Integrated Calendar

We introduce first-passage resetting, in which a diffusing particle is reset to its starting point whenever it reaches a specified threshold.  We present two applications of this mechanism: (1) Optimization in a finite domain, in which a cost is incurred whenever the diffuser is reset to the origin and a reward is given when the particle stays near the reset (maximal performance) point. We derive the condition to optimize the net reward minus the net cost.  (2) We also explore consequences of first-passage resetting in a toy model of wealth sharing to try to determine whether altruism or selfishness is the optimal strategy.

Gene expression emerges from a dynamic interplay between transcription factors (TFs) and RNA polymerases operating on crowded DNA templates. In this seminar, I will present two complementary single-molecule studies using optical tweezers to probe this interplay. First, we show that intrinsically disordered regions (IDRs) of the yeast transcription factor Msn2 drive an efficient target-search mechanism by promoting non-specific DNA binding and one-dimensional diffusion toward specific motifs. Promoter-derived sequences enhance both binding and scanning kinetics, demonstrating that Msn2–DNA interactions alone can confer promoter selectivity beyond canonical motifs. Second, we examine what occurs when an elongating RNA polymerase encounters a DNA-bound TF within gene bodies. We find that polymerase progression is transiently delayed but progressively destabilizes the bound factor. CpG methylation increases TF dissociation, attenuating its barrier effect on elongation and providing a mechanistic rationale for gene-body methylation. Together, these studies highlight how dynamic protein–DNA interactions shape transcription from target recognition to elongation.FOR THE LATEST UPDATES AND CONTENT ON SOFT MATTER AND BIOLOGICAL PHYSICS AT THE WEIZMANN, VISIT OUR WEBSITE: https://www.bio

MXenes are the fastest-growing family of two-dimensional (2D) materials. Unlike most other 2D materials, they lack bulk analogues when restacked because of their unique structure and surface terminations. They represent a new class of 2D transition-metal carbides/nitrides, not merely exfoliated van der Waals solids. They have a general formula Mn+1XnTx, where M is a transition metal, X is carbon and/or nitrogen, T represents surface terminations (O, OH, halogen, chalcogen, etc.), and n = 2—5. About 50 stoichiometric MXene compositions and dozens of solid solutions on M and X sites have already been reported. Given the infinite number of possible solid-solution compositions and combinations of surface terminations, MXenes offer an opportunity for computationally driven atomistic design of inorganic 2D structures with unique properties. MXenes exhibit electronic, optical, mechanical, and electrochemical properties that clearly distinguish them from other materials. Moreover, these properties are tunable by design and can be modulated using an ionotronic approach, leading to breakthroughs in fields ranging from optoelectronics and communication to electrochemical energy storage, catalysis, sensing, and medicine. In this talk, I’ll discuss methods for MXene synthesis and processing, the effects of MXene chemistry on their properties, and provide examples of important applications where MXenes outperform other materials. 

Most efficient chemical processes used in industry rely on heterogeneous catalysis. While the search for more sustainable processes and the changes in environmental policies impose the continuous development of more efficient catalysts, we have currently little understanding of the structure of the actives in these processes. Hence, due to their inherent complexity, heterogeneous catalysts have been mostly developed empirically.Here, we will show how constructing active sites, one atom at a time on surfaces, enables molecular-level understanding and implementation of rational approaches for the improvement of catalytic processes. We will first illustrate how this approach enables to generate selective single-site catalysts. We will next show how from these isolated (single) sites, one can generate and understand far more complex systems such as supported nanoparticles, where interfaces, alloying… play a critical role. This lecture will be developed around these themes and will show how the development of advanced characterization tools augmented by computational approaches can provide useful information to bridge the gap between fundamental and applied (industrial) catalysis.