Integrated Calendar

Zoom: https://weizmann.zoom.us/j/95703489711?pwd=Tyt5cU1tV2YrMFhYUytBU001bm4yQT09


Viable, global-scale photoelectrochemical energy conversion of cheap, abundant resources such as water into chemical fuels (“solar fuels”) depends on the progress of semiconducting light-absorbers with good carrier transport properties, suitable band edge positions, and stability in direct-semiconductor/electrolyte junctions. Investigations concentrated mainly on metal-oxides that offer good chemical stability yet suffer from poor charge transport than non-oxide semiconductors (e.g., Si, GaAs). Fortunately, only a fraction of the possible ternary and quaternary combinations (together ~ 105 – 106 combinations) were studied, making it likely that the best materials are still awaiting discovery. Unfortunately, designing controlled synthesis routes of single-phase oxides with low defects concentration will become more difficult as the number of elements increases; and 2) there are currently no robust and proven strategies for identifying promising multi-elemental systems.
These challenges demand initial focusing on synthesis parameters of novel non-equilibrium synthesis approaches rather than chemical composition parameters by high-throughput combinatorial investigations of synthesis-parameter spaces. This would open new avenues for stabilizing metastable materials, discovering new chemical spaces, and obtaining light-absorbers with enhanced properties to study their physical working mechanisms in photoelectrochemical energy conversion.
I will introduce an approach to exploring non-equilibrium synthesis-parameter spaces by forming gradients in synthesis-parameters without modifying composition-parameters, utilizing two non-equilibrium synthesis components: pulsed laser deposition and rapid radiative-heating. Their combination enables reproducible, high-throughput combinatorial synthesis, resulting in high-resolution observation and analysis. Even minor changes in synthesis can impact significantly material properties, physical working mechanisms, and performances, as demonstrated by studies of the relationship between synthesis conditions, crystal structures of α-SnWO4, and properties over a range of thicknesses of CuBi2O4, both emerging light-absorbers for photoelectrochemical water-splitting that were used as model multinary oxides.

Zoom Link: https://weizmann.zoom.us/j/97777492731?pwd=YXZDR0lqYUtMbHVidUlIWkl2TGxjdz09

Protein-metal interactions play an important regulatory role in the modulation of protein folding and in enabling the “correct” biological function. In material science, protein self-assembly and metal-protein interaction have been utilized for the generation of multifunctional supramolecular structures beneficial for bio-oriented applications, including biosensing, drug delivery, antibacterial activity, and many more. Even though, the nature and the mechanisms of metal-protein interaction have been extensively studied and utilized for the functionalization of protein-based materials, mainly with metal-based nanoparticles, our understanding of how metals shape protein folds, the inter-and intramolecular interactions, the associative behavior, and evolve material characteristics of protein constructs, is limited. To address these highly challenging scientific questions, I have explored the self-assembling behavior of silk fibroin protein and its’ interaction with metal nanoparticles for the formation of multifunctional composites. The central goal of my research was to explore the full potential of metal nanoparticles (NP), in particular, copper oxide (CuO) to modify the self-assembly pathway of fiber-forming protein- silk fibroin. CuO NP has been chosen as a candidate for this study, due to its versatile properties and bio-relevant functionalities applicable for sensing, antibacterial function, and capability to regulate cellular activity. Thus, to address this challenge I first focused on the understanding of metal NP-induced structural transformations in natively folded protein and on probing whether these structural changes can be artificially imposed on the assembled, β-sheet rich protein complexes. My experimental results showed that CuO NPs are indeed capable of template the assembly of natively folded silk fibroin, on the one hand, and on the other hand, exhibited variations in NPs-silk fiber interaction when added at the post-synthetic stage.
Yet, the fundamental questions of how RSF-CuO NPs self-assembly occurs remain to be addressed. The exploration of biomaterial applications for silks is only a relatively recent advance; therefore, the future for this family of structural proteins appears promising.

We are studying the mechanistic basis of epigenetic regulation in the Polycomb system, a vital epigenetic silencing pathway that is widely conserved from flies to plants to humans. We use the process of vernalization in plants in our experiments, which involves memory of winter cold to permit flowering only when winter has passed via quantitative epigenetic silencing of the floral repressor FLC. Utilising this system has numerous advantages, including slow dynamics and the ability to read out mitotic heritability of expression states through clonal cell files in the roots. Using mathematical modelling and experiments (including ChIP and fluorescent reporter imaging), we have shown that FLC cold-induced silencing is essentially an all-or-nothing (bistable) digital process. The quantitative nature of vernalization is generated by digital chromatin-mediated FLC silencing in a subpopulation of cells whose number increases with the duration of cold. We have further shown that Polycomb-based epigenetic memory is indeed stored locally in the chromatin (in cis) via a dual fluorescent labelling approach. I will also discuss how further predictions from the modelling, including opposing chromatin modification states and extra protein memory storage elements, are being investigated. I will also discuss the mechanisms by which long term fluctuating temperature signals are sensed before being converted into digital chromatin states for long term memory storage.

In this talk I will review the basic methods and the current state-of-the-art in trapped ion quantum computing and compare the advantages and disadvantages of this to other QC technologies. I will further describe the progress towards building the WeizQC - a trapped ion quantum computer at the Weizmann Institute of Science. In the second part of the talk I will describe one unique feature of trapped-ion qubits: their all-to-all connectivity. I will describe methods that use this connectivity to engineer multi-qubit gates and operations. Multi-qubit gates have many advantages, both for near term noisy quantum computers, as well as for achieving fault-tolerance. As an example I will show that using multi-qubit gates, the threshold for fault-tolerant quantum computing can be enlarged and the ratio of logical to physical qubit error reduced.

Chemical reactions serve as central units for cellular information processing and control. However, reaction chemistry inside cells is “noisy”, leading to significant variability in the molecular constitution of living systems. How cells control and mitigate noise when precision is important is still poorly understood. In this talk, I will show that compartmentalization of protein via phase separation provides a potential cellular mechanism to protect biochemical pathways against noise. Using a simple theoretical model that links protein concentration fluctuations to the physics of phase separation I will show that noise can be significantly attenuated in the presence of phase separated compartments. I will then present experimental single-cell data in engineered and endogenous condensates, which support this prediction. I will conclude my talk by discussing potential implications and future challenges.