Callens F J, Verbeeck R M, Naessens D E, Matthys P F, Boesman E R
Laboratory of Crystallography, State University Gent, Belgium.
Calcif Tissue Int. 1991 Apr;48(4):249-59. doi: 10.1007/BF02556376.
The ESR spectrum of X-irradiated carbonated apatites precipitated from aqueous solutions was studied as a function of their carbonate content and drying temperature. When the latter increases from 25 to 400 degrees C, the ESR spectrum is gradually modified and becomes similar to the spectrum of carbonated apatites, synthesized at high temperatures by solid state reactions. The latter ESR spectrum is dominated by CO3(3-)-contributions whereas the spectrum of precipitated samples dried at 25 degrees C can mainly be interpreted in terms of CO2-, CO3-, and O- ions. The behavior of these earlier-reported CO2-, CO3-, and O- centers is now studied as a function of drying temperature. In addition, the Spin Hamiltonian parameters of the CO3(3-) centers are determined and some other new paramagnetic radicals are discussed. It is shown that a CO3(2-) ion at a phosphate lattice site (B-type substitution) may give rise to either a CO2-, CO3-, or CO3(3-) radical on X-irradiation, depending on the sample preparation conditions. A surface CO3(2-) ion may cause a surface CO2-, CO3-, or O- radical. From the reported results it is not unambiguously clear whether the CO3(3-) ion detected in the samples with the relatively lowest carbonate content should be located on the surface or on a hydroxyl lattice site (A-type substitution). An important result is that the absolute concentration of the B-type CO3(3-) ion increases with increasing carbonate content as was also the case for the earlier reported B-type radicals (isotropic CO2- and CO3-). On the other hand, the absolute concentration of the surface radicals decreases with increasing carbonate content. The reported results show that similar deconvolution techniques can be applied in the future for the study of ESR spectra of calcified tissues. This will allow a more efficient phenomenological investigation of the latter.
研究了从水溶液中沉淀出的经X射线辐照的碳酸化磷灰石的电子自旋共振（ESR）谱，该谱是其碳酸盐含量和干燥温度的函数。当干燥温度从25℃升高到400℃时，ESR谱逐渐改变，变得类似于通过固态反应在高温下合成的碳酸化磷灰石的谱。后一种ESR谱以CO₃³⁻的贡献为主，而在25℃干燥的沉淀样品的谱主要可以用CO₂⁻、CO₃⁻和O⁻离子来解释。现在研究这些先前报道的CO₂⁻、CO₃⁻和O⁻中心的行为随干燥温度的变化。此外，确定了CO₃³⁻中心的自旋哈密顿参数，并讨论了一些其他新的顺磁自由基。结果表明，磷酸盐晶格位点上的CO₃²⁻离子（B型取代）在X射线辐照下可能产生CO₂⁻、CO₃⁻或CO₃³⁻自由基，这取决于样品制备条件。表面的CO₃²⁻离子可能导致表面的CO₂⁻、CO₃⁻或O⁻自由基。从报道的结果尚不能明确确定，在碳酸盐含量相对最低的样品中检测到的CO₃³⁻离子是位于表面还是位于羟基晶格位点（A型取代）。一个重要的结果是，B型CO₃³⁻离子的绝对浓度随着碳酸盐含量的增加而增加，早期报道的B型自由基（各向同性的CO₂⁻和CO₃⁻）也是如此。另一方面，表面自由基的绝对浓度随着碳酸盐含量的增加而降低。报道的结果表明，类似的去卷积技术未来可应用于钙化组织的ESR谱研究。这将使对钙化组织进行更有效的唯象学研究成为可能。
