NHS-PEG5-bis-PEG3-azide

NHS-PEG5-bis-PEG3-azide is a heterobifunctional, PEG-based click chemistry reagent that pairs an N-hydroxysuccinimide (NHS) ester for efficient reaction with primary amines with two terminal azide groups for subsequent copper-free or copper-mediated azide–alkyne cycloaddition. Its flexible, hydrophilic PEG architecture supports aqueous conjugation workflows and helps tune solubility, spacing, and accessibility of the reactive handles for downstream labeling. Because it delivers a defined density of azide functionalities onto amine-bearing biomolecules, surfaces, and materials, it is widely used in probe construction, multivalent tagging, and modular bioconjugation strategies.

1. Protein Surface Azide Labeling

NHS-PEG5-bis-PEG3-azide is commonly used to install azide functional groups onto lysine-rich proteins and other primary-amine containing biomolecules, enabling subsequent click-based attachment of fluorophores, affinity ligands, or imaging tags. The dual-azide format supports multivalent labeling schemes where multiple payloads can be introduced from a single conjugation step, improving handle availability for downstream conjugation. PEG spacing helps maintain colloidal stability and reduces steric crowding that can otherwise limit labeling efficiency in dense protein environments, which is particularly valuable for preparing homogeneous probe reagents used in biochemical assays and analytical workflows.

2. Multivalent Probe Construction

NHS-PEG5-bis-PEG3-azide is well suited for building multivalent research probes that require controlled presentation of multiple clickable sites on a single scaffold. Researchers use the reagent to generate azide-functional intermediates that can be coupled to complementary alkyne-bearing components, such as polymeric reporters, cell-surface targeting modules, or branched molecular imaging constructs. The bis-PEG3-azide motif provides two reactive termini, supporting higher local loading of imaging or detection moieties while retaining the aqueous compatibility characteristic of PEG-based linkers. This makes the reagent a practical choice for constructing modular libraries of click-ready conjugates for platform screening and method development.

3. Biomaterials and Surface Functionalization

NHS-PEG5-bis-PEG3-azide is frequently applied to functionalize amine-containing biomaterials, coatings, and solid supports with azide groups for later attachment of alkyne-bearing biomolecules or polymer brushes. The NHS ester enables rapid coupling to amine functionalities present on many surface chemistries, while the PEG spacer and dual azides promote accessibility of click handles after immobilization. This approach is used to prepare click-reactive materials for biosensing interfaces, microarray reagents, and engineered extracellular-matrix mimics where spatial control of reactive sites can influence labeling uniformity and subsequent binding of attached probes. The resulting azide-functional surfaces are compatible with common click workflows used in materials characterization and assay development.

4. Orthogonal Conjugation Workflows

NHS-PEG5-bis-PEG3-azide is often integrated into orthogonal bioconjugation pipelines where azide handles are introduced without interfering with other functional groups on complex biomolecules. The PEG-based linker architecture helps preserve the reactivity of the azide termini for later coupling to alkyne-bearing partners, supporting sequential labeling strategies that separate amine-targeting steps from downstream click attachment. In workflows that require careful staging of modifications—such as preparing intermediate conjugates for later assembly into larger constructs—this reagent provides a convenient, click-ready azide installation step with a defined geometry that supports reproducible downstream coupling across batches.