The skeleton of the staghorn coral Acropora millepora: molecular and structural characterization

15 pagesInternational audienceThe scleractinian coral Acropora millepora is one of the most studied species from the Great Barrier Reef. This species has been used to understand evolutionary, immune and developmental processes in cnidarians. It has also been subject of several ecological studies in order to elucidate reef responses to environmental changes such as temperature rise and ocean acidification (OA). In these contexts, several nucleic acid resources were made available. When combined to a recent proteomic analysis of the coral skeletal organic matrix (SOM), they enabled the identification of several skeletal matrix proteins, making A. millepora into an emerging model for biomineralization studies. Here we describe the skeletal microstructure of A. millepora skeleton, together with a functional and biochemical characterization of its occluded SOM that focuses on the protein and saccharidic moieties. The skeletal matrix proteins show a large range of isoelectric points, compositional patterns and signatures. Besides secreted proteins, there are a significant number of proteins with membrane attachment sites such as transmembrane domains and GPI anchors as well as proteins with integrin binding sites. These features show that the skeletal proteins must have strong adhesion properties in order to function in the calcifying space. Moreover this data suggest a molecular connection between the calcifying epithelium and the skeletal tissue during biocalcification. In terms of sugar moieties, the enrichment of the SOM in arabinose is striking, and the monosaccharide composition exhibits the same signature as that of mucus of acroporid corals. Finally, we observe that the interaction of the acetic acid soluble SOM on the morphology of in vitro grown CaCO3 crystals is very pronounced when compared with the calcifying matrices of some mollusks. In light of these results, we wish to commend Acropora millepora as a model for biocalcification studies in scleractinians, from molecular and structural viewpoints

Catalytic and anticancer activities of sawhorse-type diruthenium tetracarbonyl complexes derived from fluorinated fatty acids

The reaction of fluorinated fatty acids, perfluorobutyric acid (C3F7CO2H), and perfluorododecanoic acid (C11F23CO2H), with dodecacarbonyltriruthenium (Ru-3(CO)(12)) under reflux in tetrahydrofuran, followed by addition of two-electron donors (L) such as pyridine, 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane, or triphenylphosphine, gives stable diruthenium complexes Ru-2(CO)(4)((2)-(2)-O2CC3F7)(2)(L)(2) (1a, L=C5H5N; 1b, L=PTA; 1c, L=PPh3) and Ru-2(CO)(4)((2)-(2)-O2CC11F23)(2)(L)(2) (2a, L=C5H5N; 2b, L=PTA; 2c, L=PPh3). The catalytic activity of the complexes for hydrogenation of styrene under supercritical carbon dioxide has been assessed and compared to the analogous triphenylphosphine complexes with non-fluorinated carboxylato groups Ru-2(CO)(4)((2)-(2)-O2CC3H7)(2)(PPh3)(2) (3) and Ru-2(CO)(4)((2)-(2)-O2CC11H23)(2)(PPh3)(2) (4). In addition, the cytotoxicities of the fluorinated complexes 1 were also evaluated on several human cancer cell lines (A2780, A549, Me300, HeLa). The complexes appear to be moderately cytotoxic, showing greater activity on the Me300 melanoma cells. Single-crystal X-ray structure analyses of 1a and 3 show the typical sawhorse-type arrangement of the diruthenium tetracarbonyl backbone with two bridging carboxylates and two terminal ligands occupying the axial positions

Variability of shell repair in the Manila clam Ruditapes philippinarum affected by the Brown Ring Disease : a microstructural and biochemical study

For more than two decades, the Manila clam Ruditapes philippinarum has been regularly affected by Brown Ring Disease (BRD), an epizootic event caused by the bacterium Vibrio tapetis and characterized by the development of a brown deposit on the inner face of valves. Although BRD infection is often lethal, some clams recover by mineralizing a new repair shell layer, which covers the brown deposit and fully isolates it from living tissues. In order to understand this specific shell repair process, the microstructures of repaired zones were compared to those of shells unaffected by BRD. In addition, the organic matrix associated with unaffected shells and to repair patches were extracted and compared by biochemical and immunological techniques. Our results show that the repaired zones exhibit microstructures that resemble the so-called homogeneous microstructure of the internal layer, with some marked differences, like the development of crossed-acicular crystals, which form chevron-like patterns. In the three tested batches of repaired layers, the matrices exhibit certain heterogeneity, i.e., they are partially to widely different from the ones of shells unaffected by BRD, as illustrated by SOS-PAGE and by serological comparisons. Our results strongly suggest a modification of the secretory regime of calcifying mantle cells during the shell repair process. Polyclonal antibodies, which were developed against specific protein fractions of the shell, represent relevant tools for localizing by immunohistology the cells responsible for the repair

