title: Anisotropic deformation response of single protein molecules.
abstract: Single-molecule methods have given experimental access to the mechanical properties of single protein molecules. So far, access has been limited to mostly one spatial direction of force application. Here, we report single-molecule experiments that explore the mechanical properties of a folded protein structure in precisely controlled directions by applying force to selected amino acid pairs. We investigated the deformation response of GFP in five selected directions. We found fracture forces widely varying from 100 pN up to 600 pN. We show that straining the GFP structure in one of the five directions induces partial fracture of the protein into a half-folded intermediate structure. From potential widths we estimated directional spring constants of the GFP structure and found values ranging from 1 N/m up to 17 N/m. Our results show that classical continuum mechanics and simple mechanistic models fail to describe the complex mechanics of the GFP protein structure and offer insights into the mechanical design of protein materials.
authors.affiliation: Physik Department E22, Technische Universität München, James-Franck-Strasse, D-85748 Garching, Germany.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Dietz
authors.forename: Felix
authors.initials: F
authors.lastname: Berkemeier
authors.forename: Morten
authors.initials: M
authors.lastname: Bertz
authors.forename: Matthias
authors.initials: M
authors.lastname: Rief
mesh_terms: D016880:Anisotropy; D004548:Elasticity; D049452:Green Fluorescent Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D017510:Protein Folding; D017434:Protein Structure, Tertiary
chemical_list: D049452:Green Fluorescent Proteins