Protein mass spectrometry refers to the use of mass spectrometry in the study and characterization of proteins, including their quantification, profiling, interaction mapping, and identification of their post-translational modifications (1,2). Protein mass spectrometry may also be referred to as mass spectrometry-based proteomics. Mass spectrometry-based proteomics consist of three approaches: top-down, middle-down, and bottom-up proteomics