Extended Data Fig. 2: HRTEM of uranyl acetate and lead citrate stained HAP nanoparticles on the impact surface.

HRTEM of uranyl acetate and lead citrate stained HAP nanoparticles on the impact surface. The reduced ordering in protein complexes provide a higher permeability for the heavy metal staining solution, resulting in greater contrast in the TEM micrograph. a, HRTEM of a HAP nanoparticle, showing chitin macromolecules wrapping around the HAP crystal. b, FFT of the HAP crystal lattice indicated with a purple box in (a). Both diffraction spots and rings are observed in the FFT pattern. Inverse Fast Fourier Transform (IFFT) is performed on the diffraction spots and rings, separately. The yellow box (upper, right inset) shows the HAP lattice after IFFT, while red box (lower, left) shows the location of chitin macromolecules. c, HRTEM of a HAP nanoparticle. d, FFT of the HAP nanoparticle in (c). The (201) reflection from HAP is indicated with a yellow arrow, whereas the (003) planes of chitin (diffraction ring) are highlighted by the green arrow. e, f, HRTEM showing the interface between chitin macromolecules and a HAP nanocrystal. The (201) crystal planes of HAP appear adjacent with (003) planes of chitin, suggesting a potential epitaxial growth of HAP on chitin macromolecules. Three independent dactyl clubs from 3 different mantis shrimps were examined in HRTEM. Similar results as shown in (a–f) were observed.