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  • Artikel: DFG Deutsche Nationallizenzen  (3)
  • Amorphous calcium phosphate  (2)
  • Key words: FTIR microspectroscopy — Apatite — Cortical bone — Trabecular bone — Iliac crest biopsies.  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 23 (1977), S. 245-250 
    ISSN: 1432-0827
    Schlagwort(e): Stabilization ; Amorphous calcium phosphate ; Mitochondria ; Mg and ATP ; Nucleation poisoning
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary A synergistic effect has been demonstrated when magnesium and adenosine triphosphate (ATP) are used together in solution to delay the conversion of a slurry of amorphous calcium phosphate (ACP) to crystalline hydroxyapatite (HA). Conversion is delayed in some instances more than 10 times as long as with either ATP or Mg alone. In all experiments conversion did not begin until ATP in solution had decreased through hydrolysis to an undetectable level. The effect of Mg is to decrease substantially the rate at which ATP hydrolysis occurs. Once conversion began it proceeded more slowly in the presence of both Mg and ATP than with Mg or ATP alone. ATP was also found to prevent the formation of HA from metastable solutions of calcium and phosphate which did not contain any solid phase. Over the time period of these experiments, ATP hydrolyzed to a negligible extent in Tris-HCl buffer and in solutions containing Ca, PO4, and Ca plus PO4 ions. Hydrolysis of ATP does occur in the presence of ACP or HA, presumably by transphosphorylation on the surface of the solid calcium phosphate phase. It was concluded that ATP stabilized ACP, not by affecting its dissolution, but either by poisoning heteronuclear growth sites, or by poisoning the growth of embryonic HA nuclei (formed heterogeneously or homogeneously) before their critical size is reached, or by poisoning both. In the case of embryonic HA nuclei, the poisoned nuclei would go back into solution preventing HA crystal formation. In addition, it was found that the neutral Ca9(PO4)6 clusters, which are believed to be the basic structural unit of ACP, break down into individual Ca and PO4 ions when ACP dissolves in aqueous medium.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 33 (1981), S. 111-117 
    ISSN: 1432-0827
    Schlagwort(e): Calcium-deficient hydroxyapatite ; Amorphous calcium phosphate ; Bone ; Radial distribution function ; Carbonate apatite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary When amorphous calcium phosphate (ACP) was transformed to crystalline hydroxyapatite (HA) in a series of aqueous slurry concentrations ranging from low to high, the higher slurry concentrations produced more Ca-deficient HA as measured by Ca/P ratio and heat-produced pyrophosphate. We feel that the excess solution phosphate produced in the higher slurry transformations results in lower Ca/P ratio HA. It has been suggested that an ACP is the precursor to bone apatite. Regulation of the in vivo ACP slurry concentration could then control the stoichiometry and, therefore, the metabolic activity of bone apatite. X-ray radial distribution function (RDF) analyses showed that CO 3 2− substitution in HA creates far greater structural distortions than do Ca deficiencies. The latter, however, do produce small, but observable, structural distortions when compared to stoichiometric HA. It now seems clear that the RDF of bone apatite can be modeled by a synthetic, Ca-deficient, CO 3 2− -containing HA.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 61 (1997), S. 480-486 
    ISSN: 1432-0827
    Schlagwort(e): Key words: FTIR microspectroscopy — Apatite — Cortical bone — Trabecular bone — Iliac crest biopsies.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract. Fourier transform infrared microspectroscopy (FTIRM) has been used to study the changes in mineral and matrix content and composition in replicate biopsies of nonosteoporotic human cortical and trabecular bone. Changes in osteonal bone in these same samples were reported previously. Spectral maps along and across the lamellae were obtained from iliac crest biopsies of two necropsy cases. Mineral:matrix ratios, calculated from the integrated areas of the phosphate ν1, ν3 band at 900–1200 cm−1 and the amide I band at ≈1585–1725 cm−1, respectively, were relatively constant in both directions of analysis, i.e., along and across the lamellae. Analysis of the components of the ν1, ν3 phosphate band with a combination of second-derivative spectroscopy and curve fitting revealed the presence of 11 major underlying moieties. Of these, the ratio of the relative areas of the two underlying bands at ≈1020 and ≈1030 cm−1 has been shown to be a sensitive index of variation in crystal perfection in both human osteonal bone and in synthetic, poorly crystalline apatites. This ratio was calculated in both cortical and trabecular bone from human iliac crest biopsies along and across the lamellae. The ratio decreased, going from the periosteum to the medullary cavity in the cortical bone, and from the periphery towards the center of trabeculae. These observations were consistent within serial sections obtained from the same biopsy, multiple biopsies obtained from the same necropsy specimen, and biopsies obtained from the two different necropsy specimens. The results presented here along with previously reported changes in osteonal bone show a relation between bone age and ``crystallinity/maturity'' (a parameter dependent on crystallite size, hydroxyapatite-like stoichiometry, abundance of substituting ions such as CO3 2−; the more crystalline/mature, the more hydroxyapatite-like stoichiometry, the bigger the crystallite size, the less the ion substitution by ions such as CO3 2−) as deduced by the 1020/1030 cm−1 ratio. Invariably, younger normal bone is less mature/crystalline than older. These results provide a ``baseline'' for description of mineral properties, to which diseased bones may be compared.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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