Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Didi Margulies Dept. of Organic Chemistry Using Synthetic Molecules to Communicate with Proteins and Make Them Talk to Each Other Our group's research is concerned with diverse aspects of bioorganic chemistry, with emphasis on designing synthetic receptors that interact with proteins and sense or regulate their function. In this talk I will give a brief overview of the novel classes of fluorescent molecular sensors that we developed over the last few years, and show how they can be used to detect individual proteins, protein combinations, as well as dynamic changes that occur on their surfaces. In the second part of this talk I will describe the first step toward establishing artificial signal transduction pathways. Specifically, I will discuss the design and operating principles of a synthetic ‘chemical transducer’ that can generate (in vitro) an artificial communication channel between two unrelated proteins. Hagen Hofmann Dept. of Structural Biology Single-molecule dynamics in transcription factor interactions Genomic and proteomic methods have afforded a wealth of genetic network architectures in systems biology. However, the mechanisms of how genes are actually switched on and off are much less understood. At a molecular level, this understanding is particularly complicated by the multi-functionality of many transcription factors, which is typically mediated by disordered regions with substantial flexibility. In the first part of the talk, I demonstrate that single-molecule fluorescence methods are ideal to quantify this flexibility. Using single-molecule Förster resonance energy transfer (FRET), fast large-scale distance dynamics on a sub-microsecond timescale are identified in the high-affinity complex of the interaction domains of CBP/p300 and ACTR, a p160 coactivator. Mapping three distances at the same time in a three-color FRET approach additionally shows that the observed motions are collective, suggesting that high-affinity and high flexibility are not mutually exclusive. In the second part of my talk, I present future targets of our single-molecule approach that aims to link the dynamics of gene activation to the biological phenotype of simple organisms. Yohai Kaspi Dept. of Earth and Planetary Sciences Jets and macroturbulence in the atmosphere Atmospheric jets carry the bulk of momentum, heat and moisture in the extratropics, and are therefore dominant in the dynamics of midlatitude climate. Jets are also prominent in other planetary atmospheres in the Solar System such as those of Jupiter and Saturn, and have been shown to exist on exoplanets as well. In this talk, I will discuss mechanisms for formation of atmospheric jets, and show recent work where we explained the poleward migration of zonal wind anomalies in the atmosphere as poleward migration of eddy-driven jets. We provide a mechanism for the migration using idealized General Circulation Model simulations at high rotation rates, where the fast rotation allows to separate the eddy-driven and subtropical jets. Using multiple-jet simulations we show how inverse cascades and macroturbulence control the meridional scale of the jets, and how energy is partitioned and transferred up and down scale through eddy-eddy and eddy-mean interactions at different latitudinal regimes. Oren Tal Dept. of Chemical Physics New electronic transport effects in atomic and molecular conductors The study of electronic transport at the scale of atoms and molecules allows the demonstration of new material properties, fundamental quantum effects, and general strategies for controlling electronics at the ultimate limit of miniaturization. I will review several recently discovered effects, including the onset of conductance saturation across pi-conjugated molecules, electron-vibration interaction in a molecular-based many-body electronic system, remarkable enhancement of magnetoresistance by molecules and the emergence of half-metallicity (i.e., perfect spin filtering) in atomic scale nickel-oxide. This diverse range of phenomena is achieved by different manifestations of selective orbital hybridization, paving the way for controlled atomic scale electronic transport by “orbital engineering”. Barak Dayan Dept. of Chemical Physics Controlling Light with Light: Demonstration of Deterministic Photon-Photon Interactions Controlling light with light at the level of single photons, namely obtaining deterministic photon-photon interactions, has been the goal of extensive research efforts worldwide in the last couple of decades. I will present our recent demonstration of deterministic photon-photon interactions based on a single atom. We use ultrahigh quality chip-based optical microresonator to couple light from an optical nano-fiber to a single atom. our device then operates as a single-photon toggle-switch: the first photon arriving from one direction of the fiber is reflected by the atom, and any subsequent photons are transmitted. To toggle the state back a photon is simply sent to the atom from the other direction of the fiber – truly control of one (or more) photons just by the command of another single photon. Based on a novel mechanism of passive, interference-based nonlinearity, this scheme requires no control fields, and can function as a quantum memory and even a universal quantum gate. It can therefore provide a building block for scalable quantum networks based on completely passive photonic devices interconnected and activated solely by single photons Refs: [1] S. Rosenblum, A. S. Parkins, and B.Dayan, "Photon routing in cavity QED: Beyond the fundamental limit of photon blockade", Phys. Rev. A. 84, 033854 (2011) [2] I. Shomroni, S. Rosenblum, Y. Lovsky, O. Bechler, G. Guendelman, and B. Dayan, "All-optical routing of single photons by a one-atom switch controlled by a single photon", Science 345, 903 (2014) Emmanuel Levy Dept. of Structural Biology Functional, dysfunctional assemblies. and engineered protein super- A single yeast cell is a few microns in diameter and yet contains about a hundred million proteins. Interactions between these proteins are crucial for most cellular functions, which has fuelled efforts to characterize how proteins assemble into functional complexes. Considerable information thus exists on the composition and structure of protein complexes, but less is known about their higher-order organization in living cells – i.e., we know much about “teams” of proteins, but we know little about how they collaborate with other teams. We will present work that