Microscopic Evidence for Liquid-Liquid Separation in Supersaturated CaCO
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Wallace, Adam F.; Hedges, Lester O.; Fernández-Martı́nez, Alejandro; Raiteri, Paolo; Gale, Julian D.; Waychunas, Glenn A.; Whitelam, Stephen; Banfield, Jillian F.; Yoreo, James J. De

doi:10.1126/science.1230915

Cited by 474 publications

(593 citation statements)

References 61 publications

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“…Such structures were observed in recent computational studies on the nucleation of CaCO 3 from solution. 12 Our results show that the tendency to form expanded polymeric clusters is dependent on solubility. The solubility of CaCO 3 is pH dependent, but equilibrium Ca 2+ concentrations are on the order of 10 mM under most relevant conditions.…”

Section: A Insights Into the Behavior Of Real Systemsmentioning

confidence: 70%

“…8 Many phases also appear to precipitate by twostep processes, whereby liquid-like droplets form first and crystals subsequently form within these droplets. [9][10][11][12] Finally, the structural properties of very small clusters have been called into question, with several studies suggesting that the smallest clusters may be polymeric or liquid-like in structure, rather than being compact crystal-like objects. 12,13 Taken together, these behaviors suggest that the energy landscape for cluster formation can be significantly more complex than imagined in the early formulations of CNT, especially when clusters are very small.…”

Section: Introductionmentioning

confidence: 99%

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The energetics of prenucleation clusters in lattice solutions

Legg

Yoreo

2016

The Journal of Chemical Physics

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According to classical nucleation theory, nucleation from solution involves the formation of small atomic clusters. Most formulations of classical nucleation use continuum "droplet" approximations to describe the properties of these clusters. However, the discrete atomic nature of very small clusters may cause deviations from these approximations. Here, we present a self-consistent framework for describing the nature of these deviations. We use our framework to investigate the formation of "polycube" atomic clusters on a cubic lattice, for which we have used combinatoric data to calculate the thermodynamic properties of clusters with 17 atoms or less. We show that the classical continuum droplet model emerges as a natural approach to describe the free energy of small clusters, but with a size-dependent surface tension. However, this formulation only arises if an appropriate "site-normalized" definition is adopted for the free energy of formation. These results are independently confirmed through the use of Monte Carlo calculations. Our results show that clusters formed from sparingly soluble materials (µM solubility range) tend to adopt compact configurations that minimize the solvent-solute interaction energy. As a consequence, there are distinct minima in the cluster-size-energy landscape that correspond to especially compact configurations. Conversely, highly soluble materials (1M) form clusters with expanded configurations that maximize configurational entropy. The effective surface tension of these clusters tends to smoothly and systematically decrease as the cluster size increases. However, materials with intermediate solubility (1 mM) are found to have a balanced behavior, with cluster energies that follow the classical "droplet" scaling laws remarkably well. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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Section: A Insights Into the Behavior Of Real Systemsmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

The energetics of prenucleation clusters in lattice solutions

Legg

Yoreo

2016

The Journal of Chemical Physics

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“…4). Consequently, despite the recent reports of prenucleation clusters (41)(42)(43), liquid-liquid separation (44)(45)(46), and multiphase aggregationbased pathways of calcite formation (41,42,47) in bulk solutions, the results presented here provide strong evidence that the classical theory of nucleation provides a good description of calcite formation on ionized surfaces and that interfacial energy is a useful concept even when critical nuclei are in the nanometer range. Calculations of γ assume rhombohedral nuclei.…”

Section: Significancementioning

confidence: 79%

Reconciling disparate views of template-directed nucleation through measurement of calcite nucleation kinetics and binding energies

Hamm

Giuffre

Han

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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173

