Physicochemical properties of artificial proteins that accelerate nucleation of crystalline calcium phosphate

We have created 18 artificial proteins by embedding two calcification motifs found in a protein involved in bone and dentin formation. The relationship between the physicochemical properties of the proteins and their in vitro mineralization activities was investigated. Two slightly acidic proteins nucleated octacalcium phosphate (OCP) at a low protein concentration from a solution where precipitation did not occur without the proteins. Among 16 basic proteins, only one protein nucleated OCP at the same protein concentration. At a higher protein concentration, four proteins self-assembled to become large aggregates, and these four proteins nucleated OCP. Among 14 proteins without the self-assembling property, only five proteins nucleated OCP. None of the proteins formed α-helix or ß-sheet structures. These results suggest that the proteins that had the self-assembling property appeared to exhibit nucleation activity with high frequency and that the formation of the ordered backbone conformation was not required for proteins to promote nucleation.