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类基本无序的蛋白质，它们形成可调节的纳米组合体，从而能够瞬时改变它们的体色。在体外，这些组件表现出极好的质子电导，可与最先进的人造材料相媲美。该项目将阐明反射蛋白可调谐着色和卓越质子电导率的分子机制。这些知识将使基于具有可编程光学和电学特性的反射蛋白的生物相容性人造材料的合理设计成为可能。将培训多名本科生和一名研究生。 PI 将在当地 K-12 学校的外展活动中利用该蛋白质的迷人性质，以促进 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几个保守的氨基酸序列，概括了全长蛋白质的特性。有趣的光学和电学特性归因于组件中有序的分层结构和伴随的氢键网络。然而，亚基蛋白的严重无序性阻碍了通过冷冻电镜或 X 射线衍射等技术进行高分辨率表征。该项目将应用固态核磁共振 (ssNMR)（非晶样品的理想技术）来确定由称为 (ref2C)4 的保守片段之一形成的组装体的原子结构模型。这些知识将解决这个悖论：很大程度上无序的亚基蛋白质如何在光波长尺度上组装成有序的布拉格反射器以调节光学特性。将进行进一步的 ssNMR 实验来探测组装中的质子扩散，这将以残基特异性分辨率剖析分子基序，从而产生出色的质子传导性。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 NSF 的法定使命，并被认为值得支持通过使用基金会的智力优点和更广泛的影响审查标准进行评估。

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.