Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth, 76100, Israel.
Department of Structural Biology, Weizmann Institute of Science, Rehovoth, 76100, Israel.
Angew Chem Int Ed Engl. 2017 Aug 1;56(32):9420-9424. doi: 10.1002/anie.201704801. Epub 2017 Jul 6.
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.
鸟嘌呤晶体被广泛用作多层反射镜的组成部分。在桡足类动物的外骨骼和扇贝眼睛的镜子中发现的基于鸟嘌呤的反射系统是独特的，因为多层反射镜被平铺成连续的紧密堆积阵列。在桡足类动物的外骨骼中，六方晶体紧密堆积产生鲜艳的颜色。在扇贝眼睛中，方形晶体被平铺以获得形成图像的反射镜。这些瓦片的大小约为 1μm，厚度为 70nm。根据对其电子衍射图谱的分析，六边形和正方形瓦片不是单晶。相反，每种类型的瓦片都是由三个不同取向和堆叠在一起的晶畴组成的复合材料，这是通过在各自的 ⟨011 ⟩ 和 ⟨021 ⟩ 晶体轴上进行两次重复的孪晶来实现的。通过这种方式，单斜鸟嘌呤晶体模拟了更高的对称六边形和四方结构，以实现独特的形态。
