Department of Chemistry, Center for Biomaterials and Biopathways, Zhejiang University, Hangzhou, Zhejiang 310027, China.
Proc Natl Acad Sci U S A. 2009 Dec 29;106(52):22096-101. doi: 10.1073/pnas.0909040106. Epub 2009 Dec 10.
Many animals such as crustacean periodically undergo cyclic molt of the exoskeleton. During this process, amorphous calcium mineral phases are biologically stabilized by magnesium and are reserved for the subsequent rapid formation of new shell tissue. However, it is a mystery how living organisms can regulate the transition of the precursor phases precisely. We reveal that the shell mineralization from the magnesium stabilized precursors is associated with the presence of Asp-rich proteins. It is suggested that a cooperative effect of magnesium and Asp-rich compound can result into a crystallization switch in biomineralization. Our in vitro experiments confirm that magnesium increases the lifetime of amorphous calcium carbonate and calcium phosphate in solution so that the crystallization can be temporarily switched off. Although Asp monomer alone inhibits the crystallization of pure amorphous calcium minerals, it actually reduces the stability of the magnesium-stabilized precursors to switch on the transformation from the amorphous to crystallized phases. These modification effects on crystallization kinetics can be understood by an Asp-enhanced magnesium desolvation model. The interesting magnesium-Asp-based switch is a biologically inspired lesson from nature, which can be developed into an advanced strategy to control material fabrications.
许多动物如甲壳类动物周期性地经历外骨骼的周期性蜕皮。在这个过程中，无定形的钙矿相被镁生物稳定，并为随后新壳组织的快速形成保留下来。然而，生物体如何精确地调控前体相的转变仍然是一个谜。我们揭示了从镁稳定的前体中进行的壳矿化与富含天冬氨酸的蛋白质的存在有关。有人认为，镁和富含天冬氨酸的化合物的协同作用可能导致生物矿化中的结晶转变。我们的体外实验证实，镁增加了溶液中无定形碳酸钙和磷酸钙的寿命，从而可以暂时关闭结晶。虽然天冬氨酸单体本身抑制纯无定形钙矿的结晶，但它实际上降低了镁稳定前体的稳定性，从而开启了从无定形到晶形相的转变。通过天冬氨酸增强的镁去溶剂化模型可以理解对结晶动力学的这些修饰作用。基于镁-天冬氨酸的有趣开关是来自大自然的生物启发式教训，可以开发成一种控制材料制备的先进策略。
