title: Structural characterization of siliceous spicules from marine sponges.
abstract: Siliceous sponges, one of the few animal groups involved in a biosilicification process, deposit hydrated silica in discrete skeletal elements called spicules. A multidisciplinary analysis of the structural features of the protein axial filaments inside the spicules of a number of marine sponges, belonging to two different classes (Demospongiae and Hexactinellida), is presented, together with a preliminary analysis of the biosilicification process. The study was carried out by a unique combination of techniques: fiber diffraction using synchrotron radiation, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetric (DSC), Fourier transform infrared spectroscopy (FTIR), and molecular modeling. From a phylogenetic point of view, the main result is the structural difference between the dimension and packing of the protein units in the spicule filaments of the Demospongiae and the Hexactinellida species. Models of the protein organization in the spicule axial filaments, consistent with the various experimental evidences, are given. The three different species of demosponges analyzed have similar general structural features, but they differ in the degree of order. The structural information on the spicule axial filaments can help shed some light on the still unknown molecular mechanisms controlling biosilicification.
authors.affiliation: Dipartimento di Scienze e Tecnologie Avanzate, Università del Piemonte Orientale A. Avogadro, I-15100 Alessandria, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Croce
authors.forename: Alberto
authors.initials: A
authors.lastname: Frache
authors.forename: Marco
authors.initials: M
authors.lastname: Milanesio
authors.forename: Leonardo
authors.initials: L
authors.lastname: Marchese
authors.forename: Mauro
authors.initials: M
authors.lastname: Causà
authors.forename: Davide
authors.initials: D
authors.lastname: Viterbo
authors.forename: Alessia
authors.initials: A
authors.lastname: Barbaglia
authors.forename: Vera
authors.initials: V
authors.lastname: Bolis
authors.forename: Giorgio
authors.initials: G
authors.lastname: Bavestrello
authors.forename: Carlo
authors.initials: C
authors.lastname: Cerrano
authors.forename: Umberto
authors.initials: U
authors.lastname: Benatti
authors.forename: Marina
authors.initials: M
authors.lastname: Pozzolini
authors.forename: Marco
authors.initials: M
authors.lastname: Giovine
authors.forename: Heinz
authors.initials: H
authors.lastname: Amenitsch
mesh_terms: D000818:Animals; D002403:Cathepsins / Q000032:analysis / Q000737:chemistry* / Q000648:ultrastructure*; D016326:Extracellular Matrix Proteins / Q000032:analysis / Q000737:chemistry / Q000648:ultrastructure; D008386:Marine Biology / Q000379:methods; D008958:Models, Molecular; D011161:Porifera / Q000737:chemistry* / Q000145:classification / Q000648:ultrastructure*; D011487:Protein Conformation; D012822:Silicon Dioxide / Q000032:analysis / Q000737:chemistry*; D013045:Species Specificity
chemical_list: D016326:Extracellular Matrix Proteins; C112571:silicatein alpha; D012822:Silicon Dioxide; D002403:Cathepsins