1,721,164 research outputs found
CoralWarm: Corals and global warming: the Mediterranean versus the Red Sea [(FP7/2007-2013)/ERC grant agreement n: 249930]
No full textCoralWarm will generate for the first time projections of temperate and subtropical coral survival by
integrating sublethal temperature increase effects on metabolic and skeletal processes in Mediterranean and Red
Sea key species. CoralWarm unique approach is from the nano- to the macro-scale, correlating molecular events to
environmental processes. This will show new pathways to future investigations on cellular mechanisms linking
environmental factors to final phenotype, potentially improving prediction powers and paleoclimatological
interpretation. Biological and chemical expertise will merge, producing new interdisciplinary approaches for
ecophysiology and biomineralization. Field transplantations will be combined with controlled experiments under
IPCC scenarios. Corals will be grown in aquaria, exposing the Mediterranean species native to cooler waters to
higher temperatures, and the Red Sea ones to gradually increasing above ambient warming seawater. Virtually all
state-of-the-art methods will be used, by uniquely combining the investigators’ expertise. Expected results include
responses of algal symbionts’ photosynthesis, host, symbiont and holobiont respiration, biomineralization rates and
patterns, including colony architecture, and reproduction to temperature and pH gradients and combinations.
Integration of molecular aspects of potential replacement of symbiont clades, changes in skeletal crystallography,
with biochemical and physiological aspects of temperature response, will lead to a novel mechanistic model
predicting changes in coral ecology and survival prospect. High-temperature tolerant clades and species will be
revealed, allowing future bioremediation actions and establishment of coral refuges, saving corals and coral reefs
for future generations
Crystallization of calcium carbonate salts into beta-chitin scaffold
No full textComposites of β-chitin with calcium carbonate polymorphs were prepared by precipitation of the mineral into a chitin scaffold by means of a double diffusion system. The β-chitin was obtained from the pen of the Loligo sp. squid. The three main polymorphs of calcium carbonate: aragonite, calcite and vaterite, were observed. Their location within the matrix is a function of the polymorph. The supersaturation inside the compartmentalized space in the chitin governs the location and polymorphism of the crystals. © 2002 Elsevier Science Inc. All rights reserved
Oriented crystallization of octacalcium phosphate into beta-chitin scaffold
No full textComposites of β-chitin with octacalcium phosphate (OCP) or hydroxylapatite (HAP) were prepared by precipitation of the mineral into a chitin scaffold by means of a double diffusion system. The β-chitin was obtained from the pen of the Loligo sp. squid. Only oriented precipitation of OCP was observed. The OCP crystals with the usual form of (001) blades grow inside chitin layers preferentially oriented with the {100} faces parallel to the surface of the squid pen and were more stable to the hydrolysis to HAP with respect to that precipitated in solution. Reasons are given why mechanical factors are thought to be the predominant cause for the orientation of the OCP crystals with the a-axis almost normal to the chitin fibers. We conclude that in these in vitro experiments the compartmentalized space in the chitin governs the orientation of the crystals, even if epitaxial factors may play a role in the nucleation processes. © 2001 Elsevier Science B.V. All rights reserved
Crystal growth mechanism of vaterite in the systems containing charged synthetic Poly(Amino Acids)
No full textNegatively ionisable poly-L-glutamic acid (pGlu) and poly-L-aspartic acid (pAsp), considered as analogues of the naturally occurring acidic macromolecules involved in biomineralization processes, were used as additives in the calcium carbonate precipitation systems in order to investigate their interactions with the vaterite crystallites. Poly-L-lysine (pLys), a positively ionisable poly(amino acid), was also used in order to elucidate the impact of the side chain charge. The growth kinetics of vaterite was found parabolic, indicating that the integration of growth units into the spiral step at the vaterite crystal surfaces is the rate-determining mechanism. The presence of small amounts of pGlu and pAsp inhibited the crystal growth. At the highest concentrations of both acidic macromolecules the exponential rate law was observed, which indicates the surface nucleation as the rate controlling mechanism. The addition of pLys in the range of applied concentrations did not significantly influence the crystal growth of the vaterite. Thus, the kinetic results, corroborated by morphological observations, pointed out to the significance of the negative charge of the side chains of selected polypeptides in the interfacial interactions with mineral planes
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Oriented crystallization of vaterite in collagenous matrices
No full textThe influence of high supersaturation on kinetic control and the importance of the polypeptide structure in the crystallization of calcium carbonate polymorphs were studied in crosslinked gelatin films containing high concentrations of the polypeptides poly-L-aspartate and poly-L-glutamate. Oriented crystallization of vaterite occurs in uniaxially deformed gelatin films containing poly-L-aspartate at concentations greater than 100 mg per gram of gelatin. The fact that no orientation of the mineral phase was observed with entrapped poly-L-glutamate at the same concentrations suggests that the oriented crystallization is controlled by the beta sheet structure assumed by poly-L-aspartate in the presence of calcium ions. These results indicate that local supersaturation in the microenvironment in which nucleation and growth occur plays an important role in controlling the deposition of vaterite in cross-linked gelatin films. However, collagen bundles se and the ordered and oriented polypeptide chains of poly-L-aspartate can contribute to the control of polymorphism by inducing the formation of a specific phase by epitaxial crystallization, as suggested by the preferentially oriented deposition of vaterite and aragonite. This is of potential significance in biomineralization processes and in materials science
Revalorizing shellfish waste: exploratory study of the composition and bioactive properties of mollusk shell matrices
No full textInvestigating mollusk shells organic matrix composition: isolation and characterization of bioactive molecules
No full textBiomimetic crystallization of calcium carbonate polymorphs by means of collagenous matrices
No full textCrosslinked gelatin films with entrapped poly-L-aspartate were used to induce the crystallization of calcite and aragonite polymorphs. Calcite with high degrees of isomorphous substitution (up to 12 mol% magnesium) has been obtained. The morphology and layered organization of magnesium calibre crystals grown inside the crosslinked gelatin films with entrapped poly-L-aspartate resemble some structural features of radial calcitic colds. The concentration of entrapped poly-L-aspartate and the uniaxial deformation of the films control the growth of aragonite aggregates inside the films. Such aggregates grown inside uniaxially deformed films consist of parallel rods with an architectural assembly similar to that found in some marine organisms. The crystals' aggregation and the control of calcium carbonate polymorphism are related to the modelling of the nucleation sites by poly-L-aspartate structure and concentration, local supersaturation and microenvironment shape. The results indicate that the collagenous matrices with entrapped polyelectrolytes are versatile systems which can contribute to the elucidation of strategies for biomimetic materials chemistry
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