Przeniosło Radosław, Stolarski Jarosław, Mazur Maciej, Brunelli Michela
Institute of Experimental Physics, University of Warsaw, Hoza 69, PL-00-681 Warsaw, Poland.
J Struct Biol. 2008 Jan;161(1):74-82. doi: 10.1016/j.jsb.2007.09.020. Epub 2007 Oct 5.
Microscopic (AFM and FESEM) observations show that scleractinian coral biomineral fibers in extant Desmophyllum and Favia, and fossil Jurassic Isastrea are composed of nanocrystalline grains of about 30-100 nm in size. In contrast to these findings, SR diffraction data on the same coral materials exhibit narrow Bragg peaks suggesting much larger crystallite size. These seemingly contradicting results of microscopic and diffraction studies are reconciled within a new, minute-scale model of scleractinian biomineral fibers. In this model, nanocrystalline aragonite units are interconnected by mineral bridges and form aggregates usually larger than 200 nm. Most likely, the size of the aggregates is resulting from physiological biomineralization cycles that control cellular secretion of ions and biopolymeric species. Intercalation of biopolymers into crystal lattice may influence consistently several structural parameters of the scleractinian coral bio-aragonite in all studied samples: (i) the lattice parameters and internal strains of the bio-aragonite are larger than in mineral aragonite, (ii) lattice parameter elongations and internal strains reveal directional anisotropy with respect to crystallographic axes.
微观（原子力显微镜和场发射扫描电子显微镜）观察表明，现存的Desmophyllum和Favia中的石珊瑚生物矿物纤维，以及侏罗纪化石Isastrea，都是由尺寸约为30 - 100纳米的纳米晶粒组成。与这些发现相反，对相同珊瑚材料的同步辐射衍射数据显示出窄的布拉格峰，表明微晶尺寸要大得多。微观和衍射研究中这些看似矛盾的结果，在一个新的、微小尺度的石珊瑚生物矿物纤维模型中得到了调和。在这个模型中，纳米晶文石单元通过矿物桥相互连接，形成通常大于200纳米的聚集体。聚集体的尺寸很可能是由控制离子和生物聚合物细胞分泌的生理生物矿化循环导致的。生物聚合物插入晶格可能会一致地影响所有研究样本中石珊瑚生物文石的几个结构参数：（i）生物文石的晶格参数和内部应变大于矿物文石；（ii）晶格参数伸长和内部应变相对于结晶轴显示出方向各向异性。
