Structural nanomechanics of self-assembled protein filaments

Over the last few years, I have been excited by a group of proteins, ubiquitously present in the human body and other mammals that can self-assemble into ultrathin filaments. These "intermediate filaments" are responsible for the unique mechanical properties of some of our tissues, like the upper layer of the skin and our hairs. They are also important structural elements of each of our cells. The aim of this proposal is to obtain a structural understanding of the mechanical properties of individual filaments. I am especially interested in elucidating how the self-assembly process generates mechanical properties that are different from the ones of the protein building-blocks. This self-assembled protein system offers us an opportunity to learn from nature in order to design nanomaterials with tailored mechanical properties. To achieve this goal, I propose to develop atomic force microscopy approaches to probe the mechanical properties of protein assemblies in aqueous solution. I will also use a strategy based on counter-ion condensation, a well-known mechanism in soft condensed matter physics, to assemble these filaments into micro- and macro-scale fibers or networks that will serve as a proof of principle for protein based materials. Possible applications include textiles, tissue engineering scaffolds, and high-specificity membranes for filtration. The last application will take advantage of the fact that the protein building-blocks can in theory be functionalized while conserving potent self-assembly properties. If all this works, I will have at hand a tunable system that I will use to explore the role of protein domains, ionic conditions and crosslinkers on the mechanical properties of filamentous networks at distance scales of nanometer to centimeter. This knowledge will be essential to understand the material behaviours of living cells and tissues.