Biomineralization Processes on Natural and Synthetic Substrates

生物矿化材料，如软体贝壳，是在低温下形成的具有特殊强度和结晶有序性的无机单晶和生物聚合物的复杂片层聚集体。生物合成过程给出了令人难以置信的规律性：1)纳米尺度(原子)的无机和蛋白质结构，以及2)中尺度(大于约0.1微米)的生长的开始和终止，从而产生高度有序的微层压复合材料的形成，从而使所得到的生物材料具有其强度和灵活性。这项跨学科的研究将研究基本的化学和立体化学相互作用，这些相互作用在分子水平上在纳米和介观结构水平上控制这种生物中介的矿物成核和生长。无机相的成核和生长将在低温和压力下从溶液中进行：i)无机和生物矿物模板；ii)合成有机模板，其光学活性基团和离子中心的表面阵列与体内生物聚合物模板表面相似；以及iii)生物模板多肽。拟议的实验将使用一种新的合成和表征技术的组合，包括多肽测序和合成以形成结构定向模板、原位原子力显微镜和掠入射X射线衍射。自然对模板的使用涉及到在低温和压力下从溶液中生长材料，这一过程目前只有很少的人了解，材料科学家很少使用。越来越明显的是，这些被称为“化学结合陶瓷”的新材料具有出众的弯曲强度。这项研究的拟议活动有望导致利用纳米结构设计和合成技术开发低温合成机械性能优越和/或高度定向的材料的新方法。人们希望，随着对模板机理的更多了解，模板动力学将得到改善，模板导向材料的合成可以在更快的时间尺度上完成。虽然这项研究最初将集中在软体动物的矿化过程，特别是涉及CaCO3的生长，但所有多细胞生物似乎都进化出了类似的化学工具，用于对矿物的成核和生长进行遗传控制。因此，我们预计我们的实验将增加对生物矿化相关领域的洞察，包括骨生长。通过更充分地了解矿化是如何在一个特定物种中进行编排的，更复杂的生物矿化问题的答案肯定会随之而来。我们的结果对医学领域的影响是可以预见的；骨成核生长基于与软体动物贝壳相同的基本化学和结构相互作用，只是成核大分子是包裹矿化空间的胆脂膜的一部分。因此，羟基磷灰石在这种脂质双层表面上的成核作用的研究可能会随之而来。另一方面，更多地了解可溶生长抑制剂有助于防止不希望看到的晶体生长。医学上的例子包括牙菌斑、器官结石、动脉硬化和植入的心脏瓣膜钙化。在工业冷却系统、石油回收系统和市政供水系统中，CaCO3和CaSO4污垢处理设施中形成的不希望看到的水垢沉积物。新的有机化合物可以抑制结垢，具有成本效益，并且在更大的温度、pH和盐度范围内都是有用的。

Biomineralized materials such as molluscan shells are complex lamellar aggregates of inorganic single crystals and biopolymers that form at low temperature with exceptional strength and crystalline ordering. The biosynthesis process gives and incredible regularity to 1) inorganic and protein structure at nanoscale (atomic) dimensions, and 2) the initiation and termination of growth at mesoscale (is greater than approximately 0.1 microns) dimensions, thus generating the highly ordered microlaminate composite formation that gives the resulting biomaterial its strength and flexibility. This interdisciplinary research will investigate the fundamental chemical and stereochemical interactions which, at the molecular level control such biologically mediated mineral nucleation and growth at both the nano- and mesostructure level. Nucleation and growth of inorganic phases will be carried out from solutions at low temperatures and pressures on: i) inorganic and biological mineral templates; ii) synthetic organic templates with optically active groups and surface arrays of ionic sites similar to those found on biopolymeric templating surfaces in vivo; and iii) biogenic templating polypeptides. The proposed experiments will use a novel combination of synthesis and characterization techniques, including polypeptide sequencing and synthesis to form structure directing templates, in situ atomic force microscopy and grazing incidence X-ray diffraction. %%% Nature's use of templating involves material growth from solutions at low temperatures and pressures, a process that is currently only poorly understood and little used by materials scientists. Increasingly, it is becoming apparent that these new materials, which have been referred to as "chemically bonded ceramics", have exceptional flexural strength. The proposed activity of this research is expected to lead to the development of new methods for the low temperature synthesis of mechanically superior and/or highly oriented materials using nanostructure design and synthesis techniques. It is hoped that as more light is shed on templating mechanisms involved, templating kinetics will be improved and template-directed materials synthesis can be done on a faster time scale. While the research will initially be centered around the mineralization processes of molluscs, which specifically involves CaCO3 growth, all multicellular organisms appear to have evolved with chemically similar tools for carrying out genetic control over mineral nucleation and growth. We therefore expect that our experimentation will increase insight on related areas of biomineralization, including bone growth. By more fully realizing how mineralization is orchestrated in one particular species, the answers to more complex biomineralization problems will surely follow. Implications of our results for the medical field are foreseeable; bone nucleation growth is based on the same fundamental chemical and structural interactions as occurs in mollusc shells, except that the nucleating macromolecules are part of a bilipid membrane which encloses the mineralization space. Thus, the study of hydroxyapatite nucleation onto such lipid bilayer surfaces may follow. On the other hand, a greater understanding of soluble growth inhibitors can be useful for the prevention of undesirable crystal growth. Medical examples include dental plaque, organ stones, hardening of the arteries, and calcification of implanted heart valves. In industrial cooling systems, oil recovery systems, and municipal water supplies, undesirable water-formed scale deposits of CaCO3 and CaSO4 foul treatment facilities. New organic compounds may inhibit scale formation, be cost effective, and be useful over a larger range of temperatures, pH, and salinity.