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Medical treatment options for bones and teeth can be significantly enhanced by taking control over the crystallization of biomaterials like hydroxyapatite in the healing process. Light‐induced techniques are particularly interesting for this approach as they offer tremendous accuracy in spatial resolution. However, in the field of calcium phosphates, light‐induced crystallization has not been investigated so far. Here, proof of principle is established to successfully induce carbonate‐hydroxyapatite precipitation by light irradiation. Phosphoric acid is released by a photolabile molecule exclusively after irradiation, combining with calcium ions to form a calcium phosphate in the crystallization medium. 4‐Nitrophenylphosphate (4NPP) is established as the photolabile molecule and the system is optimized and fully characterized. A calcium phosphate is crystallized exclusively by irradiation in aqueous solution and identified as carbonate apatite. Control over the localization and stabilization of the carbonate apatite is achieved by a pulsed laser, triggering precipitation in calcium and 4NPP‐containing gel matrices. The results of this communication open up a wide range of new opportunities, both in the field of chemistry for more sophisticated reaction control in localized crystallization processes and in the field of medicine for enhanced treatment of calcium phosphate containing biomaterials. [ABSTRACT FROM AUTHOR]

Although calcium oxalates are relevant biominerals, their formation mechanisms remain largely unresolved. Here, we investigate the early stages of calcium oxalate formation in pure and citrate-bearing solutions. Citrate is used as a well-known oxalate precipitation inhibitor; moreover, it resembles the functional domains of the biomolecules that modulate biomineralization. Our data suggest that calcium oxalate forms after Ca2+ and C2O42- association into polynuclear stable complexes that aggregate into larger assemblies, from which amorphous calcium oxalate nucleates. Previous work has explained citrate inhibitory effects according to classical theories. Here we show that citrate interacts with all early stage CaC2O4 species (polynuclear stable complexes and amorphous precursors), inhibiting calcium oxalate nucleation by colloidal stabilization of polynuclear stable complexes and amorphous calcium oxalate. The control that citrate exerts on calcium oxalate biomineralization may thus begin earlier than previously thought. These insights provide information regarding the mechanisms governing biomineralization, including pathological processes (e.g., kidney stone formation). [ABSTRACT FROM AUTHOR]

Many phenomena depend on CaCO3 nucleation where the role of water remains enigmatic. Changes in THz absorption during the early stages of CaCO3 nucleation evidence altered coupled motions of hydrated calcium and carbonate ions. The direct link between these changes and the continuous development of the ion activity product reveals the locus of a liquid-liquid binodal limit. The data strongly suggest that proto-structured amorphous CaCO3 forms through solidification of initially liquid precursors. Furthermore, polycarboxylates, which stabilize liquid precursors of CaCO3, significantly enhance the kinetic stability of the metastable liquid-liquid state, but they do not affect the locus of the binodal limit. The importance of water network dynamics in phase separation mechanisms can be understood based on the notions of the pre-nucleation cluster pathway, and is likely to be more general for aqueous systems. [ABSTRACT FROM AUTHOR]

Synergistic relations between organic molecules and mineral precursors regulate biogenic mineralization. Given the remarkable material properties of the egg shell as a biogenic ceramic, it serves as an important model to elucidate biomineral growth. With established roles of complex anionic biopolymers and a heterogeneous organic scaffold in egg shell mineralization, the present study explores the regulation over mineralization attained by applying synthetic polymeric counterparts (polyethylene glycol, poly(acrylic acid), poly(aspartic acid) and poly(4-styrenesulfonic acid-co-maleic acid)) as additives during remineralization of decalcified eggshell membranes. By applying Mg2+ ions as a co-additive species, mineral retrosynthesis is achieved in a manner that modulates the polymorph and structure of mineral products. Notable features of the mineralization process include distinct local wettability of the biogenic organic scaffold by mineral precursors and mineralization-induced membrane actuation. Overall, the form, structure and polymorph of the mineralization products are synergistically affected by the additive and the content of Mg2+ ions. We also revisit the physicochemical nature of the biomineral scaffold and demonstrate the distinct spatial distribution of anionic biomolecules associated with the scaffold-mineral interface, as well as highlight the hydrogel-like properties of mammillae-associated macromolecules. [ABSTRACT FROM AUTHOR]

