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Milk caseins stabilize calcium and phosphate ions and make them available to the neonate. Tryptic digestion of the caseins yields phosphopeptides from their polar N-terminal regions that contain clusters of phosphorylated seryl residues. These phosphoseryl clusters have been hypothesized to be responsible for the interaction between the caseins and calcium phosphate that lead to the formation of casein micelles. The casein phosphopeptides stabilize calcium and phosphate ions through the formation of complexes. The calcium phosphate in these complexes is biologically available for intestinal absorption and remineralization of subsurface lesions in tooth enamel. We have studied the structure of the complexes formed by the casein phosphopeptides with calcium phosphate using a range of physicochemical techniques including x-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and equilibrium binding analyses. The amorphous nature of the calcium phosphate phase was confirmed by two independent methods: x-ray powder diffraction and selected area diffraction. In solution, the ion activity product of a basic amorphous calcium phosphate phase was the only ion product that was a function of bound phosphate independent of pH, consistent with basic amorphous calcium phosphate being the phase stabilized by the casein phosphopeptides. Detailed investigations of calcium and calcium phosphate binding using a library of synthetic homologues and analogues of the casein phosphopeptides have revealed that although the fully phosphorylated seryl-cluster motif is pivotal for the interaction with calcium and phosphate, other factors are also important. In particular, calcium binding and calcium phosphate stabilization by the peptides was influenced by peptide net charge, length, and sequence. Milk caseins stabilize calcium and phosphate ions and make them available to the neonate. Tryptic digestion of the caseins yields phosphopeptides from their polar N-terminal regions that contain clusters of phosphorylated seryl residues. These phosphoseryl clusters have been hypothesized to be responsible for the interaction between the caseins and calcium phosphate that lead to the formation of casein micelles. The casein phosphopeptides stabilize calcium and phosphate ions through the formation of complexes. The calcium phosphate in these complexes is biologically available for intestinal absorption and remineralization of subsurface lesions in tooth enamel. We have studied the structure of the complexes formed by the casein phosphopeptides with calcium phosphate using a range of physicochemical techniques including x-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and equilibrium binding analyses. The amorphous nature of the calcium phosphate phase was confirmed by two independent methods: x-ray powder diffraction and selected area diffraction. In solution, the ion activity product of a basic amorphous calcium phosphate phase was the only ion product that was a function of bound phosphate independent of pH, consistent with basic amorphous calcium phosphate being the phase stabilized by the casein phosphopeptides. Detailed investigations of calcium and calcium phosphate binding using a library of synthetic homologues and analogues of the casein phosphopeptides have revealed that although the fully phosphorylated seryl-cluster motif is pivotal for the interaction with calcium and phosphate, other factors are also important. In particular, calcium binding and calcium phosphate stabilization by the peptides was influenced by peptide net charge, length, and sequence. Bovine milk contains ∼30 mm calcium and 22 mm inorganic phosphate in solution with most of the calcium (68%) and phosphate (47%) associated with the proteins αS1-, αS2-, β-, and κ-casein in casein micelles (1Walstra P. Jenness R. Dairy Chemistry and Physics. John Wiley 40: 297-313Google Scholar). The αS1-, αS2-, and β-caseins have a number of Ser(P) residues in a specific motif, Ser(P)3-Glu2, that is involved in the interaction with calcium phosphate (3Holt C. Sawyer L. Protein Eng. 1988; 2: 251-259Crossref PubMed Scopus (129) Google Scholar). Many techniques have been used to investigate the ultrastructure of the casein micelles. Although the structural details are still being elucidated, the