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Guanine-Based Photonic Crystals in Fish Scales Form from an Amorphous Precursor


  • We thank Dr. S. Siegel, Dr. C. Li and Dr. I. Zizak for their invaluable help in the μ-Spot X-ray diffraction studies. We thank the Mag Noi company from Kibbutz Gan Shmuel Israel, for supplying the fish. X-ray studies were conducted at the μ-Spot beamline of the BESSY II synchrotron radiation facility, which is part of the Helmholtz-Zentrum Berlin für Materialien und Energie, and received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 226716. The research was supported by a German Research Foundation grant, within the framework of the Deutsch-Israelische Projektkooperation DIP. L.A. is the incumbent of the Dorothy and Patrick Gorman Professorial Chair of Biological Ultrastructure, and S.W. of the Dr. Trude Burchardt Professorial Chair of Structural Biology.


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Starting from disorder: Anhydrous guanine crystals compose the photonic arrays responsible for the skin and scale iridescence found in Japanese Koi fish. These guanine crystals were found to form in intracellular vesicles (see picture) through an amorphous precursor phase. A combined cryo-SEM and synchrotron radiation X-ray diffraction study showed the evolution of the crystals in great detail.