Aqueous solvent was added to weighed peptide. Otherwise stated, the solvent contained 130 mM NaCl (Fisher Scientific) dissolved in pure water (resistivity 18.2 MΩ cm during dispensation). After sealing sample vials with Parafilm®, they were vortexed for ≈30 s using a Scientific Industries Vortex Genie 2 vortex mixer, and placed in a Bandelin Sonorex RK52H sonicator for ≈30 min.