Molecular mechanics of beta sheets

Beta-sheet protein structures and domains are widely found in biological materials such as silk. These assemblies play a major role in the extraordinary strength and unique properties of bio-materials. At the molecular level, the single beta-sheet structure comprises polypeptide chains in a zig-zag conformations that are held together by hydrogen bonds. Beta-sheet domains comprise multiple beta-sheets that originate from hydrophobic interactions between sheets and are held together by van der Waals interactions. In this work we introduce molecular models that capture the response of such domains upon mechanical loading and illustrate the mechanisms behind their collapse. We begin by modeling the force that is required to pull a chain out of a beta-sheet. Next, we employ these models to study the behavior of beta-sheets that are embedded into and connected to an amorphous protein matrix. We show that the collapse of a beta-sheet occurs upon application of a sufficiently high force that is transferred from ...