The aqueous calcium carbonate system is rigorously investigated with respect to ionic activity. Ideal treatment is found to be a good approximation at relevant concentrations. The data further show that bound CaCO3 species cannot be regarded as "inactive" during nucleation but rather appear to play a key role in the phase-separation process, and that amorphous calcium carbonate (ACC) can be precipitated from much lower levels of supersaturation than previously believed.

Abstract. Proteins have found their way into many of Nature's structures due to their structural stability, diversity in function and composition, and ability to be regulated as well as be regulators themselves. In this study, we investigate the constitutive amino acids that make up some of these proteins which are involved in CaCO 3 mineralization -either in nucleation, crystal growth, or inhibition processes. By assaying all 20 amino acids with vapor diffusion and in situ potentiometric titration, we have found specific amino acids having multiple effects on the early stages of CaCO 3 crystallization. These same amino acids have been independently implicated as constituents in liquid-like precursors that form mineralized tissues, processes believed to be key effects of biomineralization proteins in several biological model systems.

Controlled aggregation of polymer-stabilized calcium silicate hydrate nanoparticles leads to elastic cementitious materials.

Phage display experiments on industrially important calcium silicate hydrates (C-S-H), the main hydration product of ordinary Portland cement, suggest fundamentally different specific binding motifs compared to hitherto existing commercial cement additives. According to that, a strong and specific adsorbing additive on C-S-H should have three features which are a negative charge, H-bond formers (especially amide functions) and a hydrophobic part.

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.

The Japanese pearl oyster (Pinctada fucata) n16 framework matrix protein is an integral part of the growth and formation of the mollusk shell biomineralization mechanism. It is a required component of the extracellular matrix with a dual mineralization role, as an anchor component to synchronize the assembly of the beta-chitin and N-series, Pif-series protein extracellular matrix for aragonite formation and as a regulator of aragonite formation itself. However, the mechanism by which this protein controls aragonite formation is not understood. Here, we investigate the mineralization potential and kinetics of the 30 AA N-terminal portion of the n16 protein, n16N. This sequence has been demonstrated to form either vaterite or aragonite depending upon conditions. Using in situ potentiometric titration methods, we find that n16N is indeed responsible for the self-assembly characteristics found in vivo and in vitro but is not involved with active Ca2+ binding or mineral nucleation processes. Upon the basis of time- and peptide concentration-dependent sampling of mineral deposits that form in solution, we find that n16N is responsible for controlling where mineralization occurs in bulk solution. This protein sequence acts as a molecular spacer that organizes the mineralization space and promotes the formation of mineral constituents that contain ACC, vaterite, and aragonite. Without the concerted action of the n16N assemblage, unregulated calcite formation occurs exclusively. Thus, the n16 protein provides the regulation needed to have the characteristic polymorph, crystalline orientations, and related mechanical properties associated to the microstructure of mollusk shells.

Giant polymer vesicles made by electroformation have been shown to encapsulate salts up to concentrations of about 10 mM. The impermeability of these "polymersomes" to calcium ions is demonstrated by the use of fluorescent probes dedicated to calcium analysis. Permeability to calcium ions can be triggered by the addition of calcimycin, an ionophore molecule that is able to transport cations selectively through the membrane. As a result, we show that the mineralization of calcium carbonate can be induced within the polymersomes, which were previously loaded with carbonate ions. This is a further step toward the use of polymersomes as microreactors and the study of mineralization schemes, including biomimetic ones, in confined environments.

Durch Zugabe zweier verschiedener Additive wurden die im Titel bezeichneten Strukturen erhalten. Ein Bildungsmechanismus basierend auf nichtklassischer partikelvermittelter Kristallisation wird vorgeschlagen, der die individuellen und kooperativen Effekte des Polymers Poly(natrium‐4‐styrolsulfonat) mit der niedermolekularen Substanz Folsäure auf die Bildung von Heterostrukturen während verschiedener Reaktionsstufen demonstriert.