Octacalcium Phosphate and Hydroxyapatite: Crystallographic and Chemical Relations between Octacalcium Phosphate and Hydroxyapatite

Brown, W. E.; Smith, James P.; Lehr, James R.; Frazier, A. W.

doi:10.1038/1961050a0

Cited by 511 publications

(384 citation statements)

References 20 publications

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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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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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“…Figure S3. Calculated diffraction patterns for several different forms of calcium phosphate, based on previously published crystal structures of: primitive monetite (dicalcium phosphate anhydrous; Catti et al 1980), β-TCP (Yashima et al 2003), hexagonal HA , DCPD (Sainz-Díaz et al 2004), and OCP (Brown 1962). The patterns were simulated for (a) X-rays of λ = 1.54Å and (b) neutrons of λ = 4.76Å.…”

Section: Neutron and X-ray Diffraction Simulationsmentioning

confidence: 99%

Structural studies of hydrated samples of amorphous calcium phosphate and phosphoprotein nanoclusters

et al. 2016

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There are abundant examples of nanoclusters and inorganic microcrystals in biology.Their study under physiologically relevant conditions remains challenging due to their instability, the requirements of sample preparation and other intrinsic limitations of the techniques used. Advantages of using neutron diffraction and contrast matching to characterize biomaterials are highlighted in this article. We have applied these methods and complementary techniques to search for long-range order within nanoclusters of calcium phosphate sequestered by bovine phosphopeptides, derived from osteopontin or casein. Hydrated and dried samples with different nanocluster radii were analyzed and compared to samples of known calcium phosphate phases. The absence of a distinct diffraction pattern from the nanoclusters is consistent with the presence of amorphous calcium phosphate structure.

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“…1975), bone phosphoproteins (Glimcher et al 1979), sialoproteins (Fisher et al 1987) and osteonectin (Termine et al 1981). OCP, one of the precursor of HA , has been reported to have high affinity to F- (Brown et al 1962) , succinate (Monma and Goto 1983) and DNA (Spencer and Grynpas 1978). Termine and Conn (1976) have presented that phosphorylated metabolites and macromolecules are incorporated into ACP, and inhibit amorphous-crystalline conversion in vitro .…”

mentioning

confidence: 99%

Bone Formation on Synthetic Precursors of Hydroxyapatite.

Сузукі

Nakamura

Miyasaka

et al. 1991

Tohoku J. Exp. Med.

265

312

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The aim of this study was to investigate the reaction of skeletal tissue to various synthetic calcium phosphate (Ca-P) compounds in vivo. Five synthetic Ca-P compounds were implanted into the subperiosteal area of the calvaria of 7-week-old BALB/c mice for one to 15 weeks. Synthetic compounds were dicalcium phosphate (DCP), octacalcium phosphate (OCP), amorphous calcium phosphate (ACP), Ca-deficient hydroxyapatile and hydroxyapatile (HA). Implanted DCP, OCP and ACP were found to be converted to apatitic phase by x-ray microdiffraction analysis using undecalcified specimens. Structure of bone was found out on all of Ca-P compounds eventually at late stage under the light microscope, but the rate of bone formation calculated from a number of experiments varied on respective synthetic Ca-P compound. It was high as 80% for DCP, OCP and ACP, but was low as 5.6% for Ca-deficient HA, and no reaction was found for HA at the stage of 3 weeks. Fine filaments and granular materials in the newly formed bone matrix were detected at 7 days around the remnants of OCP particles which already converted to apatitic phase by ultrastructural study of decalcified specimens. These structures were very similar to the components of bone nodules seen in intramembranous osteogenesis. It is postulated that the precursors of HA have an important role in intramembranous osteogenesis.calcium phosphate (Ca-P) compounds ; precursors ; hydroxyapatile ; bone formation ; bone matrix

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Octacalcium Phosphate and Hydroxyapatite: Crystallographic and Chemical Relations between Octacalcium Phosphate and Hydroxyapatite

Cited by 511 publications

References 20 publications

Citrate bridges between mineral platelets in bone

Citrate bridges between mineral platelets in bone

Structural studies of hydrated samples of amorphous calcium phosphate and phosphoprotein nanoclusters

Bone Formation on Synthetic Precursors of Hydroxyapatite.

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