Ubiquitin, an important post-translational modification that regulates a variety of biological processes is found in free and conjugated (monoubiquitin and polyubiquitin) forms in the cell. A method for precisely measuring these cellular pools using protein standard absolute quantification mass spectrometry is described; the approach should yield insights into ubiquitin signaling.
- Stephen E Kaiser
- Brigit E Riley
- Ron R Kopito