Proteins are known to play various key roles in the formation of complex inorganic solids during natural biomineralisation processes. However, in most cases our understanding of the actual underlying mechanisms is rather limited. One interesting example is perlucin, a protein involved in the formation of nacre, where it is believed to promote the crystallisation of calcium carbonate. In the present work, we have used potentiometric titration assays to systematically investigate the influence of recombinant GFP-labeled perlucin derivatives on the early stages of CaCO3 formation. Our results indicate that different parts of the protein can impact nucleation in distinct ways and act in either a retarding or promoting fashion. The most important finding is that full-length GFP-perlucin changes the nature of the initially precipitated phase and seems to favour the direct formation of crystalline polymorphs over nucleation of ACC and subsequent phase transformation, as observed in reference experiments without protein. This confirms the supposed role of perlucin in nacre biomineralisation and may rely on specific interactions between the protein and the crystal lattice of the emerging mineral phase. [ABSTRACT FROM AUTHOR]

Biogenic mineralization processes are generally regulated by soluble additives and insoluble matrices. This endows precise control over the different stages of mineralization such as the uptake, transport of mineral precursors as well as the subsequent deposition of the mineral phases with consistent compositions and morphologies. Programmed in the interactions of organic molecules with different precursor species and the fine modulation of the niche environments, a formative elegance is reflected in the biological means for crystal formation in comparison to the synthetic counterparts. In order to spotlight the role of prevalent biophysical environments in the emergence of fascinating materials, we revisit biologically modulated mineralization to describe nucleation and crystallization under physicochemical highly non-ideal conditions on account of macromolecular crowding and the gel-like nature of cellular matrices. [ABSTRACT FROM AUTHOR]

Materials based on biodegradable polyesters, such as poly(butylene terephthalate) (PBT) or poly(butylene terephthalate-co-poly(alkylene glycol) terephthalate) (PBTAT), have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16)), that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering. [ABSTRACT FROM AUTHOR]

An easy design route via simple evaporation is reported for macroscopic mosaic thin films comprising the quaternary system of dl-lysine·HCl, poly(acrylic acid), water, and EtOH. By depositing droplets of the quaternary dispersions onto hydrophilic cover slips, the formation of macroscopic crack-free mosaic mesocrystal thin films are produced. The formation follows a multistage crystallization process, which includes the formation of a polymer-induced liquid-precursor (PILP) phase, the formation of spherulitic thin films, and the recrystallization of mosaic mesocrystal thin films. A slow cooling rate is noted to be beneficial for the mesocrystal thin films, enabling the films to be crack-free and to display low surface roughness at the nanoscale. [ABSTRACT FROM AUTHOR]

It takes two different functional additives to produce the title structures. The proposed mechanism based on the nonclassical particle‐mediated crystallization of calcium carbonate demonstrates the individual and cooperative effects of the polymer poly(sodium 4‐styrenesulfonate) and small folic acid molecules on the formation of heterostructures at different reaction stages. [ABSTRACT FROM AUTHOR]

Biomineralization can afford crystal frameworks of great diversity and utmost complexity, frequently featuring hierarchical structures and morphologies beyond any crystallographic restrictions. The formation of such architectures is usually directed by organic molecules or matrices, which modify crystallization in a deliberate manner. Their influence often leads to sinuous forms, which, by intuition, suggest the presence of life and distinguish these minerals from their inanimate, mostly euhedral counterparts. However, such a strict distinction does not hold. In fact, smooth curvature and higher-order structuring can occur also in purely inorganic environments: simply by precipitating alkaline earth carbonates in silica-containing media, aggregates of highly oriented carbonate nanocrystals can be obtained that display striking noncrystallographic morphologies such as regular helicoids. Thereby, individual crystallites as well as the entire assembly are sheathed by amorphous silica, thus giving a composite material with various levels of hierarchy. These exceptional forms, called 'silica biomorphs', self-assemble through a bottom-up process, which relies on local variations in the conditions and is driven by a pH-based coupling of the carbonate and silicate. Here, we review recent progress in the field of silica biomorphs with particular focus on their mechanism of formation, provide insight into structural details at different length scales, and discuss implications of these biomimetic crystal aggregates for both primitive life detection and materials science. [ABSTRACT FROM AUTHOR]