casein micelles are believed to be roughly spherical particles with a radius of ∼100 nm, dispersed in a continuous phase of water, salt, lactose, and whey proteins (4Schmidt D.G. Dev. Dairy Chem. 1982; 1: 61-86Google Scholar). The calcium phosphate isolated after exhaustive hydrazine deproteination of micelles has been reported to exhibit a fine and uniform granularity under the electron microscope with the particles consisting of small subunits of 2.5-nm diameter (5McGann T.C. Kearney R.D. Buchheim W. Posner A.S. Betts F. Blumenthal N.C. Calcif. Tissue Int. 1983; 35: 821-833Crossref PubMed Scopus (53) Google Scholar, 6McGann T.C. Buchheim W. Kearney R.D. Richardson T. Biochim. Biophys. Acta. 1983; 760: 415-420Crossref PubMed Scopus (56) Google Scholar). The calcium phosphate, present as nanometer-sized ion clusters, and caseins are not covalently bound; hence the casein micelle is known as an association colloid (7de Kruif C.G. Int. Dairy J. 1999; 9: 183-188Crossref Scopus (202) Google Scholar). Nevertheless, the casein micelles are extremely stable and can withstand boiling, freeze-drying, and the addition of salt and ethanol. It is believed that the amphipathic, glycosylated C-terminal end of κ-casein protrudes from the micelle surface forming a so-called “hairy layer” that sterically stabilizes the complexes (8Holt C. Horne D.S. Neth. Milk Dairy J. 1996; 50: 85-111Google Scholar). The literature on casein interactions has been reviewed by Horne (9Horne D. Int. Dairy J. 1998; 8: 171-177Crossref Scopus (536) Google Scholar), and a model of the casein micelle has been formulated that accounts for many of the physicochemical properties of the micelle. The model involves electrostatic interactions between colloidal calcium phosphate particles and multiple α- and β-casein molecules and hydrophobic interactions between the α-, β-, and κ-caseins forming a cross-linked network (9Horne D. Int. Dairy J. 1998; 8: 171-177Crossref Scopus (536) Google Scholar). Electron microscopy of casein micelles (10Dalgleish D.G. Spagnuolo P.A. Goff H.D. Int. Dairy J. 2004; 14: 1025-1031Crossref Scopus (187) Google Scholar) has provided evidence that the caseins are organized into tubular structures within the micelle. The casein micelles serve as a carrier of calcium phosphate providing the neonate with a bioavailable source of calcium and phosphate ions for bone and teeth formation (3Holt C. Sawyer L. Protein Eng. 1988; 2: 251-259Crossref PubMed Scopus (129) Google Scholar). It has been postulated that the ability of casein to form stable complexes with calcium phosphate is intrinsic to a general mechanism for avoiding pathological calcification and regulating calcium flow in tissues and biological fluids containing high concentrations of calcium (11Holt C. Wahlgren N.M. Drakenberg T. Biochem. J. 1996; 314: 1035-1039Crossref PubMed Scopus (156) Google Scholar). The ability of casein micelles to maintain calcium and phosphate ions in a soluble and bioavailable state is retained by the tryptic multiphosphorylated peptides of the caseins known as the casein phosphopeptides (CPP) 1The abbreviations used are: CPP, casein phosphopeptide(s); ACP, amorphous calcium phosphate; CN, casein; DCPD, dicalcium phosphate dihydrate; HA, hydroxyapatite; OCP, octacalcium phosphate; SEM, scanning electron microscopy; TEM, transmission electron microscopy; HPLC, high performance liquid chromatography.1The abbreviations used are: CPP, casein phosphopeptide(s); ACP, amorphous calcium phosphate; CN, casein; DCPD, dicalcium phosphate dihydrate; HA, hydroxyapatite; OCP, octacalcium phosphate; SEM, scanning electron microscopy; TEM, transmission electron microscopy; HPLC, high performance liquid chromatography. (12Reynolds E.C. Black C.L. Cai F. Cross K.J. Eakins D. Huq N.L. Morgan M.V. Nowicki A. Perich J.W. Riley P.F. Shen P. Talbo G. Webber F. J. Clin. Dent. 1999; 10: 86-88Google Scholar). The major tryptic CPP are β-CN(1–25) (sequence 1 below) and αS1-CN(59–79) (sequence 2 below) with smaller amounts of αS2-CN(46–70) (sequence 3 below) and αS2-CN(1–21) (sequence 4 below) (13Reynolds E.C. Riley P.F. Adamson N.J. Anal. Biochem. 1994; 217: 277-284Crossref PubMed Scopus (95) Google Scholar, 14Adamson N.J. Riley P.F. Reynolds E.C. J. Chromatogr. 