Biological minerals formed from strontium and barium sulphates. II. Crystallography and control of mineral morphology in desmids
Biological minerals formed from strontium and barium sulphates. II. Crystallography and control of mineral morphology in desmids
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由硫酸锶和硫酸钡形成的生物矿物质。
DOI：
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
A. J. Brook
中科院分区：
文献类型：
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作者：
J. Wilcock;C. Perry;Robert J.P. Williams;A. J. Brook
用电子显微镜和电子衍射仪研究了由一系列结晶物生成的硫酸钡晶体的结晶学和形貌。BaSO4晶体的形态因结晶物和水化学的不同而不同。板状、菱形晶体通常由新月球藻产生，六方或椭圆形晶体由米氏微体产生。高分辨电子显微镜(HRTEM)证实了生物沉淀物的单晶性质。这些晶体都具有垂直于[001]带轴线的平面，与地质和合成硫酸钡的典型结晶习性相当，表明对降水的生物控制程度有限。体内外M2+(Ba2+或Sr2+)：SO2-4离子的比例影响晶体的形态。对于新月球藻，M2+：SO2-4离子比小于1：1时产生菱形晶体，离子比大于10：1时产生六方晶体。对于米氏藻，离子比为0.01：1产生六方晶体；离子比为1：1产生六角形和椭圆形晶体的混合物，离子比超过10：1产生椭圆形晶体。将结晶法生成的晶体形态与离子比相近的合成晶体进行了比较。讨论了生物控制的明显有限程度和离子环境对晶体形态发展的重要性。结果表明，桥粒晶体形态可作为细胞内局部晶体形成环境的诊断依据。
The crystallography and morphology of barium sulphate crystals produced by a range of desmid species have been examined by electron microscopy and electron diffraction. The morphology of the BaSO4 crystals varies between desmid species and water chemistry. Tabular, rhombic crystals are commonly produced by Closterium lunula and hexagonal or elliptical crystals by Micrasterias thomasiana. High-resolution transmission electron microscopy (hrtem) has confirmed the single-crystal nature of the biological precipitates. The crystals all lie with their tabular faces perpendicular to the [001] zone axis and are comparable with the typical crystal habit of geological and synthetic barium sulphates, suggesting a limited degree of biological control over precipitation. M2+ (Ba2+ or Sr2+) : SO2-4 ion ratios in vivo and in vitro have been shown to affect the morphology of the crystals produced. For Closterium lunula an M2+: SO2-4 ion ratio of less than 1:1 produces rhombic crystals and an ion ratio of more than 10:1 produces hexagonal crystals. For Micrasterias thomasiana, an ion ratio of 0.01:1 produces hexagonal crystals; an ion ratio of 1:1 produces a mixture of hexagonal and elliptical crystals, and an ion ratio of more than 10:1 produces elliptical crystals. Crystal morphologies produced by desmids have been compared with those of synthetic crystals produced at similar ion ratios. The apparently limited extent of biological control and the importance of the ionic environment on the development of crystal morphology are discussed. It is proposed that desmid crystal morphology may provide a diagnostic for the local environment of crystal formation in the cell.