Summary: In this contribution, we review the recent literature on an alternative crystallization pathway involving stable clusters prior to nucleation and show that the prenucleation cluster pathway is a truly non-classical concept of nucleation. Prenucleation clusters are solutes with “molecular” character in aqueous solution. It becomes evident that the stable clusters may have been concealed by the so-called ion pair concept and activity effects. We show that non-classical nucleation via stable prenucleation clusters is a highly valuable concept for a novel understanding of phenomena observed in bio- and biomimetic mineralization, which however may hardly be rationalized by means of classical nucleation theory. The importance to combine experimental and theoretical studies is emphasized. [Copyright &y& Elsevier]

Abstract: In this overview, some new applications of micelles, vesicles and lyotropic phases used for mineralization are described. Special focus is put on cases where a complex fluid built from “stiff” structures is used as a scaffold for mineralization events in the aqueous phase. Various minerals and metals have been successfully crystallized in these templates showing that it is possible to mimic the natural vesicle archetypes in biomineralization processes, although colloidal interactions can also well over compensate the templating effect of the organic matrix. [Copyright &y& Elsevier]

The recent progress in carbonate precipitation with complex shapes mainly concerns CaCO3 due to its importance for industry and biomineralization. Two general morphogenesis approaches were pursued: Either, soluble—predominately polymeric—additives were employed in the precipitation process leading to microparticles with complex shape which are partly even hybrids of two different crystal polymorphs, or macroscopic templates were used as confined reaction environments for precipitation. Despite a considerable amount of work and knowledge gain, the investigation of the structure formation processes with impact on understanding of biomineralization principles still remains a challenge. Nevertheless, some remarkable progress is reported in the areas of template and additive controlled CaCO3 crystallization as well as its morphogenesis based on mesoscopic transformation which lead to a deeper understanding of the underlying structuration principles. [Copyright &y& Elsevier]

A facile biomimetic method is reported for the synthesis of novel BaCO3 nanofibres with double-stranded and cylindrical helical morphologies via a phosphonated block co-polymer-controlled mineralization process. [ABSTRACT FROM AUTHOR]

Nonclassical particle mediated crystallization has been found to be a relevant alternativecrystallization pathway to classical atom/ion/molecule-based crystallization. Nonclassicalcrystallization can involve clusters, liquid or amorphous precursors or nanoparticlebuilding units, which allow for the realization of different crystallization scenarios.Mesocrystals, built from iso-oriented nanocrystals are a relevant intermediate. Magnetitemesocrystals will be demonstrated as intermediate to single crystals, which canform by oriented attachment involving crystallographic fusion of the iso-orientednanoparticles. Nonclassical crystallization also seems to play a role in Biomineralization sincemesocrystalline structures as well as amorphous precursor particles have been identified inseveral Biominerals and liquid precursors are discussed for their formation. For theexample of the SM50 protein from a sea urchin, it will be shown how a proteincan control the nonclassical crystallization process of CaCO3. SM50 stabilizesamorphous CaCO3 (ACC) in vesicles just like the ones found in sea urchins totransport ACC to the developing site of the spicule. Upon enzymatic cleavage of theprotein, a protein domain is generated, which controls the crystallization of the ACCnanoparticles to mesocrystals. This is the structure found in spicules of the sea urchin. Thisclose analogy to the CaCO3 forms found in the living sea urchin demonstrates, howa nonclassical crystallization event can be controlled and triggered by proteins. [ABSTRACT FROM AUTHOR]

The article discusses the biomineralization, considering pathological mineralization. It states that biominerals are dependent on their biological constituents, like the biomacromolecule for mineralization regulation. It says that pathological mineralization enables the development of undesired biominerals, such as dental calculus, artherosclerosis, and kidney stones. Meanwhile, high-resolution images' attraction is the potential of mineralization mechanism deduction.

