Manual solid-phase synthesis was performed in polypropylene syringes (2 or 5 mL) fitted with a polyethylene porous disk. Solvents and soluble reagents were removed by suction. Most chemicals were from commercial suppliers Merck (Madrid, Spain), Iris Biotech GmbH (Marktredwitz, Germany), Carlo Erba (Sabadell, Spain), and used without further purification.

Peptides were analyzed using standard analytical high-performance liquid chromatography (HPLC) conditions with a Dionex liquid chromatography instrument composed of a UV/Vis Dionex UVD170U detector (Thermo Fisher Scientific, Sunnyvale, CA, USA), a P680 Dionex bomb, an ASI-100 Dionex automatic injector, and CHROMELEON 6.60 software (Thermo Fisher Scientific, Sunnyvale, CA, USA). Detection was performed at a wavelength of 220 nm. Solvent A was 0.1% aqueous trifluoroacetic acid (TFA), and solvent B was 0.1% TFA in CH3CN. Analyses were carried out with a Kromasil 100 C18 (4.6 mm × 40 mm × 3.5 µm) column with a 2–100% B over 7 min at a flow rate of 1 mL/min.

All peptides were purified on a CombiFlash Rf200 automated flash chromatography system using RediSep Rf Gold reversed-phase C18 column packed with high-performance C18 derivatized silica (Teledyne ISCO, Lincoln, NE, USA).

Electrospray-ionization mass spectrometry (ESI-MS) analyses were performed at the Serveis Tècnics de Recerca of the University of Girona with an Esquire 6000 ESI ion Trap LC/MS (Bruker Daltonics, Billerica, MA, USA) instrument equipped with an electrospray ion source. The instrument was operated in the positive ESI(+) ion mode. Samples (5 µL) were introduced into the mass spectrometer ion source directly through an HPLC autosampler. The mobile phase (80:20 CH3CN/H2O at a flow rate of 100 µL/min) was delivered by a 1200 Series HPLC pump (Agilent, Santa Clara, CA, USA). Nitrogen was employed as both the drying and nebulizing gas.

High-resolution mass spectrometry (HRMS) data were recorded on a Bruker MicroTof-QIITM instrument (Bruker Daltonics, Billerica, MA, USA) using ESI ionization source at the Serveis Tècnics de Recerca of the University of Girona. Samples were introduced into the mass spectrometer ion source by direct infusion using a syringe pump and were externally calibrated using sodium formate. The instrument was operated in the positive ion mode.

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