Azido-PEG4-NHS-ester | CAS 1807534-82-2

Azido-PEG4-NHS-ester is a PEG-based heterobifunctional linker that combines an NHS ester for efficient acylation of nucleophilic amines with a terminal azide handle for subsequent copper-free or copper-mediated click chemistry. As a widely used azide-bearing bioconjugation reagent, it enables modular assembly of labeled biomolecules, surfaces, and polymeric materials while providing a short, flexible PEG spacer that helps preserve target accessibility. Its PEG4 architecture and NHS reactivity make it particularly relevant for preparing click-ready conjugates for downstream probe attachment, imaging reagent construction, and materials functionalization.

1. Protein Surface Labeling

Azido-PEG4-NHS-ester is commonly used to functionalize proteins and peptides by forming stable amide bonds with lysine residues or N-terminal amines, generating click-compatible azide-bearing conjugates. Researchers frequently select this reagent when they need a controlled PEG spacer to reduce steric hindrance and improve labeling uniformity for subsequent azide-reactive steps. The resulting azido-functional proteins are then carried into workflows for attaching fluorophores, affinity tags, or other molecular motifs via click chemistry, supporting applications such as assay reagent preparation and mechanistic studies in chemical biology.

2. Antibody and Binder Conjugates

Azido-PEG4-NHS-ester is frequently applied in the preparation of antibody conjugates and other binding proteins where an azide handle is required for orthogonal attachment of imaging or detection components. The NHS-ester reactivity allows convenient pre-functionalization under standard bioconjugation conditions, while the PEG4 spacer helps maintain binding-site accessibility and reduces nonspecific steric effects during labeling. Downstream, the installed azide enables rapid coupling to complementary cyclooctyne or alkyne partners, supporting modular generation of click-assembled probe panels used in research-oriented diagnostics development and targeted binding studies.

3. Cell Surface and Biomaterial Functionalization

Azido-PEG4-NHS-ester is used to introduce azide functionality onto cell-surface proteins and onto biomaterial scaffolds that present accessible amines, enabling subsequent click-based patterning and immobilization. In biomaterials research, the NHS ester provides a practical route to covalently anchor PEG-azide linkers onto surfaces, hydrogels, or coatings, creating defined reactive sites for later conjugation with imaging dyes, affinity ligands, or crosslinking partners. The PEG spacer improves surface compatibility and can help maintain reactivity for downstream click attachment, which is valuable for constructing functional materials used in molecular imaging reagent development and platform prototyping.

4. Fluorophore and Probe Assembly

Azido-PEG4-NHS-ester is widely used as a key intermediate for producing azide-functional labeling reagents, including fluorophore conjugates and multi-component chemical probes. By first converting amine-containing targets (such as dyes, small biomolecules with amines, or amine-functional carriers) into azido-PEG conjugates, the reagent supports subsequent click coupling to complementary partners with high chemoselectivity. This approach is particularly useful when probe design requires modular exchange of targeting groups, reporters, or solubility-enhancing elements, allowing rapid generation of probe libraries for biochemical characterization and imaging workflow optimization.