Luxembourg Institute of Health 1 article published in JoVE Biochemistry Ubiquitin Chain Analysis by Parallel Reaction Monitoring Joseph Longworth1, Marta L. Mendes1, Gunnar Dittmar1 1Quantitative Biology Unit, Luxembourg Institute of Health This method describes the assessment of global changes in ubiquitin chain topology. The assessment is performed by the application of a mass spectrometry-based targeted proteomics approach.