Hierarchical Architecture of Sponge Spicules: Bio-inspired assembly of multifunctional structures by biocatalytically active and structure-guiding proteins

硅质海绵、蠕形海绵和六角海绵(玻璃海绵)以及钙质海绵的层级结构骨架具有特殊的光学机械特性，已被证明是仿生方法的优秀模型。硅质海绵的生物硅是由一组独特的酶--硅酸盐形成的，事实证明，这种酶既具有生物催化活性，又具有结构引导/形成活性。它们骨骼的物种特异性三维结构既受基因水平的控制，受Silicatein和Silicatein相互作用蛋白的顺序基因表达控制，也受这些蛋白与丝状结构的特定相互作用和组装以及细胞过程的控制。在第一个资助期，对针状体的无机-有机杂化结构和生物硅的形成机制有了基本的见解，这一点明确地被证明是在酶的作用下发生的。在第二个资助期，发现了新的硅酸盐相互作用蛋白(Silinaphins)，并对其进行了功能表征，不仅使人们了解了硅酸盐组装/活性的调节，而且还了解了引导针状体纵向和对位生长的细胞外圆柱状有机支架的形成。此外，首次展示了酶促形成的软生物二氧化硅的脱水和硬化/老化过程，为海绵生物二氧化硅的仿生/仿生应用开辟了新的途径。在第三阶段，我们将使用这些工具来生成层次化结构和多功能的纳米材料，应用生物启发的分子开关，并模仿在自然界海绵中实现的精密生物二氧化硅成型过程。其中，应研究硅酸盐对CaCO3/硅酸盐杂化纤维(合成针状物)形成的影响。来自无机化学和分子生物学的小组之间的密切合作将使其能够利用参与生物矿化的海绵蛋白的自组装、结构定向和生物催化能力，以及碳酸钙和金属氧化物的纳米颗粒，以产生具有新的性能组合的仿生纳米结构材料，其机械和光学性能应作为其组成的函数进行检查。

The hierarchically structured skeletons of the siliceous sponges, the Demospongia and the Hexactinellida (glass sponges), and of the calcareous sponges, the Calcarea, with their exceptional opto-mechanical properties have turned out to be excellent models for biomimetic approaches. The biosilica of the siliceous sponges is formed by a unique group of enzymes, the silicateins, that turned out to show both biocatalytic and structure-guiding/forming activity. The species-specific 3D structure of their skeleton is controlled both on gene level, by a sequential gene expression of silicatein and silicatein interacting proteins, and by the specific interaction and assembly of these proteins to filamentous structures, as well as by cellular processes. In the first funding period, fundamental insights have been gained in the inorganic-organic hybrid structure of the spicules and in the mechanism of biosilica formation which was unequivocally proven to occur enzymatically. In the second funding period, new silicatein interactors (silintaphins) have been discovered and functionally characterized, allowing an understanding of the regulation not only of silicatein assembly/activity but also of the formation of the extracellular cylinder-like organic scaffold guiding the longitudinal and appositional growth of the spicules. Moreover, the processes of syneresis and hardening/ageing of the enzymatically formed soft biosilica to solid silica rods have been demonstrated for the first time, opening new avenues for biomimetic/bio-inspired applications of sponge biosilica. In the third period, we will use these tools for the generation of hierarchically structured and multifunctional nanomaterials, applying bio-inspired molecular switches and mimicking precision biosilica molding processes realized in sponges in nature. Among others, the effect of silicatein on the formation of CaCO3/silicatein hybrid fibers (synthetic spicules) shall be studied. The close collaboration between groups from inorganic chemistry and molecular biology shall allow it to exploit the self-assembly, structure-directing and biocatalytic capabilities of the sponge proteins involved in biomineralization, along with nanoparticles of calcium carbonate and metal oxides, for the generation of biomimetic nanostructured materials with new property combinations, whose mechanical and optical properties shall be examined as a function of their composition.