4.1.1. Peptides Synthesis Preparation

Rink amide AM resin and the amino acids Fmoc-Lys (Boc)-OH, Fmoc-Lys (Fmoc)-OH, Fmoc-Arg (Pbf)-OH, and Fmoc-Trp (Boc)-OH were obtained from Iris Biotech (Marktredwitz, Germany). Dodecanoic acid, coupling reagents, and solvents such as N,N-dimethyl formamide (DMF), dichloromethane (DCM), 1-hydroxybenzotriazole (HOBt), trifluoroacetic acid (TFA), and acetonitrile (ACN) were obtained from from Merck (Darmstadt, Germany).

Peptide sequences were de novo designed to present positive charge by the incorporation of arginine or lysine residues. Tryptophan residues and dodecanoic fatty acid were used to facilitate insertion into bacterial membranes. Peptide compounds were manually synthesized by Fmoc solid-phase peptide synthesis using Rink amide AM resin (100–200 mesh; loading 0.48 mmol/g). The coupling reaction of the amino acids was made with the activators DIC and HOBt, with three times the molar excess of each amino acid and activator, and dissolved in DMF/DCM (1:1; v/v) mixture. Deprotection was carried out with 20% (v/v) of piperidine in DMF. Deanchoring of the peptides from the resin was achieved with a TFA/TIS/H2O mixture in a volume ratio (95:2.5:2.5).