Hydrogen environments in calcium phosphates: proton MAS NMR at high spinning speeds

Yesinowski, James P.; Eckert, Hellmut

doi:10.1021/ja00255a009

Cited by 270 publications

(318 citation statements)

References 4 publications

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“…In the spectrum of bone, two characteristic correlation signals at ca. 0 ppm and 5 ppm in the 1 H dimension are assigned, respectively, to PO4 3− /OH − groups in the apatite structure and to structural/surface water protons spatially related to the mineral phase, according to Yesinowski and Eckert [27]. Similar correlation signals have been observed in synthetic biomimetic nanocomposites [22,28] as well as in biominerals such as animal bone [17,29], joint mineralized cartilage [14], and rat dentine [12].…”

Section: Resultsmentioning

confidence: 68%

Early Stages of Biomineral Formation—A Solid-State NMR Investigation of the Mandibles of Minipigs

et al. 2017

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Solid-state nuclear magnetic resonance (NMR) spectroscopy allows for the identification of inorganic species during the biomineral formation, when crystallite particles visible in direct imaging techniques have not yet been formed. The bone blocks surrounding dental implants in minipigs were dissected after the healing periods of two, four, and eight weeks, and newly formed tissues formed around the implants were investigated ex vivo. Two-dimensional 31 P-1 H heteronuclear correlation (HETCOR) spectroscopy is based on the distance-dependent heteronuclear dipolar coupling between phosphate-and hydrogen-containing species and provides sufficient spectral resolution for the identification of different phosphate minerals. The nature of inorganic species present at different mineralization stages has been determined based on the 31 P chemical shift information. After a healing time of two weeks, pre-stages of mineralization with a rather unstructured distribution of structural motives were found. After four weeks, different structures, which can be described as nanocrystals exhibiting a high surface-to-volume ratio were detected. They grew and, after eight weeks, showed chemical structures similar to those of matured bone. In addition to hydroxyapatite, amorphous calcium phosphate, and octacalcium phosphate, observed in a reference sample of mature bone, signatures of ß-tricalcium phosphate and brushite-like structures were determined at the earlier stages of bone healing.

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Section: Resultsmentioning

confidence: 68%

Early Stages of Biomineral Formation—A Solid-State NMR Investigation of the Mandibles of Minipigs

et al. 2017

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“…S2) is dominated by a broad signal centered at ∼5.5 ppm because of the water in the structure (32) and (presumably) overlies signals from citrate 1 H as well. The water 1 H signal in OCP is motionally narrowed because of the mobility of the water molecules in that structure (22,32,33). The 5.5-ppm signal because of water in OCP-citrate is significantly broader than the water 1 H signal of OCP (Fig.…”

Section: Resultsmentioning

confidence: 95%

Citrate bridges between mineral platelets in bone

Davies

Müller

Wong

et al. 2014

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

254

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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“…NMR investigations of proton environments have shown that the position of the 1 H NMR shift is correlated to the distance between the hydrogen and oxygen atoms and can be considered as a witness of the hydrogen bond strength (Yesinowski and Eckert, 1987;Eckert et al, 1988;Xue and Kanzaki, 2007): the higher the 1 H ppm shift, the shorter hydrogen -oxygen atoms distance. In Figure 7, the Na + … CO 3 2-… H + unit is related to hydrogen atoms with a very short distance from the oxygen atom.…”

Section: Free Carbonate Clusters As Precursors To Liquid Immiscibilitmentioning

confidence: 99%

Carbon dioxide in silica-undersaturated melt. Part I: The effect of mixed alkalis (K and Na) on CO2 solubility and speciation

Morizet

Paris

Gaillard

et al. 2014

Geochimica et Cosmochimica Acta

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Hydrogen environments in calcium phosphates: proton MAS NMR at high spinning speeds

Cited by 270 publications

References 4 publications

Early Stages of Biomineral Formation—A Solid-State NMR Investigation of the Mandibles of Minipigs

Early Stages of Biomineral Formation—A Solid-State NMR Investigation of the Mandibles of Minipigs

Citrate bridges between mineral platelets in bone

Carbon dioxide in silica-undersaturated melt. Part I: The effect of mixed alkalis (K and Na) on CO2 solubility and speciation

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