1993; 646: 391-396Crossref PubMed Scopus (51) Google Scholar). These peptides all contain the cluster sequence motif Ser(P)3-Glu2 with three contiguous phosphoserines. This peptide motif is thought to be critical for calcium and calcium phosphate binding by these peptides (12Reynolds E.C. Black C.L. Cai F. Cross K.J. Eakins D. Huq N.L. Morgan M.V. Nowicki A. Perich J.W. Riley P.F. Shen P. Talbo G. Webber F. J. Clin. Dent. 1999; 10: 86-88Google Scholar). The sequences of the four major casein tryptic phosphopeptides are shown with the motif underlined: sequence 1 (β-CN(1–25)), Arg1-Glu-Leu-Glu-Glu-Leu-Asn-Val-Pro-Gly-Glu-Ile-Val-Glu-Ser(P)-Leu-Ser(P)3-Glu2-Ser-Ile-Thr-Arg25; sequence 2 (αS1-CN(59–79)), Gln59-Met-Glu-Ala-Glu-Ser(P)-Ile-Ser(P)3-Glu2-Ile-Val-Pro-Asn-Ser(P)-Val-Glu-Gln-Lys79; sequence 3 (αS2-CN(46–70)), Asn46-Ala-Asn-Glu-Glu-Glu-Tyr-Ser-Ile-Gly-Ser(P)3-Glu2-Ser(P)-Ala-Glu-Val-Ala-Thr-Glu-Glu-Val-Lys70; and sequence 4 (αS2-CN(1–21)), Lys1-Asn-Thr-Met-Glu-His-Val-Ser(P)3-Glu2-Ser-Ile-Ile-Ser(P)-Gln-Glu-Thr-Tyr-Lys21. The CPP stabilize calcium and phosphate ions under neutral and alkaline conditions forming metastable solutions that are supersaturated with respect to the basic calcium phosphate phases (15Reynolds E.C. Cain C.J. Webber F.L. Black C.L. Riley P.F. Johnson I.H. Perich J.W. J. Dent. Res. 1995; 74: 1272-1279Crossref PubMed Scopus (184) Google Scholar). Under these conditions, the CPP bind their equivalent weights of calcium and phosphate (16Reeves R.E. Science. 1958; 128: 472Crossref PubMed Scopus (65) Google Scholar). The CPP are formed in vivo by normal digestion of casein and, because they are relatively resistant to further proteolytic degradation, accumulate in the distal portion of the small intestine (17Mykkanen H.M. Wasserman R.H. J. Nutr. 1980; 110: 2141-2148Crossref PubMed Scopus (143) Google Scholar, 18Lee Y.S. Noguchi T. Naito H. Brit. J. Nutr. 1983; 49: 67-76Crossref PubMed Scopus (99) Google Scholar, 19Lee S.L. Veis A. J. Pept. Prot. Res. 1980; 16: 231-232Crossref PubMed Scopus (31) Google Scholar, 20Meisel H. Fristar H. Biol. Chem. Hoppe-Seyler. 1988; 369: 1275-1279Crossref PubMed Scopus (99) Google Scholar, 21Sato R. Noguchi T. Naito H. J. Nutr. Sci. Vitaminol. 1986; 32: 67-76Crossref PubMed Scopus (227) Google Scholar). It has been proposed that this accumulation together with the ability of the peptides to form soluble complexes with calcium phosphate are responsible for the enhanced intestinal calcium absorption that has been observed even in vitamin D-deficient animals consuming dietary CPP (17Mykkanen H.M. Wasserman R.H. J. Nutr. 1980; 110: 2141-2148Crossref PubMed Scopus (143) Google Scholar, 18Lee Y.S. Noguchi T. Naito H. Brit. J. Nutr. 1983; 49: 67-76Crossref PubMed Scopus (99) Google Scholar, 19Lee S.L. Veis A. J. Pept. Prot. Res. 1980; 16: 231-232Crossref PubMed Scopus (31) Google Scholar, 20Meisel H. Fristar H. Biol. Chem. Hoppe-Seyler. 1988; 369: 1275-1279Crossref PubMed Scopus (99) Google Scholar, 21Sato R. Noguchi T. Naito H. J. Nutr. Sci. Vitaminol. 1986; 32: 67-76Crossref PubMed Scopus (227) Google Scholar). In addition, CPP increase the calcification of in vitro cultured embryonic rat bone, and again the mechanism is to be associated with the ability of the peptide to form soluble complexes with calcium and phosphate ions R. Calcif. Tissue Int. 1986; PubMed Scopus Google Scholar). phosphate complexes have been shown to be and to of in and (12Reynolds E.C. Black C.L. Cai F. Cross K.J. Eakins D. Huq N.L. Morgan M.V. Nowicki A. Perich J.W. Riley P.F. Shen P. Talbo G. Webber F. J. Clin. Dent. 1999; 10: 86-88Google Scholar, E.C. Cain C.J. Webber F.L. Black C.L. Riley P.F. Johnson I.H. Perich J.W. J. Dent. Res. 1995; 74: 1272-1279Crossref PubMed Scopus (184) Google Scholar, C. Scholar, E.C. Cai F. Shen P. J. Dent. Res. PubMed Scopus Google Scholar, P. Cai F. Nowicki A. J. Reynolds E.C. J. Dent. Res. PubMed Scopus Google Scholar). In the ability to stabilize calcium phosphate and and T. Brit. J. Nutr. PubMed Scopus Google Scholar) the CPP the to be biological for calcium and phosphate A. A. C. A. G. J. Nutr. PubMed Scopus Google Scholar). of into the of proteins involved in and calcium phosphate have studied the interaction of tryptic phosphopeptides from milk caseins with the amorphous and phases of calcium In this investigations of the calcium and phosphate binding properties of the two major CPP, β-CN(1–25) and