Azido-PEG3-S-PEG4-propargyl | CAS 2055041-24-0

Azido-PEG3-S-PEG4-propargyl is a bifunctional, PEG-based click chemistry reagent that combines an azide handle with a terminal propargyl (alkyne) group connected through a thioether/PEG scaffold. As a modular platform for copper-free or copper-mediated azide–alkyne cycloaddition workflows, it is commonly used to introduce controlled, flexible linkers into bioconjugates, surface coatings, and imaging or materials constructs. The extended PEG segments provide water compatibility and spacing control, making this reagent attractive for assembling multivalent probes, tethering biomolecules to surfaces, and building well-defined polymer or hydrogel architectures.

1. Protein And Peptide Conjugation

Azido-PEG3-S-PEG4-propargyl is used in chemical biology to generate defined protein–protein, protein–polymer, or protein–surface conjugates where orthogonal click handles are required. Researchers employ the azide and propargyl termini to couple biomolecules that have been functionalized with complementary click partners, enabling modular assembly of multivalent reagents such as biotinylated or affinity-tagged constructs, PEGylated carriers, and spaced labeling reagents. The PEG-rich framework helps reduce nonspecific interactions and supports efficient conjugate formation in aqueous buffers commonly used for protein labeling and reagent development.

2. Surface Patterning And Coatings

Azido-PEG3-S-PEG4-propargyl supports materials and biomaterials workflows that require controlled tethering of biomolecules to functional surfaces, including patterned immobilization for biosensing and cell-interaction studies. By incorporating this reagent into surface modification strategies, teams can create stable, flexible linkers that improve accessibility of immobilized ligands while maintaining surface hydration. The dual click functionality is particularly valuable when sequential or modular surface functionalization is needed, such as building layered coatings, preparing ligand gradients, or integrating reactive handles for downstream probe attachment.

3. Molecular Imaging Probe Assembly

Azido-PEG3-S-PEG4-propargyl is widely applied in the development of click-assembled molecular imaging probes and fluorescent or luminescent labeling reagents that require a flexible spacing element between targeting motifs and reporter groups. In probe build-outs, the PEG scaffold can help maintain reporter mobility and reduce steric hindrance, which is important when attaching dyes, chelators, or reporter-bearing biomolecules to targeting ligands through azide–alkyne coupling. The reagent’s bifunctional nature also enables rapid interchange of labeling partners during optimization of imaging reagents for research-grade molecular imaging toolkits.

4. Hydrogel to Polymer Linker Engineering

Azido-PEG3-S-PEG4-propargyl is used in biomaterials science to engineer hydrogel and polymer networks where controlled linker placement and modular post-functionalization are required. Formulations that incorporate azide or alkyne functionalities can use this PEG-based connector to tune mesh spacing, improve water compatibility, and provide reactive sites for subsequent attachment of biomolecules such as peptides, growth-factor mimics, or affinity ligands. This approach is common in scaffold design and materials development pipelines that prioritize reproducible functionalization and the ability to swap reactive components without redesigning the entire material chemistry.