Meeting Abstract

106.4  Sunday, Jan. 6  Building a Lens from a Single Protein: Small Angle X-ray Scattering on Squid Eyes CAI, J*; HEINEY, P.A.; SWEENEY, A.M.; University of Pennsylvania; University of Pennsylvania; University of Pennsylvania caij@sas.upenn.edu

Throughout evolution, camera-type animal eyes developed spherical, graded refractive index lenses which eliminate spherical aberration. The graded refractive index is achieved by changing the density of proteins within the lens. To reduce unwanted scattering of light, the protein density fluctuations in the lens must be small. This effect becomes more significant in the periphery of the lens, where the protein density is lower than in the center. Squid lens material is dominated by only one protein isoform, making it a tractable system to understand how changes in protein biophysical properties contribute to bulk lens optical and material properties — in contrast, vertebrate lenses are an experimentally intractable mix of multiple, polydisperse isoforms. Our previous work has shown that the isoforms in the periphery of the lens have a more positive surface charge, implying that Coulomb interaction assembles the protein in repulsive glass phase, with lower surface charges mediating assembly of progressively higher index lens regions. Here, we perform small angle x-ray scattering experiments on squid lenses. Each lens sample is separated into four concentric layers based on radius. Experiments show that the packing properties change gradually from the central core of the lens to the periphery. We also discuss how squid lens proteins interact with each other and how they are packed to form graded index glass. Future studies will apply the lessons learned from squid lens materials to manufacturing artificial self-assembling lenses with graded refractive index, which can be applied widely in industry.