Azido-PEG4-propionic acid | CAS 1257063-35-6

Azido-PEG4-propionic acid is a PEG-based azide building block designed for click chemistry workflows, most commonly in copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC). The reagent combines a terminal azide handle with a short PEG4 spacer and a carboxylic acid functionality, enabling robust conjugation to alkyne-bearing partners while maintaining aqueous compatibility and reducing nonspecific interactions. Its compact, water-soluble structure makes it a widely used intermediate for preparing clickable biomaterials, labeling reagents, and functionalized surfaces for chemical biology and analytical research.

1. Bioconjugation Linker Use

Azido-PEG4-propionic acid is frequently used as a flexible, water-compatible linker for attaching biomolecules and biomolecule-derived constructs to alkyne-functional targets through CuAAC. The PEG4 spacer helps maintain conjugate solubility and reduces steric crowding at the conjugation site, which is valuable when preparing multicomponent labeling reagents, affinity probes, and modular assay components. The terminal carboxylic acid also supports downstream coupling strategies to biomolecule scaffolds or solid supports, allowing researchers to integrate the azide handle into larger bioconjugation schemes without sacrificing aqueous processability.

2. Surface And Material Functionalization

Azido-PEG4-propionic acid is commonly incorporated into polymer, hydrogel, and surface modification workflows where azide presentation is required for subsequent click attachment to alkyne-bearing coatings or nanoparticles. The PEG4 segment provides a hydrated, antifouling-like interface that can improve accessibility of the azide group after immobilization, which is particularly useful for creating patterned or functionalized materials for chemical biology and materials science applications. Researchers use the carboxylic acid functionality to anchor the reagent to reactive surfaces or to introduce clickable handles into material formulations before post-functionalization by CuAAC.

3. Molecular Imaging Probe Preparation

Azido-PEG4-propionic acid is used as a practical azide component in the assembly of molecular imaging and detection probes that require modular coupling to alkyne-bearing reporter units. The combination of a short PEG spacer and a carboxylic acid handle supports consistent probe architectures by improving solubility and spacing between the targeting or recognition element and the imaging moiety. In probe development workflows, the azide group enables late-stage conjugation to diverse alkyne-functional reporters, facilitating rapid interchange of labels while keeping the overall probe format chemically consistent.

4. Diagnostic Reagent And Assay Building

Azido-PEG4-propionic acid is widely applied in the development of diagnostic and analytical reagent platforms where clickable attachment of labels, capture ligands, or signal-generating components is needed. The reagent’s azide functionality supports orthogonal, high-yield coupling to alkyne partners under CuAAC conditions, enabling researchers to build assay-ready conjugates with controlled linker length and improved aqueous handling. The carboxylic acid group supports integration into reagent formats that require additional coupling steps, such as immobilization on activated surfaces or incorporation into multifunctional assay constructs.