Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Physics

Supervisor

Profs. John R. de Bruyn

2nd Supervisor

Harvey A. Goldberg

Joint Supervisor

Abstract

Biomineralization is the process by which living organisms synthesize minerals. Some bone-related proteins, such as bone sialoprotein (BSP), have been found to enhance biomineralization, while others, including osteopontin (OPN), act as inhibitors of this process. Dynamic light scattering was used to investigate the effect of several native and recombinant proteins and peptides on the formation and growth of hydroxyapatite (HA) crystals from solutions of Ca2+ and PO43- ions. We studied two isoforms of OPN, the OPN-derived peptides P0, P3, OPAR and pOPAR, and recombinant BSP. X-ray diffraction was used to identify the precipitate as HA crystals. Native OPN inhibits the nucleation of HA crystals, while recombinant OPN strongly inhibits their growth. Among the peptides studied, the non-phosphorylated P0 weakly inhibits HA growth, while P3, which has three phosphates, is a potent inhibitor of HA nucleation. OPAR is found to moderately inhibit nucleation, while its phosphorylated isoform pOPAR more strongly inhibits the nucleation of the HA crystals as well as having a small effect on their growth. This work confirms that phosphorylation of OPN is essential to its capability to prevent mineral growth. Our results show that for high enough ion and protein concentrations, rBSP inhibits the nucleation of HA, while there is some evidence that it enhances nucleation at very low protein concentrations.

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