Biomolecules Supramolecular Assemblies
In many significant biological functions the four basic building blocks (proteins, lipids, sugars and nucleic acids) aggregate to form supramolecular structures and assemblies. The forces and interactions responsible for these assemblies are composed of a set of interactions with energy scales from the order of thermal fluctuation (few KBT) to specific covalent bonds on the order of 100’s KBT. Moreover, relevant length scales in biological systems span over many orders of magnitude, from the single amino acid through polypeptide chains, protein complexes, organelles and up cells and organs. These different length scales present an enormous challenge both experimentally and theoretically. Therefore, in order to properly study biological systems and the interactions within them, it is important to have complementary techniques covering different length-scales and energies, with proximity to their natural environment. In our laboratory we purify the subunit building-blocks using various biochemical and molecular procedures and reassemble them in various conditions to study their supramolecular forces, dynamics and steady-state structures as appear in healthy and diseased states.
Supramolecular Forces within Intermediate Filaments
Cytoskeletal proteins are the major structural components of cells. In recent years, much fruitful research has dealt with the structures and interactions of microtubules (25 nm in diameter hollow nanotube) and actin filaments (8 nm in diameter). However, little is known about the third component of the cytoskeleton, intermediate filaments (IFs), which, in contrast to actin and microtubules, are cell specific. IFs principal function is to mechanically support the cell and its membrane. The common denominator to all IFs is that they form a 10 nm filament core while the difference is found mainly in the unstructured brushes. In our laboratory we aim to understand the forces and interactions responsible for the assemblies of the different IFs from the single filament properties to the condensed hydrogel network composed from many interacting filaments.
Small Angle X-ray Scattering
X-ray scattering and diffraction has been a leading tool in the past century in characterizing material structures. Traditionally, strong repeating scatters were needed, usually in a crystal state, in order to gain structural information. In such cases, x-ray studies can enable ångström resolution. Advances in the field introduced the possibility for non-invasive studies of softer and more flexible materials, such as biological macromolecules. In our laboratory we use small angle x-ray scattering (SAXS) technique to cover length scales from 0.1-100 nm. This technique is suitable to measure weak scattering from biological system in their natural environment. Detailed analysis and advanced computational techniques are regularly used to convert the reciprocal space to real-space structures and enable studies on the nature of the interactions within the biological assemblies. SAXS, in particular, provides a ready means of determining inter-filament spacing and interactions. Recent advances in solid-state type x-ray detectors and the high flux microfocous x-ray sources allow investigation of dynamic structural events and highly penetrated lens-less tomography of biomolecular samples. Conveniently, these approaches do not require staining or other modifications, and thus do not perturb our system, allowing more ready access to the supramolecular forces underlying self-assembly and simplifying data analysis.
Ph.D. and M.Sc. positions for experimental biophysics research