Solid and Solution State NMR Spectra and the Structure of the Gallium Citrate Complex (NH4)3[Ga(C6H5O7)2]·4H2O

Hawkes, Geoffrey E.; O’Brien, Paul; Salacinski, Henryk J.; Motevalli, Majid; Abrahams, Isaac

doi:10.1002/1099-0682(200104)2001:4<1005::aid-ejic1005>3.0.co;2-w

Cited by 10 publications

(7 citation statements)

References 29 publications

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“…In general, the CASTEP calculations indicated that the 13 C COO − signals at higher frequency are likely to correspond to Cq-COOH or Cq-COO − environments rather than -CH 2 COOH, consistent with reports of solution-state NMR of metal-citrate complexes (38,39).…”

Section: Resultssupporting

confidence: 86%

“…The ranges of 1 H chemical shifts for each hydrogen environment for the structural model in Fig. 5A is given in Table S2 and are consistent with those ranges expected (38,39), although lack of resolution in the 1 H spectrum precludes detailed comparison; we note, however, that the citrate methylene 1 H chemical shift (average) is calculated to be 2.9 ppm (±0.4 ppm SD), which compares well with the experimental value of 2.7 ppm found from the 1 H-31 P HETCOR experiments (Fig. S4).…”

Section: Resultssupporting

confidence: 84%

See 1 more Smart Citation

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: Resultssupporting

confidence: 86%

Section: Resultssupporting

confidence: 84%

Citrate bridges between mineral platelets in bone

Davies

Müller

Wong

et al. 2014

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

256

246

View full text Add to dashboard Cite

show abstract

“…There are no reliable thermodynamic formation constants for such complexes available in the literature, but recent NMR studies have indeed suggested the existences of GaH Àn ðCitÞ À3Àn 2 complexes in aqueous solution [2,5]. In the Al(III) citrate system, an AlðCitÞ 3À 2 complex was suggested by Ö hman and Sjöberg [11] to be important at high citrate to aluminum(III) ratios, where the formation of 1:1 complexes is suppressed.…”

Section: Solution Amentioning

confidence: 99%

“…The composition and structures of the gallium(III) citrate complexes that are important in aqueous solution has, however, been subject to debate. The system has been studied with a variety of techniques, including NMR spectroscopy [2][3][4][5][6][7][8], X-ray crystallography [3,5] and potentiometric titrations [6,8,9], but there is no consensus regarding the composition and structure of the species formed. Commonly, the system is described in terms of the formation of GaH m L ð3þmÀ3nÞ n complexes (L = citrate 3À = Cit 3À ), sometimes in combination with oligomeric complexes at near neutral pH values.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic studies of aqueous gallium(III) and aluminum(III) citrate complexes

Clausén

Öhman

Persson

2005

Journal of Inorganic Biochemistry

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“…The synthetic and binding chemistry of citrate acid chelating with various metal ions with biological significance is much concerned because of their potential to influence the migration of metal ions in cellular fluids of lower and higher organisms [1][2][3]. It has been found that 3D metal-citrate complexes exhibit different coordination modes and diverse structural topologies such as mono-, di-, and multi-nuclear complexes which are highly influenced by the coordination ability [4], counter cations [5], pH value [6], and etc.…”

Section: Introductionmentioning

confidence: 99%