To further probe the key structural features affecting PFK fibrils-catalyzed β-lactam hydrolysis, we investigated the structural and catalytic properties of several PFK-derived peptide variants, exhibiting different fiber morphologies, surface charges, and nucleophilic properties (Figure ). Figure presents the sequences tested, highlighting the cationic and anionic residues (blue and red, respectively), formal charges (at neutral pH), and surface charges of the peptide assemblies (i.e., ζ-potential). Figure presents cryo-TEM images of the aggregates formed by the different variants. Notably, only variants consisting of alternating cationic/non-polar amino acid sequences (PFR, PFDK,) adopted fibril organization. The formation of organized β-sheet amyloid fibrils for these variants was further confirmed by circular dichroism (CD) and Fourier transform infrared (FTIR) experiments (Figures S6). Altogether, the variant assembly data are consistent with previous studies linking amphiphilic sequence patterns with β-sheet folding and fibril formation .