Search results for "Vaterite"
showing 4 items of 24 documents
Bio-vaterite formation by glycoproteins from freshwater pearls
2010
Abstract A 48 kDa acidic and putative calcium-binding glycoprotein was isolated from pearls of the freshwater mussel Hyriopsis cumingii . This protein was compared with a related 46 kDa polypeptide, obtained from the nacreous shell of the same species. Separation by two-dimensional gel electrophoresis revealed that the difference in molecular weight is due to the higher extent of glycosylation of the 48 kDa protein existing in pearls. Evidence is presented that the sugar moieties of the protein contribute to crystal growth, starting with the nucleation step. In in vitro precipitation experiments, the 48 kDa glycoprotein of pearls directed the formation of round-shaped vaterite crystals whil…
Amorphous calcium carbonate in the shells of adult Unionoida
2011
Shells of adult individuals from two different bivalve families, Hyriopsis cumingii and Diplodon chilensis patagonicus, were studied by Micro-Raman spectroscopy and Focussed Ion Beam-assisted TEM. The shells contain amorphous calcium carbonate in a zone at the interface between the periostracum and the prismatic layer. In this area, the initial prism structures protrude from the inner periostracum layer and it is demonstrated that these structures systematically consist of highly disordered and amorphous calcium carbonate. Within this zone, ordered and disordered areas are intermingled discounting the existence of a crystallization front and favouring models of domainal crystallization proc…
Designed peptides for biomineral polymorph recognition: a case study for calcium carbonate
2020
With their unique ability for substrate recognition and their sequence-specific self-assembly properties, peptides play an important role in controlling the mineralization of inorganic materials in natural systems and in controlling the assembly of soft materials into complex structures required for biological functions. Here we report the use of an engineered heptapeptide that can differentiate between the crystalline anhydrous polymorphs of calcium carbonate. This peptide contains the positively charged amino acid arginine as well as proline rather than the prototypical negatively charged aspartate or glutamate units. Its affinity to vaterite compared to aragonite was demonstrated by fluo…
Observaciones sobre algunos caracteres de valor taxonómico en el grupo de los carófitos
1990
The variability of the microstructurals characters and mineralogical composition of the oogonia of some charophytes extant and fossils is described. Two types of microstructures (W & V) are find. These are conservative into populations and are not able to change by the environmental factors. Moreover, these structures are quite constant in some of the phylogenetics groups studied. Consequently it is proposed its utilization in taxonomy. The apparition of original compounds in the Charophyta (vaterite. whewelite, aragonite, etc.) is important because it supports an old idea that considerates the Charophyta as an autonomous class between the Clorophyta and the Traqueophyta.<br><b…