Molecular Dynamics Simulation Of The Early Nucleation Of Calcium Phosphate Crystals In Solution

Molecular dynamics is a kind of computer simulation technology for molecular system, which is widely recognized with a high degree of accuracy. Biomimetic mineralization is to mimic the process of compounding inorganic biological minerals in the body physiological environment. The calcium phosphate crystal biomimetic mineralization has caused a great interest in study, which widely exists in bone, teeth, and other parts of the body.This study mainly uses the molecular dynamics simulation technology, with the help of simulation software NAMD and the visualization software VMD. From the molecular-ion-atom level, this article explores the interaction between particles in solution specific physical and chemical conditions, such as Na+, Ca2+, HPO42-, PO43-, OH-, citrate and water molecules. Particle clusters’ composition, shape, size and structure, which forms in solution, are characterized in several methods, such as, the simulated trajectory, statistics, radial atomic particle type and distance of distribution function, the average radius of cyclotron, root mean square deviation. Thereby the physical adsorption and chemical reaction process among particles at the early stage of calcium phosphate type of crystal nucleation in the solution are studied in detail.The results indicated that three HPO42- ion and Ca2+ would form an aggregate similar to that of hydroxyapatite crystals in parallel to the axis c of the isosceles triangle structure. The aggregate is very stable, and it mostly can’t influenced by the citrate and other highly negatively charged groups. Thus this makes it possible that the aggregate can remain in the aggregate until the crystal nucleus formation and crystal grown up. Secondly, six HPO42-(or PO43-) ions and Ca2+, can get a relatively stable clusters, and it has a similar size and dimension to the Posner model. Moreover, in the stable clusters there is a special loop quadrilateral structure. Finally, in the process of HPO42- and PO43- combined with Ca2+ forming an aggregate, it forms a short chain structure first, then the fore and aft clasped a circular planar structure, finally a three-dimensional structure forms through continuously turning.