Fig. 2: Characterization of building blocks and biochemical composition.

a Characteristics of the identified periostracin proteins. Yellow circle: Cys; blue circle: DOPA; SP: signal peptide. b Overall biochemical components, including inorganic compounds, pigments, proteins, and water. c Amino acid analysis. Inset: Changes in the contents of DOPA and possible crosslinking amino acids such as Tyr, His, and Cys.