Squid lens and pidan: their material similarities
University of Pennsylvania
Underwater vision requires a spherical lens to enable enough photon flux injecting into the camera-like eyes. The refractive index in the lens has a gradient to eliminate spherical aberration. Here, I present the squid lens system, where the whole lens is self-assembled using only one type of proteins. Using small angle X-ray scattering and computational methods, I studied how the proteins interact and the resulted in the homogeneous phase of the lens system. Results showed that the proteins are patchy particles with various patch numbers. The lens is assembled by distributing different patch number proteins at different radial positions to achieve both graded refractive index while maintaining transparency.
The lens system is very similar to pidan where the egg white proteins experienced a transition to form the gelled structure. We found that during this transition, the beta-sheet structure was preserved, whereas most of the other parts of the protein was unfolded. The unfolded part serves as the patches and the gelled structure was formed by this attractive interaction. At the end, I also compared the pidan to the squid lens, and generalized the requirements of proteins as patchy particle that form transparent gels.