A simple evaporation method for the preparation of mosaic mesocrystal thin films is studied by Helmut Cölfen and co‐workers. As reported on page 1547, the multistep process starts with the formation of a polymer–induced liquid–precursor phase, followed by the formation of spherulitic thin films and their recrystallization into mesocrystal thin films. The image shows a polarized light (Abrio) image of a mesocrystalline thin film of dl‐lysine·HCl. [ABSTRACT FROM AUTHOR]

This Communication addresses the effects of egg membrane- and shell-associated proteoglycans, namely, keratan sulfate and dermatan sulfate, respectively, on the nascent stages of CaCO3 mineralization. Composed of calcitic columns intimately associated with a collagen membrane, the mechanisms underlying mineral growth are regulated by biomolecules. Of these, the role of proteoglycans is crucial because of their defined temporal and spatial distributions that direct mineral growth. The proteoglycans analyzed here induce dissimilar effects on the early stages of calcium carbonate mineralization. Egg-membrane associated keratan sulfate has a stabilizing effect toward soluble calcium carbonate prenucleation clusters and promotes formation of phases with lower solubility products after nucleation. In contrast, dermatan sulfate destabilizes prenucleation clusters and leads to more soluble phases of calcium carbonate postnucleation. The distinct effects of proteoglycans on calcium carbonate crystallization elucidate their unique spatiotemporal localization during egg mineralization. [ABSTRACT FROM AUTHOR]

Although biomimetic designs are expected to play a key role in exploring future structural materials, facile fabrication of bulk biomimetic materials under ambient conditions remains a major challenge. Here, we describe a mesoscale “assembly-and-mineralization” approach inspired by the natural process in mollusks to fabricate bulk synthetic nacre that highly resembles both the chemical composition and the hierarchical structure of natural nacre.The millimeter-thick synthetic nacre consists of alternating organic layers and aragonite platelet layers (91 weight percent) and exhibits good ultimate strength and fracture toughness.This predesigned matrix-directed mineralization method represents a rational strategy for the preparation of robust composite materials with hierarchically ordered structures,where various constituents are adaptable, including brittle and heat-labile materials. [ABSTRACT FROM AUTHOR]

Electrospun submicrometer-sized poly(ε-caprolactone) (PCL) meshes and nanosized multiwalled carbon nanotubes (MWCNTs) were used as a template for preparing porous and interconnected inorganic-organic hybrid materials composed of CaCO3. Herein, we describe the proportion and incorporation method of submicrometer-sized plasma-treated PCL meshes over areas >1 mm² with CaCO3 using three crystallization methods including the use of poly(acrylic acid) (PAA). We found that flexible and rigid acid-functionalized MWCNTs showed a clear capacity and effects to penetrate calcite particles. MWCNTs interacted differently with the individual growth planes of CaCO3, indicating that fibers can undergo changes depending on sulfonate or carboxylate groups, adopt different orientations in solution, and thereby elicit changes in CaCO3 morphology. In summary, the use of PCL and acidic MWCNT fibers as an additive for substrate templates and experimental crystallization provides a viable approach for studying various aspects of biomineralization, including the production of controlled particles, control of porosities, and defined morphologies at microscale and nanoscale levels. [ABSTRACT FROM AUTHOR]

In the nacre or aragonite layer of the mollusk shell, proteomes that regulate both the early stages of nucleation and nano-to-mesoscale assembly of nacre tablets from mineral nanoparticle precursors exist. Several approaches have been developed to understand protein-associated mechanisms of nacre formation, yet we still lack insight into how protein ensembles or proteomes manage nucleation and crystal growth. To provide additional insights, we have created a proportionally defined combinatorial model consisting of two nacre-associated proteins, C-RING AP7 (shell nacre, Haliotis rufescens) and pseudo-EF hand PFMG1 (oyster pearl nacre, Pinctada fucata), whose individual in vitro mineralization functionalities are well-documented and distinct from one another. Using scanning electron microscopy, flow cell scanning transmission electron microscopy, atomic force microscopy, Ca(II) potentiometric titrations, and quartz crystal microbalance with dissipation monitoring quantitative analyses, we find that both nacre proteins are functionally active within the same mineralization environments and, at 1:1 molar ratios, synergistically create calcium carbonate mesoscale structures with ordered intracrystalline nanoporosities, extensively prolong nucleation times, and introduce an additional nucleation event. Further, these two proteins jointly create nanoscale protein aggregates or phases that under mineralization conditions further assemble into protein-mineral polymer-induced liquid precursor-like phases with enhanced ACC stabilization capabilities, and there is evidence of intermolecular interactions between AP7 and PFMG1 under these conditions. Thus, a combinatorial model system consisting of more than one defined biomineralization protein dramatically changes the outcome of the in vitro biomineralization process. [ABSTRACT FROM AUTHOR]

