Cy5.5 bis-NHS ester | CAS 2183440-77-7

Cy5.5 bis-NHS ester is a reactive cyanine dye scaffold provided as two N-hydroxysuccinimide (NHS) ester groups, enabling efficient covalent labeling of primary amines on proteins, peptides, and other amine-containing biomolecules. Its Cy5.5 spectral profile supports red/far-red fluorescence workflows where bright signal and convenient conjugate handling are required. Researchers commonly use this bifunctional NHS reagent to prepare fluorescent bioconjugates for imaging, binding assays, and labeling controls.

1. Protein And Antibody Labeling

Cy5.5 bis-NHS ester is widely used to fluorescently tag antibodies, antibody fragments, and other protein reagents by covalent coupling to lysine residues and N-terminal amines. This labeling format is favored in fluorescence microscopy and fluorescence-based binding studies because the dye is installed directly onto the targeting protein, producing stable dye-protein conjugates for downstream imaging reagent development. Bioconjugation teams also use the two-NHS design to tune labeling density and generate conjugates for assay development workflows where consistent fluorescent readout is important.

2. Peptide Conjugates For Imaging

Cy5.5 bis-NHS ester supports fluorescent labeling of peptides and small protein domains that contain accessible primary amines, enabling construction of imaging reagents for cellular and molecular studies. Chemical biology groups often prepare dye-peptide conjugates as probes for localization experiments, fluorescent standards, or as components in multicolor labeling panels where far-red excitation/emission is advantageous for reduced background from shorter-wavelength fluorophores. The NHS-ester chemistry is particularly convenient for rapid conjugate preparation in labeling workflows that rely on amine-reactive coupling rather than affinity-based dye attachment.

3. Biomolecule Labeling For Flow Cytometry

Cy5.5 bis-NHS ester is used to generate flow cytometry dyes by covalently labeling amine-containing biomolecules such as proteins used in immunostaining workflows, including secondary reagents and other fluorescent labeling components. In cytometry assay development, the covalent attachment helps maintain dye association with the staining reagent during washing and incubation steps, supporting reproducible staining behavior across experimental runs. Researchers also use Cy5.5-labeled conjugates as spectral partners in multicolor panels, leveraging the far-red channel to separate signals from green and orange fluorophores.

4. Surface Coating For Amine-Functional Materials

Cy5.5 bis-NHS ester can be incorporated into biomaterials and surface-functionalized platforms by coupling to amine-bearing surfaces, including amine-terminated polymers, coatings, and other functionalized substrates. Materials scientists and biomaterials teams use the dye to create fluorescently traceable surfaces for microscopy-based characterization, coating uniformity checks, and labeling of engineered constructs used in materials research. This application is especially practical when the goal is stable covalent immobilization of a far-red fluorophore onto an amine-functional material for long-term imaging experiments.