Amelogenin Nanospheres Supra-Molecular Assembly and the Preferential Orientation of Apatite Crystals
J. Moradian-Oldak, C. Du and G. Falini
University of Southern California, US
tooth enamel, amelogenin nanospheres, biomineralization, assembly
Amelogenin self-assembly into nanospheres has been recognized as a key factor in controlling the oriented and elongated growth of carbonated apatite crystals during tooth enamel formation. We investigated the process of amelogenin self-assembly into higher order structures in vitro. Amelogenins form the typical nanospheres with the hydrodynamic radii (RH) of 10-25 nm under a wide variety of solution conditions. The sub-units of nanosphere with 4~8 nm in diameter were detected in the diluted protein solutions by dynamic light scattering and directly revealed by transmission and atomic force microscopy. Micro-ribbon structures of rP172 were obtained upon slow solvent evaporation. Nanosphere-chains of >100nm in length were formed and assembled into the birefringent micro-ribbons (~100X10X3 microns). The x-ray diffraction pattern (European Synchrotron Radiation Facility, Grenoble) of the micro-ribbon was suggestive of a unique conformation and secondary structure of folded amelogenins. The immersion of the micro-ribbons in the calcium phosphate solution resulted in the formation of remarkably ordered apatite crystals oriented with their c-axes parallel to the long ribbon axes. The intrinsic property of the full-length amelogenin to self-assemble into ordered supramolecular structures gives us a valuable clue to its function as a scaffold in facilitating the oriented growth of apatite crystals.
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Nanotech 2005 Conference Program Abstract