Acid-PEG4-S-PEG4-acid
CAS No.: 2055041-21-7
Cat No.: BP-501118
4.5 
Acid-PEG4-S-PEG4-acid is a bifunctional, PEG-based linker featuring two terminal carboxylic acid groups connected through two short polyethylene glycol segments that are joined via a thioether (S) linkage. The PEG4 spacers provide conformational flexibility and hydrophilicity, helping PROTAC constructs maintain productive geometry and reduce non-specific hydrophobic interactions, while the central thioether offers a stable yet chemically addressable connection point during linker assembly. In targeted protein degradation designs, this linker can be used to connect two PROTAC modules—typically a ligand for an E3 ligase and a ligand or warhead for the target protein—so that the overall conjugate can form a ternary complex more efficiently. Its dual acidic termini enable straightforward coupling to amine- or activated ester–bearing partners and facilitate downstream formulation and purification. Overall, Acid-PEG4-S-PEG4-acid is a practical, research-grade building block for constructing flexible, water-compatible PROTACs for systematic structure–activity studies.
Structure of 2055041-21-7
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* For research and manufacturing use only. Not for human or clinical use.
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Acid-PEG4-S-PEG4-acid is a PEG-based, thioether-containing bifunctional linker designed to connect ligand fragments in PROTAC architectures while promoting solubility and conformational flexibility. Its diacid functionality enables robust conjugation strategies, and the internal sulfur linkage provides a defined tether for assembling targeted protein degraders. The molecule will be described in detail below, including its structural features and practical considerations for PROTAC construction.
Structure: The linker is built from repeating polyethylene glycol segments connected through a thioether (sulfide) unit, with terminal carboxylic acid groups. It contains ether-rich segments that enhance hydrophilicity, along with stable carbon–sulfur and carbon–oxygen linkages. Overall, it behaves as a flexible, water-compatible scaffold suitable for bioconjugation.
Reactivity: Terminal carboxylic acids are typically activated for amide-bond formation to couple to amine-bearing ligands or intermediate handles used in PROTAC synthesis. Common approaches include carbodiimide-mediated activation with an appropriate coupling base, often in polar aprotic solvents under controlled pH to minimize side reactions. The thioether linkage is generally compatible with standard peptide-coupling conditions, but reaction planning should consider potential oxidation sensitivity during workup.
* Our calculator is based on the following equation:
Concentration (start) x Volume (start) = Concentration (final) x Volume (final)
It is commonly abbreviated as: C1V1 = C2V2
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