Both PASylated peptide preparations had a purity > 96% as indicated by reverse-phase chromatography (Figure 2c and Figure 3c). For Tα1-PAS, we performed a final AEX polishing step, which also allowed concentration of the peptide. At pH 10, the acetylated Tα1-PAS bound to a strong AEX resin and eluted as a homogenous peak in a salt concentration gradient. The endotoxin content of this fraction was very low, with < 0.1 EU/mg, and the final yield was 15 mg acetylated Tα1-PAS per 1 L bacterial culture. In comparison, the final yield of the fully column-bound (non-acetylated) PAS-Tα1 reached 50 mg per 1 L bacterial culture after CEX chromatography and, again, the endotoxin content was below 0.1 EU/mg. Analytical size exclusion chromatography (SEC) of both PASylated peptide versions revealed a single symmetric peak without any signs of aggregation or truncation (Figure 2d and Figure 3d). The N-terminally acetylated Tα1-PAS eluted at 13.5 mL (bed volume: 24 mL), whereas PAS-Tα1 eluted at 13.2 mL, thus indicating apparent molecular sizes of 557 kDa and 665 kDa, respectively. This is more than 10 times (Tα1-PAS) or even 12 times (PAS-Tα1) larger than the true molecular mass of both PASylated peptides (52.7 kDa), which demonstrates the huge expansion of the hydrodynamic molecular volume caused by the random-coil structure of the PAS polymer, in line with previous observations [35].