Azido-PEG3-O-NHS ester | CAS 2110448-98-9

Azido-PEG3-O-NHS ester is a PEG-based azide functionalization reagent that combines a terminal azide handle with an NHS ester for efficient coupling to primary amines on biomolecules and polymeric scaffolds. As a click chemistry reagent, it is commonly used as a versatile precursor for strain-promoted or copper-catalyzed azide–alkyne cycloaddition workflows, enabling modular attachment of fluorescent tags, affinity ligands, or imaging moieties. The short, flexible PEG3 spacer helps improve solubility and spacing between the conjugation site and the azide, which is frequently valuable in bioconjugation and molecular imaging probe development.

1. Protein Labeling Workflows

Azido-PEG3-O-NHS ester is widely used to introduce azide functionality onto proteins and peptide carriers via NHS-ester coupling to lysine residues or N-terminal amines. Researchers employ this reagent to generate azide-bearing bioconjugates that can subsequently be clicked to alkyne-functional dyes, affinity probes, or other imaging/assay components, supporting streamlined probe assembly in chemical biology and analytical workflows. The PEG3 spacer often reduces steric crowding around the reactive handle, which can be advantageous when downstream click labeling is performed on complex protein mixtures or multicomponent conjugates.

2. Antibody and Ligand Conjugation

Azido-PEG3-O-NHS ester is commonly selected for preparing azide-functional antibodies, antibody fragments, and targeting ligands where a robust, modular attachment point is required for later conjugation steps. By first installing the azide through NHS chemistry, teams can decouple the targeting-ligand preparation from the final construction of the reporter or payload, facilitating parallel synthesis of probe libraries for binding assays and imaging reagent optimization. This approach is particularly useful in workflows that require consistent linker length and improved conjugate handling, since the PEG3 element can help maintain solubility and reduce aggregation during labeling and purification.

3. Surface and Material Functionalization

Azido-PEG3-O-NHS ester is used to functionalize amine-containing surfaces and materials such as polymer films, hydrogel networks, and bead-based supports that present accessible primary amines. After coupling, the resulting azide-modified surfaces serve as platforms for subsequent click attachment of alkyne-bearing biomolecules, fluorescent reporters, or affinity tags, enabling spatially defined labeling and modular assembly of diagnostic or research surfaces. The PEG3 spacer contributes to better accessibility of the azide at the interface, which can improve the efficiency and uniformity of downstream surface click conjugation steps.

4. Fluorophore and Probe Assembly

Azido-PEG3-O-NHS ester is frequently incorporated into workflows that build fluorescent and affinity-based probes through sequential conjugation: first installing the azide handle on a carrier, then performing click coupling to alkyne-functional reporters. This strategy supports the rapid generation of imaging reagents and assay tools where the reporter identity can be varied without repeating the initial carrier functionalization step. The reagent’s PEG-based design helps maintain conjugate solubility and provides a short, flexible separation between the carrier attachment point and the clickable azide, which is beneficial when optimizing probe brightness, labeling uniformity, or multicolor reagent compatibility in molecular imaging and diagnostics research tool development.