New model for the hydroxyapatite–octacalcium phosphate interface

Fernández, M.; Zorrilla-Cangas, C.; Garcı́a-Garcı́a, R.; Ascencio, J.A.; Reyes‐Gasga, J.

doi:10.1107/s0108768103002167

Cited by 43 publications

(31 citation statements)

References 17 publications

(31 reference statements)

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“…The OCP-HAP relationship reported by Ferná ndez et al [23] is supported by the use of a minimum free-energy optimization argument. Moreover, a HAP is only 0.942 nm and b OCP is 0.953 nm, then there will be a misfit of 1.2% in the case of Ferná ndez et al [23], while Xin et al [12], reports that a OCP is 0.985 nm, producing a misfit of 4.5%. This difference is enough to give rise to several types of interfacial defects, such as dislocations.…”

Section: Discussionmentioning

confidence: 66%

See 1 more Smart Citation

Synthesis and hydrolysis of octacalcium phosphate and its characterization by electron microscopy and X-ray diffraction

Arellano-Jiménez

Garcı́a-Garcı́a

Reyes‐Gasga

2009

Journal of Physics and Chemistry of Solids

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Section: Discussionmentioning

confidence: 66%

“…The second one was proposed by Ferná ndez et al [23] wherea HAP is glued with b OCP forming an angle of 1311 between a HAP and a OCP . And the third has been recently proposed by Xin [12] where a HAP is glued with a OCP forming and angle of 1281 between a HAP and b OCP .…”

Section: Discussionmentioning

confidence: 98%

Synthesis and hydrolysis of octacalcium phosphate and its characterization by electron microscopy and X-ray diffraction

Arellano-Jiménez

Garcı́a-Garcı́a

Reyes‐Gasga

2009

Journal of Physics and Chemistry of Solids

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“…However, bone mineral undeniably has a significant component with a structure related to hydroxyapatite (albeit with many substitutions), and although OCP-citrate has an apatitic layer, it is not large enough to account for the amount of apatitic mineral in bone. It is well-known that hydroxyapatite and OCP can form an epitaxial interface with the minimum of interfacial energy (42,43) between the (200) plane of hydroxyapatite and the (100) plane of OCP. Hydroxyapatite layers could be incorporated within the apatitic layers of OCP-citrate in a similar manner to form thicker mineral platelets.…”

Section: Resultsmentioning

confidence: 99%

Citrate bridges between mineral platelets in bone

Davies

Müller

Wong

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

256

246

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We provide evidence that citrate anions bridge between mineral platelets in bone and hypothesize that their presence acts to maintain separate platelets with disordered regions between them rather than gradual transformations into larger, more ordered blocks of mineral. To assess this hypothesis, we take as a model for a citrate bridging between layers of calcium phosphate mineral a double salt octacalcium phosphate citrate (OCPcitrate). We use a combination of multinuclear solid-state NMR spectroscopy, powder X-ray diffraction, and first principles electronic structure calculations to propose a quantitative structure for this material, in which citrate anions reside in a hydrated layer, bridging between apatitic layers. To assess the relevance of such a structure in native bone mineral, we present for the first time, to our knowledge, 17 O NMR data on bone and compare them with 17 O NMR data for OCP-citrate and other calcium phosphate minerals relevant to bone. The proposed structural model that we deduce from this work for bone mineral is a layered structure with thin apatitic platelets sandwiched between OCP-citrate-like hydrated layers. Such a structure can explain a number of known structural features of bone mineral: the thin, plate-like morphology of mature bone mineral crystals, the presence of significant quantities of strongly bound water molecules, and the relatively high concentration of hydrogen phosphate as well as the maintenance of a disordered region between mineral platelets.NMR crystallography | biomineralization B one is a complex organic-inorganic composite material (1), in which calcium phosphate nanoparticles are held within a primarily collagen protein matrix. The mineral component is a poorly crystalline phase, closely related to hydroxyapatite. The currently accepted model of bone mineral is ∼50-to 150-nmthick stacks of very closely packed apatitic platelets, each of order 2.5-4 nm in thickness (1-4), arranged so that their large (100) faces are parallel to each other and their c axes are strongly ordered (parallel to collagen fibrils) (5). NMR studies show that, in addition to the largely ordered but nonstoichiometric apatitic phase, there is a substantial, highly hydrated, disordered phase containing up to 55% of the bone mineral phosphatic ions (6, 7) but in the form of hydrogen phosphate or phosphate strongly hydrogen-bonded to water rather than apatitic orthophosphate (8). This phase has been assigned as a surface phase, but whether the surface in question is that of individual mineral platelets or the surface of the overall structure formed by a stack of such platelets is not yet clear. There is, however, significant experimental evidence that is not explained by this model as it stands. First, there has never been any observation of an isolated mineral platelet in mature bone, even in preparations in which there have been attempts to disperse the mineral structures (9). This feature suggests that the mineral platelets are not independent structures-indeed, their ordered aggregati...

