Azido-PEG3-t-butyl ester | CAS 252881-73-5

Azido-PEG3-t-butyl ester is a PEG-based azide click handle designed for copper-free and copper-mediated azide–alkyne cycloaddition workflows in chemical biology and materials research. The reagent combines a short, flexible poly(ethylene glycol) spacer with a t-butyl ester functionality, enabling downstream conversion to carboxylate-bearing conjugates while retaining the azide for selective ligation. Its amphiphilic PEG architecture and compact azide motif make it a common building block for constructing bioconjugates, surface coatings, and imaging/assay reagents where controlled attachment and improved solubility are required.

1. Surface Functionalization

Azido-PEG3-t-butyl ester is widely used to introduce azide-bearing PEG linkers onto polymeric and inorganic surfaces for subsequent click attachment of biomolecules, affinity ligands, or fluorescent reporters. Researchers often select this reagent when they need a short hydrophilic spacer to reduce nonspecific adsorption and to improve accessibility of the reactive handle on surfaces such as glass, polymer films, and nanoparticle coatings. After immobilization, the azide group serves as a modular platform for attaching alkyne-functional probes under mild conditions that preserve sensitive surface-bound components.

2. Protein and Peptide Conjugation

Azido-PEG3-t-butyl ester supports labeling strategies where PEG-mediated spacing improves conjugate behavior, including solubility and reduced steric hindrance during subsequent functionalization. Bioconjugation workflows frequently incorporate this reagent as an azide-containing intermediate that can be transformed into carboxylate-bearing derivatives for coupling to amine-reactive chemistries or for building multi-component conjugates. The resulting azide-functional PEG linkers are then used to attach imaging tags, affinity handles, or assay components through click chemistry, enabling rapid generation of probe libraries with consistent linker geometry.

3. Molecular Imaging Probes

Azido-PEG3-t-butyl ester is commonly used in the development of modular molecular imaging and detection probes that require orthogonal assembly steps. The azide handle enables late-stage conjugation to alkyne-functional dyes, radiolabeling scaffolds, or enrichment motifs, allowing probe construction to be decoupled from the preparation of the PEG-linked precursor. The short PEG spacer provided by Azido-PEG3-t-butyl ester helps tune probe hydrophilicity and reduces aggregation tendencies, which is particularly valuable when preparing fluorescent or luminescent conjugates for imaging-oriented research assays.

4. Diagnostic and Assay Reagents

Azido-PEG3-t-butyl ester is frequently employed as a click-ready reagent for assembling diagnostic and analytical reagents, including affinity capture constructs and signal-generating conjugates. In assay development, the azide group provides a convenient handle for attaching reporter groups, biorecognition elements, or polymeric scaffolds via azide–alkyne cycloaddition, supporting streamlined workflows for generating multiple reagent variants. The PEG linker functionality helps maintain reagent dispersibility and accessibility of the attached components, which can be important for consistent performance in binding and detection assays that rely on well-defined conjugate architecture.