multi-proton, multi-electron transformations. Ligand etching, ligand exchange, and covalent functionalization will be presented as complementary methods to alter electrocatalytic interfaces by tuning the activity, selectivity, and bulk interfacial properties. Second, we will explore how interfacial chemistry can be used to control the photophysics, reactivity, and assembly of colloidal semiconductor nanocrystals for emissive applications. Ultimately, we are viewing nanocrystal interfaces as platforms for coordination chemistry that will direct function.
Connor Bischak, University of Washinton
From Solar Cells to Bioelectronics: The Interplay Between Electron and Ion Transport in Soft Semiconducting Materials
Joel Yuen-Zhou, Department of Chemistry, University of Calfornia-San Diego
Polariton Chemistry: Molecules in Optical CavitiesOrganic molecules interact strongly with confined electromagnetic fields in plasmonic arrays or optical microcavities owing to their bright transition dipole moments. This interaction gives rise to molecular polaritons, hybrid light-matter quasiparticles. Molecular polaritonics opens doors for new room-temperature opportunities for the nontrivial control of physico-chemical properties of molecular assemblies . In this talk, I’ll showcase some of these opportunities that we have been theoretically (and, together with our experimental collaborators) exploring in the past few years. I will briefly discuss the relevant time and energy scales associated with molecular polaritons [1,2] and strategies to exploit them to control photoexcited processes including singlet fission , triplet harvesting , remote and topologically-protected energy transfer [5-7], and anomalous nonlinear optical effects [8,9,10]. Finally, I will conclude by explaining how vibrational polaritons can steer ground-state chemical reactions even in the absence of optical pumping , or be used to realize exotic processes such as remote control of chemical reactions . Host: Suri Vaikuntanathan via email at firstname.lastname@example.org or at 2-7256. Persons with a disability who may need assistance please contact Brenda Thomas by email at email@example.com or at 2-7156.
Jens Koch, Northwestern University
Intrinsically Protected Superconducting Qubits: From Concepts to RealizationThe transmon qubit owes its success to robust protection from the detrimental effects of 1/f charge noise, and to its relative simplicity as one of the smallest anharmonic superconducting circuits. However, the transmon remains fully sensitive todepolarization processes, making T1 limitations an
ongoing challenge. Several proposals exist for achieving universal protection from both depolarization and dephasing in superconducting qubits - among them the 0-π qubit and the current mirror qubit. In this talk, I will present the overarching concepts of disjoint-support wavefunctions and robust ground state degeneracy, and illustrate how they emerge in concrete circuits. Following a discussion of spectra and coherence-times estimates for the 0-π qubit, I will address some of the new challenges associated with simulating and operating protected qubits. Finally, I will discuss new data on the first experimental realization of the 0-π qubit in the Houck lab. Host: Aashish Clerk, firstname.lastname@example.org or by phone at 4-2943 For more information please contact Alisha Manning-Beard at email@example.com or by phone at 4-2351.
Alex Levine, UCLA
Exploring soft low-dimensional structures in the cell: Fluctuations, mechanics, and geometryBiology provides us with a number of effectively one- and two-dimensional elastic structures. The cytoskeleton of cells abounds with long, stiff protein filaments organized into bundles and networks. Cells are bound by and contain a wide variety of membranes, some of which have complex geometries. These lower dimensional structures are sufficiently soft to be strongly fluctuating at ambient temperature. In addition, evolution has engineered a plethora of cross-linking proteins and molecular motors that interact with these structures.
In this talk, I discuss a few examples of the role of fluctuations in soft low-dimensional biological structures, introducing the fluctuation-induced (Casimir) interaction between linkers in filament bundles. The Casimir interaction drives a new type of first-order filament bundling transition, leading to a disordered “line glass” network. I report on the collective mechanics of such filament networks. Finally, within a single bundle, I show that quenched-in braids introduce kinks (localized bends) in the time-averaged contour of the bundle, and explore how such kinks anneal over time.
Jessie Shelton, UIUC
Tyrel McQueen, John Hopkins University
The Materials Synthesis FrontierMaterials chemistry by design is the rational prediction and creation of functional materials with defined properties. Its goal is to meet current and future societal needs for better or more complex materials, from biocompatible materials in medicine to lightweight alloys for space applications and energy generation, storage, and transport. Unfortunately, materials chemistry has lagged other sub-fields in an extremely critical area: the ability to selectively make and break bonds in the solid state. This is due to limited synthetic methodology and method development. True materials by design cannot be achieved until reliable synthetic capabilities are developed that can actually produce the specified materials. In this talk, I will highlight the progress being made in such synthesis by design, with a particular focus on quantum materials – a class of material in which quantum phenomena not only underlie but are ‘writ large’ across macroscopic materials. Examples will range from utilizing materials discovery to test theories of the high photovoltaic performance of halide perovskites, to the development of exfoliatable quantum magnets that reveal new phenomenology as a consequence of the dimensional reduction.
Pallab Goswami, Northwestern University
Topology of three-dimensional Dirac semimetals: a tale of SO(5) monopoles and Hopf defectsThree-dimensional massless Dirac fermions can describe the dynamics of ultra-relativistic particles, as well as the low-energy physics of emergent, gapless excitations for many solid-state systems that preserve spatial-inversion and time-reversal symmetries. Such solid-state materials are collectively known as Dirac semimetals, which support linear touching of two Kramers-degenerate bands at isolated points in momentum space. For example, the massless Dirac fermions can arise as stable excitations in Cd3As2 and Na3Bi, and also as unstable excitations at topological quantum phase transitions in bismuth-antimony alloys and indium doped bismuth selenide.
What are the bulk topological invariants of Dirac semimetals? Are the surface states of stable Dirac semimetals topologically protected? In this talk, I will provide affirmative answers to these open questions, by considering minimal models of band-structures for Dirac semimetals. These models generally involve a five-component vector field defined in momentum space, whose amplitude vanishes at Dirac points. By addressing the nature of non-Abelian SO(5) Berry’s vector potential, I will show that the topological properties of unstable and stable Dirac semimetals can be respectively understood in terms of Hopf defects and a pair of monopole and anti-monopole. I will discuss the absence of helical Fermi arcs, the precise nature of surface states, and the bulk-boundary correspondence for stable Dirac semimetals, and additional experimental consequences for many materials.