Fleet Michael E
Department of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7, Canada.
Front Biosci (Elite Ed). 2013 Jan 1;5(2):643-52. doi: 10.2741/e645.
The location and orientation of the carbonate ion in the channel (A) and phosphate (B) positions of hydroxyapatite (CHAP) have been investigated by single-crystal X-ray structure and Fourier transform infrared (FTIR) spectroscopy, using crystals synthesized at high pressure. The type A carbonate ion is oriented in the apatite channel with two oxygen atoms close to the c-axis and the B carbonate ion is located near a sloping face of the substituted phosphate tetrahedron. Close comparison of FTIR and X-ray structure results shows that a Na-bearing CHAP containing approximately equal amounts of A and B carbonate ions is a realistic model for the overall crystal structure of biological apatite. However, the absence of distinct OH stretch and OH libration bands indicates that the hydroxyl content of biological apatite is disordered in respect to its orientation and precise location both in the channel and elsewhere in the structure.
通过单晶X射线结构和傅里叶变换红外（FTIR）光谱，利用高压合成的晶体，研究了碳酸根离子在羟基磷灰石（CHAP）的通道（A）和磷酸盐（B）位置的位置和取向。A型碳酸根离子在磷灰石通道中取向，两个氧原子靠近c轴，而B型碳酸根离子位于取代磷酸四面体的倾斜面附近。FTIR和X射线结构结果的仔细比较表明，含有大致等量A型和B型碳酸根离子的含钠CHAP是生物磷灰石整体晶体结构的一个现实模型。然而，没有明显的OH伸缩和OH摆动带表明，生物磷灰石的羟基含量在其在通道内以及结构中其他位置的取向和精确位置方面是无序的。
