Evidence of hydroxyl-ion deficiency in bone apatites: An inelastic neutron-scattering study

The novelty of very large neutron-scattering intensity from the nuclear-spi n incoherence in hydrogen has permitted the determination of atomic motion of hydrogen in synthetic hydroxyapatite and in deproteinated isolated apati te crystals of bovine and rat hone without the interference of vibrational modes from other structural units. From an inelastic neutron-scattering exp eriment, we found no sharp excitations characteristic of the vibrational mo de and stretch vibrations of OH ions around 80 and 450 meV (645 and 3630 cm (-1)), respectively, in the isolated, deproteinated crystals of bone apatit es; such salient features were clearly seen in micron- and nanometer-size c rystals of pure hydroxyapatite powders. Thus, the data provide additional d efinitive evidence for the lark of OH- ions in the crystals of hone apatite . Weak features at 160-180 and 376 meV, which are clearly observed in the a patite crystals of rat bone and possibly in adult mature bovine bone, but t o a much lesser degree, but not in the synthetic hydroxyapatite, are assign ed to the deformation and stretch modes of OH ions belonging to HPO4-like s pecies. (Bone 26:599-602; 2000) (C) 2000 by Elsevier Science Inc. All right s reserved.