Integrated Calendar

Hybrid @ Schmidt Lecture Hall
Zoom : Zoom Link: https://weizmann.zoom.us/j/98811093126?pwd=RVVDK3RieStHY3R6T0xMZndZeGIwZz09


We propose a new method, displacement spectrum (DiSpect) imaging, for probing in vivo complex tissue dynamics such as motion, flow, diffusion, and perfusion. Based on stimulated echoes and image phase, our flexible approach enables observations of the spin dynamics over short (milliseconds) to long (seconds) evolution times.

Non-equilibrium thermodynamics is a contemporary research subject that crosses fields from stellar evolution, nonlinear turbulence to biological organisms. Active matter is a subclass of non-equilibrium materials, where symmetry is broken locally and energy is consumed at the constituent level. The scale of the energy input is elementary in revealing new rich non-equilibrium physics. Currently, there is no unifying thermodynamical framework to describe non-equilibrium systems and energy propagation across scales. Therefore, it is instrumental to develop new programmable active systems that allow for a quantitative parameter space study. Biological building blocks offer reproducibility, uniformity, monodispersity, programmability at the molecular scale, and high efficiency of energy consumption. Using these design principles, we assembled new men made DNA-based active systems that exhibit spontaneous flows of materials and self-organization at the mesoscale. We study the phase behavior of soft materials in particular liquid phase separation in a non-equilibrium environment. Unexpectedly, we found that the coexistence region of phase separation shifts due to the non-equilibrium nature of the environment in low-shear regime that cannot be explained by existing theoretical frameworks. We further study the propagation of active forces across length scales, measuring molecular arrangement and mechanical loads that power active turbulent like dynamic. The unique capabilities of the developed system provide insight into possible mechanisms by which nanometer-sized molecular machines drive macroscale chaotic flows.

A critical factor determining the biological activities of sphingolipids (SLs) is their N-acyl chain length, which in mammals is determined by a family of six ceramide synthases (CerS). Using site-directed mutagenesis and biochemical analyses, we have found a short sequence in a loop located between the last two putative transmembrane domains (TMDs) of the CerS, determines their acyl-CoA specificity. The specificity of a chimeric protein based on the backbone of CerS5 (which generates C16-ceramide), but containing 11 residues from CerS2 (which generates C22–C24-ceramides), allowed the enzyme to generated C22– C24 and other ceramides. Moreover, a similar chimeric protein based on the backbone of CerS4 (which normally generates C18–C22 ceramides) displayed significant activity toward C24:1-CoA.

Microbes use protein toxins to kill competitors and to infect host cells. Discovering new toxins and describing their function is important to understand processes in microbial ecology and host-microbe interactions. Moreover, the toxins can be used in various applications, including drugs, pesticides, vaccines, potent enzymes, etc. We study toxins in the lab by combining large-scale computational genomics and molecular microbiology. In the talk, I will tell two recent stories from the lab on microbial toxins and their secretion systems. The first study is about the mysterious extracellular contractile injection system. This toxin delivery system evolved from a phage into a molecular weapon employed by bacteria against eukaryotic cells. In the second study, I will tell about the exciting group of polymorphic toxins. These are large toxin proteins that undergo recombination to create large diversity of antimicrobial toxins. We developed methods to discover toxins from both groups, study the ecological role of the toxins, and their molecular function. These approaches led to discovery of over 30 novel microbial toxins that we study in the lab.

A state of matter whose constituents are quarks and gluons governed by strong force interactions is a fascinating state of matter. This “Quark-Gluon Plasma” can be created in collisions of heavy ions at high energy. Since the beginning of ion collisions at the LHC in 2010, the heavy-ion program has produced a series of very interesting and sometimes surprising discoveries from the four major LHC experiments. These findings not only changed our understanding of the new state of matter but also gave us new tools to study it. In this talk I’ll review the heavy-ion research program ongoing at the ATLAS detector, and show how the discoveries made a few years ago have become new instruments to understand the laws of quantum chromodynamics.