Metal-Halogen Biomaterials and Wear Resistance

标题：金属-卤素生物材料与耐磨性PI：罗伯特·斯科菲尔德，俄勒冈大学尤金分校许多节肢动物和其他无脊椎动物的下巴、腿爪、刺和其他工具，含有超高含量的重金属，如锌和锰，以及卤素，如溴和氯。尽管其浓度达到了干重的25%，但与钙化的人类牙齿不同的是，无脊椎动物组织中不会充满这种生物矿物质。相反，金属卤素生物材料似乎是一种截然不同的系统，在小型生物中得到了更广泛的应用。人们对这些金属卤素生物材料知之甚少，尽管它们在较大生物体中的主要对应物--钙化--被认为是如此重要，以至于它的出现使软体动物和脊椎动物等生物的进化成为可能。在他们之前由美国国家科学基金会资助的项目中，PIS发表了第一张关于富锌“工具”的发展和微观结构的全面图片，表明锌在外骨骼发育中沉积很晚，富锌组织包含一个独特的沟渠网络，锌通过这个网络沉积。PI测试的假设是，金属卤素组织代表一种不同类别的生物材料，与生物矿化组织有很大不同。此外，他们还提出，由于远亲生物的金属卤素组织具有相似性，这一系统很可能在昆虫和螯合物进化之前就已经进化得很早了。PI指数表明，在成年早期，随着锌的加入，切叶蚁下颌齿的硬度增加了三倍，这表明这种与锌相关的硬度增加是年轻人和老年人叶加工行为差异的原因。在这项研究中，4个假说将集中在两个方面进行检验：1)锌改变机械性能的化学形式和机制，2)无脊椎动物与更常见的生物矿化组织的机械性能的比较。预计，对于小型生物，金属卤素生物材料将比钙化提供更有利的硬度和耐磨性的平衡。这项研究将加深我们对与耐磨性相关的无机生物化学的基本理解，这可能对无脊椎动物的进化、行为和寿命具有重要意义。此外，这项研究可能会导致模仿自然设计的新材料的开发。

Title: Metal-Halogen Biomaterials and Wear resistance PI: Robert Schofield, University of Oregon EugeneThe jaws, leg claws, stings and other "tools" of a many arthropods and other invertebrates, contain extraordinarily high amounts of heavy metals, such as zinc and manganese, and halogens such as bromine and chlorine. Although the concentrations reach 25% of dry mass, unlike calcified human teeth, invertebrate tissue is not filled with the biomineral. Instead, metal-halogen biomaterials appear to be a distinctly different system that is more widely employed among small organisms. Very little is known about these metal-halogen biomaterials, though their main counterpart in larger organisms, calcification, is thought to be of such importance that its advent made possible the evolution of organisms such as mollusks and vertebrates.In their previous NSF-funded project, the PIs published the first comprehensive picture of the development and microscopic structure of Zn-enriched 'tools', showing that Zn was deposited very late in exoskeleton development, and that Zn-rich tissue contained a unique network of canals, through which Zn was deposited. The PIs test the hypothesis that metal-halogen tissues represent a distinct class of biomaterials, differing substantially from biomineralized tissues. Further they suggest that because of similarities in the metal-halogen tissues of distantly related organisms, that this system is likely to have evolved very early, before the evolution of insects and chelicerates. The PIs have shown that the hardness of the mandibular teeth of leaf cutting ants increases by three times as Zn is incorporated during early adult life and suggested that this Zn-correlated hardness increase is responsible for the differences in leaf-processing behavior between young and older adults. In the present study, 4 hypotheses will be tested focusing on two areas; 1) the chemical form and mechanism by which Zn alters mechanical properties, and, 2) a comparison of the mechanical property in invertebrates with more familiar biomineralized tissue. It is expected that, for small organisms, metal-halogen biomaterials will impart a more advantageous balance of hardness and wear resistance than will calcification. This research will improve our basic understanding of inorganic biochemistry related to wear resistance, which may have been important to the evolution, behavior and life span of invertebrates. In addition, this research may lead to the development of new materials that mimic those designed by nature.