title: Highly sensitive single-fibril erosion assay demonstrates mechanochemical switch in native collagen fibrils.
abstract: It has been established that the enzyme susceptibility of collagen, the predominant load-bearing protein in vertebrates, is altered by applied tension. However, whether tensile force increases or decreases the susceptibility to enzyme is a matter of contention. It is critical to establish a definitive understanding of the direction and magnitude of the force versus catalysis rate (k C ) relationship if we are to properly interpret connective tissue development, growth, remodeling, repair, and degeneration. In this investigation, we examine collagen/enzyme mechanochemistry at the smallest scale structurally relevant to connective tissue: the native collagen fibril. A single-fibril mechanochemical erosion assay with nN force resolution was developed which permits detection of the loss of a few layers of monomer from the fibril surface. Native type I fibrils (bovine) held at three levels of tension were exposed to Clostridium histolyticum collagenase A. Fibrils held at zero-load failed rapidly and consistently (20 min) while fibrils at 1.8 pN/monomer failed more slowly (35-55 min). Strikingly, fibrils at 23.9 pN/monomer did not exhibit detectable degradation. The extracted force versus k C data were combined with previous single-molecule results to produce a "master curve" which suggests that collagen degradation is governed by an extremely sensitive mechanochemical switch.
authors.affiliation: Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
authors.forename: Brendan P
authors.initials: BP
authors.lastname: Flynn
authors.forename: Graham E
authors.initials: GE
authors.lastname: Tilburey
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Ruberti
mesh_terms: D000818:Animals; D001671:Biochemistry / Q000379:methods*; D001696:Biomechanical Phenomena / Q000502:physiology; D002417:Cattle; D003013:Clostridium / Q000201:enzymology; D017364:Collagenases / Q000378:metabolism; D024022:Fibrillar Collagens / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D024022:Fibrillar Collagens; D017364:Collagenases