Solid state NMR (ssNMR) can characterize mineral (31P) and organic (13C) components of
human salivary stones (n = 8). All show apatitic 31P spectra. 13C ssNMR indicates more
protein, of more consistent composition, than apatitic uroliths, with signals from Tyr, Phe and
His prominent. Citrate and lipid, identified by dipolar dephasing (DD), and polysaccharides
are also observable in varying amounts. 13C{31P} rotational echo double resonance (13C{31P}
REDOR) identifies carbon atoms in close (< ca. 0.5 nm) proximity to phosphorus and
therefore probably binding with mineral. Citrate, sugar and carboxylate signals undergo
strong 13C{31P} REDOR, also seen to signals between 50 and 60 ppm, from protein α-
carbons and, possibly, phosphoserines and phospholipids, and sometimes to a 35 – 40 ppm
envelope containing Asp-Cβ and Glu-Cγ signals. Amino acid analysis indicates high proline
and aromatic content. 13C ssNMR and amino acid composition is consistent with
preponderance of proline-rich salivary proteins such as statherin.The U.K. EPSRC (Y. L.) and MRC (D. G. R.) for fundingThis is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.crci.2015.07.00
