Sulfo-Cyanine 5 Carboxylic Acid (ethyl) | CAS 146368-11-8

Sulfo-Cyanine 5 Carboxylic Acid (ethyl) is a sulfonated cyanine dye designed for water-compatible fluorescent labeling, commonly used as a Cy5-class reporter in fluorescence imaging workflows. Its carboxylic acid functionality enables conjugation to amine-containing biomolecules or incorporation into labeling strategies that produce stable fluorescent conjugates for microscopy and fluorescence-based assays. The dye's long-wavelength emission supports multicolor experiments where red-channel detection is required.

1. Protein Fluorescent Labeling

Sulfo-Cyanine 5 Carboxylic Acid (ethyl) is frequently used by protein chemistry and chemical biology groups to prepare fluorescently labeled antibodies, enzymes, and affinity reagents for downstream fluorescence imaging and binding studies. Researchers typically convert the dye's carboxylate functionality into a reactive labeling handle (or use it in established dye-activation workflows) to generate Cy5-like conjugates that can be tracked in solution or after immobilization. This makes the reagent useful for characterizing biomolecular interactions, monitoring labeling efficiency during conjugate preparation, and generating fluorescent standards for red-channel assays.

2. Fluorescence Microscopy Tracing

Sulfo-Cyanine 5 Carboxylic Acid (ethyl) supports cellular and molecular microscopy workflows where long-wavelength fluorescence improves visualization and reduces interference from shorter-wavelength background. Imaging teams use Cy5-class conjugates to trace labeled biomolecules in fixed-cell experiments, map distribution patterns on surfaces, and follow uptake or binding readouts in fluorescence microscopy platforms. The sulfonated dye character also helps maintain aqueous compatibility during staining and washing steps, supporting reproducible imaging reagent preparation for routine microscopy studies.

3. Flow Cytometry Red-Channel Assays

Sulfo-Cyanine 5 Carboxylic Acid (ethyl) is used in flow cytometry development to generate red-emitting fluorescent conjugates for cell-surface and biomolecule labeling experiments. Assay developers prepare Cy5-labeled antibodies or protein reagents and then use them as detection reagents in multicolor panels that require a far-red/near-red channel. The dye's fluorescence properties and water-compatible sulfonation support consistent staining and instrument-ready workflows for screening labeled binding reagents, optimizing panel composition, and quantifying fluorescence intensity distributions across populations.

4. Fluorescent Bioassay Reagents

Sulfo-Cyanine 5 Carboxylic Acid (ethyl) is also applied in fluorescence assay development where long-wavelength readouts are advantageous for reducing spectral overlap with common green fluorophores. Biochemical assay groups use Cy5-labeled biomolecule conjugates as reporters in binding assays, reagent tracking experiments, and endpoint fluorescence measurements. In these workflows, the dye's carboxylic acid functionality is leveraged to construct fluorescent assay reagents that remain compatible with aqueous assay buffers and enable straightforward readout on standard fluorescence plate readers and imaging systems.