Biologically Controlled Morphology and Twinning in Guanine Crystals

Anna Hirsch, Benjamin A. Palmer, Nadav Elad, Dvir Gur, Steve Weiner, Lia Addadi, Leeor Kronik, Leslie Leiserowitz

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

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.

Original languageEnglish
Pages (from-to)9420-9424
Number of pages5
JournalAngewandte Chemie - International Edition
Volume56
Issue number32
DOIs
StatePublished - 1 Aug 2017
Externally publishedYes

Keywords

  • crystal twinning
  • electron diffraction
  • morphological engineering
  • photonic crystals
  • tiling

ASJC Scopus subject areas

  • Catalysis
  • Chemistry (all)

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