Probing the Mechanical Properties of Single Scleroproteins with Optical Tweezers

Abstract

Stretching and relaxing single proteins provides quantitative information on their elasticity and other mechanical properties. This can be done with optical tweezers, a technique in which the ends of the protein are chemically attached to micron-scale spheres, used to manipulate the protein and measure its response. We are working on the application of this technique to scleroproteins, nonglobular proteins whose mechanical properties are of direct relevance to their physiological roles. These proteins self-assemble into hierarchically organized load-bearing structures, often found in the extracellular matrix. The ability of optical tweezers to manipulate single molecules and higher-order structures suggests their application to probing the mechanical response at different hierarchies of assembly. Applying this technique to stretch these single proteins presents many challenges, including the production of constructs with appropriate labels for attachment to microspheres, relatively short contour lengths which can introduce experimental artifacts, and self-aggregation and binding interactions of these predominantly insoluble proteins, which make it difficult to isolate and manipulate single molecules. We discuss our work to overcome these challenges, with a specific focus on elastin.