aims to better understand this high-order organization. First, we will describe a strategy to probe the local environment of proteins in living cells, and thereby measure functional interactions. Second, we will discuss the narrow gap that separates functional and dysfunctional interactions, by showing that single point mutations frequently lead to uncontrolled protein super-assembly. Finally, we will present a synthetic system consisting of two proteins engineered to self-assemble into micronscale compartments. Taken together, these studies contribute to our understanding of how the cellular machinery is organized, and what challenges and opportunities it faces during its evolution. Rafal Klajn Dept. of Organic Chemistry Dynamically self-assembling nanoflasks Chemists seek to mimic the approach of natural systems, which utilize the effects of nanoscale confinement to perform chemical reactions at astonishing rates and selectivities and to synthesise complex molecules. To this end, chemists have synthesized a variety of nanostructured materials, such as colloidal crystals selfassembled from inorganic nanoparticles, that typically feature nanosized pores in which chemical reactions could potentially be accelerated. However, product inhibition and the slow diffusion rate into and out of the pores hamper progress. We have shown that colloidal crystal “nanoflasks” created by UV illumination of appropriate nanoparticles occlude small molecules from the surrounding solution such that they undergo chemical reactions with greatly increased kinetics and different stereoselectivities from those in solution. Illumination with visible light disassembles the nanoflasks, releases the product into solution and thereby establishes a catalytic cycle. This novel method avoids problems associated with product inhibition and overcomes the diffusion limitation. Furthermore, the dynamically self-assembling nanoflasks have tuneable dimensions and offer a powerful tool for studying chemical reactivities in confined environments and for synthesising diverse classes of molecules. Assaf Tal Dept. of Chemical Physics Nuclear Magnetic Resonance as a Tool for Probing In-vivo Brain Metabolism Magnetic resonance can be used in-vivo to probe the brain's biochemistry and metabolism. This is achieved by shaping the electromagnetic fields inside an MRI scanner in order to coherently control the nuclear spins' time dynamics. This talk will outline some of our work on fast, high-quality pulse sequences specifically tuned for imaging real time metabolic changes and hard-to-detect metabolites, and sketch some of the future applications of these methodologies. Ron Diskin Dept. of Structural Biology Structural insights for Old World Arenaviruses A crucial step in the life cycle of a virus is its ability to recognize and attach to its host cell. Viral glycoproteins that we study in our lab play a major role in this process. They are located on the viral membrane and specifically recognize their host cell receptors by forming specific molecular complexes. We aim to understand the molecular mechanisms underlying viral tropism and pathogenicity. In my talk I will describe some of our recent progress in understanding the molecular mechanisms for Lassa virus infection. I will also describe a few of our current ongoing efforts to characterize Arenavirus-derived glycoproteins. Amnon Bar-Shir Dept. of Organic Chemistry “Multicolor” Imaging Sensors: Beyond “Monochromatic” MRI Genetically engineered optical reporters (i.e., reporter genes) have become the felt highlighter pens of science, since they enable to tag molecules (or cell) of interest with striking contrast to show their location, levels and roles in colorful relief. The evolution of the green fluorescent protein (GFP) as reporter gene and the extension of the fluorescent proteins palette beyond green allow scientists to give multiple proteins and cells variable colors and follow several different biological processes simultaneously. Nevertheless, their light signal source restricts their ability to penetrate tissues and excludes detectability from deep biological organs. Developing novel genetically engineered reporter systems for MRI can dramatically improve our ability to follow dynamic gene expression changes non-invasively, in deep tissues, and combine sub-cellular information with high spatial resolution anatomical images. After decades of using gadolinium- or iron-based metallic sensors for MRI, the recently developed chemical exchange saturation transfer (CEST) contrast mechanism has created an opportunity for rational design of nonmetallic biosensors for MRI. The CEST approach allows the use of bioorganic molecules as the contrast enhancers that generate a frequency-encoded contrast in MRI, which tolerates their simultaneous monitoring. Since CEST-MRI sensors are chemically tunable and biochemically compatible, they enable spatially mapping of reporter genes expression with a novel and fundamental “multicolor” feature. Itay Halevy Dept. of Earth and Planetary Sciences Microbial to global insights into the sulfur cycle The sulfur cycle shuttles large masses of material through Earth's surface environment, influencing the chemical composition of seawater, the oxidation state of the oceans and atmosphere and the biogeochemical cycles of other major redoxsensitive elements, such as carbon and iron. Information about the long-term operation of these large-scale processes is encoded in the geologic record of sulfur isotopes, which can only be read given an understanding of the major sources and sinks of sulfur and of the processes that fractionate sulfur isotopes. These processes operate over a wide range of spatio-temporal scales, from the microbial, to the global ocean and sedimentary rock reservoir. Novel theoretical understanding of sulfur isotope fractionation during microbial sulfate reduction, coupled with data from ocean sediment cores and reactive transport models of the sediment column, suggests a muted record of large inherent microbial fractionations. The much smaller and more variable apparent fractionation of sulfur isotopes observed in present-day natural environments and preserved in the geologic record, does not, as previously suggested, directly reflect variability in environmental sulfate concentrations or in the rates of microbial sulfate respiration. Instead, these records reflect the degree of exchange of sulfate and sulfide between seawater and sediment porewater and may allow reconstruction of seawater sulfate concentrations over Earth history.