Bone mineral: evidence for hydroxy groups by inelastic neutron scattering

Abstract

Inelastic neutron scattering (INS) spectroscopy which is especially sensitive to vibrations of groups with hydrogen has been used to resolve the extent of substitutions at the hydroxy group site in bone. Bone is a complex material consisting of a mineral apatite (Ca₅(PO₄)₃ OH), in an extracellular protein matrix. Many aspects concerning the composition of the mineral are controversial. It has been suggested that there is complete substitution by carbonate at the hydroxy site. Bands assigned to hydroxy vibrations are often not resolved in the infrared and Raman spectra. We show, by INS, that in ox femur bone 40–50% of the hydroxy groups are not substituted. The inelastic neutron scattering experiment opens up new opportunities to monitor changes in bone composition which are important in bone ageing and some pathological conditions.