Using the PDBe REST API secondary structure module, we obtained the ranges of secondary structure (H: helices, E: extended strand/β-sheets and C: coils) from residues found in the selected 435 PDBe structures. In some cases, we noted that multiple PDBe structures associated with the same GRAMPA sequence presented inconsistencies with their secondary structure annotations, as illustrated in Figure . We only kept 261 GRAMPA and PDBe sequences with only one experimentally known PDBe structure. We displayed the results on a ternary plot (Figure ), where each point in the figure represents a peptide structure, and its location in the plane alludes to its composition in secondary structures (H, E, C), expressed in percentages. These 261 structures, painted in dark blue, represent our experimental references or ground truth. We selected six peptides (1-6) and their respective known experimental structures to illustrate the structural trends across the ternary plot (PBDe IDs in parentheses). Complete helical structures are located on the top corner of the plot (e.g. pepG1 -(1) / 7NS1), whereas coiled and stranded structures (i.e., circulin A -(5) / 1BH4 and arenicin-3 analogue -(3) / 5V11) would show at the bottom-right and bottom-left corners, respectively. The general examination of the 261 GRAMPA-related structures revealed that coiled motifs were the most common, accounting for 47.53% of the entire dataset. This was followed by helices (H) and extended strands/β-sheets (E), which made up 34.48% and 17.98% of the dataset, respectively (Figure ). The prevalence of coiled motifs can be attributed to their role as linker between helical and strand segments. As a result, it is not surprising that there are no structures made entirely of extended strands (E), as each pair of parallel or antiparallel chains forming a β-sheet will be linked by a coiled segment. (2MN1), (5) circulin A (1BH4) and ( ) pleurocidin-like peptide 1a-1 (6RY9). The lines indicate the error between the three-state secondary structures (H, E, C) measured between PEP2D predictions and corresponding experimental references. (B) General distribution of each secondary structure (H, E, C) across our experimental references.