Biomimetic Models of "Acidic" Biomineralization Proteins

在生物矿化结构中，存在一组大分子，其主要功能是无机晶体成核并调节其生长。这些分子被称为“酸性”模板大分子。根据分子互补性的范例，一个有效的模板大分子必须将其配体原子组织成一个紧凑的阵列，这样这个阵列就可以与晶体基序上相应的金属原子阵列互补（Mann, 1993）。问题是，模板大分子的这种“组织”是如何实现的？以蛋白质模板大分子为例，如软体动物外壳、牙本质和骨骼中发现的“酸性”蛋白质，实现这种组织的问题成为蛋白质折叠的一个问题。因此，如果我们能够确定“酸性”蛋白质在二价阳离子和/或矿物晶体表面存在下是如何折叠的，我们就可以(1)了解这些复杂蛋白质是如何工作的，(2)最终将这些信息应用于设计无机基元识别聚合物，这些聚合物可以用作制造新型复合材料的组件。基于对“酸性”模板磷蛋白磷酸化蛋白的开创性NMR蛋白质折叠研究，我已经确定“酸性”模板蛋白经历pH和阳离子诱导的全局折叠转变，这些折叠转变是由铰链或中间结构域介导的，这些结构域两侧是金属结合的多电解质结构域。我假设这种铰链介导的折叠过程可能代表了一种可能的机制，可以创建有组织的模板分子表面，以补充某些晶体基序。在这个CAREER研究计划中，我将通过以下策略来完善我们对聚电解质-铰链折叠过程的了解：利用合成聚电解质-铰链-聚电解质（PHP）肽模拟学，核磁共振波谱学和mo分子模型来探索铰链功能阳离子诱导折叠过程。生物矿化组织，如骨骼、牙齿、海贝壳和浮游生物，代表了一种自然存在的复合材料：蛋白质和多糖与无机矿物晶体结合，形成高度结构化、定义明确的材料，这些材料已经存在了数百万年。作为科学家，我们能从这些结构中学到什么东西，帮助我们寻找新的生物和生态兼容材料吗？答案是肯定的，因为我们现在开始了解某些蛋白质可以通过特定的折叠途径与矿物质结合，这反过来又可以在微观层面上影响矿物晶体的尺寸和大小。该提案计划研究某些生物矿化蛋白的氨基酸序列，并确定金属离子如何影响蛋白质的形状或“折叠”。我们的方法将包括核磁共振波谱和计算机建模。这些信息将使我们了解蛋白质本身如何调节矿物晶体大小的形成，并最终形成复合结构。我的教学建议将强调师生项目，这将有助于改变纽约大学本科和研究生阶段的学习过程，并为高中和小学学生在大学阶段发展所需的科学技能做好准备。＊＊＊

9513250 Evans Within biomineralized structures, there exists a group of macromolecules whose primary function is the nucleation of inorganic crystals and the regulation of their growth. These molecules are referred to as "acidic" template macromolecules. According to the paradigm of molecular complementarity, an effective template macromolecule must organize its ligand atoms in a compact array, such that this array complements the corresponding metal atom array on a crystal motif (Mann, 1993). The question is, how is this "organization" of the template macromolecule achieved? In the case of protein template macromolecules, such as the "acidic" proteins found in mollusc shell, tooth dentine, and bone, the problem of attaining this organization becomes a problem in protein folding. Hence, if we can determine how "acidic" proteins fold in the presence of divalent cations and/or mineral crystal surfaces, we can (1) learn how these complex proteins work, and (2) eventually apply this information towards the design of inorganic motif-recognition polymers that can be utilized as components in the fabrication of novel composite materials. Based on pioneering NMR protein-folding studies of an "acidic" template phosphoprotein, phosphophoryn, I have determined that an "acidic" template protein undergoes pH- and cation-induced global folding transitions, and that these folding transitions are mediated by hinge or intervening domains that are flanked on either side by the metal-binding polyelectrolyte domains. I hypothesize that this hinge-mediated folding process may represent a possible mechanism for creating organized template molecular surfaces that will complement certain crystal motifs. In this CAREER research proposal, I will refine our knowledge of the polyelectrolyte-hinge folding process by using the following strategy: Explore hinge function the cation-induced folding process by utilizing synthetic polyelectrolyte-hinge-polyelectrolyte (PHP) peptidomimetics, NMR spectroscopy, and mo lecular modeling. %%% Biomineralized tissues, such as bone, teeth, sea shells, and plankton, represent a naturally-occuring composite material: Proteins and polysaccharides combine with inorganic mineral crystals to form highly structured, well-defined materials which have existed for millions of years. Can we, as scientists, learn anything about these structures that might help us in our quest for new bio- and eco-compatible materials? The answer is yes, since we are now beginning to understand that certain proteins can bind to minerals via a specific folding pathway, which, in turn, can affect the dimension and size of mineral crystals on a microscopic level. This proposal plans to study the amino acid sequences of certain biomineralization proteins, and, determine how metal ions affect the shape or "folding" of the protein. Our methods will include nuclear magnetic resonance spectroscopy and computer modeling. This information will give us some idea of how the proteins themselves regulate the formation of mineral crystal sizes, and ultimately, the formation of composite structures. My teaching proposal will emphasize teacher-student programs which will help to change the learning process at the undergraduate and graduate level at NYU, and, prepare high school and elementary school students for what science skills they will need to develop in their college years. ***