Environmentally friendly surface modification treatment of flax fibers by supercritical carbon dioxide

The present work investigates the effects of an environmentally friendly treatment based on supercritical carbon dioxide (scCO2) on the interfacial adhesion of flax fibers with thermoset matrices. In particular, the influence of this green treatment on the mechanical (by single yarn tensile test), thermal (by TGA), and chemical (by FT-IR) properties of commercially available flax yarns was preliminary addressed. Results showed that scCO2 can significantly modify the biochemical composition of flax fibers, by selectively removing lignin and hemicellulose, without altering their thermal stability and, most importantly, their mechanical properties. Single yarn fragmentation test results highlighted an increased interfacial adhesion after scCO2 treatment, especially for the vinylester matrix, in terms of reduced debonding and critical fragment length values compared to the untreated yarns by 18.9% and 15.1%, respectively. The treatment was less effective for epoxy matrix, for which debonding and critical fragment length values were reduced to a lesser extent, by 3.4% and 3.7%, respectively

<span style="font-size:11.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-GB;mso-fareast-language:JA;mso-bidi-language:HI" lang="EN-GB">Synthesis of 1,2-glycerol carbonate from carbon dioxide: The role of methanol in fluid phase equilibrium</span>

1330-1338The effect of methanol on the synthesis of 1,2-glycerol carbonate from CO2 and glycerol is studied in the presence of Bu2Sn(OCH3)2, <i style="mso-bidi-font-style: normal">n-Bu2SnO, and tert-Bu2SnO. At 423 K, up to 2.7 mol% yield in glycerol carbonate, based on glycerol, could be obtained in the pressure range 14-20 MPa. Addition of acetonitrile promotes notably the yield to 7 mol%. Fluid phase equilibrium experiments with the ternary mixture CO2/glycerol/methanol show that the reaction takes place in a liquid phase where methanol dissolves glycerol, CO2, and the tin complexes. Above ~0.6 mole fraction, CO2 behaves as an anti-solvent, separating methanol from glycerol, thus inhibiting the formation of 1,2-glycerol carbonate. Dimethyl carbonate is a side-product of glycerol carbonation resulting mainly from transesterification between glycerol carbonate and methanol. Glycerol coordination to tin center is evidenced by the isolation of di-tert-Bu2Sn(1,2-glycerolate) complex. Its structure determination by single-crystal X-ray diffraction shows that the remaining OH group of glycerol promotes the formation of one-dimensional polymeric chain

Synthesis of 1,2-glycerol carbonate from carbon dioxide: the role of methanol in fluid phase equilibrium

ERA-Chemistry thematic call Chemical Activation of Carbon Dioxide and Methane (project 510192).The effect of methanol on the synthesis of 1,2-glycerol carbonate from CO2 and glycerol is studied in the presence of Bu 2Sn(OCH3)2, n-Bu2SnO, and tert-Bu2SnO. At 423 K, up to 2.7 mol% yield in glycerol carbonate, based on glycerol, could be obtained in the pressure range 14-20 MPa. Addition of acetonitrile promotes notably the yield to 7 mol%. Fluid phase equilibrium experiments with the ternary mixture CO2/glycerol/methanol show that the reaction takes place in a liquid phase where methanol dissolves glycerol, CO2, and the tin complexes. Above ∼0.6 mole fraction, CO 2 behaves as an anti-solvent, separating methanol from glycerol, thus inhibiting the formation of 1,2-glycerol carbonate. Dimethyl carbonate is a sideproduct of glycerol carbonation resulting mainly from transesterification between glycerol carbonate and methanol. Glycerol coordination to tin center is evidenced by the isolation of di-tert-Bu2Sn(1,2-glycerolate) complex. Its structure determination by single-crystal X-ray diffraction shows that the remaining OH group of glycerol promotes the formation of onedimensional polymeric chain.publishersversionpublishe

Design of an inversion center between two helical segments

A new strategy is proposed to control the relative orientation of two folded helical oligomers in such a way that they diverge from an aromatic linker and have opposite helical handedness..