N-(azide-PEG3)-N'-(Mal-PEG4)-Cy5 | CAS 2107273-74-3

N-(azide-PEG3)-N'-(Mal-PEG4)-Cy5 is a Cy5-based fluorescent labeling building block that combines an azide handle with a maleimide-functional PEG linker. This reagent is used to assemble targeted fluorescent conjugates through orthogonal chemistries, enabling attachment to azide-reactive partners while simultaneously providing a thiol-reactive maleimide for coupling to cysteine-containing biomolecules, peptides, or engineered proteins. In fluorescence workflows, Cy5 provides far-red imaging readouts that are commonly leveraged for microscopy, imaging-based assays, and fluorescence tracking in complex biological samples.

1. Dual-Handle Bioconjugation

N-(azide-PEG3)-N'-(Mal-PEG4)-Cy5 supports modular fluorescent conjugate construction where two orthogonal reactive groups are required in the same reagent. Researchers use the maleimide functionality to couple the Cy5 label to thiol-containing biomolecules such as cysteine-bearing peptides, antibody fragments, or engineered protein constructs, then retain the azide for downstream click chemistry (e.g., attachment to complementary azide/alkyne partners on targeting ligands, affinity handles, or imaging scaffolds). This dual-handle design is particularly useful for building multicomponent probes, where the fluorescent tag must be positioned on one component while the remaining handle is reserved for later assembly steps.

2. Fluorescent Protein And Peptide Labeling

N-(azide-PEG3)-N'-(Mal-PEG4)-Cy5 is frequently used to generate far-red fluorescent conjugates for protein and peptide labeling workflows. The maleimide group enables straightforward coupling to accessible thiols, supporting preparation of fluorescently tagged biomolecules for binding studies, localization experiments, and fluorescence-based characterization of bioconjugates. Because the Cy5 chromophore is integrated into a PEGylated linker system, conjugates prepared with this reagent are commonly used to improve labeling consistency and reduce unwanted aggregation during assay development and imaging experiments.

3. Targeting Ligand And Probe Assembly

N-(azide-PEG3)-N'-(Mal-PEG4)-Cy5 is used as a fluorescent intermediate in the construction of targeting probes and imaging reagents that require further functionalization after Cy5 installation. After initial maleimide-mediated attachment to a cysteine-containing targeting component, the remaining azide handle allows subsequent conjugation to additional modules such as cell-labeling moieties, polymer or nanoparticle surfaces, or affinity capture elements via click chemistry. This approach is widely adopted in chemical biology and molecular imaging development, where researchers need a reliable way to integrate a far-red fluorophore while keeping a second reactive site available for final probe assembly.

4. Multicolor Imaging Development

N-(azide-PEG3)-N'-(Mal-PEG4)-Cy5 can be incorporated into multicolor fluorescence imaging panels where far-red Cy5 emission is used to separate signals from spectrally distinct fluorophores. Imaging teams often employ this reagent to prepare fluorescent conjugates that can be combined with other labeled targets in microscopy or imaging-based assays, benefiting from the PEG linker format that helps maintain probe performance in complex labeling mixtures. The azide and maleimide functionalities also support staggered labeling strategies, enabling researchers to build conjugates stepwise to match experimental timing and sample handling constraints.