title: Nanoscale structures and mechanics of barnacle cement.
abstract: Polymerized barnacle glue was studied by atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and chemical staining. Nanoscale structures exhibiting rod-shaped, globular and irregularly-shaped morphologies were observed in the bulk cement of the barnacle Amphibalanus amphitrite (=Balanus amphitrite) by AFM. SEM coupled with energy dispersive X-ray (EDX) provided chemical composition information, making evident the organic nature of the rod-shaped nanoscale structures. FTIR spectroscopy gave signatures of beta-sheet and random coil conformations. The mechanical properties of these nanoscale structures were also probed using force spectroscopy and indentation with AFM. Indentation data yielded higher elastic moduli for the rod-shaped structures when compared with the other structures in the bulk cement. Single molecule AFM force-extension curves on the matrix of the bulk cement often exhibited a periodic sawtooth-like profile, observed in both the extend and retract portions of the force curve. Rod-shaped structures stained with amyloid protein-selective dyes (Congo red and thioflavin-T) revealed that about 5% of the bulk cement were amyloids. A dominant 100 kDa cement protein was found to be mechanically agile, using repeating hydrophobic structures that apparently associate within the same protein or with neighbors, creating toughness on the 1-100 nm length scale.
authors.affiliation: Department of Chemistry, University of Toronto, Toronto, Canada.
authors.forename: Ruby May A
authors.initials: RM
authors.lastname: Sullan
authors.forename: Nikhil
authors.initials: N
authors.lastname: Gunari
authors.forename: Adrienne E
authors.initials: AE
authors.lastname: Tanur
authors.forename: Yuri
authors.initials: Y
authors.lastname: Chan
authors.forename: Gary H
authors.initials: GH
authors.lastname: Dickinson
authors.forename: Beatriz
authors.initials: B
authors.lastname: Orihuela
authors.forename: Dan
authors.initials: D
authors.lastname: Rittschof
authors.forename: Gilbert C
authors.initials: GC
authors.lastname: Walker
mesh_terms: D000682:Amyloid; D000818:Animals; D004548:Elasticity; D057927:Hydrophobic and Hydrophilic Interactions; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D049329:Nanostructures / Q000648:ultrastructure*; D013055:Spectrophotometry, Infrared; D001468:Thoracica / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: D000682:Amyloid