Figure 4.

Implication of octacalcium phosphate (OCP) in the non-apatitic environments of bone mineral. (A) Two-dimensional (2D) {¹H}³¹P Heteronuclear Correlation (HetCor) magic angle spinning (MAS) solid-state Nuclear Magnetic Resonance (ssNMR) spectrum of a fresh 2-year-old sheep bone tissue sample (contact time, t_CP = 1000 µs). Signal intensity increases from blue to red. (B) One-dimensional (1D) individual ³¹P NMR signal of the H₂O and HPO₄²⁻-containing non-apatitic environments attributed to the amorphous surface layer that coats bone mineral particles (blue line); and 1D individual ³¹P NMR signal of the OH⁻-containing apatitic environments that compose the internal crystalline core of bone mineral particles (orange line). These individual ³¹P NMR signals were generated from the 2D {¹H}³¹P HetCor ssNMR spectrum shown in (A). To do so, the F2 slices taken at the bound water molecules position [from δ(¹H) = 3 to 7 ppm, blue area] and hydroxyl ions position [from δ(¹H) = −2 to 2 ppm, orange area] in F1 have been summed. (C) 1D ³¹P CP MAS ssNMR spectrum (t_CP = 1000 µs) of a synthetic octacalcium phosphate (OCP) sample. P1 to P6 correspond to the six different phosphate groups present in the OCP crystal lattice according to the work of Davies et al.⁶⁰. The red dashed-line marks the most intense resonance in the signal of OCP which is not detected in bone mineral (B).