Azido-PEG3-S-PEG4-t-butyl ester | CAS 2055041-19-3

Azido-PEG3-S-PEG4-t-butyl ester is a PEG-based azide-containing click chemistry reagent designed for bioconjugation workflows that benefit from enhanced aqueous solubility and controlled linker spacing. The molecule combines an azide functional group for copper-catalyzed azide–alkyne cycloaddition (CuAAC) with a thioether-linked PEG architecture and a t-butyl ester handle that can be used to tune stability and downstream functionalization. This reagent is commonly selected when researchers need reliable azide presentation on PEGylated scaffolds for attaching biomolecules, surfaces, or imaging/assay components with minimal nonspecific interactions.

1. Protein And Peptide Conjugation

Azido-PEG3-S-PEG4-t-butyl ester is used to introduce a click-ready azide motif onto PEGylated proteins and peptides, enabling modular coupling to alkyne-bearing partners such as fluorescent dyes, affinity tags, or engineered probes. The PEG3/PEG4 spacing helps reduce steric crowding around the reactive site, which is particularly valuable when labeling complex biomacromolecules or preparing multicomponent conjugates for biochemical assays. The t-butyl ester functionality supports workflows where a protected carboxylate equivalent is advantageous during conjugate assembly, allowing subsequent derivatization or activation steps to be integrated into the overall bioconjugation strategy.

2. Surface Functionalization For Biomaterials

Azido-PEG3-S-PEG4-t-butyl ester is well suited for functionalizing biomaterial surfaces and polymer coatings with azide groups for later CuAAC attachment of biomolecule ligands and diagnostic or imaging components. The PEG-based linker improves compatibility with aqueous environments and can help mitigate nonspecific adsorption on surfaces, which is important for creating reproducible material interfaces used in assays, biosensing formats, and cell-interaction studies. By incorporating this reagent as a surface-presented azide, downstream attachment of alkyne-functional reporters or targeting moieties becomes a modular step that can be optimized independently from the initial material preparation.

3. Fluorophore And Imaging Probe Assembly

Azido-PEG3-S-PEG4-t-butyl ester is frequently used as an azide building block for constructing PEGylated imaging probes and fluorescent conjugates via CuAAC with alkyne-tagged dyes or imaging reporters. The inclusion of PEG3 and PEG4 segments supports improved solubility and can help maintain probe accessibility, which is beneficial when preparing multivalent or sterically demanding labeling constructs. The thioether-linked PEG scaffold also supports consistent linker presentation, making the reagent a practical choice for assembling probe libraries where azide density and spacing are tuned to match the imaging chemistry and labeling format.

4. Diagnostic Reagent And Assay Labeling

Azido-PEG3-S-PEG4-t-butyl ester supports the preparation of assay reagents that require azide-functional handles for click-based installation of detection elements, including enzyme labels, affinity reagents, and signal-generating reporters bearing terminal alkynes. PEGylation helps maintain reagent behavior in assay buffers by improving aqueous compatibility and reducing aggregation tendencies that can complicate signal readouts. The reagent’s protected ester functionality can be leveraged during reagent assembly to coordinate multi-step synthesis, enabling consistent conjugate construction for platform development in research diagnostics and analytical chemistry workflows.