CeNS Colloquium

Prof. Hongbin Li
Chemistry Department, The University of British Columbia, Vancouver

Elastomeric proteins underlie the elasticity of natural adhesives, cell adhesion and muscle proteins. Single molecule force spectroscopy has made it possible to directly probe the mechanical properties of elastomeric proteins at the single molecule level. Combining single molecule atomic force microscopy (AFM) and protein engineering techniques, researchers have started to understand the molecular design principles of elastomeric proteins and use such knowledge to engineer novel elastomeric proteins of tailored nanomechanical properties. Here I describe how we use single molecule AFM studies to guide the design of artificial elastomeric proteins to mimic the mechanical properties of the giant muscle protein titin, and employ such proteins to engineer biomaterials that mimic the passive elastic properties of muscles. The passive elasticity of muscle is largely governed by the I-band part of titin, a complex molecular spring composed of a series of individually folded immunoglobulin-like (Ig) domains as well as largely unstructured unique sequences. These mechanical elements have distinct mechanical properties, and when combined, they provide desired passive elastic properties of muscle, which are a unique combination of strength, extensibility and resilience. Our prior single molecule AFM studies demonstrated that the macroscopic behavior of titin in intact myofibrils can be reconstituted by combining mechanical properties of these mechanical elements measured at the single-molecule level. Based on such insight, we used well-characterized protein domains GB1 and resilin to engineer artificial elastomeric proteins that mimic the molecular architecture of titin. We showed that these artificial elastomeric proteins can be photocrosslinked and cast into solid biomaterials. These biomaterials behave as rubber-like materials showing high resilience at low strain and as shock absorber-like materials at high strain by effectively dissipating energy. These properties are comparable to passive elastic properties of muscles within the physiological range of sarcomere length and thus these materials represent a novel muscle-mimetic biomaterial. The mechanical properties of these biomaterials can be fine-tuned by adjusting the composition of the elastomeric proteins, providing possibilities for molecular level engineering of macroscopic mechanical properties of biomaterials. We anticipate that these novel biomaterials will find applications in tissue engineering as scaffold and matrix for artificial muscles.