Eye patches: Protein assembly of index-gradient squid lenses

Science. 2017 Aug 11;357(6351):564-569. doi: 10.1126/science.aal2674.

Abstract

A parabolic relationship between lens radius and refractive index allows spherical lenses to avoid spherical aberration. We show that in squid, patchy colloidal physics resulted from an evolutionary radiation of globular S-crystallin proteins. Small-angle x-ray scattering experiments on lens tissue show colloidal gels of S-crystallins at all radial positions. Sparse lens materials form via low-valence linkages between disordered loops protruding from the protein surface. The loops are polydisperse and bind via a set of hydrogen bonds between disordered side chains. Peripheral lens regions with low particle valence form stable, volume-spanning gels at low density, whereas central regions with higher average valence gel at higher densities. The proteins demonstrate an evolved set of linkers for self-assembly of nanoparticles into volumetric materials.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Crystallins / chemistry*
  • Crystallins / genetics
  • Crystallins / ultrastructure
  • Decapodiformes*
  • Lens, Crystalline / chemistry*
  • Lens, Crystalline / ultrastructure
  • Molecular Dynamics Simulation
  • Protein Conformation
  • Protein Interaction Maps
  • RNA, Messenger / genetics
  • Scattering, Small Angle
  • Sequence Analysis, RNA

Substances

  • Crystallins
  • RNA, Messenger