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“…The more open p6 form occurs when the PS content of the planar membrane is low (5-20%); the p3 form occurs when the PS level is high (Ն40%). Comparison of the lattice parameters of the p3 crystal form of Anx-A5 with those of hydroxyapatite (43), octacalcium phosphate (44,45), and the core structure of ACP (46) indicates that the pattern formed by the clusters of PO 4 3Ϫ and Ca 2ϩ ions of the unit cell (ϳ9.5-Å radius) match the trilobate space at the center of each Anx-A5 trimer. Thus, the PS-CPLX-Anx-A5 arrays appear to form a two-dimensional crystalline pattern that facilitates nucleation of crystalline CaP i mineral formation.…”

Section: Discussionmentioning

confidence: 99%

In Vitro Modeling of Matrix Vesicle Nucleation

Genge

Wuthier

2007

Journal of Biological Chemistry

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Annexins A5, A2, and A6 (Anx-A5, -A2, and -A6) are quantitatively major proteins of the matrix vesicle nucleational core that is responsible for mineral formation. Anx-A5 significantly activated the induction and propagation of mineral formation when incorporated into synthetic nucleation complexes made of amorphous calcium phosphate (ACP) and Anx-A5 or of phosphatidylserine (PS) plus ACP (PS-CPLX) and Anx-A5. Incorporation of Anx-A5 markedly shortened the induction time, greatly increasing the rate and overall amount of mineral formed when incubated in synthetic cartilage lymph. Constructed by the addition of Ca 2؉ to PS, emulsions prepared in an intracellular phosphate buffer matched in ionic composition to the intracellular fluid of growth plate chondrocytes, these biomimetic PS-CPLX nucleators had little nucleational activity. However, incorporation of Anx-A5 transformed them into potent nucleators, with significantly greater activity than those made from ACP without PS. The ability of Anx-A5 to enhance the nucleation and growth of mineral appears to stem from its ability to form twodimensional crystalline arrays on PS-containing monolayers. However, some stimulatory effect also may result from its ability to exclude Mg 2؉ and HCO 3 ؊ from nucleation sites. Comparing the various annexins for their ability to activate PS-CPLX nucleation yields the following: avian cartilage Anx-A5 > human placental Anx-A5 > avian liver Anx-A5 > avian cartilage Anx-A6 Ͼ Ͼ cartilage Anx-A2. The stimulatory effect of human placental Anx-A5 and avian cartilage Anx-A6 depended on the presence of PS, since in its absence they either had no effect or actually inhibited the nucleation activity of ACP. Anx-A2 did not significantly enhance mineralization. Matrix vesicles (MVs)2 are extracellular, lipid bilayer-enclosed microstructures released by cells that initiate mineral formation in newly forming bone (1-4). MVs have also been found to initiate ectopic calcification in calcific tendonitis, apatite deposition osteoarthritis, cardiac valve calcification, and atherosclerotic lesions (5-7). MVs isolated from growth plate cartilage by gentle proteolytic digestion and trituration of growth plate tissue (8) retain the ability to induce mineral formation when incubated in synthetic cartilage lymph (SCL) (9). They have been shown to be enriched in several phospholipids, especially phosphatidylserine (PS) (10, 11), a lipid with high affinity for Ca 2ϩ (12,13 MVs contain a detergent-stable core that can induce mineral formation (22, 23). The activity of this nucleational core is inhibited by Zn 2ϩ and is destroyed by treatment with pH 6 citrate buffer. Fourier-transform infrared, NMR, and SDS-PAGE characterization (8,(23)(24)(25) has shown that the nucleational core contains three main components: 1) amorphous calcium phosphate (ACP), 2) membrane-associated CPLX, and, of special interest here, 3) the annexins, lipid-dependent Ca 2ϩ -binding proteins that are especially rich in MVs (8,[25][26][27][28].To elucidate the roles of these components...

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New model for the hydroxyapatite–octacalcium phosphate interface

Cited by 43 publications

References 17 publications

Synthesis and hydrolysis of octacalcium phosphate and its characterization by electron microscopy and X-ray diffraction

Synthesis and hydrolysis of octacalcium phosphate and its characterization by electron microscopy and X-ray diffraction

Citrate bridges between mineral platelets in bone

In Vitro Modeling of Matrix Vesicle Nucleation

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