When the N-term Met is acetylated before cleavage, the result of Met cleavage is almost always acetylation of the resulting N-term amino acid. For multiple AAV serotypes, VP1 and VP3 contain Nterm Met which is cleaved, resulting in the acetylation of the subsequent amino acid residue . For AAV2, this results in acetylated A1 (A2 if considering the Met residue) and acetylated A203, the N-term amino acids for VP1 and VP3, respectively, after Met cleavage. As expected, we saw near 100% acetylation present at both A1 (100%) and A203 (97.1%). Additionally, the presence of multiple peptides starting with acetylated A211, signified the presence of a VP3 variant A211(Ac) -L735 (A211(Ac)-VP3) previously detected in AAV2 by Oyama et al. (see Table and Figure ). Its