title: 1H NMR investigations of the molecular nature of low-molecular-mass calcium ions in biofluids.
abstract: High-resolution 1H NMR spectroscopy was employed to explore the complexation of Ca2+ by low-molecular-mass biomolecules in human saliva. The results acquired revealed that the organic acid anion (OAA) citrate acts as a powerful oxygen-donor chelator for salivary Ca2+, and accurate determination of its resonances' frequencies and spin-system pattern could be successfully utilized to determine its degree of saturation with this metal ion. Computer modelling studies demonstrated that the OAA lactate is the only competing salivary Ca2+ complexant available. Moreover, the Ca2+-complexation status of salivary citrate is substantially modified by dentifrice-mediated elevations in its concentration. 1H NMR analysis was also applied to determinations of the Ca2+ saturation status of citrate in a variety of alternative biofluids and the biochemical significance of these results is discussed.
authors.affiliation: Medical Unit, St Bartholomew's and the Royal London School of Medicine and Dentistry, Alexandra Wing, Royal London Hospital, London E1 1BB, UK.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Silwood
authors.forename: Martin
authors.initials: M
authors.lastname: Grootveld
authors.forename: Edward
authors.initials: E
authors.lastname: Lynch
mesh_terms: D000653:Amniotic Fluid / Q000737:chemistry; D000818:Animals; D000838:Anions / Q000737:chemistry; D001826:Body Fluids / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D019355:Calcium Citrate / Q000032:analysis* / Q000097:blood / Q000134:cerebrospinal fluid / Q000652:urine; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D051381:Rats; D012463:Saliva / Q000737:chemistry; D013582:Synovial Fluid / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D000838:Anions; D019355:Calcium Citrate; D002118:Calcium