Sulfo-Cyanine5.5 NHS ester

Sulfo-Cyanine5.5 NHS ester is a water-soluble, N-hydroxysuccinimide (NHS) ester form of a cyanine dye designed for efficient covalent labeling of primary amines. Its sulfonated structure supports aqueous conjugation workflows, while the Cy5.5 spectral region makes it a widely used fluorophore for fluorescence imaging and labeling strategies where far-red emission improves background performance. Researchers commonly use this reagent to prepare fluorescent protein, peptide, and polymer conjugates for microscopy, flow cytometry, and fluorescence-based assay development.

1. Protein And Antibody Labeling

Sulfo-Cyanine5.5 NHS ester is frequently used by bioconjugation teams to generate fluorescently labeled proteins, including antibodies, antibody fragments, and enzyme conjugates, via amine-reactive NHS ester chemistry. The sulfonated dye format supports labeling in aqueous buffers commonly used for immunoreagents and binding proteins, enabling downstream fluorescence microscopy and plate-based readouts. This reagent is also used to prepare fluorescent standards and tracking reagents for binding and uptake studies where far-red emission helps reduce interference from autofluorescence.

2. Fluorescence Microscopy Tracing

Sulfo-Cyanine5.5 NHS ester is commonly incorporated into cellular imaging workflows to fluorescently tag biomolecules that localize to specific compartments or structures through the biomolecule's inherent targeting (for example, labeled ligands, carrier proteins, or extracellular matrix components). After conjugation to amine-containing biomolecules, the resulting Cy5.5 conjugates are used for fluorescence microscopy to visualize distribution, transport, and colocalization in culture models. The far-red spectral output is particularly valued for multicolor imaging panels where spectral separation from visible fluorophores is required.

3. Flow Cytometry Dye Conjugates

Sulfo-Cyanine5.5 NHS ester is used in flow cytometry reagent development to prepare amine-labeled detection reagents and labeling controls for fluorescence-activated cell analysis. Conjugates generated from this NHS ester format can be used to stain cells through binding proteins, affinity reagents, or other amine-containing components used in cytometry panels. Researchers leverage the Cy5.5 emission window to design gating strategies with reduced spectral overlap relative to common green and orange channels, supporting robust panel design for fluorescent labeling experiments.

4. Fluorescent Bioassay Reagents

Sulfo-Cyanine5.5 NHS ester supports fluorescence assay development by enabling covalent attachment of the dye to assay components such as proteins, peptides, and amine-bearing polymers. Labeled reagents prepared from this NHS ester are used as fluorescent tracers in binding assays, kinetic monitoring formats, and imaging-compatible assay systems where far-red fluorescence provides a convenient readout. In many labs, the reagent is also used to generate calibration materials and conjugated controls that help standardize fluorescence measurements across experiments and instrument settings.