Amino-PEG3-C2-acid CAS:784105-33-5_News

A Monodisperse Heterobifunctional PEG Linker for ADC and PROTAC Applications
1. Overview
Amino-PEG3-C2-acid (CAS 784105-33-5) is a small-molecule, monodisperse heterobifunctional polyethylene glycol (PEG) linker. It carries an amino group (−NH₂) at one end and a carboxylic acid (−COOH) at the other, connected by a precisely defined triethylene glycol (PEG3) spacer.
Because the acid-bearing terminus features a two-carbon (−CH₂CH₂−) bridge to the carboxyl group, the compound is also referred to as Amino-PEG3-propionic acid.
With a discrete molecular weight of 221.25 g/mol and the molecular formula C₉H₁₉NO₅, this compound is widely used as a building block in the synthesis of antibody–drug conjugates (ADCs) and PROTACs (proteolysis-targeting chimeras),as well as in a broad range of bioconjugation and surface-modification applications.

2.Key Features
Heterobifunctional design — two orthogonally reactive handles (−NH₂ and −COOH) enable stepwise, chemoselective conjugation.
Monodisperse PEG3 spacer — exact molecular weight, high reproducibility, and well-defined pharmacokinetic behavior in conjugates.
Hydrophilic and biocompatible — PEG spacing improves aqueous solubility, reduces immunogenicity, and helps shield hydrophobic payloads.
Cleavable / biodegradable profile — the PEG-based linker is classified as a cleavable-type linker in ADC and PROTAC design, facilitating traceless payload release.
Small footprint (221.25 Da) — minimizes impact on the overall molecular properties of the final conjugate.

3. Applications
3.1 Antibody–Drug Conjugates (ADCs)   -- Amino-PEG3-C2-acid is a cleavable, 4-unit PEG ADC linker. It is used to tether cytotoxic payloads to monoclonal antibodies. The PEG spacer enhances the hydrophilicity of the conjugate, improves plasma stability, 
and can modulate drug-to-antibody ratio (DAR) and pharmacokinetics. The amine and carboxyl termini allow attachment of the drug on one side and the antibody (often via a lysine or cysteine residue) on the other.
3.2 PROTACs (Targeted Protein Degradation)    -- As a PEG-based PROTAC linker, the compound connects an E3 ligase ligand (e.g., pomalidomide, lenalidomide, VHL ligand) to a target-protein-binding moiety. 
The short PEG3 chain provides an optimal distance and geometry for ternary complex formation, while improving solubility of the often hydrophobic degrader molecules.
3.3 Bioconjugation & Click Chemistry   --The amino group can be derivatized with azide, alkyne, DBCO, or other click handles, converting the molecule into a versatile intermediate for copper-catalyzed azide–alkyne cycloaddition (CuAAC) or 
strain-promoted (SPAAC) reactions in labeling, imaging, and drug delivery studies.
3.4 Surface Modification & Material Science    --The carboxylic acid terminus enables covalent anchoring onto amine-functionalized surfaces, nanoparticles, gold substrates, or polymer matrices, while the exposed amine (or PEG chain) provides 
anti-fouling and biocompatible properties — useful for biosensors, drug delivery carriers, and biomaterials.
3.5 Solid-Phase Peptide Synthesis (SPPS)    --The amino group serves as a starting handle for peptide chain elongation, while the acid group can be protected or used for cyclization and head-to-tail conjugation.

4.Comparison with Related Linkers