We that the ion activity product of a basic amorphous calcium phosphate phase with the calcium bound by the peptide αS1-CN(59–79) a range of calcium and phosphate concentrations and from to the regions and residues of these peptides that are responsible for calcium phosphate We the of peptide length, and of residues on the binding to calcium and calcium phosphate using a library of synthetic the ultrastructure of the casein phosphate as using a range of physicochemical techniques including powder diffraction x-ray scanning electron microscopy and transmission electron microscopy of casein phosphopeptides β-CN(1–25) and αS1-CN(59–79) from a tryptic of casein using calcium and and further by liquid and phase (13Reynolds E.C. Riley P.F. Adamson N.J. Anal. Biochem. 1994; 217: 277-284Crossref PubMed Scopus (95) Google Scholar). The of the peptides was by and sequence (13Reynolds E.C. Riley P.F. Adamson N.J. Anal. Biochem. 1994; 217: 277-284Crossref PubMed Scopus (95) Google Scholar, 14Adamson N.J. Riley P.F. Reynolds E.C. J. Chromatogr. 1993; 646: 391-396Crossref PubMed Scopus (51) Google Scholar). to sequence the phosphoseryl residues to residues by (13Reynolds E.C. Riley P.F. Adamson N.J. Anal. Biochem. 1994; 217: 277-284Crossref PubMed Scopus (95) Google Scholar). of peptide to was by the of in the of peptide by of the peptides N.J. Riley P.F. Reynolds E.C. J. Chromatogr. 1993; 646: 391-396Crossref PubMed Scopus (51) Google Scholar, J.W. Reynolds E.C. J. Chem. Scopus Google Scholar, J.W. Reynolds E.C. Int. J. Pept. Prot. Res. 40: PubMed Scopus Google Scholar). The synthetic peptides with an the and a the In the of a of a was for to a associated with a C-terminal The of the other synthetic analogues have been J.W. Reynolds E.C. Int. J. Pept. Prot. Res. 40: PubMed Scopus Google Scholar, J.W. PubMed Scopus Google Scholar, J.W. R. Int. J. Pept. Prot. Res. 1994; PubMed Scopus Google Scholar). The peptides by phase HPLC, and the was confirmed by sequence and (13Reynolds E.C. Riley P.F. Adamson N.J. Anal. Biochem. 1994; 217: 277-284Crossref PubMed Scopus (95) Google Scholar, 14Adamson N.J. Riley P.F. Reynolds E.C. J. Chromatogr. 1993; 646: 391-396Crossref PubMed Scopus (51) Google Scholar, C. Scholar, J.W. Reynolds E.C. J. Chem. Scopus Google Scholar, J.W. Reynolds E.C. Int. J. Pept. Prot. Res. 40: PubMed Scopus Google Scholar, J.W. PubMed Scopus Google Scholar, J.W. R. Int. J. Pept. Prot. Res. 1994; PubMed Scopus Google Scholar). to and calcium binding using a of the of PubMed Scopus Google Scholar) the addition of The solutions using mm to a of was to using The for of the was as by for using with These not to calcium phosphate ions ion ion concentrations of by absorption using model with the addition of to phosphate concentrations from to mm for αS1-CN(59–79) and mm for the and mm for the The calcium concentrations of the after to and of the and the calcium was as the between these binding by the peptides was by the number of independent has a by the The for the complexes and the number of calcium of peptide by a to the to αS1-CN(59–79) and β-CN(1–25) and was by phosphate to solutions containing mm calcium and 4 peptide using mm to a of was to the for to the homologues and binding was The and as for calcium The phosphate from to was Clin. Acta. 14: PubMed Scopus Google Scholar), with on a and phosphate concentrations in the solution and the The peptide bound calcium and peptide bound phosphate as the between the and calcium and phosphate, that the for and the calcium and phosphate concentrations to and to contain calcium phosphate is as the number of calcium ions and phosphate ions of The ion activity for phases of calcium phosphate from the calcium and phosphate concentrations and using an that the ion activity using the This into ion and the of and and the PubMed Scopus Google Scholar, Calcif. Tissue Res. 8: PubMed Scopus Google Scholar, R. J. Res. Google Scholar, 9: Scholar, E.C. J. Res. PubMed Google Scholar, A. R. J. Chem. PubMed Scopus Google Scholar). The activity of the ion was to be used from the and and The of the H. J. Res. A. Google Scholar), octacalcium phosphate L. J. in The of the of calcium and of New Scholar), dicalcium phosphate E.C. J. Res. PubMed Google Scholar), and L. Richardson C. PubMed Scopus Google Scholar). and phosphate binding was as multiple