Strongly bound citrate stabilizes the apatite nanocrystals in bone

TitleStrongly bound citrate stabilizes the apatite nanocrystals in bone
Publication TypeJournal Article
Year of Publication2010
AuthorsHu YY, Rawal A, Schmidt-Rohr K
Journal TitleProceedings of the National Academy of Sciences of the United States of America
Date Published12/28
ISBN Number0027-8424
Accession NumberISI:000285684200018
Keywordsbiomolecules, bone composition, calcium-carbonate, citric-acid, composites, dynamics, hydroxyapatite, mineral interface, nanocomposite, nanocrystal stabilization, organic-inorganic interface, precipitation, solid-state nmr, spectroscopy

Nanocrystals of apatitic calcium phosphate impart the organic-inorganic nanocomposite in bone with favorable mechanical properties. So far, the factors preventing crystal growth beyond the favorable thickness of ca. 3 nm have not been identified. Here we show that the apatite surfaces are studded with strongly bound citrate molecules, whose signals have been identified unambiguously by multinuclear magnetic resonance (NMR) analysis. NMR reveals that bound citrate accounts for 5.5 wt% of the organic matter in bone and covers apatite at a density of about 1 molecule per (2 nm)(2), with its three carboxylate groups at distances of 0.3 to 0.45 nm from the apatite surface. Bound citrate is highly conserved, being found in fish, avian, and mammalian bone, which indicates its critical role in interfering with crystal thickening and stabilizing the apatite nanocrystals in bone.

URL<Go to ISI>://000285684200018
Alternate JournalP Natl Acad Sci USA