Nonuniform Curvature and Bending Rigidity of Adsorbed Collagen Molecules in Aqueous Solution

Abstract

Collagen, the most abundant protein in mammals, plays a key role in tissue formation and mechanics due to its triple-helix structure. We used atomic force microscopy to study individual type-I and type-III human collagen molecules adsorbed on smooth mica surfaces from low-salt, near-neutral aqueous solutions. Statistical analysis of their two-dimensional contours revealed nonuniform curvature in both collagen types, which persisted after surface drying and molecular dehydration, owing to robust collagen–mica adsorption. In addition, the angle between tangent vectors at the ends of molecular segments followed a non-Gaussian probability distribution, indicative of nonequilibrium quenching of fluctuations upon adsorption to mica. These results suggest that collagen either possesses an intrinsic three-dimensional curvature in solution or acquires a two-dimensional curvature upon adsorption. The first scenario has implications for the self-assembly and elasticity of collagen fibrils, whereas the second has implications in biomaterial design and tissue-engineering strategies.