PRM2 forms identified with a top-down strategy for intact protein analysis. A) MS1 trace of the most abundant charge states of PRM2 (+11 to +19). B) MS1 trace of the 14+ charged unmodified PRM2 (no post-translational modification (PTM)), and PRM2 modified by acetylation (A), acetylation and methylation (A + Me), phosphorylation (P), and double acetylation and methylation (2A + Me). C) MS2 sequence coverage of PRM2 forms. The sequence coverage is indicated and shows c ions from the right (⌉) and z ions from the left (⌊).