Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
Curtin Institute for Computation/The Institute for Geoscience Research, School of Molecular and Life Sciences, Curtin University, PO Box U1987, Perth, Western Australia 6845, Australia.
J Phys Chem B. 2022 Jul 14;126(27):5103-5109. doi: 10.1021/acs.jpcb.2c03440. Epub 2022 Jun 28.
Amorphous calcium carbonate (ACC) has been found in many different organisms. Biogenic ACC is frequently a precursor in the formation of calcite and aragonite. The process of structural transformation is therefore of great interest in the study of crystallization pathways in biomineralization. Changes in the prepeak/main peak (L'/L) intensity ratio of the Ca L-edge X-ray absorption spectroscopy (XAS) of Ca-rich particles in skeleton-building cells of sea urchin larva revealed that ACC precipitates through a continuum of states rather than through abrupt phase transitions involving two distinct phases as formerly believed. Using an atomic multiplet code, we show that only a tetragonal or "umbrella-like" distortion of the Ca coordination polyhedron can give rise to the observed continuum of states. We also show on the basis of the structures obtained from previous molecular dynamics simulations of hydrated nanoparticles that the Ca L-edge is not sensitive to atomic arrangements in the early stages of the transformation process.
无定形碳酸钙 (ACC) 已在许多不同的生物体中被发现。生物成因的 ACC 通常是方解石和文石形成的前体。因此，在生物矿化的结晶途径研究中，结构转化过程非常有趣。通过对富含钙的颗粒在海胆幼虫骨架形成细胞中的钙 L 边 X 射线吸收光谱 (XAS) 的预峰/主峰 (L'/L) 强度比的变化的研究，揭示了 ACC 沉淀是通过连续状态而不是以前认为的涉及两个不同相的突然相变来实现的。使用原子多重态代码，我们证明只有 Ca 配位多面体的四方或“伞状”变形才能导致观察到的连续状态。我们还基于先前水合纳米颗粒的分子动力学模拟获得的结构表明，Ca L 边在转化过程的早期阶段对原子排列不敏感。
