Building Biominerals: finding the tools that shape biogenic calcite and its signatures

在古气候学研究中，气候和地球表面环境是在整个地质历史中重建的，信息通常从化石贝壳、珊瑚和其他生物形成的矿物(生物矿物)的信号中获得。例如，这些信号或替代物是在化石中测量的痕量金属浓度或同位素比率，它们告诉我们生物在建造外壳期间经历了什么海洋表面温度，或者有多少营养物质可用；即使存在多少极地冰也可以重建。然而，可靠地应用这些替代物来重建过去的环境和气候，需要充分了解导致生物矿物记录这些替代物的过程。矿物吸收痕量金属的第一步发生在这些矿物的表面，这一步的关键是该表面的结构。一些痕量金属倾向于附着在非常“开放”的部位，而另一些则倾向于较“封闭”的部位。这种对特定表面位置的偏好是可能影响最终被解释为代理的信号的许多因素之一。生物体高度有能力控制它们所形成的生物矿物质的形状。通过控制这种形状，它们控制了含有微量金属的表面的结构。我们知道，有机体将氨基酸等有机化合物用作塑造生物矿物质的工具。为了了解这些有机化合物对生长的生物矿物表面的影响，以及在生物矿物生长过程中记录替代物的过程，我将进行实验和理论研究。实验研究的重点是在模拟方解石生物矿化过程中确定氨基酸与选定的痕量金属之间的相互作用。其中，我将在氨基酸和微量金属存在的情况下生长方解石晶体。这些结果将量化晶体形态的生物调节在多大程度上解释生物源方解石微量金属特征的变化。理论研究的重点是理解通过实验观察到的相互作用背后的机制。在东道国研究所内开发的方解石原子尺度模拟技术是详细了解方解石表面与痕量金属和有机分子相互作用的理想工具。我之前开发的方解石地球化学模型将用于连接宏观、微观和原子尺度的结果。最终，所有的结果都将与当前的生理生物矿化概念合并成一个最先进的生物矿化模型。我雄心勃勃的研究项目的成果在分子水平的表面化学和宏观尺度的地球化学模型之间架起了桥梁，并通过实验数据在所有阶段进行了验证。该项目的具体应用是生物矿化和古气候学领域。

In paleoclimatological studies, where the climate and Earth's surface environment are reconstructed throughout the geological past, information is often obtained from signals in fossil shells, corals and other biologically formed minerals (biominerals). These signals, or proxies, are for example trace metal concentrations or isotope ratios measured in fossils, that tell us what sea surface temperature the organism experienced during the building of its shell, or how much nutrients were available; even how much polar ice was present can be reconstructed. However, reliable application of these proxies to reconstruct past environments and climate requires sound knowledge of the processes that lead to the recording of these proxies by biominerals The first step in the uptake of trace metals by minerals occurs at the surface of those minerals and crucial in this step is the structure of that surface. Some trace metals prefer to attach to very "open" sites, while others prefer more "closed" sites. This preference for particular surface sites is one of the many factors that can affect the signal ultimately interpreted as a proxy. Organisms are highly capable of controlling the shape of the biominerals they build. By controlling this shape, they control the structure of the surface through which trace metals incorporate.We know that organic compounds such as amino acids are used by organisms as tools to shape their biominerals. In order to understand the effects these organic compounds have on the growing biomineral surface, and on the process of recording proxies during biomineral growth, I will conduct both experimental and theoretical research. The experimental line of research focuses on determining the interaction between amino acids and selected trace metals during mimicked calcite biomineralisation. Among others, I will grow calcite crystals in the presence of amino acids and trace metals. The results will quantify the extent to which biological regulation of crystal morphology may explain variations in trace metal signatures of biogenic calcites. The theoretical line of research focuses on understanding the mechanisms behind the interactions observed experimentally. Atomic-scale simulation techniques developed for calcite within the host institute are the ideal tool to obtain detailed insight into the interaction of the calcite surface with trace metals and organic molecules. Previous geochemical models I developed for calcite will be used to bridge the macroscopic, microscopic and atomic-scale results. Ultimately, all results will be merged with current physiological biomineralisation concepts into a state-of-the-art biomineralisation model.The outcome of my ambitious research project bridges between molecular level surface chemistry and macroscale geochemical modelling, validated at all stages by experimental data. Specific applications of the project are in the fields of biomineralisation and paleoclimatology.