title: Measurement of Elastic Modulus of Collagen Type I Single Fiber.
abstract: Collagen fibers are the main components of the extra cellular matrix and the primary contributors to the mechanical properties of tissues. Here we report a novel approach to measure the longitudinal component of the elastic moduli of biological fibers under conditions close to those found in vivo and apply it to type I collagen from rat tail tendon. This approach combines optical tweezers, atomic force microscopy, and exploits Euler-Bernoulli elasticity theory for data analysis. This approach also avoids drying for measurements or visualization, since samples are freshly extracted. Importantly, strains are kept below 0.5%, which appear consistent with the linear elastic regime. We find, surprisingly, that the longitudinal elastic modulus of type I collagen cannot be represented by a single quantity but rather is a distribution that is broader than the uncertainty of our experimental technique. The longitudinal component of the single-fiber elastic modulus is between 100 MPa and 360 MPa for samples extracted from different rats and/or different parts of a single tail. Variations are also observed in the fibril-bundle/fibril diameter with an average of 325±40 nm. Since bending forces depend on the diameter to the fourth power, this variation in diameter is important for estimating the range of elastic moduli. The remaining variations in the modulus may be due to differences in composition of the fibril-bundles, or the extent of the proteoglycans constituting fibril-bundles, or that some single fibrils may be of fibril-bundle size.
authors.affiliation: Center For Molecular Study Of Condensed Soft Matter, Illinois Institute of Technology, Chicago, IL, United States of America.|Chemical and Biological Engineering Department, Illinois Institute of Technology, Chicago, IL, United States of America.
authors.forename: Pavel
authors.initials: P
authors.lastname: Dutov
authors.affiliation: Center For Molecular Study Of Condensed Soft Matter, Illinois Institute of Technology, Chicago, IL, United States of America.|Departments of, Biology, Physics and Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States of America.|BioCAT, Sector 18, APS/Argonne National Laboratory, 9700 S. Cass Ave. Argonne, IL, United States of America.
authors.forename: Olga
authors.initials: O
authors.lastname: Antipova
authors.affiliation: Department of Cell Biology, Microbiology and Molecular Biology, Department of Physics, University of South Florida, Tampa, FL, United States of America.
authors.forename: Sameer
authors.initials: S
authors.lastname: Varma
authors.affiliation: Center For Molecular Study Of Condensed Soft Matter, Illinois Institute of Technology, Chicago, IL, United States of America.|Departments of, Biology, Physics and Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States of America.|BioCAT, Sector 18, APS/Argonne National Laboratory, 9700 S. Cass Ave. Argonne, IL, United States of America.
authors.forename: Joseph P R O
authors.initials: JP
authors.lastname: Orgel
authors.affiliation: Center For Molecular Study Of Condensed Soft Matter, Illinois Institute of Technology, Chicago, IL, United States of America.|Chemical and Biological Engineering Department, Illinois Institute of Technology, Chicago, IL, United States of America.|Department of Physics, Illinois Institute of Technology, Chicago, IL, United States of America.
authors.forename: Jay D
authors.initials: JD
authors.lastname: Schieber
mesh_terms: D000818:Animals; D024042:Collagen Type I / Q000737:chemistry / Q000502:physiology*; D055119:Elastic Modulus / Q000502:physiology*; D018625:Microscopy, Atomic Force / Q000295:instrumentation / Q000379:methods*; D051381:Rats; D013623:Tail; D013710:Tendons / Q000502:physiology
chemical_list: D024042:Collagen Type I