Amino-PEG25-acid
Cat No.: BP-501999
4.5 
Amino-PEG25-acid is a heterobifunctional PEG-based linker featuring a terminal primary amine and a terminal carboxylic acid separated by a long, flexible poly(ethylene glycol) chain. The extended PEG length provides conformational flexibility and hydrophilicity, which can reduce steric interference and improve solubility of PROTAC conjugates. In targeted protein degradation designs, this linker serves as a spacer that connects two functional modules—typically a ligand for an E3 ubiquitin ligase and a ligand or reactive handle for the target-binding moiety—while maintaining sufficient distance and mobility for productive ternary complex formation. The carboxylic acid and amino group enable chemoselective coupling strategies (for example, amide-bond formation or other standard linker-to-ligand conjugation workflows), allowing controlled attachment without rigidifying the overall architecture. As a research-grade PEG spacer, it is valuable for systematically tuning linker length and flexibility to optimize degradation potency and selectivity in PROTAC development.
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* For research and manufacturing use only. Not for human or clinical use.
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Amino-PEG25-acid is a polyethylene glycol (PEG)-based PROTAC linker designed to provide conformational flexibility, aqueous compatibility, and a functional handle for conjugation to targeting ligands. Its hydrophilic spacer characteristics can help modulate effective distance and orientation between the ligand and the recruited E3 ligase, supporting efficient ternary complex formation. The detailed structural and synthetic considerations for PROTAC construction are provided below.
Structure: The linker comprises a PEG chain bearing terminal amino and carboxylic acid functionalities. It contains repeating ether linkages that confer hydrophilicity and flexibility, along with amide- or ester-forming reactive termini. The presence of both nucleophilic and electrophilic groups enables modular attachment strategies under standard bioconjugation chemistries.
Reactivity: The amino group is suitable for coupling reactions that form stable amide bonds with activated carboxyl groups on ligands, commonly using carbodiimide-based or uronium-type coupling systems in polar aprotic solvents with aqueous buffers. The carboxylic acid can be converted to an activated ester or acid chloride for subsequent nucleophilic substitution by amines. These chemistries proceed via well-established acyl-transfer mechanisms and are typically optimized to minimize PEG chain degradation and side reactions.
* 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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