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Probing the calcium and sodium local environment in bones and teeth using multinuclear solid state NMR and X-ray absorption spectroscopy

Laurencin, Danielle and Wong, Alan and Chrzanowski, Wojciech and Knowles, Jonathan C. and Qiu, Dong and Pickup, David M. and Newport, Robert J. and Gan, Zhehong and Duer, Melinda J. and Smith, Mark E. (2010) Probing the calcium and sodium local environment in bones and teeth using multinuclear solid state NMR and X-ray absorption spectroscopy. Physical chemistry chemical physics, 12 (5). pp. 1081-1091. ISSN 1463-9076

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Abstract

Despite the numerous studies of bone mineral, there are still many questions regarding the exact structure and composition of the mineral phase, and how the mineral crystals become organised with respect to each other and the collagen matrix. Bone mineral is commonly formulated as hydroxyapatite, albeit with numerous substitutions, and has previously been studied by P-31 and H-1 NMR, which has given considerable insight into the complexity of the mineral structure. However, to date, there has been no report of an NMR investigation of the other major component of bone mineral, calcium, nor of common minority cations like sodium. Here, direct analysis of the local environment of calcium in two biological apatites, equine bone (HB) and bovine tooth (CT), was carried out using both Ca-43 solid state NMR and Ca K-edge X-ray absorption spectroscopy, revealing important structural information about the calcium coordination shell. The Ca-43 delta(iso) in HB and CT is found to correlate with the average Ca-O bond distance measured by Ca K-edge EXAFS, and the Ca-43 NMR linewidths show that there is a greater distribution in chemical bonding around calcium in HB and CT, compared to synthetic apatites. In the case of sodium, Na-23 MAS NMR, high resolution 3Q-MAS NMR, as well as Na-23P-31 REDOR and H-1Na-23 R-3-HMQC correlation experiments give the first direct evidence that some sodium is located inside the apatite phase in HB and CT, but with a greater distribution of environments compared to a synthetic sodium substituted apatite (Na-HA).

Item Type: Article
Journal or Publication Title: Physical chemistry chemical physics
Subjects: UNSPECIFIED
Departments: VC's Office
ID Code: 52909
Deposited By: ep_importer_pure
Deposited On: 28 Feb 2012 10:40
Refereed?: Yes
Published?: Published
Last Modified: 09 Apr 2014 23:11
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/52909

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