6-Carboxy-X-rhodamine | CAS 194785-18-7

6-Carboxy-X-rhodamine is a xanthene-based rhodamine fluorescent dye bearing a carboxylic acid for convenient covalent attachment to amine-containing biomolecules and polymers. In fluorescence labeling workflows, it is commonly used as a bright, visible-spectrum reporter for microscopy and fluorescence assay development, where its dye scaffold provides strong emission and straightforward conjugation chemistry.

1. Protein And Antibody Labeling

6-Carboxy-X-rhodamine is frequently selected for fluorescent labeling of proteins, including antibodies and antibody fragments, to generate imaging reagents and assay tracers. Researchers use the dye's carboxyl functionality to build stable conjugates that retain robust fluorescence for tracking binding events, monitoring reagent distribution, and supporting fluorescence-based characterization of immunoreagents in laboratory workflows. The rhodamine emission profile makes it a practical choice for standard fluorescence microscopes and plate readers configured for visible detection.

2. Fluorescence Microscopy Tracing

6-Carboxy-X-rhodamine is used as a molecular tracer in fluorescence microscopy experiments aimed at visualizing labeled biomolecules and macromolecular conjugates within cells, extracellular matrices, or biomaterial environments. By incorporating the dye into protein or polymer constructs, investigators can follow localization patterns, wash-out behavior, and spatial distribution during staining and imaging sessions. The dye's bright rhodamine fluorescence supports clear visualization in multicolor experiments when instrument filters are matched to the dye's emission.

3. Flow Cytometry Labeling Reagents

6-Carboxy-X-rhodamine is employed to prepare fluorescence labeling reagents for flow cytometry, where conjugated proteins and affinity reagents are used to quantify binding to cell-associated targets. In these workflows, the dye is typically incorporated into antibody conjugates or other amine-reactive labeling constructs to generate stable fluorescent signals for population analysis. Researchers value the dye for visible-channel compatibility and the ability to generate reproducible staining reagents for repeated cytometry runs.

4. Fluorescent Bioassay Standards

6-Carboxy-X-rhodamine is also used in fluorescence assay development as a labeled reference material for assay optimization and calibration of readout conditions. Conjugated dye standards help researchers verify excitation/emission alignment, establish assay working ranges, and monitor batch-to-batch consistency in fluorescence-based protocols. Its carboxyl-bearing rhodamine scaffold supports preparation of defined fluorescent conjugates that can be used as internal controls in plate-based fluorescence measurements.