Azido-PEG5-CH2COOH | CAS 217180-81-9

Azido-PEG5-CH2COOH is a PEG-based azide building block that combines a terminal azide handle with a carboxylic acid for aqueous compatibility and downstream conjugation. As a click chemistry reagent, it is designed for copper-catalyzed azide–alkyne cycloaddition (CuAAC) workflows, enabling efficient attachment of PEG spacers to biomolecules, surfaces, and imaging/diagnostic platforms. The flexible PEG5 chain and the carboxylate functionality make it particularly useful when a hydrophilic linker, improved solubility, or a defined spacing element is required in molecular imaging and bioconjugation programs.

1. Bioconjugation Linker Chemistry

Azido-PEG5-CH2COOH is widely used as a PEG spacer in bioconjugation workflows where a carboxyl-bearing, hydrophilic linker is needed to connect targeting ligands, affinity reagents, or carrier scaffolds to alkyne-functional partners via click chemistry. Researchers commonly incorporate the PEG5 chain to reduce nonspecific interactions and to provide steric separation between the conjugated moieties, improving handling and stability during labeling and assay development. The terminal azide group enables modular assembly with alkyne-tagged biomolecules, while the carboxylic acid supports additional coupling strategies for preparing multi-component constructs.

2. Surface Functionalization And Coatings

Azido-PEG5-CH2COOH supports click-driven modification of polymeric and material surfaces, particularly in laboratory and industrial settings that require controlled grafting of PEG-based linkers. The azide handle allows attachment to alkyne-functional coatings or patterned substrates through CuAAC, while the PEG5 spacer helps create hydration layers that can influence protein adsorption and surface wettability. Downstream, the carboxylic acid functionality is useful for further derivatization steps, enabling the construction of multi-functional surfaces used in assay development, biosensing component fabrication, and materials research.

3. Molecular Imaging Probe Assembly

Azido-PEG5-CH2COOH is commonly selected for assembling imaging and labeling reagents that benefit from a hydrophilic PEG spacer between a reactive handle and the reporter component. In molecular imaging and chemical biology tool development, the azide group provides a reliable click handle for coupling to alkyne-bearing fluorophores, affinity tags, or scaffold elements, allowing rapid generation of probe libraries under standardized labeling conditions. The presence of a carboxylic acid also facilitates incorporation into probe designs where additional conjugation or buffer-compatible formulation is required for consistent probe behavior in experimental workflows.

4. Diagnostic Reagent Development

Azido-PEG5-CH2COOH is used in the preparation of diagnostic and analytical reagent components that require modular conjugation and robust aqueous compatibility. Teams developing assay reagents often employ this azido-PEG5-CH2COOH to introduce a defined PEG spacer that can improve conjugate solubility and help manage steric accessibility of binding or recognition elements after click attachment to alkyne-functional partners. The carboxylic acid offers a practical handle for building multi-step reagent formats, including coupling to capture platforms or integrating additional functional groups for assay workflow optimization.