endo-BCN-PEG4-acid | CAS 1421932-54-8

Endo-BCN-PEG4-acid is a strained-alkyne BCN (bicyclononyne) click chemistry reagent equipped with a four-unit PEG linker and a terminal carboxylic acid for convenient conjugation and handle-based coupling. As a bioorthogonal cycloaddition partner, BCN reagents are widely used to label or functionalize biomolecules and materials under mild conditions, including in complex biological mixtures. The PEG spacer supports aqueous compatibility and reduces steric effects, while the acid functionality enables downstream attachment to amines, hydrazides, or other coupling partners commonly used in probe and surface engineering workflows.

1. Cell Surface Labeling

Endo-BCN-PEG4-acid is commonly used to functionalize cell-associated targets in chemical biology workflows where BCN-based labeling is preferred for its fast, selective reactivity with azide or tetrazine-compatible partners in labeling schemes. The PEG4 spacer improves dispersion in aqueous media and helps maintain efficient access to reactive sites on proteins, glycans, or engineered biomolecular scaffolds. Researchers use the terminal carboxylic acid as a practical conjugation handle to incorporate the BCN moiety into larger probe constructs, such as affinity-tagged reagents or imaging/assay reagents that require robust solubility and controlled attachment chemistry.

2. Protein and Peptide Conjugation

Endo-BCN-PEG4-acid serves as a versatile building block for installing BCN functionality onto proteins and peptides used in pull-down experiments, assay development, and mechanistic studies of biomolecular interactions. The carboxylic acid group supports standard coupling strategies to introduce the BCN handle onto carrier proteins, antibody scaffolds, enzyme substrates, or peptide ligands, enabling modular assembly of multi-component bioconjugates. The PEG4 linker helps preserve the native behavior of the biomolecule by mitigating steric hindrance around the strained-alkyne group, which is particularly valuable when BCN-modified biomolecules are incorporated into complex reagent panels for biochemical characterization.

3. Biomaterial Surface Functionalization

Endo-BCN-PEG4-acid is frequently applied in biomaterials science to introduce clickable BCN functionality onto polymer surfaces, hydrogels, and coating layers where subsequent conjugation to complementary partners is required. The PEG4 chain enhances compatibility with hydrated material environments and can reduce nonspecific interactions during surface modification and washing steps. The acid functionality provides a convenient anchor for coupling to surface-reactive chemistries, allowing researchers to build BCN-functional interfaces for downstream attachment of capture ligands, fluorescent reporters, or other modular components used in materials characterization and platform development.

4. Molecular Imaging Probe Building

Endo-BCN-PEG4-acid is used as a BCN-functional reagent in the construction of imaging-oriented chemical probes, where the PEG spacer and carboxyl handle support modular integration into probe architectures. In molecular imaging and fluorescence-based assay development, BCN functionality is often leveraged to attach reporters to biomolecular targeting components through orthogonal click-compatible strategies, enabling controlled probe assembly with defined linker lengths. The reagent’s design supports aqueous probe formulation and helps maintain labeling efficiency when probes are assembled as multi-part conjugates for microscopy, flow-based readouts, or imaging reagent libraries used in chemical biology research.