Sulfo-Cyanine3.5, SE | CAS 871518-83-1

Sulfo-Cyanine3.5, SE is a sulfonated cyanine dye equipped with an N-hydroxysuccinimide (NHS) ester for efficient covalent labeling of primary amine groups in water. Its bright red/orange fluorescence and anionic sulfonate functionality make it well suited for aqueous bioconjugation workflows where background from nonspecific adsorption is a practical concern. Researchers use this reactive dye to generate fluorescent conjugates for microscopy, flow cytometry, and fluorescence-based assay development, particularly when dye stability in biological buffers and straightforward NHS coupling are required.

1. Protein And Antibody Labeling

Sulfo-Cyanine3.5, SE is widely used by protein and antibody labeling teams to prepare fluorescent immunoreagents and detection conjugates through NHS-ester coupling to lysine residues or N-terminal amines. In practice, it supports labeling of affinity reagents for fluorescence imaging of binding events, as well as reagent development for plate-based fluorescence readouts. The sulfonated dye format helps maintain solubility in aqueous labeling buffers, enabling consistent conjugation and downstream handling for research-grade fluorescence workflows.

2. Flow Cytometry Staining

Sulfo-Cyanine3.5, SE is commonly employed in flow cytometry staining workflows to fluorescently tag cell-surface proteins, engineered constructs, or carrier proteins that present accessible amines for coupling. Flow cytometry users rely on the dye's strong visible emission to track labeled populations while maintaining compatibility with typical staining and washing steps used in cytometry sample preparation. Because the reagent is reactive toward primary amines, it is frequently incorporated into labeling pipelines for antibody conjugates and secondary labeling reagents used to quantify fluorescence intensity on a per-cell basis.

3. Fluorescence Microscopy Imaging

Sulfo-Cyanine3.5, SE is used in fluorescence microscopy to generate labeled biomolecules and conjugates for cellular imaging and localization studies. Microscopy teams often choose amine-reactive cyanine dyes to fluorescently mark proteins, peptides, or other amine-bearing targets, then visualize distribution using standard fluorescence imaging instrumentation matched to the dye's red/orange emission. The sulfonate substitution supports aqueous labeling and reduces dye aggregation tendencies that can complicate imaging, improving the practicality of preparing conjugates for repeated imaging sessions.

4. Fluorescent Conjugate Standards

Sulfo-Cyanine3.5, SE is also used by assay development and instrumentation teams to prepare fluorescent conjugate standards and reference materials for method setup, workflow qualification, and spectral channel verification. By covalently attaching the dye to amine-containing carriers, users can generate reproducible fluorescent reagents that behave consistently across labeling batches. This approach is particularly useful when establishing fluorescence assay conditions, confirming imaging/analysis settings, or calibrating relative signal in research laboratories that rely on cyanine-based visible fluorophores.