Molecular basis of tunable iridescence and excellent proton conductance of the reflectin assembly

反射蛋白是头足类动物中一个很大程度上紊乱的蛋白质家族，它们形成可调节的纳米组装体，使它们的身体颜色能够瞬间改变。在体外，这些组件表现出极好的质子导电性，可与最先进的人造材料相媲美。本项目将阐明反射体可调着色和极好的质子导电性的分子机制。这些知识将使基于具有可编程光学和电学特性的反射体的生物相容性人工材料的合理设计成为可能。培养本科生多名，研究生1名。PI将在当地K-12学校的推广活动中利用这种蛋白质的迷人性质，推广STEM，并激励下一代普通科学家和工程师。在同源反射蛋白中发现了一些保守的氨基酸序列，再现了全长蛋白的特性。有趣的光学和电学性质归因于有序的层次结构和组件中伴随的氢键网络。然而，亚基蛋白的强无序性阻碍了低温电子显微镜或x射线衍射等技术在高分辨率下的表征。该项目将应用固态核磁共振（ssNMR），这是非晶体样品的理想技术，来确定由一个称为（ref2C）4的保守片段组成的组装的原子结构模型。这一知识将解决一个悖论：在波长尺度上，无序的亚基蛋白质在多大程度上组装成有序的布拉格反射器来调节光学性质。进一步的ssNMR实验将用于探测质子在组装中的扩散，这将以残基特异性分辨率解剖分子基序，这是杰出的质子导电性的原因。该提案由材料研究部（MPS/DMR），化学，生物工程，环境和运输系统部（ENG/CBET）以及分子和细胞生物科学部（BIO/MCB）共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Reflectins are a family of largely-disordered proteins in cephalopods that form tunable nano-assemlies to enable instantaneous change of their body color. In vitro these assemblies exhibit superb protonic conductance, comparable to the-state-of-the-art artificial materials. This project will elucidate the molecular mechanism underpinning the tunable coloration and superb protonic conductivity of reflectins. This knowledge will enable rational design of bio-compatible artificial materials based on reflectins with programmable optical and electrical properties. Multiple undergraduates and one graduate will be trained. The PI will exploit the fascinating nature of the protein in his outreach activities for local K-12 schools to promote STEM and to inspire next general scientists and engineers.Several conserved amino acid sequences were found in homologous reflectins, recapitulating the properties of the full-length proteins. The intriguing optical and electrical properties were attributed to the ordered hierarchical structures and accompanied hydrogen bonding network in assemblies. However, the strong disorder of subunit proteins prohibits characterization at high resolution by techniques such as cryoEM or X-ray diffraction. This project will apply solid state NMR (ssNMR), the ideal technique for noncrystalline sample, to determine the atomic structural model of the assembly formed by one of the conserved fragments called (ref2C)4. This knowledge will resolve the paradox: how largely disordered subunit proteins assemble into ordered Bragg reflectors at light wavelength scale to modulate optical properties. Further ssNMR experiments will be performed to probe proton diffusion in the assembly, which will dissect the molecular motif at a residue-specific resolution responsible for the outstanding protonic conductivity.This proposal is co-funded by Division of Materials Research (MPS/DMR), Division of Chemical, Bioengineering, Environmental, and Transport Systems (ENG/CBET) and Division of Molecular and Cellular Biosciences (BIO/MCB).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.