*4.1. Peptide Synthesis*

Peptides were synthesized by solid-phase peptide synthesis using Fmoc-based chemistry [29,30]. The disulfide bond in the Cys-containing HPTFXaaZbb peptides was formed via charcoal-mediated air oxidation [31]. All peptides were purified by reverse-phase highperformance liquid chromatography (RP-HPLC) (Waters, Milford, MA, USA) to higher than 95% purity. The identity of the peptides was confirmed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) (Bruker, Billerica, MA, USA). More detailed procedures and peptide characterization data are provided in the Supplementary Materials.
