Sulfo-Cyanine5.5, SE (ethyl) | CAS 172777-84-3

Sulfo-Cyanine5.5, SE (ethyl) is a water-soluble, sulfonated cyanine dye supplied as an N-hydroxysuccinimide (NHS) ester for efficient fluorescent labeling of primary amines. Its long-wavelength emission supports sensitive red-channel fluorescence imaging, making it a common reagent for preparing fluorescent conjugates used in microscopy, flow cytometry, and fluorescence-based bioassays. The reactive NHS ester enables straightforward attachment to proteins, peptides, and other amine-containing biomolecules, including labels for bioconjugation workflows and molecular imaging reagent development.

1. Protein And Antibody Labeling

Sulfo-Cyanine5.5, SE (ethyl) is frequently used by bioconjugation and assay-development teams to generate fluorescently labeled proteins and antibodies for research workflows that require red-channel detection. The NHS-ester reactivity toward lysine side-chain amines and N-termini supports preparation of dye-protein conjugates used in binding studies, immunoassays, and fluorescence imaging experiments. Because the dye is sulfonated, conjugates are typically easier to handle in aqueous buffers and are commonly incorporated into labeling strategies for immunofluorescence reagents, secondary antibody labeling, and fluorescent standards for instrument calibration.

2. Fluorescence Microscopy Imaging

Sulfo-Cyanine5.5, SE (ethyl) enables cellular and molecular imaging studies where long-wavelength fluorescence improves separation from shorter-wavelength autofluorescence. Researchers label amine-containing targeting ligands, carrier proteins, or biomolecular probes with the dye to visualize localization in fixed-cell or in vitro imaging formats using standard fluorescence microscopes equipped with appropriate red excitation/emission filters. The resulting conjugates are routinely used in multi-color staining panels, where the dye's spectral position helps allocate signal to a distinct detection channel for co-localization experiments and fluorescence tracking of labeled biomolecules.

3. Flow Cytometry Dye Conjugates

Sulfo-Cyanine5.5, SE (ethyl) is used in flow cytometry workflows to prepare fluorescent conjugates that report on biomolecule binding or cell-associated labeling. By coupling the NHS ester to primary amines on antibodies, streptavidin/affinity reagents, or other amine-functional binders, researchers generate red-fluorescent reagents for analyzing binding to cell-surface targets or tracking labeled biomolecular interactions in suspension assays. The sulfonated cyanine structure supports aqueous conjugate handling, and the long-wavelength signal is typically collected in the red detection range on common cytometers configured for far-red/near-red channels.

4. Fluorescent Bioassay Reagent Development

Sulfo-Cyanine5.5, SE (ethyl) is widely applied in fluorescence assay development to produce labeled assay components such as detection antibodies, recombinant proteins, or amine-functional probes used as reporters in binding and workflow monitoring assays. Assay teams use the dye-conjugated reagents to construct fluorescence-based readouts in plate formats, including endpoint detection assays and imaging-compatible binding studies. The NHS-ester labeling format supports rapid generation of fluorescent reagents for method development, including reagent screening and optimization of labeling density for consistent fluorescence output across experimental batches.