Azido-PEG5-propionic acid | CAS 1425973-16-5

Azido-PEG5-propionic acid is a PEG-based azide building block designed for bioconjugation workflows that rely on copper-free or copper-catalyzed click chemistry. As an azide functional handle, it is commonly incorporated into PEGylated linkers and surface coatings to enable subsequent ligation with complementary alkynes, including strained cyclooctynes and terminal alkynes used in labeling, materials functionalization, and probe assembly. The presence of the PEG5 spacer and a terminal carboxylic acid makes this reagent particularly relevant for constructing water-compatible conjugates and for attaching biomolecule- or surface-reactive moieties downstream.

1. PEGylated Probe Labeling

Azido-PEG5-propionic acid is widely used to introduce an azide functionality into fluorescent, affinity, or activity-based labeling reagents where polyethylene glycol spacing improves aqueous solubility and reduces nonspecific interactions. Researchers incorporate this reagent into probe designs that later undergo click conjugation to install targeting ligands, reporters, or capture handles via azide–alkyne coupling. The terminal carboxylic acid also supports common conjugation strategies for immobilizing or coupling the PEG chain to amine-bearing biomolecules or to solid supports, enabling modular probe construction for imaging and assay development.

2. Biomolecule Conjugation Linkers

Azido-PEG5-propionic acid serves as a practical linker component for generating azide-functional biomolecule conjugates, including PEGylated antibody fragments, peptides, proteins, and nucleic-acid-associated reagents used in chemical biology. The PEG5 segment helps maintain colloidal stability and can provide steric spacing that improves accessibility of the reactive partners during subsequent click steps. By providing both an azide and a carboxylic acid, the reagent fits into workflows where the PEG chain must be appended first, followed by click installation of an alkyne-bearing tag such as a fluorophore, biotin analog, or affinity moiety for downstream detection and enrichment.

3. Surface Functionalization And Coatings

Azido-PEG5-propionic acid is commonly employed to functionalize surfaces and biomaterials with azide groups for subsequent immobilization of ligands using click chemistry. Materials scientists use the carboxylic acid functionality to anchor PEG layers onto polymer films, nanoparticles, or other substrate chemistries, while the azide handle provides a robust coupling point for attaching alkynyl biomolecules, peptides, or imaging reporters. This approach is frequently selected for creating well-defined, water-compatible interfaces that support reproducible labeling and controlled presentation of binding elements.

4. Molecular Imaging Reagent Assembly

Azido-PEG5-propionic acid is used as a building block in the assembly of molecular imaging and detection reagents where modular late-stage conjugation is advantageous. The azide group enables efficient installation of imaging reporters or enrichment tags through click reactions with complementary alkyne-bearing components, supporting flexible probe architectures across different labeling formats. The PEG5 spacer contributes to improved solubility and reduced aggregation tendencies in aqueous labeling buffers, which is valuable when preparing probe conjugates for microscopy, flow-based assays, or other analytical workflows requiring stable, well-behaved reagent formulations.

5. Diagnostic And Enrichment Platforms

Azido-PEG5-propionic acid is frequently integrated into diagnostic reagent development and enrichment platform design to create clickable capture materials and modular assay components. By installing azide functionality onto PEG-containing linkers, developers can later attach alkynyl recognition elements such as affinity ligands, nucleic-acid probes, or reporter tags through click conjugation. The combination of PEG spacing and a terminal carboxylic acid supports practical coupling to carrier particles and solid-phase formats, enabling reproducible construction of multivalent reagents used for sample processing, signal generation, and analytical readouts.