Peptide mapping was performed to help verify the presence of identified VP PTMs, VP variants and VP fragments. Digestion of each empty and full capsid sample for peptide mapping was performed using a SMART Digest™ magnetic bead bulk pepsin kit (Thermo Scientific) and followed a slightly modified version of the protocol previously described by Guapo et al. (Supplementary Information (SI) 1). Peptide mapping was performed in technical triplicate using a Vanquish Neo Ultra-High-Performance Liquid Chromatography (UHPLC) platform coupled to an Orbitrap Exploris 480 MS (Thermo Scientific, Bremen, Germany) following a modified version of the procedure described in Guapo et al (9) (SI 2). Peptide identification and relative PTM quantitation was performed using BioPharma Finder™ (BPF) Version 5.1 (Thermo Scientific, San Jose, CA, USA) (SI 3 and Table ).