Bis-PEG6-acid is a PEG-based PROTAC linker can be used in the synthesis of PROTACs[1].
PROTACs contain two different ligands connected by a linker; one is a ligand for an E3 ubiquitin ligase and the other is for the target protein. PROTACs exploit the intracellular ubiquitin-proteasome system to selectively degrade target proteins.
[1]. Zorba A, et al. Delineating the role of cooperativity in the design of potent PROTACs for BTK. Proc Natl Acad Sci U S A. 2018 Jul 31;115(31):E7285-E7292.