Sulfo-Cyanine5 NHS ester

Sulfo-Cyanine5 NHS ester is a water-soluble cyanine dye activated as an N-hydroxysuccinimide ester for covalent fluorescent labeling of primary amines on biomolecules. Its bright far-red emission and high labeling utility make it a common reagent for preparing fluorescent conjugates used in fluorescence microscopy, imaging workflows, and fluorescence-based assays. Because the reactive NHS ester targets amine-containing targets under standard bioconjugation conditions, it is frequently employed by cell biology and analytical chemistry teams to generate stable dye conjugates for tracking, quantification, and visualization.

1. Protein And Antibody Labeling

Sulfo-Cyanine5 NHS ester is routinely used to fluorescently label proteins, including antibodies, enzymes, and affinity reagents, by coupling to accessible lysine residues or N-terminal amines. Research groups use the resulting Cy5 conjugates for fluorescence imaging of binding interactions, reagent tracking in biochemical workflows, and labeling of detection antibodies for immunoassay development. The sulfonate functionality supports aqueous handling during conjugate preparation and downstream assay steps, which is particularly useful when preparing labeling reagents for microscopy or plate-based fluorescence readouts.

2. Fluorescence Microscopy Labeling

Sulfo-Cyanine5 NHS ester is widely applied for cellular and molecular imaging workflows where far-red fluorescence provides strong contrast against typical biological autofluorescence. Laboratories use Cy5-labeled proteins, antibodies, or other amine-bearing biomolecules to visualize targets in fixed-cell immunostaining, immunofluorescence assays, and fluorescence microscopy experiments. The NHS ester format enables convenient conjugate generation for staining reagents used to map biomolecular distributions, track binding to cell-surface or extracellular targets, and support multi-color imaging strategies that separate far-red signals from shorter-wavelength channels.

3. Flow Cytometry Conjugate Preparation

Sulfo-Cyanine5 NHS ester is frequently employed to prepare Cy5-labeled antibodies and protein probes for flow cytometry panels that include far-red detection. Cytometry users rely on NHS-ester labeling to generate amine-reactive fluorescent conjugates that bind their targets after conjugation, enabling quantitative measurement of labeled binding in suspension assays. The water-soluble sulfonated dye structure supports practical conjugation and buffer compatibility during reagent preparation, helping teams standardize fluorescent labeling reagents for routine cytometry experiments and gating workflows.

4. Fluorescent Bioassay Reagents

Sulfo-Cyanine5 NHS ester is used to construct fluorescent assay reagents by covalently attaching Cy5 to amine-containing components used as reporters in fluorescence-based measurements. Assay developers incorporate Cy5 conjugates into binding assays, labeling controls, and fluorescence readout systems where far-red emission is advantageous for background reduction relative to shorter-wavelength fluorophores. In many laboratory settings, the NHS-ester chemistry supports rapid generation of labeled reagents for method development, calibration experiments, and comparative studies across assay formats that read fluorescence intensity from dye-conjugated biomolecular reagents.