Coomassie Blue RL C.I. 13390 is a dye with a chemical formula of C28H26N2Na2O10S2 and a molecular weight of 622.58. It is also known as Brilliant Blue G-250 and is commonly used as a protein and peptide stain for gel electrophoresis. PubMed link: https://pubmed.ncbi.nlm.nih.gov/12142099/. It can also be used to measure the protein concentration in solutions.