Time filter

Source Type

Wang X.,Johannes Gutenberg University Mainz | Wang X.,National Research Center for Geoanalysis | Schlossmacher U.,Johannes Gutenberg University Mainz | Wiens M.,Johannes Gutenberg University Mainz | And 3 more authors.
FEBS Journal | Year: 2012

Biomineralization processes are characterized by controlled deposition of inorganic polymers/minerals mediated by functional groups linked to organic templates. One metazoan taxon, the siliceous sponges, has utilized these principles and even gained the ability to form these polymers/minerals by an enzymatic mechanism using silicateins. Silicateins are the dominant protein species present in the axial canal of the skeletal elements of the siliceous sponges, the spicules, where they form the axial filament. Silicateins also represent a major part of the organic components of the silica lamellae, which are cylindrically arranged around the axial canal. With the demosponge Suberites domuncula as a model, quantitative enzymatic studies revealed that both the native and the recombinant enzyme display in vitro the same biosilica-forming activity as the enzyme involved in spicule formation in vivo. Monomeric silicatein molecules assemble into filaments via fractal intermediates, which are stabilized by the silicatein-interacting protein silintaphin-1. Besides the silicateins, a silica-degrading enzyme silicase acting as a catabolic enzyme has been identified. Growth of spicules proceeds in vivo in two directions: first, by axial growth, a process that is controlled by evagination of cell protrusions and mediated by the axial filament-associated silicateins; and second, by appositional growth, which is driven by the extraspicular silicateins, a process that provides the spicules with their final size and morphology. This radial layer-by-layer accretion is directed by organic cylinders that are formed around the growing spicule and consist of galectin and silicatein. The cellular interplay that controls the morphogenetic processes during spiculogenesis is outlined. Silicateins are sponge-specific enzymes that facilitate silica polycondensation, resulting in biosilica formation. Biosilica represents the scaffold for the skeletal elements of the sponges, the spicules. The genes/cDNAs for the silicateins and the silintaphins are known. This review summarizes the characteristics of these proteins as well as the regulatory network underlying the formation of one of the most intricately structured skeletal structures of Metazoa, the siliceous spicules. © 2012 The Authors Journal compilation © 2012 FEBS.

Jochum K.P.,Max Planck Institute for Chemistry | Wang X.,National Research Center for Geoanalysis | Vennemann T.W.,University of Lausanne | Sinha B.,Max Planck Institute for Chemistry | Muller W.E.G.,Universitatsmedizin Mainz
Chemical Geology | Year: 2012

The deep-sea sponge Monorhaphis chuni forms giant basal spicules, which can reach lengths of 3. m; they represent the largest biogenic silica structures on Earth that is formed from an individual metazoan. The spicules offer a unique opportunity to record environmental change of past oceanic and climatic conditions. A giant spicule collected in the East China Sea in a depth of 1110. m was investigated. The oxygen isotopic composition and Mg/Ca ratios determined along center-to-surface segments are used as geochemical proxies for the assessment of seawater paleotemperatures. Calculations are based on the assumption that the calculated temperature near the surface of the spicule is identical with the average ambient temperature of 4. °C. A seawater temperature of 1.9. °C is inferred for the beginning of the lifespan of the Monorhaphis specimen. The temperature increases smoothly to 2.3. °C, to be followed by sharply increased and variable temperatures up to 6-10. °C. In the outer part of the spicule, the inferred seawater temperature is about 4. °C. The lifespan of the spicule can be estimated to 11,000 ± 3000. years using the long-term trend of the inferred temperatures fitted to the seawater temperature-age relationships since the Last Glacial Maximum. Specimens of Monorhaphis therefore represents one the oldest living animals on Earth. The remarkable temperature spikes of the ambient seawater occurring 9500-3100. years. B.P. are explained by discharges of hydrothermal fluids in the neighborhood of the spicule. The irregular lamellar organization of the spicule and the elevated Mn concentrations during the high-temperature growth are consistent with a hydrothermal fluid input. © 2012 Elsevier B.V..