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The physical basis for how macromolecules regulate the onset of mineral formation in calcifying tissues is not well established. A popular conceptual model assumes the organic matrix provides a stereochemical match during cooperative organization of solute ions. In contrast, another uses simple binding assays to identify good promoters of nucleation. Here, we reconcile these two views and provide a mechanistic explanation for template-directed nucleation by correlating heterogeneous nucleation barriers with crystal-substrate-binding free energies. We first measure the kinetics of calcite nucleation onto model substrates that present different functional group chemistries (carboxyl, thiol, phosphate, and hydroxyl) and conformations (C11 and C16 chain lengths). We find rates are substrate-specific and obey predictions of classical nucleation theory at supersaturations that extend above the solubility of amorphous calcium carbonate. Analysis of the kinetic data shows the thermodynamic barrier to nucleation is reduced by minimizing the interfacial free energy of the system, γ. We then use dynamic force spectroscopy to independently measure calcitesubstrate-binding free energies, ΔG b . Moreover, we show that within the classical theory of nucleation, γ and ΔG b should be linearly related. The results bear out this prediction and demonstrate that low-energy barriers to nucleation correlate with strong crystal-substrate binding. This relationship is general to all functional group chemistries and conformations. These findings provide a physical model that reconciles the long-standing concept of templated nucleation through stereochemical matching with the conventional wisdom that good binders are good nucleators. The alternative perspectives become internally consistent when viewed through the lens of crystal-substrate binding.B iological systems are unique in their ability to organize minerals into functional materials with complex patterns and architectures. A substantial body of evidence suggests specialized macromolecules, particularly proteins (1, 2) and carbohydrates (3, 4), provide preferential sites for nucleation to direct the placement, timing, and orientation of crystals (5), both intra-and extracellular. Within the biomineralization community, the conventional view of biologically directed nucleation is that macromolecular matrices present an interfacial match to the crystal lattice that assists in forming the crystal nucleus. This cooperative view of directed nucleation is rooted in the collective action of multiple residues that guide the organization of ions into a configuration defining the energetic minimum for the system. A series of in vitro observations have reinforced this picture by showing that highly ordered organic monolayers can control the location and orientation of calcite crystals precipitated from solution (6). In this approach, good templates are revealed through a direct functional assay, i.e., nucleation. Over the years, this view of mineralization, both in the context of natural stru...

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“…The classical view of ions forming a nucleus in solution is now combined with, or challenged by, aggregation type models involving cluster formation 2,3 , polymer-induced liquid phases 4 , amorphous precursors 5 and spinodal phase separation 6 . In many cases of calcite formation the amorphous calcium carbonate (ACC) phase is seen before crystallisation.…”

Section: Introductionmentioning

confidence: 99%

How does an amorphous surface influence molecular binding? – ovocleidin-17 and amorphous calcium carbonate

Freeman

Harding

Quigley

et al. 2015

Phys. Chem. Chem. Phys.

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Atomistic molecular dynamics simulations of dehydrated amorphous calcium carbonate interacting with the protein Ovocleidin-17 are presented. These simulations demonstrate that the amorphisation of the calcium carbonate surface removes water structure from the surface. This reduction of structure allows the protein to bind with many residues, unlike on crystalline surfaces where binding is strongest when only a few residues are attached to the surface. Basic residues are observed to dominate the binding interactions. The implications for protein control over crystallisation are discussed.

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Microscopic Evidence for Liquid-Liquid Separation in Supersaturated CaCO ₃ Solutions

Cited by 474 publications

References 61 publications

The energetics of prenucleation clusters in lattice solutions

The energetics of prenucleation clusters in lattice solutions

Reconciling disparate views of template-directed nucleation through measurement of calcite nucleation kinetics and binding energies

How does an amorphous surface influence molecular binding? – ovocleidin-17 and amorphous calcium carbonate

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Microscopic Evidence for Liquid-Liquid Separation in Supersaturated CaCO 3 Solutions

Cited by 474 publications

References 61 publications

The energetics of prenucleation clusters in lattice solutions

The energetics of prenucleation clusters in lattice solutions

Reconciling disparate views of template-directed nucleation through measurement of calcite nucleation kinetics and binding energies

How does an amorphous surface influence molecular binding? – ovocleidin-17 and amorphous calcium carbonate

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Product

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Microscopic Evidence for Liquid-Liquid Separation in Supersaturated CaCO ₃ Solutions