Firstly, we acquired attenuated total reflectance (ATR) spectra on assemblies in bulk (Fig. ) and compared the two-component samples to those of the individual tripeptides. Infrared spectra showed a prominent band in the 1750-1600 cm⁻¹ range, mainly due to amide I modes, and a minor one peaked at 1553 cm⁻¹, ascribed to amide II modes. The comparison between the spectra revealed that the presence of Asp could be traced unambiguously by the signals in the 1400-1360 cm⁻¹ range, which were ascribed to the symmetric stretching of the COO⁻ group.25 Conversely, the antisymmetric stretching of COO⁻ was assigned to the shoulder at 1586 cm⁻¹ that occurred in a crowded region, thus resulting difficult to interpret unambiguously. The 2nd-derivative analysis (Fig. ) did not highlight significant differences in the amide I profiles, suggesting similarities in the overall arrangement of peptide bonds in the fibrils, as expected for β-sheets formed by this type of gelators.