Post-translational modification of proteins and peptides is a robust way to regulate function of existing proteins or peptides. Methylation on arginine residues is one example of post-translational modification and is performed by a variety of protein methyl transferases in the cell. Arginine methylation of Rad9 for example is performed by protein arginine methyltransferase 5 (PRMT5) is important for regulation of Rad9 function and is a major element for maintaining genome integrity (1). The Methylated Arginine antibody detects methylation on arginine residues in proteins and peptide.