European School of Molecular Medicine (SEMM) 1 article published in JoVE Biochemistry A Mass Spectrometry-Based Proteomics Approach for Global and High-Confidence Protein R-Methylation Analysis Marianna Maniaci*1,2, Federica Marini*1, Enrico Massignani1,2, Tiziana Bonaldi1 1Department of Experimental Oncology, European Institute of Oncology IRCCS (IEO), 2European School of Molecular Medicine (SEMM), c/o Campus IFOM-IEO Protein Arginine (R)-methylation is a wide-spread post-translational modification regulating multiple biological pathways. Mass spectrometry is the best technology to globally profile the R-methyl-proteome, when coupled to biochemical approaches for modified peptide enrichment. The workflow designed for the high confidence identification of global R-methylation in human cells is described here.