From 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 β-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 clusters, 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. [ABSTRACT FROM AUTHOR]

The impacts of glycosylation on biomineralization protein function are largely unknown. This is certainly true for the mollusk shell, where glycosylated intracrystalline proteins such as AP24 (Haliotis rufescens) exist but their functions and the role of glycosylation remain elusive. To assess the effect of glycosylation on protein function, we expressed two recombinant variants of AP24: an unglycosylated bacteria-expressed version (rAP24N) and a glycosylated insect cell-expressed version (rAP24G). Our findings indicate that rAP24G is expressed as a single polypeptide containing variations in glycosylation that create microheterogeneity in rAP24G molecular masses. These post-translational modifications incorporate O- and N-glycans and anionic monosialylated and bisialylated, and monosulfated and bisulfated monosaccharides on the protein molecules. AFM and DLS experiments confirm that both rAP24N and rAP24G aggregate to form protein phases, with rAP24N exhibiting a higher degree of aggregation, compared to rAP24G. With regard to functionality, we observe that both recombinant proteins exhibit similar behavior within in vitro calcium carbonate mineralization assays and potentiometric titrations. However, rAP24G modifies crystal growth directions and is a stronger nucleation inhibitor, whereas rAP24N exhibits higher mineral phase stabilization and nanoparticle containment. We believe that the post-translational addition of anionic groups (via sialylation and sulfation), along with modifications to the protein surface topology, may explain the changes in glycosylated rAP24G aggregation and mineralization behavior, relative to rAP24N. [ABSTRACT FROM AUTHOR]

The article discusses research on particle attachment crystallization (CPA) in synthetic, biogenic, and geologic environments. Topics include the nonclassical thermodynamic and dynamic mechanisms for crystallization pathways, the control of nanomaterials synthesis, and the role of free-energy landscapes and reaction dynamics in allowing for multiple pathways. The relation of ensemble behavior to synthetic systems, biominerals, and natural mineralization is addressed.

Conspectus: Mesocrystals, which originally was a term to designate superstructures of nanocrystals with a common crystallographic orientation, have now evolved to a materials concept. The discovery that many biominerals are mesocrystals generated a large research interest, and it was suggested that mesocrystals result in better mechanical performance and optical properties compared to single crystalline structures. Mesocrystalline biominerals are mainly found in spines or shells, which have to be mechanically optimized for protection or as a load-bearing skeleton. Important examples include red coral and sea urchin spine as well as bones. Mesocrystals can also be formed from purely synthetic components. Biomimetic mineralization and assembly have been used to produce mesocrystals, sometimes with complex hierarchical structures. Important examples include the fluorapatite mesocrystals with gelatin as the structural matrix, and mesocrystalline calcite spicules with impressive strength and flexibility that could be synthesized using silicatein protein fibers as template for calcium carbonate deposition. Self-assembly of nanocrystals can also result in mesocrystals if the nanocrystals have a well-defined size and shape and the assembly conditions are tuned to allow the nanoparticles to align crystallographically. Mesocrystals formed by assembly of monodisperse metallic, semiconducting, and magnetic nanocrystals are a type of colloidal crystal with a well-defined structure on both the atomic and mesoscopic length scale. Mesocrystals typically are hybrid materials between crystalline nanoparticles and interspacing amorphous organic or inorganic layers. This structure allows to combine disparate materials like hard but brittle nanocrystals with a soft and ductile amorphous material, enabling a mechanically optimized structural design as realized in the sea urchin spicule. Furthermore, mesocrystals can combine the properties of individual nanocrystals like the optical quantum size effect, surface plasmon resonance, and size dependent magnetic properties with a mesostructure and morphology tailored for specific applications. Indeed, mesocrystals composed of crystallographically aligned polyhedral or rodlike nanocrystals with anisotropic properties can be materials with strongly directional properties and novel collective emergent properties. An additional advantage of mesocrystals is that they can combine the properties of nanoparticles with a structure on the micro- or macroscale allowing for much easier handling. In this Account, we propose that mesocrystals are defined as "a nanostructured material with a defined long-range order on the atomic scale, which can be inferred from the existence of an essentially sharp wide-angle diffraction pattern (with sharp Bragg peaks) together with clear evidence that the material consists of individual nanoparticle building units". We will give several examples of mesocrystals and discuss the structural characteristics for biominerals, biomimetic materials, and colloidal arrays of nanocrystals. The potential of the mesocrystal materials concept in other areas will be discussed and future developments envisioned. [ABSTRACT FROM AUTHOR]

