Structural, spatial, and temporal features guiding amelogenins transformation of calcium phosphate into enamel

项目概要 拟议工作的目标是建立对分子水平、结构的理解 釉原蛋白指导牙釉质的分层生长。牙釉质是已知最坚硬的生物矿物质之一， 其分层结构可防止裂纹扩展，使其能够供许多人终生使用。 然而，牙釉质确实会发生自然发生的疾病或损伤，而我们目前的治疗方法远远达不到 大自然制造了珐琅。在过去的十年中，我们逐渐了解到牙釉蛋白组装成 四级结构为含有 12 种蛋白质的寡聚物，这些单元进一步组装成纳米球。 这些组件，控制它们的分子水平相互作用，它们与磷酸钙的相互作用， 以及它们在矿物相变中的作用对于牙釉质的形成尚不清楚。我们确实知道 牙釉质蛋白是形成牙釉质环境中的主要蛋白质，对于牙釉质的形成至关重要 基于显示牙釉质表型严重受损的牙釉蛋白缺失小鼠模型。蛋白质结构 通常决定了功能，但我们才刚刚开始揭示牙釉蛋白的结构。此外，矿物质中 牙釉质环境从离子开始，在变长之前经过非晶态阶段， 结晶 HAP 针。体内和体外研究都表明釉原蛋白控制着这一点 相变过程，但该过程的结构、空间和时间方面并不 明白了。在我们提出的工作中，我们将一套先进的表征技术引入体外系统 模拟牙釉质发育以评估釉原蛋白与钙相互作用时的结构 磷酸盐，了解正在发育的磷酸钙矿物质周围牙釉蛋白的空间分布 丝带，并开发磷酸钙簇转化过程的分子水平视图， 通过非晶相，到结晶 HAP。这套技术从未被应用过 了解牙釉质生长的挑战，并将导致对牙釉质发育的了解 目前所缺乏的牙釉质。这项工作的结果与一般的生物矿化系统相关 并可能最终为牙釉质替代品提供更强大的治疗方法。

Project Summary The goal of the proposed work is to develop a molecular level, structural understanding of the role of amelogenin in directing the hierarchical growth of enamel. Enamel is one of the hardest biominerals known, and is hierarchically structured to prevent crack propagation, allowing it to last many people a lifetime. However, naturally occurring diseases or damage do occur to enamel and our current therapies fall far short of nature made enamel. Over the past decade we have come to understand that amelogenin assembles into quaternary structures as oligomers containing 12 proteins, units which further assemble into nanospheres. These assemblies, the molecular level interactions governing them, their interactions with calcium phosphate, and their role in mineral phase transformations, are not well understood for enamel formation. We do know that the protein amelogenin, the predominant protein in the forming enamel milieu, is critical in formation based on amelogenin null mouse models showing severely damaged enamel phenotypes. Protein structure often dictates function, yet we have only begun to reveal the structure of amelogenin. Further, the mineral in the enamel milieu begins as ions, and transitions through an amorphous stage prior to becoming elongated, crystallized HAP needles. Both in vivo and in vitro studies have demonstrated that amelogenin controls this phase transformation process, but the structural, spatial, and temporal aspects of this process are not understood. In our proposed work, we bring a set of advanced characterization techniques to an in vitro system simulating developing enamel to evaluate the structure of amelogenin when interacting with calcium phosphates, to understand the spatial distribution of amelogenin around developing calcium phosphate mineral ribbons, and to develop a molecular level view of the transformation process from calcium phosphate clusters, through the amorphous phase, on to crystalline HAP. This suite of techniques has never been brought to bear on understanding the challenge of enamel growth and will result in an understanding of the development of enamel that is currently lacking. The results of this work are relevant to biomineralization systems in general and may ultimately inform more robust therapeutics for enamel replacements.