title: Mineralisation of soft and hard tissues and the stability of biofluids.
abstract: Evidence is provided from studies on natural and artificial biofluids that the sequestration of amorphous calcium phosphate by peptides or proteins to form nanocluster complexes is of general importance in the control of physiological calcification. A naturally occurring mixture of osteopontin peptides was shown, by light and neutron scattering, to form calcium phosphate nanoclusters with a core-shell structure. In blood serum and stimulated saliva, an invariant calcium phosphate ion activity product was found which corresponds closely in form and magnitude to the ion activity product observed in solutions of these osteopontin nanoclusters. This suggests that types of nanocluster complexes are present in these biofluids as well as in milk. Precipitation of amorphous calcium phosphate from artificial blood serum, urine and saliva was determined as a function of pH and the concentration of osteopontin or casein phosphopeptides. The position of the boundary between stability and precipitation was found to agree quantitatively with the theory of nanocluster formation. Artificial biofluids were prepared that closely matched their natural counterparts in calcium and phosphate concentrations, pH, saturation, ionic strength and osmolality. Such fluids, stabilised by a low concentration of sequestering phosphopeptides, were found to be highly stable and may have a number of beneficial applications in medicine.
authors: Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow G12 8QQ, UK. Electronic address: carl.holt@glasgow.ac.uk.
authors: Carl
authors: C
authors: Holt
authors: EPSAM, Keele University, Staffordshire ST5 5BG, UK; Institut Laue-Langevin, 6 Rue Jules Horowitz, 38042 Grenoble, France. Electronic address: lenton@ill.fr.
authors: Samuel
authors: S
authors: Lenton
authors: Department of Chemistry, Division of Physical Chemistry, Lund University, P.O. Box 124, S-221 00 Lund, Sweden. Electronic address: tommy.nylander@fkem1.lu.se.
authors: Tommy
authors: T
authors: Nylander
authors: Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark. Electronic address: ess@mb.au.dk.
authors: Esben S
authors: ES
authors: Sørensen
authors: EPSAM, Keele University, Staffordshire ST5 5BG, UK; Institut Laue-Langevin, 6 Rue Jules Horowitz, 38042 Grenoble, France. Electronic address: teixeira@ill.fr.
authors: Susana C M
authors: SC
authors: Teixeira
mesh_terms: D001826:Body Fluids / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D006801:Humans; D053495:Osteopontin / Q000737:chemistry; D010455:Peptides / Q000737:chemistry
chemical_list: D002130:Calcium Phosphates; D010455:Peptides; C519480:amorphous calcium phosphate; D053495:Osteopontin; C020243:calcium phosphate
keywords: Biocalcification; Blood serum; Milk; Osteopontin; Saliva; Urine