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The understanding of the molecular mechanisms underlying the early stages of crystallisation is still incomplete. In the case of calcium carbonate, experimental and computational evidence suggests that phase separation relies on so-called pre-nucleation clusters (PNCs). A thorough thermodynamic analysis of the enthalpic and entropic contributions to the overall free energy of PNC formation derived from three independent methods demonstrates that solute clustering is driven by entropy. This can be quantitatively rationalised by the release of water molecules from ion hydration layers, explaining why ion association is not limited to simple ion pairing. The key role of water release in this process suggests that PNC formation should be a common phenomenon in aqueous solutions.

The sign and value of the line tension has been measured from the size dependence of the contact angle of nanometer-size sessile fullerene (C60) droplets on the planar SiO2 interface, measured with atomic force microscopy (AFM). Analysis according to the modified Young's equation indicates a negative line tension, with a magnitude between -10{-11} and -10{-10}  N/m, in good agreement with theoretical predictions. The experiments also indicate that droplets with contact area radii below 10 nm are in fact two-dimensional round terraces.

The larval spicule matrix protein SM50 is the most abundant occluded matrix protein present in the mineralized larval sea urchin spicule. Recent evidence implicates SM50 in the stabilization of amorphous calcium carbonate (ACC). Here, we investigate the molecular interactions of SM50 and CaCO3 by investigating the function of three major domains of SM50 as small ubiquitin-like modifier (SUMO) fusion proteins - a C-type lectin domain (CTL), a glycine rich region (GRR) and a proline rich region (PRR). Under various mineralization conditions, we find that SUMO-CTL is monomeric and influences CaCO3 mineralization, SUMO-GRR aggregates into large protein superstructures and SUMO-PRR modifies the early CaCO3 mineralization stages as well as growth. The combination of these mineralization and self-assembly properties of the major domains synergistically enable the full-length SM50 to fulfill functions of constructing the organic spicule matrix as well as performing necessary mineralization activities such as Ca(2+) ion recruitment and organization to allow for proper growth and development of the mineralized larval sea urchin spicule.

Amorphous and liquid precursors of calcium carbonate are believed to be central species of biomineralization, which serves as an important inspiration for materials chemists in the quest for new and improved organic-inorganic hybrid materials. It has become increasingly clear that magnesium ions exhibit an important function through kinetic stabilization of the metastable precursors. We show that they additionally tune the wettability of liquid precursors of CaCO3, which is a crucial requirement for successful mineralization of proteinaceous organic matrices. Moreover, tunable wettability offers straightforward means to control mineralization sites in organic-inorganic hybrids.

Thermoresponsive hydrogels are formed within the microporous structure of wood combining the anisotropic hierarchical wood structure with the stimuli responsive properties of the hydrogel. This hybrid material opens the way for entirely new utilizations of wood resources.

Artículo de publicación ISIFrom recent studies on bone and shell formation, the importance of polysaccharides in biomineralization processes is gradually being recognized. Through ion-complexation and self-assembly properties, such macromolecules have remarkable effects on mineralization. However, their influences on the different regimes of crystallization including the interactions with precursor species are unclear. The present study therefore addresses calcium carbonate mineralization in the presence of alginates, a class of linear copolymeric saccharides composed of beta-1,4 linked D-mannuronic and L-guluronic acid. During mineralization, this biopolymer is found to exert pH-dependent control over mineralization pathways in terms of the stability of prenucleation dusters, inhibitory effect toward nucleation and initially formed postnucleation products. Remarkably in the presence of this macromolecular additive; either amorphous or crystalline vaterite particles can be selectively nucleated in a pH-dependent manner. This is validated by electron microscopy wherein vaterite particles are intimately associated with alginate assemblies after nucleation at pH 9.75. At lower pH, aggregates, of amorphous particles are formed. Thus, in addition to the general focus on biochemical properties of additives, solution pH, a physiologically fundamental parameter significantly alters the scheme of mineralization.Chilean Council for Science and Technology (CONICYT); CONICYT/DAAD; Program U-Redes, Vice-presidency of Research and Development, University of Chil

Biomineralization involves the controlled formation of inorganic matter within hierarchical biological scaffolds. Mimicking the crystallization of biominerals in such confinement is an important goal in the field of crystal engineering. Natural porous materials offer an interesting platform for studying mineral morphogenesis and texturing through template-directed mineralization. In this paper, we precipitate barium sulfate from aqueous salt solutions in the constrained micro-and nanoenvironment of pristine wood cells and cell walls. By employing spatially resolved characterization techniques, such as scanning electron microscopy (SEM), Raman spectroscopic imaging, and scanning wide-angle X-ray scattering (WAXS), we gain important insights into the deposition pattern, morphology, and crystallographic orientation of Barite crystals in the plant cell anatomy. The experimental findings suggest directed crystallization of BaSO 4 at different hierarchical levels. SEM shows elongated, dendritic BaSO 4 crystals growing inside the cell lumina closely associated with the interfacial cell wall region. WAXS measurements acquired from mineralized cell walls show a crystallographic co-orientation of Barite and cellulose, suggesting epitaxial crystal growth.