N-(Azido-PEG4)-N-Boc-PEG4-NHS ester | CAS 2112731-96-9

N-(Azido-PEG4)-N-Boc-PEG4-NHS ester is a bifunctional PEG-based click chemistry reagent that combines an azide handle for copper-free or copper-mediated azide–alkyne cycloaddition with an NHS ester for efficient amide-bond formation with primary amines. The reagent’s multi-PEG architecture provides aqueous solubility and spacer length control, which is valuable for tuning conjugation density and minimizing steric effects in biomolecular labeling. As a research-grade linker, it is commonly used to install azide functionality onto proteins, peptides, and other amine-containing substrates prior to downstream click-based assembly of probes, materials, and imaging reagents.

1. Protein And Peptide Labeling

N-(Azido-PEG4)-N-Boc-PEG4-NHS ester is widely used to functionalize proteins and peptides by reacting the NHS ester with accessible primary amines on lysine side chains or N-termini, generating an azide-bearing conjugate that can be carried forward to click-based tagging. The PEG spacers help maintain solubility and reduce nonspecific aggregation during labeling, which is particularly useful when preparing conjugates for fluorescence, affinity reagents, or surface immobilization workflows. Researchers often choose this reagent when they need a defined azide handle for subsequent conjugation to alkynyl dyes, affinity ligands, or polymer backbones while preserving the native behavior of the biomolecule as much as possible.

2. Biomaterials Surface Functionalization

N-(Azido-PEG4)-N-Boc-PEG4-NHS ester supports azide installation on amine-functional biomaterial surfaces, enabling modular post-functionalization via click chemistry. In biomaterials and materials science settings, amine-bearing coatings, hydrogels, or polymer scaffolds are commonly modified using NHS chemistry to introduce azide groups at controlled spacing, after which alkynyl components can be attached to build multicomponent surfaces. This approach is frequently used to create tunable interfaces for biosensing, cell-interaction studies, and research-grade assay platforms where precise chemical handle placement and water-compatible linker length are important.

3. Multivalent Probe And Polymer Assembly

N-(Azido-PEG4)-N-Boc-PEG4-NHS ester is an effective intermediate for constructing multivalent probe formats and PEGylated polymer conjugates that incorporate azide “attachment points” for later click coupling. By first installing azide groups onto an amine-containing carrier (such as a PEG scaffold, polymer segment, or functional biomolecule), teams can subsequently couple multiple alkynyl reporters or targeting motifs in a controlled, modular manner. The PEG-rich structure of the reagent helps maintain colloidal stability and reduces steric crowding, which is advantageous when assembling higher-order conjugates used in chemical biology tool development and imaging-reagent preparation.

4. Molecular Imaging Reagent Building

N-(Azido-PEG4)-N-Boc-PEG4-NHS ester is commonly used in molecular imaging reagent development to generate azide-functional precursors from amine-containing targeting vectors or scaffold molecules. After azide installation through NHS reactivity, the resulting conjugates can be linked to alkynyl imaging reporters using click chemistry-compatible coupling strategies, supporting flexible design of probe architecture. The PEG spacers are particularly useful for managing hydrophilicity and controlling the effective distance between the targeting moiety and the imaging label, which can be important for reducing unfavorable interactions and improving reproducibility across probe batches.