N-(Azido-PEG3)-N-Boc-PEG3-NHS ester | CAS 2112731-51-6

N-(Azido-PEG3)-N-Boc-PEG3-NHS ester is a heterobifunctional, PEG-based click chemistry reagent that combines an NHS ester for amide coupling with an azide handle for subsequent bioorthogonal conjugation. As an azide-bearing linker, it is commonly used to install a reactive azide group onto proteins, peptides, or other amine-containing biomolecules, enabling downstream copper-free or copper-mediated azide–alkyne cycloaddition workflows. The presence of PEG spacers supports solubility and reduces steric constraints, making it suitable for generating well-defined azide-functional conjugates used in chemical biology, molecular imaging, and biomaterials research.

1. Protein Azide Labeling

N-(Azido-PEG3)-N-Boc-PEG3-NHS ester is widely used to introduce azide functionality onto proteins and protein fragments via NHS ester–mediated coupling to primary amines. Researchers employ the resulting azide-functional bioconjugates as standardized starting materials for subsequent click reactions with alkyne-bearing probes, such as fluorescent tags, affinity reagents, or enrichment handles. The PEG architecture helps maintain aqueous compatibility and can improve accessibility of both the bioconjugate and the azide group during downstream labeling steps, which is particularly valuable when preparing multi-component probe libraries for mechanistic studies and assay development.

2. Surface and Material Functionalization

N-(Azido-PEG3)-N-Boc-PEG3-NHS ester supports the creation of azide-functional surfaces and biomaterials by reacting its NHS ester with amine-containing coatings, polymer surfaces, or linker layers. This enables patterned or modular attachment of alkyne-functional capture molecules, imaging agents, or responsive elements through azide–alkyne click chemistry. In materials workflows, PEG spacing is often leveraged to reduce nonspecific interactions and to preserve reactive-group mobility, which can be important for reproducible immobilization density and for maintaining probe accessibility on complex substrates such as hydrogels, beads, or functional polymer films.

3. Targeted Probe and Imaging Conjugates

N-(Azido-PEG3)-N-Boc-PEG3-NHS ester is commonly selected to generate azide-bearing intermediates used in assembling targeted molecular imaging probes and diagnostic-reagent components. By first installing an azide handle onto a targeting scaffold (for example, an antibody fragment, peptide, or other amine-rich ligand), teams can later couple the scaffold to alkyne-functional imaging moieties, reporters, or signal-amplifying tags using click chemistry. The PEG linkers embedded in N-(Azido-PEG3)-N-Boc-PEG3-NHS ester help maintain solubility and can reduce steric hindrance that otherwise limits efficient labeling, supporting robust conjugation workflows in molecular imaging reagent development.

4. Linker Platforms for Multi-Step Conjugation

N-(Azido-PEG3)-N-Boc-PEG3-NHS ester serves as a versatile platform reagent for multi-step bioconjugation strategies where an azide group must be introduced early and reacted later under controlled conditions. Chemical biology groups use the NHS ester functionality to install the azide-bearing linker onto amine-containing biomolecules or carriers, then perform orthogonal click coupling to append diverse alkyne partners without directly modifying the original targeting or recognition element. This modular approach is particularly useful for building combinatorial reagent sets, such as libraries of click-assembled conjugates with varying reporters, affinity tags, or material-binding motifs, while keeping the initial functionalization step consistent across constructs.