Bacteria were harvested by centrifugation and disrupted in the presence of 100 mM citric acid using an EmulsiFlex C5 cell homogenizer (Avestin, Mannheim, Germany). After centrifugation for 20 min (39,200× g) at 16 °C, the supernatant was filter-sterilized using a 0.45 µm syringe filter (Sartorius, Göttingen, Germany). The clear filtrate was adjusted with ammonium sulfate to 30% saturation, stirred for 30 min at RT, and centrifuged for 30 min (39,200× g) at RT. The precipitate was solubilized in subtractive AEX buffer (sAEX; 20 mM Tris/HCl, 1 mM EDTA, pH 8.5), filter-sterilized, and dialyzed twice against a 100-fold volume of sAEX buffer at 4 °C. Subsequent chromatography steps were performed on an ÄKTA Explorer 100 system (GE Healthcare, Freiburg, Germany) operated at a flow rate of 5 mL/min. The dialyzed sample (Tα1-PAS or PAS-Tα1) was first applied to a 5 mL TOYOPEARL NH2-750F column (Tosoh Bioscience, Griesheim, Germany) equilibrated with the sAEX buffer. The flow-through containing the PASylated Tα1 was collected and dialyzed twice against a 100-fold volume of the CEX buffer (20 mM Na-citrate, pH 3.0) at 4 °C. The protein solution was then applied to an 85 mL TOYOPEARL Sulfate-650F column (Tosoh Bioscience) equilibrated with the CEX buffer. PAS-Tα1 quantitatively bound to the column and the pure protein was eluted using a NaCl concentration gradient (0–250 mM over 2 column volumes). In the case of Tα1-PAS, the CEX flow-through fraction contained the N-terminally acetylated protein, whereas the non-acetylated Tα1-PAS stayed bound to the column and could again be eluted in a NaCl concentration gradient. The acetylated Tα1-PAS fraction from the flow-through was dialyzed twice against AEX buffer (20 mM ethanolamine/HCl, pH 10) and then applied to a 100 mL Fractogel® EMD TMAE (M)strong anion exchanger (Merck Millipore, Burlington, MA, USA) equilibrated with the AEX buffer. This time, highly pure acetylated Tα1-PAS was eluted using a NaCl concentration gradient (0–200 mM over 2 column volumes) in the AEX buffer. Both purified PASylated peptides were dialyzed 5 times against a 200-fold volume of water, lyophilized, and stored at −20 °C until further use.