Oxymapure

RPMs were synthesized using the method of Hayouka et al.^{5 (link)} In brief, RPMs were synthesized, with a Liberty Blue™ automated microwave peptide synthesizer (CEM Corp., Matthews, NC, USA), by standard Fmoc-based solid-phase peptide synthesis (SPPS) on Rink amide resin (0.6 mmol/g substitution, 0.1 mmol scale). N,N-Diisopropylcarbodiimide and OxymaPure (Chem-Impex INTL) dissolved in N,N-dimethylformamide (DMF) were used for activation steps, and 20% (v/v) piperidine in DMF was used for Fmoc-deprotection steps. Each coupling step was conducted with binary combinations of protected amino acids, with a stock solution containing a 1:1 ratio between L-phenylalanine (F) and L/D-lysine (K/dK) (2 equivalents from each amino acid, 0.2 mmol). After cleavage from the resin, peptides were lyophilized and kept at − 20 °C. Evaluation of molecular weight was done using MALDI-TOF (Fig. S2).
Compounds were solubilized in 100% UltraPure water in a concentration of 100 mg/mL and stored at − 20 °C. These active substances consisted of RPMs of 20 components FK and FdK.

All solvents required for synthesis, including ethanol, methanol, acetone, acetonitrile (ACN), tetrahydrofuran (THF), petroleum spirit, chloroform, dichloromethane (DCM), N-methyl-2-pyrrolidone (NMP) and dimethylformamide (DMF), were purchased from Merck and ChemSupply Pty (Aust.). Special reagents for the solid phase peptide synthesis (SPPS), i.e., piperidine, diisopropyl carbodiimide (DIC), diisopropylethylamine (DIPEA), acetic anhydride, Oxyma Pure (ethyl cyanohydroxyiminoacetate), trifluoroacetic acid (TFA) and triisopropyl silane (TIPS), were purchased from various suppliers - Chem-Impex Inc., Novabiochem^®, Sigma-Aldrich Pty Ltd. and Thermo Fisher Scientific. Solid bed support (Rink amide AM and Wang resin) having 0.3–0.6 mmol/g loading, and Fmoc-protected amino acids were purchased from Chem-Impex Inc. and P3Biosystems.