Abstract
Shrimp, crayfish and lobsters possess a reflection superposition
compound eye, which operates by reflective optics and is suited to
vision in dim-light conditions. The reflector units in the eye are made
of millions of crystals of isoxanthopterin, a previously unknown
biocrystal. We report here the determination of the crystal structure of
isoxanthopterin using first principles calculations based on
dispersion-inclusive density functional theory. In a manner akin to the
generation of the H-bonded layer and 3D arrangement of the biogenic
photonic crystals of guanine, we constructed an H-bonded planar layer of
isoxanthopterin molecules, followed by generation of various interlayer
motifs, via monoclinic and orthorhombic symmetries. Geometry
optimization yielded an isoxanthopterin crystal structure with
orthorhombic Cmce symmetry, which gave an excellent fit to the
experimental X-ray measurements. The resulting refractive index,
calculated from the structure, is very high (n=2.0), explaining why this
material functions as an efficient reflector.
Original language | English |
---|---|
Title of host publication | APS March Meeting 2018 |
State | Published - 2018 |
Event | APS March Meeting 2018 - Duration: 5 Mar 2018 → … |
Conference
Conference | APS March Meeting 2018 |
---|---|
Period | 5/03/18 → … |