Effect of Osteopontin and Related Peptides on Hydroxyapatite Crystallization Studied by Dynamic Light Scattering
Date of Award
Master of Science
Dr. John de Bruyn
We investigate the use of dynamic light scattering for quantitatively as sessing the effectiveness of certain bone-related proteins on the formation of hydroxyapatite crystals. Hydroxyapatite, Caio(P04)6(OH)2, is the major min eral component of virtually all calcified tissue within the body. It is also present in numerous pathological calcifications including kidney stones and arterial plaque. There are a number of established assays for studying the potencies of proteins that modulate mineral formation, but they generally provide limited and often only qualitative information. We use dynamic light scattering to measure the size and growth rate of crystals precipitating from a solution of calcium and phosphate ions in the presence of various proteins. The mineral-modulating effects of bone-derived osteopontin, recombinant os- teopontin, synthetic poly-aspartic acid, and a 16-residue peptide derived from osteopontin (residues # 65-80, called pOPAR) are studied. Prom the intensity and the decay rate of the intensity autocorrelation function of the scattered light, we find that native osteopontin completely inhibits the nucléation of mineral crystals over the two-hour duration of the measurements. Poly aspar tic acid and pOPAR are also effective inhibitors, though higher concentrations of these peptides are required to completely inhibit precipitation than for na tive osteopontin. In contrast, recombinant osteopontin does not affect crystal nucléation, but appears to effectively inhibit crystal growth. These results demonstrate the utility of dynamic light scattering in the assessment of the effects of proteins and peptides on mineral formation in real time.
Dauphinee, Ron, "Effect of Osteopontin and Related Peptides on Hydroxyapatite Crystallization Studied by Dynamic Light Scattering" (2009). Digitized Theses. 3936.