Peptides 1-4 were dissolved at the desired concentration (20-40 mM) in phosphate-buffered saline solution (PBS, 0.1 M) by heating the glass vial in an oil bath at 90 °C for 15-20 min. Upon cooling down to room temperature, peptides 1-4 formed gels, and, in particular, the gel formed by peptide 4 displayed a metastable character as it converted into crystals within 2 hours.