Bis-PEG21-acid
Cat No.: BP-501978
4.5 
Bis-PEG21-acid is a bifunctional polyethylene glycol (PEG) linker featuring two terminal carboxylic acid groups separated by long PEG chains, enabling flexible, hydrophilic spacing between PROTAC-relevant moieties. Structurally, the “bis” architecture provides two attachment handles for conjugation, while the extended PEG segment confers conformational mobility and improved aqueous compatibility, which can reduce steric constraints during ternary complex formation. In PROTAC design, such linkers are used to connect an E3 ligase ligand to a target-binding ligand, allowing the linker to adapt the relative positioning of the two binding domains and thereby facilitate productive recruitment of the target protein to the ligase complex. The long, flexible, acid-terminated functionality supports robust synthetic coupling strategies (e.g., amide or ester formation with appropriately functionalized partners). This product is valuable for researchers optimizing linker length and geometry to enhance degradation potency and selectivity in targeted protein degradation workflows.
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* For research and manufacturing use only. Not for human or clinical use.
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Bis-PEG21-acid is a PEG-based bifunctional linker designed to support targeted protein degradation workflows by connecting a ligand for an E3 ligase to a second binding moiety for the target protein. Its extended, hydrophilic scaffold can improve solubility and help preserve productive ternary-complex formation. The linker’s acid functionality enables robust conjugation strategies commonly used in PROTAC assembly. Detailed structural and reactivity considerations are provided below.
Structure: Bis-PEG21-acid comprises a flexible polyethylene glycol backbone with two terminal carboxylic acid groups. The linker contains repeating ether linkages that confer high polarity and conformational mobility. The presence of carboxylates provides reactive handles for amide or ester-forming coupling chemistries under standard organic synthesis conditions.
Reactivity: Carboxylic acids are typically activated for PROTAC linker installation via amide bond formation using coupling reagents and base in polar aprotic solvents. Alternatively, acid-to-ester or acid-to-thioester intermediates can be generated for subsequent nucleophilic substitution with amine or thiol-containing partners. Mechanistically, activation forms a reactive ester that is displaced by the nucleophile to yield stable conjugates suitable for PROTAC construction.
* 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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