Raviv Uri

Associate Professor of Chemistry
Physical Chemistry, Soft-Matter, Biophysics.
• Ph.D., 2003, Weizmann Institute of Science
• M.Sc., 1998, Hebrew University of Jerusalem
• B.Sc. 1995, Hebrew University of Jerusalem
Office: 
Los Angeles 36
Phone: 
02 6586 030
Fax: 
02 5660 425
Research Focus: 

 Using solution X-ray scattering, optical, and electron microscopy, our lab investigates the structures and intermolecular forces between supramolecular self-assembled biomolecules. Using modern synchrotron facility, we follow the dynamic structures during the assembly of RNA or DNA with the capsid virus protein VP1, derived from the Simian Virus 40 (SV40), to form virus-like particles. We study the assembly nucleation stage, followed by elongation steps and determine the reaction rates and the association energies between the nucleotides and the capsid protein and between the VP1 capsid protein molecules. By combining scattering experiments with Monte Carlo simulations we reveal the packaging and organization of the nucleosomes confined within the capsid of wt SV40.
                We measure the forces between charged and dipolar lipid membranes in the presence of different ions and study the contribution of entropic and charge regulation effects to the forces acting between the membranes and the lateral organization of the lipids within the bilayers.
                We develop advanced and unique analysis tools to model the expected solution X-ray scattering curves from large self-assembled structures (e.g. viruses, membranes, microtubules, etc). We model these structures using simple geometric models and increase the resolution of the models and even attain atomic resolution, using crystallography data of the protein subunits that form the large assemblies. Our analysis tools allow us to address questions in structural biology of dynamic self-assembled structures in a unique way that was inaccessible so far. By adopting concepts from soft-matter physics, we aim to unravel the underlying physics, dictating the formation of the observed complex architectures. 

Selected Publications: 

·        Analysis tools for solution X-ray scattering from supramolecular structures:
P. Szekely, A. Ginsburg, T. Ben Nun and U. Raviv (2010). Solution X-Ray Scattering Form Factors of Supramolecular Self-Assembled Structures. Langmuir, 26, 13110-13129.
                The theory behind our unique analysis program
T. Ben Nun, A. Ginsburg, P. Szekely and U. Raviv (2010). X+: A Comprehensive, Computationally Accelerated, Structural Analysis Tool of Solution X-ray Scattering from Supramolecular Self-Assemblies. J. Appl. Cryst., 43, 1522-1531.
                Our analysis program paper.
·        High-resolution biostructures:
MA. Ojeda-Lopez, DJ. Needleman, C. Song, A. Ginsburg, PA. Kohl, Y. Li, Y, HP. Miller, L. Wilson, U. Raviv, MC. Choi, CR. Safinya (2014). Transformation of taxol-stabilized microtubules into inverted tubulin tubules triggered by a tubulin conformation switch. Nature Materials, 13, 195-203. 
                Resolving the formation kinetics and the structure of bundles of inverted helical tubulin tubules.
G. Saper, R. Asor, S. Kler, A. Oppenheim, U. Raviv, D. Harries (2013). Effect of capsid confinement on the chromatin organization of the SV40 minichromosome. Nucleic Acid Research. 41, 1569-1580.
                Using solution X-ray scattering and Monte Carlo simulations to determine the packaging and    organization of the nucleosomes confined within the capsid of wt SV40 virus and its high-    resolution structure.
·        Dynamic self-assembly of lipids, viruses, and Amyloid peptides:
N. Nadler, A. Steiner, T. Dvir, O. Szekely, P. Szekely, A. Ginsburg, R. Asor, R. Resh, C. Tamburu, M. Peres and U. Raviv (2011). Following the structural changes during zinc-induced crystallization of charged membranes using time-resolved solution X-ray scattering. Soft Matter, 7, 1512-1523. 
                Using our in-house X-ray setup, we followed (over hours) the structural changes associated with the crystallization process of lipid bilayers, induced by zinc ions.
S. Kler, R. Asor, C. Li, A. Ginsburg, D. Harries, A. Oppenheim, A. Zlotnick, and U. Raviv (2012). RNA encapsidation by SV40-derived nanoparticles follows a rapid two-state mechanism. J. Am. Chem. Soc., 134, 8823-8830.
                Using time-resolved synchrotron solution X-ray scattering with msec temporal resolution, we     measured and fully analysed the dynamic structures during the assembly of RNA with the capsid     virus protein VP1, derived from the SV40 virus, to form virus-like particles.
Belitzky, N. Melamed-Book, A. Weiss, and U. Raviv (2011). The Dynamic Nature of Amyloid Beta (1-40) Aggregation. Phys. Chem. Chem. Phys., 13, 13809–13814.
                Using florescence confocal microscopy and FRET experiments we showed that A molecules in   fibrils can detach and reattach and attain a nearly complete recycling within ca. 10 days.
·        Lipid structure, lateral order, and inter-membrane forces:
Steiner, P. Szekely, O. Szekely, T. Dvir, R. Asor, N. Yuval-Naeh, N. Keren, E. Kesselman, D. Danino, R. Resh, A. Ginsburg, V. Guralnik, E. Feldblum, C. Tamburu, M. Peres, and U. Raviv (2012). Entropic attraction condenses like-charged interfaces composed of self-assembled molecules. Langmuir, 28, 2604-2613.
                Entopic effects can partially melt multilamellar phase of charged lipids, and condense it.
T. Dvir, L. Fink, R. Asor, Y. Schilt, A. Steiner, U. Raviv (2013). Membranes under confinement induced by polymer-, salt-, or ionic liquid solutions. Soft Matter. 9, 10640-10649.
                Under strong confinement, charged lipid molecules undergo a first-order phase transition and most of their countions condense back into the surface.
O. Szekely, Y. Schilt, A. Steiner, and U. Raviv (2011). Regulating the size and stabilization of lipid raft-like domains and using calcium ions as their probe. Langmuir, 27, 14767–14775. (16). + Langmuir, 27, 7419–7438.
                We showed how to measure and control the size of dipolar lipid domains, based on their  interactions with divalent ions.