m-PEG25-NHS ester
Cat No.: BP-501755
4.5 
m-PEG25-NHS ester is a mono-functional methoxy-terminated polyethylene glycol linker bearing an N-hydroxysuccinimide (NHS) ester for amide-bond formation. Structurally, it consists of a PEG chain of intermediate length with a terminal NHS-activated carboxylate, allowing efficient conjugation to primary amines on targeting ligands (e.g., lysine residues, amine-bearing small molecules, or engineered peptides) under standard aqueous or mixed-solvent coupling conditions. In PROTAC and related targeted degradation constructs, this PEG linker serves as a flexible, hydrophilic spacer that can reduce steric clashes, improve solubility, and help preserve the binding conformations of both the recruiting ligand and the target-binding moiety. The NHS ester provides a straightforward, chemoselective handle for stable amide linkage, facilitating modular assembly and optimization of linker length and attachment site to tune degradation efficiency and physicochemical properties for experimental evaluation.
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* For research and manufacturing use only. Not for human or clinical use.
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m-PEG25-NHS ester is a PEG-based activated ester linker widely used to assemble PROTAC constructs through efficient amide-bond formation with primary amines on targeting ligands or E3 ligase binders. Its flexible, hydrophilic PEG spacer helps improve solubility and can modulate linker length and conformational freedom, supporting productive ternary complex formation. The following sections describe the linker’s structure and the practical reactivity considerations for PROTAC synthesis.
Structure: The linker consists of a methoxy-terminated, linear poly(ethylene glycol) chain bearing an N-hydroxysuccinimide ester at the terminus. It contains an NHS-activated carboxylate functionality designed for acyl transfer, along with ether linkages characteristic of PEG, providing high hydrophilicity and reduced aggregation.
Reactivity: The NHS ester reacts with primary amines to form stable amide bonds via nucleophilic acyl substitution. Suitable conditions typically employ mildly basic aqueous buffers or mixed aqueous/organic systems to maintain amine nucleophilicity while limiting hydrolysis. No special catalyst is required; however, freshly prepared solutions, controlled pH, and short reaction times help minimize NHS ester degradation.
* 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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