independent within the peptide with a by the The number of phosphate binding was by to an of the form of in bound and phosphate the The of from these can be shown to be by the is the calcium ion binding for the The number of calcium binding was using the is the of calcium bound with of was in and 1 by to the CPP solution in a by of of the calcium and inorganic phosphate and The colloidal phosphate by through a in a and with 3 of to calcium and phosphate The phosphate solutions of β-CN(1–25) was in the peptide solution, mm and mm The was by of mm The solution was and in of in an and in a x-ray with a x-ray source and The x-ray diffraction with a state and from to in was by of the x-ray diffraction with the powder diffraction by the for and of for was from that was and on a The with a to the electron on a SEM, on an with and with a The using the electron to and 1 the for αS1-CN(59–79) and with the bound of peptide being as a function of calcium ion the of the and the number of calcium from the for and to 2 using a In the of the C-terminal containing only a calcium binding was binding of the casein number of of number of of in a to αS1-CN(59–79) and 2 the of αS1-CN(59–79) with inorganic phosphate in the of mm calcium and calcium and phosphate by the in the and calcium and phosphate The is the calcium bound in the of phosphate, the calcium bound in the of This has been phosphate in a of bound phosphate to the number of of calcium and phosphate bound and the The to a between the of and the of was not and the of from to the phosphate with from the calcium the of the bound calcium ion phosphate of in with from the phosphate The number of calcium of peptide was not to the of The reported in are of the from a of for the pH, a between bound calcium and bound This that the binding of calcium ions and phosphate ions is The number of calcium phosphate binding of peptide a with the of the peptide as shown in the of as the peptides and phosphate binding of CPP and using the in and and and number of number of of using the in and A. 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J. 1999; PubMed Scopus Google number of number of of in a of bound calcium to peptide in calcium complexes. between the number of residues in the peptide and the number of calcium of peptide for the complexes and their The has a of of the by the calcium phosphate phase bound by the binding of calcium phosphate was to the ion activity of the biologically calcium phosphate The bound of peptide was as a function of the ion activity of the biologically 1980; Scholar), and a basic the phase a function that was independent of that this was the phase stabilized by of phases by and basic phases by These are of a range of calcium phosphate from in the basic to phosphate and in the the ion activity a number of in the to of the ion activity product was as a function of the number of and a was to the The from these and a through these to the of 4 the in the as a function of for the amorphous of bound calcium and ion activity as a function of calcium phosphate the in as a function of phase for to the number of calcium ions of peptide as a function of the ion activity of the and basic to and addition to β-CN(1–25) and the calcium phosphate binding of a of synthetic homologues and analogues as shown in The of this was to the residues for calcium phosphate stabilization and to investigate the of peptide length, and The synthetic and to the and of not bind calcium stabilize calcium The of the multiphosphorylated motif was further using a of of the number of residues in the peptide is shown in a of The of of the Ser(P) residues by residues in the peptide Ser(P)3-Glu2 the of residues by in the peptide the peptides ability to stabilize calcium the of Ser(P) by was also associated with a ability to stabilize calcium contiguous phosphoseryl residues for because the although containing four phosphoseryl stabilized calcium In in the of phosphate the CPP and their analogues bound calcium and that bound in the of The of the calcium bound the bound phosphate, independent of pH, that a specific phase of calcium phosphate was being bound The of calcium and phosphate bound by the CPP and their analogues as the The calcium phosphate phase that was to bind to αS1-CN(59–79) was a basic phase of the of number of of and studied using x-ray powder