| 0882 Effect of Recombinant Amelogenins on Hydroxyapatite Crystal Growth in vitro | ||
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E. BENIASH1, J.P. SIMMER2, and H.C. MARGOLIS1, 1Forsyth Institute, Boston, MA, USA, 2University of Michigan, Ann Arbor, USA Recent studies suggest that the regulation of enamel mineral formation and organization involves protein self-assembly and specific protein-mineral interactions. Objective: This study was undertaken to examine the influence of the major enamel matrix protein, amelogenin, on the regulation of crystal shape and orientation. Methods: Recombinant mouse amelogenin, rM179, and a primary degradation product that lacks a hydrophilic C-terminus, rM166, were dissolved in water at concentrations of 1 mg/ml. The pH of each protein solution was adjusted to 4 and then stored for 48 hours at 4oC. CaCl2 and (NH4)2HPO4 were then added to these solutions to give final concentrations of 2.5 and 1.5 mM, respectively. Control samples contained no protein. The samples were then adjusted to pH 8 (with KOH) and stored at 37oC for 24 hours. The resulting precipitates were studied using TEM in the bright field and diffraction modes (ED). Results: Based on ED data, all experiments resulted in HA (or OCP) crystal formation. The crystals grown in the presence of rM179 were ribbon-like, with their c-axes co-aligned with the long axes of the crystals. The crystals were organized into bundles, with their c-axes co-aligned. In contrast, rM166 did not have a pronounced effect on crystal growth morphology or organization. The crystals were plate-shaped and ED analysis showed that the crystals in aggregates were very poorly aligned and similar to those produced in the control. In the control the first precipitate formed was a metastable amorphous calcium phosphate that transformed into poorly crystalline hydroxyapatite (HA) in about one hour. Conclusions: Our data demonstrate that the full-length amelogenin affects both the shape of the crystals and organization of crystalline aggregates. This was not observed with rM166, suggesting that the hydrophilic C-terminus has a significant affect on the regulation of crystal growth and organization. Supported by NIDCR grant DE-13237.
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| Seq #100 - Enamel and Dentin: Surface Properties and Crystal Formation I 10:15 AM-11:30 AM, Thursday, 11 March 2004 Hawaii Convention Center Exhibit Hall 1-2 | ||
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