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Garcia N, Malini RI, Freeman CL, Demichelis R, Raiteri P, Sommerdijk NAJM, Harding JH, Gale JD. Simulation of Calcium Phosphate Prenucleation Clusters in Aqueous Solution: Association beyond Ion Pairing. CRYSTAL GROWTH & DESIGN 2019; 19:6422-6430. [PMID: 32063806 PMCID: PMC7011744 DOI: 10.1021/acs.cgd.9b00889] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 09/01/2019] [Indexed: 05/12/2023]
Abstract
Classical molecular dynamics simulations and free energy methods have been used to obtain a better understanding of the molecular processes occurring prior to the first nucleation event for calcium phosphate biominerals. The association constants for the formation of negatively charged complexes containing calcium and phosphate ions in aqueous solution have been computed, and these results suggest that the previously proposed calcium phosphate building unit, [Ca(HPO4)3]4-, should only be present in small amounts under normal experimental conditions. However, the presence of an activation barrier for the removal of an HPO4 2- ion from this complex indicates that this species could be kinetically trapped. Aggregation pathways involving CaHPO4, [Ca(HPO4)2]2-, and [Ca(HPO4)3]4- complexes have been explored with the finding that dimerization is favorable up to a Ca/HPO4 ratio of 1:2.
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Affiliation(s)
- Natalya
A. Garcia
- Curtin
Institute for Computation, The Institute for Geoscience Research (TIGeR),
and School of Molecular and Life Sciences, Curtin University, P.O. Box U1987, Perth, Western Australia 6845, Australia
| | - Riccardo Innocenti Malini
- Department
of Materials Science and Engineering, University
of Sheffield, Sheffield, S1 3JD, United Kingdom
- Laboratory
for Protection and Physiology, Empa, Swiss
Federal Laboratories for Materials Science and Technology, St. Gallen, Switzerland
| | - Colin L. Freeman
- Department
of Materials Science and Engineering, University
of Sheffield, Sheffield, S1 3JD, United Kingdom
| | - Raffaella Demichelis
- Curtin
Institute for Computation, The Institute for Geoscience Research (TIGeR),
and School of Molecular and Life Sciences, Curtin University, P.O. Box U1987, Perth, Western Australia 6845, Australia
| | - Paolo Raiteri
- Curtin
Institute for Computation, The Institute for Geoscience Research (TIGeR),
and School of Molecular and Life Sciences, Curtin University, P.O. Box U1987, Perth, Western Australia 6845, Australia
| | - Nico A. J. M. Sommerdijk
- Department
of Chemical Engineering and Chemistry, Technische
Universiteit Eindhoven, P.O. Box 513, Eindhoven, Netherlands
| | - John H. Harding
- Department
of Materials Science and Engineering, University
of Sheffield, Sheffield, S1 3JD, United Kingdom
| | - Julian D. Gale
- Curtin
Institute for Computation, The Institute for Geoscience Research (TIGeR),
and School of Molecular and Life Sciences, Curtin University, P.O. Box U1987, Perth, Western Australia 6845, Australia
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Lin TJ, Chiu CC. Structures and infrared spectra of calcium phosphate clusters by ab initio methods with implicit solvation models. Phys Chem Chem Phys 2018; 20:345-356. [PMID: 29210384 DOI: 10.1039/c7cp05975b] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Since the first detection of pre-nucleation clusters during the formation of calcium phosphate minerals, determining such clusters' compositions and structures has become crucial for understanding the early-stage nucleation of these minerals in solutions. In previous experimental studies, the composition and sizes of pre-nucleation clusters have been calculated, but their structural information has been difficult to determine because they are very small (<1 nm). In this study, we examined the structures and infrared spectra of small- and medium-sized calcium phosphate clusters using ab initio calculations combined with implicit solvation models. Adding solvent effects increased the possibility of the existence of alternative configurations of calcium phosphate clusters other than their compact configurations. The calcium atoms had a tendency to be located outside of the clusters to coordinate with water molecules in the aqueous environment. The computed infrared spectra of extended small calcium phosphate clusters captured some of the features measured in the in situ infrared spectra, which supports the network structures proposed by large-scale molecular dynamics studies and X-ray adsorption near-edge spectra. The relative stabilities of medium-sized Ca9(PO4)6 clusters with respect to the stability of Posner's cluster in water were also reviewed. We found that in water, alternative structures with low symmetry or large dipole moments had lower energies than Posner's cluster.
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Affiliation(s)
- Tzu-Jen Lin
- Department of Chemical Engineering, Chung Yuan Christian University, 200 Chung Pei Road, Chung Li District, Taoyuan City, 32023, Taiwan.
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