Sequence Directed Crystal Design in the Prismatic Layer of the Mollusk

智力优势：软体动物的外壳由两个纳米结构的相对层组成。 内层或珍珠状钠长石层由文石晶体形态的碳酸钙组成，并赋予复合材料断裂韧性。外层或棱柱层由方解石改性的单晶碳酸钙的长棱柱柱组成，该方解石改性赋予抗穿刺性和抗裂纹扩展性。 贝壳层和棱柱层最初都是在由无定形碳酸钙组成的前体相的壳发育过程中产生的。 在这里，它建议调查的详细机制，棱镜层组装通过特定的带负电荷的天冬氨酸和谷氨酸丰富的蛋白质，统称为Asprich，被认为是指导矿化过程的中介作用。 这类蛋白质在N和C末端具有高度保守的序列。 来自N-末端结构域的肽（片段1）促进径向菱形晶体排列，而来自C-末端的片段2促进晶体表面的孔隙或空隙。 这个项目将利用代表片段1和2的合成肽来了解保守序列如何控制晶体生长和设计。 特别是，一级序列组织，氨基酸身份，二级结构，金属离子结合能力与晶体形态选择和生长动力学的相关性将进行研究。 扫描电子显微镜和原子力显微镜将用于检查晶体形态。 各种生物物理技术（CD，NMR，等温滴定量热法，质谱法，纳米SIMS，X射线衍射，计算机模拟）将提供手段来检查Asprich域的Ca（II）和Mg（II）结合热力学，2-和3D结构，表面静电，和晶体结合和闭塞内的方解石矩阵的属性。 布鲁克海文国家实验室（Brookhaven National Laboratory）DiMasi）和劳伦斯利弗莫尔国家实验室（C。Orme）将提供当地无法提供的设备。 该项目为研究生提供了一个高度多学科培训的平台，从肽合成到各种显微镜，到同步加速器X射线衍射的生物物理表征，到NMR，nano-SIMS和等温滴定量热法。 该项目有可能促进对生物矿化的理解，并为仿生复合材料制造提供模型。 PI是纽约科学院高中科学夏令营的参与者，邀请1-2名高中生到实验室做研究实验。 他还参加了合作伙伴在科学高中科学教师研究计划，介绍纽约高中科学教师在他们的暑假研究项目。

INTELLECTUAL MERIT: Mollusk shells consist of two nanostructured, opposing layers. The inner, or pearl-like nacreous, layer consists of calcium carbonate in the aragonite crystal morphology and confers fracture toughness on the composite. The outer, or prismatic, layer consists of long prismatic columns of single crystal calcium carbonate in the calcite modification that confers puncture and crack propagation resistance. Both the nacreous and prismatic layers arise initially during shell development from a precursor phase, consisting of amorphous calcium carbonate. Here it is proposed to investigate the detailed mechanism by which the prismatic layer is assembled through the intermediacy of specific negatively charged aspartic acid and glutamic acid-rich proteins, known collectively as Asprich, thought to direct the mineralization process. Proteins of this class have highly conserved sequences at the N and C termini. A peptide (Fragment 1) from the N-terminal domain promotes radial rhombohedral crystal arrangements, while Fragment 2 from the C-terminus promotes porosities or voids at crystal surfaces. This project will utilize synthetic peptides representing Fragments 1 and 2 to understand how conserved sequences control crystal growth and design. In particular, the correlation of primary sequence organization, amino acid identity, secondary structure, and metal ion binding capacity with crystal morphology selection and growth kinetics will be investigated. Scanning electron and atomic force microscopies will be used to examine crystal morphologies. Various biophysical techniques (CD, NMR, isothermal titration calorimetry, mass spectrometry, nano-SIMS, X-ray diffraction, computer simulation) will provide means to examine the properties of the Asprich domains with regard to Ca(II) and Mg(II) binding thermodynamics, 2- and 3D structure, surface electrostatics, and crystal binding and occlusion within the calcite matrix. Collaborations with Brookhaven National Laboratory (E. DiMasi) and Lawrence Livermore National Laboratory (C. Orme) will provide access to equipment not available locally to the project.BROADER IMPACTS: The project provides a platform for highly multidisciplinary training of graduate students ranging from peptide synthesis, to various microscopies, to biophysical characterization with synchrotron X-ray diffraction to NMR, nano-SIMS, and isothermal titration calorimetry. The project has the potential to advance the understanding of biomineralization and to provide models for biomimetic composite fabrication. The PI is a participant in the New York Academy of Sciences High School Science Summer Camp and invites 1-2 high school students to the lab to do research experiments. He also participates in the Partners in Science high school science teacher research program which introduces NYC high school science teachers to research projects during their summer vacation.