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

项目摘要 拟议工作的目标是发展一个分子水平，结构的理解的作用， 釉原蛋白在引导釉质的分级生长中的作用。釉质是已知最坚硬的生物矿物之一， 并且是分层结构的，以防止裂纹扩展，使其能够持续许多人的一生。 然而，自然发生的疾病或损伤确实会发生在牙釉质上，我们目前的治疗方法远远达不到 自然创造了珐琅。在过去的十年里，我们已经了解到，釉原蛋白组装成 四级结构作为含有12个蛋白质的低聚物，进一步组装成纳米球的单元。 这些组件，控制它们的分子水平的相互作用，它们与磷酸钙的相互作用， 以及它们在矿物相变中的作用，对于釉质形成还没有很好的理解。我们知道 釉原蛋白是形成釉质环境的主要蛋白质， 基于显示严重受损的釉质表型的釉原蛋白缺失小鼠模型。蛋白质结构 通常决定功能，但我们才刚刚开始揭示釉原蛋白的结构。此外， 釉质环境开始为离子，并在变长之前转变为无定形阶段， 结晶的HAP针。体内和体外研究都表明，釉原蛋白控制这一过程。 相变过程，但这个过程的结构，空间和时间方面不是 明白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 模拟发育中的牙釉质以评价釉原蛋白与钙相互作用时的结构 了解釉原蛋白在发育中的磷酸钙矿物质周围的空间分布 带，并开发从磷酸钙簇转化过程的分子水平视图， 通过非晶相，到结晶HAP。这套技术从未被用于 了解牙釉质生长的挑战，并将导致对牙釉质发育的理解， 这是目前所缺乏的。这项工作的结果是相关的生物矿化系统一般 并且最终可以为牙釉质替换提供更稳健的治疗方法。

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.