Sulfo-CY5-NHS ester potassium | CAS 2230212-27-6

Sulfo-CY5-NHS ester potassium is a water-soluble, amine-reactive cyanine dye designed for fluorescent labeling of biomolecules and polymers. The NHS ester readily forms stable amide bonds with primary amines, enabling bright far-red fluorescence for imaging and fluorescence-based assays using standard Cy5-compatible optics. Its sulfonate functionality supports aqueous workflows and reduces nonspecific hydrophobic interactions during conjugate preparation.

1. Protein Antibody Labeling

Sulfo-CY5-NHS ester potassium is widely used in fluorescence labeling of proteins for immunoassays, binding studies, and microscopy. Researchers typically conjugate the NHS ester to lysine residues on antibodies, antibody fragments, and affinity reagents to generate far-red fluorescent immunoprobes that can be tracked in complex biological mixtures. The sulfonated, water-soluble dye format helps maintain labeling performance during buffer-based workflows and supports conjugate handling for downstream assay development where minimizing dye aggregation and nonspecific staining is important.

2. Fluorescence Microscopy Labeling

Sulfo-CY5-NHS ester potassium supports far-red fluorescence microscopy workflows where robust labeling of cellular or extracellular components is required. Common use cases include labeling extracellular matrix proteins, cell-surface proteins, and other amine-containing biomolecules used as imaging reagents in fixed-cell or fixed-tissue staining protocols. Because the dye is designed for NHS-ester coupling, it integrates directly into labeling strategies for fluorescent conjugate preparation without requiring additional dye-attachment steps beyond amine-reactive conjugation.

3. Flow Cytometry Conjugates

Sulfo-CY5-NHS ester potassium is used to prepare fluorescent labeling reagents for flow cytometry and related single-cell analysis platforms. In these workflows, the dye is conjugated to antibodies or other amine-bearing targeting proteins to enable far-red channel readout for cell-surface or intracellular labeling strategies using established cytometry staining formats. The water-soluble sulfonate character supports conjugate preparation in aqueous buffers commonly used for staining panels, helping maintain consistent reagent behavior during titration and washing steps.

4. Polymer And Biomaterial Functionalization

Sulfo-CY5-NHS ester potassium is also applied in biomaterials science to fluorescently tag amine-functional polymers, hydrogels, and surface coatings for imaging and materials characterization. Researchers incorporate the dye into amine-containing material systems to visualize distribution, adsorption, or surface presentation of functional components under fluorescence microscopy or imaging-based readouts. This use case is particularly relevant when fluorescent labeling must be performed under aqueous conditions and when stable amide linkage to the material backbone or pendant groups is required for reproducible fluorescence tracking.