Boston Biomedical Research Institute View Institution's Website 2 articles published in JoVE Biology Protease- and Acid-catalyzed Labeling Workflows Employing 18O-enriched Water Diana Klingler1, Markus Hardt1 1Boston Biomedical Research Institute Stable isotope labeling workflows employing 18O-enriched water (LeO-workflows) are versatile tools for quantitative and qualitative proteomics studies. In protease-assisted (PALeO) workflows, 18O-atoms are introduced by proteolytic cleavage and carboxyl oxygen exchange reactions mediated by proteases. In the acid-catalyzed (ALeO) workflow, 18O-atoms are introduced by carboxyl oxygen exchange at low pH. Biology Growth Assays to Assess Polyglutamine Toxicity in Yeast Martin L. Duennwald1 1Boston Biomedical Research Institute This manuscript describes three complementary protocols for assessing the toxicity of polyglutamine (polyQ)-expansion proteins in the yeast Saccharomyces cerevisiae. These protocols can easily be modified to monitor the toxicity of other misfolded proteins in yeast.