Using solubility (residual concentration) and pH measurements, the CaCl2-(N
H4)(2)HPO4-HN(CH2)(3)CHCOOH-NH3-H2O system is studied at 25 degreesC. The f
ormation of proline-containing hydroxyapatite Ca-10(PO4)(6)(OH)(2-x) (HN(CH
2)(3)CHCOO)(x) (x = 0.2) is established by chemical, X-ray diffraction, and
IR spectroscopic analyses of the precipitate. The compound is a product of
partial substitution of proline anions HN(CH3)(2)CHCOO- for surface OH- gr
oups located in Ca channels of the hydroxyapatite lattice.