To obtain reliable in situ information on the distribution and speciation of Pb in plants with low Pb content, special attention needs to be paid to the synchrotron radiation based micro-X-ray fluorescence and micro-X-ray absorption near edge structure (μ-XANES) spectrometry to avoid specious results in the chosen XRF region of interest and speciation linear combination fitting. First, an Arabidopsis thaliana shoot cultured in a Pb solution is analyzed to obtain two-dimensional Pb distribution graphs, where an overlap of Pb, As, Se, and Br lines in synchrotron radiation based micro-X-ray fluorescence spectra is found. To avoid this overlap, (1)As K-L3 and Pb L3-M5, (2)As K-M3, (3)Pb L2-M4, (4)Se K-L3, and (5)Br K-M3 lines should be chosen in the region of interest. The Pb content in the seed coat, root, and stem are 48.2, 17.3, and 5.8 times higher, respectively, than in the leaf, while the Pb content in the seed coat, root, stem, and leaf increased 3458, 1241, 420, and 72 times, respectively, compared with the A. thaliana sample without a Pb solution soak. Second, Pb speciation of the same shoot is analyzed using μ-XANES. It is important to define a combination fitting range because different possible Pb combinations can emerge using different ranges. Different speciations were found in the root[Pb(Ac)2 and PbSO4], stem[Pb(Ac)2 and Pb3(PO4)2], leaf[Pb(OH)2 and Pb5Cl(PO4)3], and seed coat[Pb3(PO4)2, Pb(OH)2, and PbCO3] between the fitting range of E0-20eV and E0+70eV. A more complete Pb XANES database with more references, especially organic Pb compounds, is needed. © 2013 John Wiley & Sons, Ltd.

Shen Y.-T.,National Research Center for Geoanalysis
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2012

It is difficult to get accurate, precise and reliable analytical data when using X-ray fluorescence spectrometry (XRF) to determinate sulfur in geological sample. The possible ways to improve sulfur determination accuracy are discussed. Sulfur, and the major, minor and trace elements in soils were determined by polarization energy dispersion XRF (EDXRF) spectrometry and the element profiles and vertical distribution were obtained. Based on this, replacement of two short-term vegetation soil profiles was studied. Significant correlations among the vertical distribution of soil organic carbon content (TOC), organic carbon stable carbon isotopes (δ 13C) and several elements were found. The study showed that the EDXRF method can be well applied to element soil geochemical cycle and carbon cycle researches.

Schlossmacher U.,Johannes Gutenberg University Mainz | Wiens M.,Johannes Gutenberg University Mainz | Schroder H.C.,Johannes Gutenberg University Mainz | Wang X.,National Research Center for Geoanalysis | And 2 more authors.
FEBS Journal | Year: 2011

Silicateins are unique enzymes of sponges (phylum Porifera) that template and catalyze the polymerization of nanoscale silicate to siliceous skeletal elements. These multifunctional spicules are often elaborately shaped, with complex symmetries. They carry an axial proteinaceous filament, consisting of silicatein and the scaffold protein silintaphin-1, which guides silica deposition and subsequent spicular morphogenesis. In vivo, the synthesis of the axial filament very likely proceeds in three steps: (a) assembly of silicatein monomers to form one pentamer; (b) assembly of pentamers to form fractal-like structures; and finally (c) assembly of fractal-like structures to form filaments. The present study was aimed at exploring the effect of self-assembled complexes of silicatein and silintaphin-1 on biosilica synthesis in vitro. Hence, in a comparative approach, recombinant silicatein and recombinant silintaphin-1 were used at different stoichiometric ratios to form axial filaments and to synthesize biosilica. Whereas recombinant silicatein-α reaggregates to randomly organized structures, coincubation of silicatein-α and silintaphin-1 (molecular ratio 4: 1) resulted in synthetic filaments via fractal-like patterned self-assemblies, as observed by electron microscopy. Concurrently, owing to the concerted action of both proteins, the enzymatic activity of silicatein-α strongly increased by 5.3-fold (with the substrate tetraethyl orthosilicate), leading to significantly enhanced synthesis of biosilica. These results indicate that silicatein-α-mediated biosilicification depends on the concomitant presence of silicatein-α and silintaphin-1. Accordingly, silintaphin-1 might not only enhance the enzymatic activity of silicatein-α, but also accelerate the nonenzymatic polycondensation of the silica product before releasing the fully synthesized biosiliceous polymer. © 2011 The Authors Journal compilation © 2011 FEBS.

Discover hidden collaborations