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.
