title: Plastic deformation of protein monolayers.
abstract: Globular proteins are peculiar solids that display both local stability of their conformation and the ability to undergo large cooperative changes of shape (conformational changes). If one forces a large deformation of the molecule, such that the structure is necessarily changed, it is not obvious whether the deformed globule can still remain a solid or whether it will melt. Is it possible to plastically deform a protein? Here we investigate this question with a micro-mechanical experiment on a small region (approximately 10 molecules) of a protein monolayer adsorbed on a rigid surface. For the two proteins studied, albumin and myoglobin, we observed that the molecules can be substantially deformed (approximately 1-2 nm deformation) by comparatively small stresses applied for sufficiently long times. The deformation is irreversible, and the protein remains in the solid state (i.e., displays a nonzero shear modulus). The dynamics of the deformation is approximately logarithmic in time, similar to creep in solids. These results show that globular proteins adsorbed on a surface can be plastically deformed.
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002417:Cattle; D004220:Disulfides / Q000737:chemistry; D006736:Horses; D009211:Myoglobin / Q000737:chemistry; D010969:Plastics / Q000494:pharmacology*; D011487:Protein Conformation; D011489:Protein Denaturation; D011506:Proteins / Q000737:chemistry*; D012709:Serum Albumin / Q000737:chemistry; D013997:Time Factors
chemical_list: D004220:Disulfides; D009211:Myoglobin; D010969:Plastics; D011506:Proteins; D012709:Serum Albumin