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Antibodies
are produced to target any antigen using a finite set of gene fragments generating a huge diversity (>1010)
distinct structures. In contrast, we are unaware of a system that can produce analogous diversity in enzymes. Inspired by antibody repertoires,
I have developed the first strategy to design, synthesise, and experimentally
test repertoires comprising millions of enzymes. Using evolution-guided atomistic design
simulations, I designed thousands of protein fragments that exhibited
high structure and sequence diversity, including within the active-site pocket, which can be genetically assembled into full-length enzymes. I also developed an ML-based algorithm to select a subset of the designed fragments that would give rise to stable
and active proteins. Applied to a family of xylanases (sophisticated enzymes which are
critical in biomass degradation) I designed a repertoire comprising a million enzymes at a cost of 0.3¢
per enzyme. Screening with an activity-based probe revealed thousands of functional xylanases based on nearly 1,000 unique backbones. Advanced machine-learning methods uncovered important elements that discriminate active from inactive designs, enabling us
to design even more effective enzyme repertoires targeting, in principle, any desired substrate. Thus, enzyme repertoire design will enable a new generation of highly efficient and selective enzymes, while teaching us essential rules in biomolecular design.

One of the main challenges of researchers that utilize purified proteins for in-vitro assays is the characterization of the purity and heterogeneity of their proteins in solution. To find out this information, you can employ native gel electrophoresis, gel-filtration chromatography, dynamic light scattering or mass spectroscopy. While some of these methods have low resolution and require large amounts of protein, others are time consuming and require a lot of knowledge to operate and interpret. Mass photometry is a new ground-breaking tool to analyze biomolecules. It is based on interferometric scattering microscopy and enables the accurate mass measurement of single molecules in solution, in their native state without the need for labels, and provides results within minutes. It provides a rapid, accurate and simple analysis of the oligomeric state of proteins in solution. In fact, mass photometry offers optimal conditions for studying sample heterogeneity, protein-protein and protein-nucleic acid interactions, protein oligomerization, macromolecular assemblies many more. Mass photometry represents a truly novel approach for the analysis of individual biomolecules in solution. I will illustrate the unique capabilities of mass photometry by discussing a broad selection of recently published examples and provide insight into the strengths and limitations of this approach.

* Weizmann Institute has collaborated with Refeyn Ltd to make mass photometry available to all Weizmann research community, with an on-site specialist, Dr. Adar Sonn-Segev, to help with its implementation.

Calcium signaling serves as a means of regulation of virtually all processes in a cell throughout the life of an organism, from fertilization to death. One of the multiple aspects of calcium signaling is store-operated calcium entry (SOCE) that has been raising a great interest in the last 30 years. Disregarded first for its allegedly negligible effect on calcium changes inside a cell, it is being reconsidered nowadays as a ubiquitous phenomenon regulating pivotal processes, such as transcription, immune response and others. As other pathways of calcium signaling, SOCE is regulated by multiple proteins, required for adjusting calcium levels to current cellular needs. Among them is SARAF, a protein that has been shown to negatively regulate SOCE, thus preventing calcium excess inside a cell. I will try to elaborate on my attempts to decipher the mysterious mechanism of its regulation.