Hydrolysis hydroxyapatite

Hicks and Riley [287] have described a method for determining the natural levels of nucleic acids in lake and seawaters, which involves preconcentration by adsorption onto a hydroxyapatite, elution of the nucleic acids, and then photometric determination of the ribose obtained from them by hydrolysis. 

Hydroxyapatite (with some carbonate inclusions) is the most stable of the possible calcium phosphate salts that can be formed under physiological conditions. However, it is not the most rapid one to form. Instead, octacalcium phosphate (OCP) will precipitate more readily than hydroxyapatite. This led Brown in 1987 to propose that, as the kinetically favoured compound, OCP precipitates first, and then undergoes irreversible hydrolysis to a transition product OCP hydrolyzate [68]. This hypothesis is consistent with the observation that enamel comprises hydroxyapatite crystals that have the long, plate-like morphology that is generally considered characteristic of OCP crystals [69]. Overall, it seems that enamel crystals, with their elongated form, result from early precipitation of OCP, which forms a template on which hydroxyapatite units grow epitaxially [70,71]. This leads to enamel mineralisation with the observed thin, ribbon-like structure of crystals. 

Monma. H., Ueno, S. and Kanazawa, T. (1981). Properties of hydroxyapatite prepared by the hydrolysis of tricalcium phosphate. J. Chem. Tech. Biotechnol., 31 15-24. 

Methods for the synthesis of calcium hydroxyapatite have been reported in the past,1,2 but all of them produced either poorly crystallized or somewhat impure products. The following procedure produces a very well-crystallized compound which has a high degree of purity. The reaction is simply the hydrolysis of calcium monohydrogen phosphate to hydroxyapatite in a closed system. The major disadvantage is the small amount of material obtained from each hydrolysis because of the small capacity of the bombs used. Larger reaction vessels would minimize this objection. 

Figure 7. PAGE of reaction mixture after plasmin hydrolysis of B-casein for 0, 20, 30, 40, and 70 min (Slots 1-5) and Fractions 1 ana 2 from hydroxyapatite chromatography of hydrolysis products after plasmin treatment of fi-casein for 70 min (Slots 6 and 7). Fraction 2 contains a further phosphopeptide that is not visible in Slot 7 but appears on disc gels in the expected position for proteose peptone component 8F (cf. Ref. 32) (28).

The high frequency shift in the asymmetric P—O" stretching frequency caused by adsorption on hydroxyapatite appears to be a perturbation of lattice bonds as a result of surface changes. The minimum specific surface necessary to cause a lattice shift by a particular adsorbate has not been ascertained. The difference in sensitivity between different preparations of hydroxyapatite is shown in Table IV. These differences are best explained, at present, by differences in surface groups resulting from minor differences in washing procedure. Rootare, Deitz, and Carpenter (10) discuss hydrolysis reactions of surface phosphate ions and the... 

The fo5 of the acridinium ester in the hybridized probe decreases if mismatches are present. In such experiments, hydrolysis is omitted and RNA/DNA-probe hybrids are adsorbed to hydroxyapatite. Although about 80% may be hybridized, half-lives could be reduced, for some mismatches, to close to that of unhybridized probes (Arnold et al., 1989). Probes with mismatches cannot be used in solution hybridization but can be used in hybridization on solid phase where... 

Venkatesan, J., Qian, Z.-J., Ryu, B., Noel, V. T., and Kim, S.-K. (2011b). A comparative study of thermal calcination and an alkaline hydrolysis method in the isolation of hydroxyapatite from Thunnus obesus bone. Biomed. Mater. 6,035003. 

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