Coexistence of both gyroid chiralities in individual butterfly wing scales of Callophrys rubi
Coexistence of both gyroid chiralities in individual butterfly wing scales of Callophrys rubi
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DOI：
10.1073/pnas.1511354112
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发表时间：
2015-10
期刊：
影响因子：
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通讯作者：
B. Winter;B. Butz;C. Dieker;G. Schröder-Turk;K. Mecke;E. Spiecker
中科院分区：
文献类型：
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作者：
B. Winter;B. Butz;C. Dieker;G. Schröder-Turk;K. Mecke;E. Spiecker
节肢动物生物光子纳米结构提供了大量复杂的几何形状。虽然观察到的各种几何形式反映了在两亲性自组装中发现的几何形式，但生物形成原理更为复杂。本文研究了绿纹蝶（Callophrys rubi）手性单旋体的形成过程，有力地证明了左手和右手对映体的形成过程具有明显不同的可能性。一种解释排除了几丁质的分子手性作为对映体类型的决定特征，强调需要在基于膜的生物形成模型中识别其他手性特异性因素。这些发现有助于理解自然控制结构形成的次要特征的能力，如对映体类型和晶体结构，为生物启发的自组装策略提供信息。绿毛斑蝶翅鳞由几微米大小的晶域组成，具有天然的手性多孔几丁质微观结构，被认为是手性三周期单旋结构。本文利用电子层析成像技术研究了这些结构域的手性和晶体结构。断层图明确地揭示了两种对映体形式的共存相反的手性：左旋和右旋陀螺。这两种对映体以不相等的概率出现，这意味着生物形成过程的分子手性成分可能会引起手性对称性的破坏，从而导致旋转结构的首选对映体形式。假设Ghiradella H (1989) J Morphol 202(1): 69-88和Saranathan V， et al.（2010）提出的旋回体的两个对构象迷宫结构域与细胞外和ser内空间相连的形成模型的有效性，我们的研究结果表明，单个旋回体的结构手性不是由几丁质分子手性引起的。此外，发现机翼鳞片高度纹理化，有相当一部分域显示出与鳞片表面法线平行的旋转晶体方向。这两个发现都需要完全理解单陀螺在形成陀螺的蝴蝶中的光子作用。更重要的是，它们显示了形态发生对生物纳米结构的次要特征（如手性或晶体结构）施加的控制水平，为合成自组装机制的仿生复制策略提供了灵感。
Significance Arthropod biophotonic nanostructures provide a plethora of complex geometries. Although the variety of geometric forms observed reflects those found in amphiphilic self-assembly, the biological formation principles are more complex. This paper addresses the chiral single gyroid in the Green Hairstreak butterfly Callophrys rubi, robustly showing that the formation process produces both the left- and right-handed enantiomers but with distinctly different likelihood. An interpretation excludes the molecular chirality of chitin as the determining feature of the enantiomeric type, emphasizing the need to identify other chirality-specific factors within the membrane-based biological formation model. These findings contribute to an understanding of nature’s ability to control secondary features of the structure formation, such as enantiomeric type and crystallographic texture, informing bioinspired self-assembly strategies. The wing scales of the Green Hairstreak butterfly Callophrys rubi consist of crystalline domains with sizes of a few micrometers, which exhibit a congenitally handed porous chitin microstructure identified as the chiral triply periodic single-gyroid structure. Here, the chirality and crystallographic texture of these domains are investigated by means of electron tomography. The tomograms unambiguously reveal the coexistence of the two enantiomeric forms of opposite handedness: the left- and right-handed gyroids. These two enantiomers appear with nonequal probabilities, implying that molecularly chiral constituents of the biological formation process presumably invoke a chiral symmetry break, resulting in a preferred enantiomeric form of the gyroid structure. Assuming validity of the formation model proposed by Ghiradella H (1989) J Morphol 202(1):69–88 and Saranathan V, et al. (2010) Proc Natl Acad Sci USA 107(26):11676–11681, where the two enantiomeric labyrinthine domains of the gyroid are connected to the extracellular and intra-SER spaces, our findings imply that the structural chirality of the single gyroid is, however, not caused by the molecular chirality of chitin. Furthermore, the wing scales are found to be highly textured, with a substantial fraction of domains exhibiting the directions of the gyroid crystal aligned parallel to the scale surface normal. Both findings are needed to completely understand the photonic purpose of the single gyroid in gyroid-forming butterflies. More importantly, they show the level of control that morphogenesis exerts over secondary features of biological nanostructures, such as chirality or crystallographic texture, providing inspiration for biomimetic replication strategies for synthetic self-assembly mechanisms.