The Ubiquitin Proteasome System (UPS) controls the principal functions of almost all the cellular proteins of human cells, and failures in this system often contribute directly or indirectly to the pathogenesis of many diseases, including cancer, inflammation, and neurodegeneration. There are ~700 E3 ubiquitin ligases and ~100 Deubiquitinases encoded in the human genome and the functions of most of these E3s and DUBs remain unknown. Recent development of PROTAC drugs to recruit E3 ligases and degrade therapeutic proteins highlight the value of studying E3 ligases. Evaluation of global proteome changes by PROTACs and small molecule drugs is an important tool to establish efficacy and specificity of drug molecules. Lifesensors offers whole cell proteomic services to characterize small molecules and PROTACs.