title: Flexible minerals: self-assembled calcite spicules with extreme bending strength.
abstract: Silicatein-α is responsible for the biomineralization of silicates in sponges. We used silicatein-α to guide the self-assembly of calcite "spicules" similar to the spicules of the calcareous sponge Sycon sp. The self-assembled spicules, 10 to 300 micrometers (μm) in length and 5 to 10 μm in diameter, are composed of aligned calcite nanocrystals. The spicules are initially amorphous but transform into calcite within months, exhibiting unusual growth along [100]. They scatter x-rays like twinned calcite crystals. Whereas natural spicules evidence brittle failure, the synthetic spicules show an elastic response, which greatly enhances bending strength. This remarkable feature is linked to a high protein content. With nano-thermogravimetric analysis, we measured the organic content of a single spicule to be 10 to 16%. In addition, the spicules exhibit waveguiding properties even when they are bent.
authors.affiliation: Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Mainz, Germany.
authors.forename: Filipe
authors.initials: F
authors.lastname: Natalio
authors.forename: Tomas P
authors.initials: TP
authors.lastname: Corrales
authors.forename: Martin
authors.initials: M
authors.lastname: Panthöfer
authors.forename: Dieter
authors.initials: D
authors.lastname: Schollmeyer
authors.forename: Ingo
authors.initials: I
authors.lastname: Lieberwirth
authors.forename: Werner E G
authors.initials: WE
authors.lastname: Müller
authors.forename: Michael
authors.initials: M
authors.lastname: Kappl
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Butt
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Tremel
mesh_terms: D000818:Animals; D002119:Calcium Carbonate / Q000737:chemistry*; D002403:Cathepsins / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry; D011161:Porifera; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical
chemical_list: C112571:silicatein alpha; D002403:Cathepsins; D002119:Calcium Carbonate