Thalidomide-PEG4-Propargyl is widely utilized in the field of targeted protein degradation, particularly in the development of PROTACs (Proteolysis Targeting Chimeras). Its structure allows it to act as a linker that connects a target protein-binding ligand to an E3 ubiquitin ligase recruiter, facilitating the ubiquitination and subsequent degradation of the target protein. This application is crucial in drug discovery, especially for targeting undruggable proteins in diseases like cancer, neurodegenerative disorders, and autoimmune conditions. Additionally, its propargyl group enables click chemistry reactions, making it valuable for bioconjugation and the synthesis of complex molecules in chemical biology research.