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

反射素是头足类动物中一种主要无序的蛋白质家族，它们形成可调节的纳米组装，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电导，可与最先进的人造材料相媲美。本项目将阐明反射素可调色和超强质子导电性的分子机制。这一知识将使基于具有可编程光学和电学特性的反射素的生物兼容人造材料的合理设计成为可能。将培训多名本科生和一名毕业生。PI将在他为当地K-12学校开展的推广STEM的活动中利用这种蛋白质的迷人性质，并激励下一批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性质。这种有趣的光学和电学性质归因于有序的层次化结构和伴随在组装中的氢键网络。然而，亚基蛋白质的强烈无序使其无法通过低温电子显微镜或X射线衍射等技术进行高分辨率的表征。这个项目将应用固态核磁共振(SsNMR)，这是非晶态样品的理想技术，来确定由一个被称为(Ref2C)4的保守片段形成的组装的原子结构模型。这一知识将解决悖论：如何在很大程度上无序的亚基蛋白质在光波长尺度上组装成有序的Bragg反射器来调制光学性质。将进行进一步的单核磁共振实验以探测质子在组件中的扩散，该组件将以残基特定的分辨率剖析分子基序，负责杰出的质子导电。这项提议由材料研究部门(MPS/DMR)、化学、生物工程、环境和运输系统部门(ENG/CBET)和分子和细胞生物科学部门(BIO/MCB)共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.