diffraction. of the of the of the can be from the of the for the is shown in The of in these was consistent with an amorphous calcium phosphate phase associated with the CPP and the in the of the observed and to of and the of with calcium and phosphate, J. J. and C. and x-ray powder diffraction with to a phase as shown in and of in the area electron diffraction the particles also not of The and of and the selected area diffraction the amorphous nature of the shown in αS1-CN(59–79) bound of of β-CN(1–25) bound of of The peptide bound of of of the The number of calcium to be by for the the of calcium bound being to the intrinsic of the The on the peptide is only that on the other two and the of calcium bound is be on structural to be the most for the calcium binding ability of the of proteins structures have been in the Protein that calcium ions have between and in their The structure of the is on with as two of the molecules for only two from interactions with calcium ions also with from the The structural by the multiple interactions between the peptide and the calcium ions that are to the peptide are to be to in the calcium binding ability of the The structural is consistent with of calcium structural in the of αS1-CN(59–79) and β-CN(1–25) with calcium N.L. Cross K.J. Reynolds E.C. Biochim. Biophys. Acta. 1995; PubMed Scopus Google Scholar, K.J. Huq N.L. W. Reynolds E.C. Biochem. J. PubMed Scopus Google Scholar). We have shown that these peptides structures consisting of and and that the specific structure on the peptide sequence of the motif the of phosphate the CPP and their analogues bound calcium and that bound in the of The of the calcium bound the bound phosphate, independent of pH, that a specific phase of calcium phosphate was being bound The of calcium and phosphate bound by the CPP and their analogues as the The number of in the calcium phosphate complexes with the number of residues in the peptide used to stabilize the This is consistent with a model of the complexes in the phosphorylated sequence motif, is to binding to the calcium phosphate the peptide is bound to the interactions the polar residues to with the for the between peptide and the number of of calcium and phosphate bound by these that the of the peptide with the calcium phosphate phase and the associated with the formation of calcium is that peptides bind calcium ions that are not associated with the calcium phosphate of the 4 of the calcium bound by the peptide β-CN(1–25) ion activity for the four calcium phosphate HA, DCPD, OCP, and a basic amorphous calcium phosphate the The calcium phosphate phase stabilized by β-CN(1–25) is by the of bound calcium on the ion activity product independent of of 4 that the of calcium bound is not a function of the ion activity for the phases HA, DCPD, 4 that the bound calcium with a basic amorphous calcium phosphate phase with The stabilization of a basic calcium phosphate phase is consistent with the that these complexes form a range from to The of was to increase as the of the peptide for this be that the peptides bind a calcium phosphate phase and independent calcium as the associated with the formation of calcium this an These can be by a model of the that of two calcium phosphate a phase with a of as forming the of the particles as by and Calcif. Tissue Res. PubMed Scopus Google Scholar), and a phase with a of as that is in with the the peptides a number of peptides are to fully a smaller surface hence the of the formed as the peptides The of the phase with peptide is proposed to as the complexes in the of the relatively soluble in in a increase in the of as the peptides in It is that of Ser(P) with calcium phosphate stabilization This together with in of residues to all of the proteins known to stabilize calcium phosphate contain clusters of Ser(P) residues. The ion product that with the bound calcium by αS1-CN(59–79) in a is that of a basic amorphous calcium phosphate phase the that αS1-CN(59–79) phosphate the of the is is a small using a library of synthetic homologues and analogues have revealed that the Ser(P)3-Glu2 motif in most of the CPP is a specific sequence of residues that has a for calcium the of the major peptides stabilization of the of We Webber for
Cross et al. (Wed,) studied this question.
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