5(6)-Carboxynaphthofluorescein diacetate succinimidyl ester | CAS 349561-47-3

5(6)-Carboxynaphthofluorescein diacetate succinimidyl ester is a fluorescein-derived labeling reagent that combines a cell- and esterase-activated diacetate for intracellular fluorescence generation with an N-hydroxysuccinimide (NHS) ester for covalent attachment to primary amines on proteins, peptides, and other amine-bearing biomolecules. In practice, this reagent is used to prepare fluorescent conjugates for imaging and quantitative fluorescence workflows where covalent immobilization and strong dye retention are required. The naphthofluorescein core provides a bright green emission profile that is widely compatible with standard fluorescein filter sets used in microscopy and plate-based assays.

1. Protein Fluorescent Labeling

5(6)-Carboxynaphthofluorescein diacetate succinimidyl ester is frequently used by protein engineering and chemical biology groups to generate amine-reactive fluorescent protein conjugates for downstream imaging and binding studies. After conjugation to lysine-containing proteins or amine-functional peptides, the resulting fluorescent products support consistent labeling for assays that track biomolecule localization, trafficking, or interaction in heterogeneous assay formats. Because the NHS ester enables covalent coupling, the labeled proteins are commonly used in workflows that require wash-resistant fluorescence for microscopy, gel-based readouts, and fluorescence-based binding experiments.

2. Cell Imaging And Tracking

5(6)-Carboxynaphthofluorescein diacetate succinimidyl ester is used in cellular imaging workflows where intracellular esterase activity can convert the diacetate into the fluorescent carboxynaphthofluorescein form, enabling visualization of labeled biomolecules and uptake-associated fluorescence. Researchers often employ it to generate fluorescent tagging of amine-rich targets in cells or to produce fluorescent conjugates that can be introduced into cell-based experiments for time-resolved tracking. This application is particularly relevant for microscopy studies that rely on fluorescein-like excitation/emission behavior and benefit from covalent retention of the dye on biomolecular targets.

3. Fluorescent Conjugate Standards

5(6)-Carboxynaphthofluorescein diacetate succinimidyl ester is also applied in the preparation of fluorescent labeling controls and calibration materials used to validate fluorescence readouts across instruments. Laboratories developing fluorescence assays, including plate readers and imaging systems, often prepare dye-conjugated reference materials to monitor day-to-day performance and to normalize signal across experiments. The combination of a reactive NHS ester and a fluorescein-derived fluorophore supports reproducible conjugate preparation to create consistent reference signals for assay development and method qualification in research settings.

4. Bioconjugation For Biomaterial Surfaces

5(6)-Carboxynaphthofluorescein diacetate succinimidyl ester is used in biomaterials research to covalently attach fluorescent labels to amine-functionalized surfaces and coatings. Researchers functionalize hydrogels, polymer films, and other amine-bearing materials with the NHS ester to create fluorescently traceable interfaces for microscopy-based characterization, surface mapping, and material-to-cell interaction studies. This approach supports visualization of immobilized biomolecules on engineered substrates, helping teams monitor coating uniformity, label retention after washing, and spatial distribution in materials characterization workflows.