Calcium Phosphate Prenucleation Complexes in Water by Means of ab Initio Molecular Dynamics Simulations

Abstract

The nucleation of calcium phosphates, the main inorganic component of bone and tooth tissues, is thought to proceed by aggregation of prenucleation clusters recently identified as calcium triphosphate complexes. We have performed ab initio molecular dynamics simulations to elucidate their structures and stabilities in aqueous solution. We find the calcium to be seven-coordinated by two water molecules, two bidentate phosphates, and one monodentate phosphate. Free energy results obtained using umbrella sampling simulations show that the complex with a Ca/P ratio of 1:3 is the most energetically favored and more thermodynamically stable than the free ions.

Detection of Posner's clusters during calcium phosphate nucleation: a molecular dynamics study

“…The structure of a single Posner's cluster in 101 water molecules was also investigated using ab initio MD simulations using the computational details adopted in our previous study of calcium phosphate prenucleation complexes. 27 The Ca c -Ca, Ca c -O, Ca c -P, P-P, P-O and O-O pair distribution functions (where Ca c is the central calcium of the Posner's cluster) obtained from classical and ab initio methods compare very well (see Fig. S6 and Table S6 in ESI †) and justify the use of the force field employed in this study.…”

Nanocrystalline apatites: The fundamental role of water

“…2d). Some recent papers have introduced the concept of prenucleation clusters involving Ca 2+ and HPO 4 2ions (Mancardi et al 2016;Habraken et al 2013) forming before nucleation. Although experimental evidence for such clusters is difficult to obtain, there is at least a consensus on the strong involvement of protonated phosphate ions at the early stages of apatite nanocrystal formation.…”

Molecular Dynamics Simulations of Hydroxyapatite Nanopores in Contact with Electrolyte Solutions: The Effect of Nanoconfinement and Solvated Ions on the Surface Reactivity and the Structural, Dynamical, and Vibrational Properties of Water

“…Previous computational investigations of HAP focused on its bulk and surface properties [31][32][33] as well as on the early stages of homogeneous nucleation from solution [34,35], but the collective effect of nanoconfinement and solution chemistry on the molecular-level processes controlling the surface reactivity of HAP has been entirely overlooked by molecular modelling. This aspect is particularly relevant to further our understanding of bone formation, which begins with the growth of ultrathin HAP platelets within confined volumes in the collagen fibrils [36,37] and in aqueous environments that are far from pure water but rich in ions.…”