Phthalamide-PEG3-azide | CAS 134179-44-5

Phthalamide-PEG3-azide is a PEGylated azide building block designed for bioorthogonal click chemistry workflows, most commonly used as an azide partner in strain-promoted or copper-catalyzed azide–alkyne cycloaddition. The phthalamide motif provides a stable, amide-linked handle while the short PEG3 spacer improves aqueous compatibility and reduces steric interference during conjugation. This reagent is widely used to introduce azide functionality onto biomaterials, imaging probes, and macromolecular constructs for downstream labeling, immobilization, and modular assembly.

1. Biomolecule Labeling

Phthalamide-PEG3-azide is used to install azide groups on proteins, peptides, and other biomolecular scaffolds that require subsequent click-based attachment of reporters, affinity tags, or secondary functional units. The PEG3 spacer helps maintain access to the azide moiety in crowded conjugation environments, which is particularly valuable for labeling workflows where high local density can otherwise limit reactivity. Researchers commonly pair this azide reagent with complementary cyclooctyne or alkyne-bearing partners to generate homogeneous conjugates for analytical assays, binding studies, and molecular profiling experiments.

2. Surface Immobilization

Phthalamide-PEG3-azide supports the preparation of azide-functional surfaces and coatings used in biosensing, microarray fabrication, and materials patterning. By incorporating the PEG3-linked azide handle into polymer films, hydrogel matrices, or surface-reactive layers, teams can enable spatially controlled attachment of fluorescent dyes, capture ligands, or other clickable components via subsequent cycloaddition steps. The phthalamide anchoring element and hydrophilic PEG spacer are often selected to improve stability and accessibility of the azide group during immobilization and washing-intensive processing.

3. Molecular Imaging Probes

Phthalamide-PEG3-azide is frequently incorporated into probe design for modular assembly of imaging reagents where an azide functionality serves as a reliable conjugation handle. The PEG3 segment supports solubility and reduces nonspecific interactions, which can be advantageous when constructing fluorescent or luminescent probe conjugates that must remain well-dispersed in aqueous buffers. In practice, the reagent is used as an intermediate to couple imaging reporters to targeting motifs, polymers, or scaffolded carriers through click chemistry-compatible partners.

4. Diagnostic Reagent Building

Phthalamide-PEG3-azide is used in the development of diagnostic and assay reagents that rely on modular conjugation to assemble detection components and signal-generating constructs. The azide handle enables flexible interchange of detection chemistries, such as attaching enzyme labels, fluorophores, or other reporter moieties to assay platforms using click-compatible partners. Short PEG spacing helps maintain conjugation efficiency while supporting reagent stability during typical assay preparation steps, including dilution, buffer exchange, and incubation-based workflows.