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Biologically Controlled Morphology and Twinning in Guanine Crystals
Author(s) -
Hirsch Anna,
Palmer Benjamin A.,
Elad Nadav,
Gur Dvir,
Weiner Steve,
Addadi Lia,
Kronik Leeor,
Leiserowitz Leslie
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201704801
Subject(s) - monoclinic crystal system , crystallography , tetragonal crystal system , crystal twinning , materials science , hexagonal crystal system , crystal (programming language) , lamella (surface anatomy) , morphology (biology) , guanine , selected area diffraction , optics , crystal structure , transmission electron microscopy , nanotechnology , chemistry , composite material , physics , biology , nucleotide , microstructure , biochemistry , computer science , gene , genetics , programming language
Abstract Guanine crystals are widely used in nature as components of multilayer reflectors. Guanine‐based reflective systems found in the copepod cuticle and in the mirror of the scallop eye are unique in that the multilayered reflectors are tiled to form a contiguous packed array. In the copepod cuticle, hexagonal crystals are closely packed to produce brilliant colors. In the scallop eye, square crystals are tiled to obtain an image‐forming reflecting mirror. The tiles are about 1 μm in size and 70 nm thick. According to analysis of their electron diffraction patterns, the hexagon and square tiles are not single crystals. Rather, each tile type is a composite of what appears to be three crystalline domains differently oriented and stacked onto one another, achieved through a twice‐repeated twinning about their ⟨011⟩ and ⟨021⟩ crystal axes, respectively. By these means, the monoclinic guanine crystal mimics higher symmetry hexagonal and tetragonal structures to achieve unique morphologies.