title: Stepwise unfolding of titin under force-clamp atomic force microscopy.
abstract: Here we demonstrate the implementation of a single-molecule force clamp adapted for use with an atomic force microscope. We show that under force-clamp conditions, an engineered titin protein elongates in steps because of the unfolding of its modules and that the waiting times to unfold are exponentially distributed. Force-clamp measurements directly measure the force dependence of the unfolding probability and readily captures the different mechanical stability of the I27 and I28 modules of human cardiac titin. Force-clamp spectroscopy promises to be a direct way to probe the mechanical stability of elastic proteins such as those found in muscle, the extracellular matrix, and cell adhesion.
authors.affiliation: Department of Physiology and Biophysics, Mayo Foundation, Rochester, MN 55905, USA.
authors.forename: A F
authors.initials: AF
authors.lastname: Oberhauser
authors.forename: P K
authors.initials: PK
authors.lastname: Hansma
authors.forename: M
authors.initials: M
authors.lastname: Carrion-Vazquez
authors.forename: J M
authors.initials: JM
authors.lastname: Fernandez
mesh_terms: D000818:Animals; D002417:Cattle; D064211:Connectin; D006801:Humans; D008846:Micromanipulation / Q000295:instrumentation*; D018625:Microscopy, Atomic Force; D009124:Muscle Proteins / Q000648:ultrastructure*; D009206:Myocardium / Q000737:chemistry; D015202:Protein Engineering; D017510:Protein Folding; D011494:Protein Kinases / Q000648:ultrastructure*; D013314:Stress, Mechanical
chemical_list: D064211:Connectin; D009124:Muscle Proteins; C577285:TTN protein, human; D011494:Protein Kinases