Coumarin 545 | CAS 85642-11-1

Coumarin 545 is a coumarin-family fluorescent dye commonly used as a bright, photostable labeling fluorophore for fluorescence microscopy and fluorescence-based assays. Its strong emission in the visible range and compatibility with standard optical filters make it a frequent choice for preparing fluorescent conjugates and calibration reagents, including dye-labeled biomolecules and polymeric materials. In many workflows, Coumarin 545 is selected for experiments where a compact, environment-sensitive coumarin signal is advantageous for tracking labeling efficiency and spatial distribution.

1. Fluorescent Labeling Conjugates

Coumarin 545 is widely applied to generate fluorescent labeling conjugates for biomolecule tracking in chemical biology and materials research. Researchers use this dye to label proteins, peptides, and other amine- or thiol-containing targets when preparing imaging reagents for microscopy studies and quantitative fluorescence readouts. In these workflows, the dye's compact coumarin scaffold supports efficient incorporation into conjugates used to monitor binding, distribution, and relative labeling levels across experimental conditions.

2. Fluorescence Microscopy Imaging

Coumarin 545 is frequently used as a fluorescence microscopy stain for visualizing labeled biomolecules and tagged materials in cell and tissue culture imaging experiments. Investigators rely on its visible emission to image fluorescent conjugates with common epifluorescence and confocal microscope filter sets, enabling straightforward localization of dye-containing constructs in fixed samples and labeled biological preparations. Coumarin 545 labeling is also used in microscopy method development, such as optimizing labeling density and imaging parameters for multicolor experiments where coumarin emission can be separated from other fluorophores.

3. Fluorescence Bioassay Standards

Coumarin 545 is used in fluorescence assay development as a reference fluorophore and calibration component for verifying instrument performance and normalizing fluorescence signals. Assay developers incorporate the dye into standard curves and fluorescence controls when quantifying labeled reagents, monitoring reaction progress in fluorescence-based formats, or comparing batch-to-batch performance of fluorescent conjugates. This application is especially common in laboratories that require consistent, reproducible fluorescence intensity for method qualification and assay workflow optimization.

4. Polymer And Nanomaterial Labeling

Coumarin 545 is applied to label polymers, hydrogels, and nanomaterials for tracking material distribution, diffusion, and surface association in biomaterials research. Researchers incorporate the dye into material formulations or attach it to functionalized polymer backbones to create fluorescent materials used in imaging and characterization studies. The resulting labeled materials support visualization of coating uniformity, diffusion behavior, and structural integrity during experimental handling, while maintaining compatibility with standard fluorescence detection workflows.