The mollusk shell is a complex biological material that integrates mineral phases with organic macro-molecular components such as proteins. The role of proteins in the formation of the nacre layer (aragonite mineral phase) is poorly understood, particularly with regard to the organization of mineral deposits within the protein extracellular matrix and the identification of which proteins are responsible for this task. We report new experiments that provide insight into the role of the framework nacre protein, n16.3 (Pinctada fucata), as an organizer or assembler of calcium carbonate mineral clusters. Using a combination of biophysical techniques, we find that recombinant n16.3 (r-n16.3) oligomerizes to form amorphous protein films and particles that possess regions of disorder and mobility. These supramolecular assemblies possess an intrinsically disordered C-terminal region (T64-W98) and reorganize in the presence of Ca2+ ions to form clustered protein oligomers. This Ca2+-induced reorganization leads to alterations in the molecular environments of Trp residues, the majority of which reside in putative aggregation-prone cross-β strand regions. Potentiometric Ca2+ titrations reveal that r-n16.3 does not significantly affect the formation of prenucleation clusters in solution, and this suggests a role for this protein in postnucleation mineralization events. This is verified in subsequent in vitro mineralization assays in which r-n16.3 demonstrates its ability to form gel-like protein phases that organize and cluster nanometer-sized single-crystal calcite relative to protein-deficient controls. We conclude that the n16 nacre framework proteome creates a protein gel matrix that organizes and dimensionally limits mineral deposits. This process is highly relevant to the formation of ordered, nanometer-sized nacre tablets in the mollusk shell. [ABSTRACT FROM AUTHOR]

TheJapanese pearl oyster (Pinctada fucata) n16 framework matrix protein is an integral part of the growthand formation of the mollusk shell biomineralization mechanism. Itis a required component of the extracellular matrix with a dual mineralizationrole, as an anchor component to synchronize the assembly of the beta-chitinand N-series, Pif-series protein extracellular matrix for aragoniteformation and as a regulator of aragonite formation itself. However,the mechanism by which this protein controls aragonite formation isnot understood. Here, we investigate the mineralization potentialand kinetics of the 30 AA N-terminal portion of the n16 protein, n16N.This sequence has been demonstrated to form either vaterite or aragonitedepending upon conditions. Using in situ potentiometric titrationmethods, we find that n16N is indeed responsible for the self-assemblycharacteristics found in vivo and in vitro but is not involved withactive Ca2+binding or mineral nucleation processes. Uponthe basis of time- and peptide concentration-dependent sampling ofmineral deposits that form in solution, we find that n16N is responsiblefor controlling where mineralization occurs in bulk solution. Thisprotein sequence acts as a molecular spacer that organizes the mineralizationspace and promotes the formation of mineral constituents that containACC, vaterite, and aragonite. Without the concerted action of then16N assemblage, unregulated calcite formation occurs exclusively.Thus, the n16 protein provides the regulation needed to have the characteristicpolymorph, crystalline orientations, and related mechanical propertiesassociated to the microstructure of mollusk shells. [ABSTRACT FROM AUTHOR]

Abstract: 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 Ca2+ ion recruitment and organization to allow for proper growth and development of the mineralized larval sea urchin spicule. [Copyright &y& Elsevier]

The interaction between poly(L-glutamic acid) (PLE) and calcite crystals was studied with AFM-based single molecule force spectroscopy. Block copolymers of poly(ethylene oxide) (PEO) and PLE were synthesized and covalently attached to the tip of an AFM cantilever. In desorption measurements the molecules were allowed to adsorb on the calcite crystal faces and afterward successively desorbed. The corresponding desorption forces were detected with high precision, showing for example a force transition between the two blocks. Because of its importance in the crystallization process in biominerals, the PLE-calcite interaction was investigated as a function of the pH as well as the calcium concentration of the aqueous solution. The sensitivity of the technique was underlined by resolving different interaction forces for calcite (104) and calcite (100). [ABSTRACT FROM AUTHOR]