Cy5 | CAS 146368-15-2

Cy5 is a cyanine-family fluorescent dye widely used as a far-red labeling reporter for fluorescence imaging and fluorescence-based assays. Its strong absorption and emission in the red spectral region make it a practical choice for multicolor experiments and for reducing background when paired with appropriate optical filters. Cy5 labeling workflows often rely on conjugate formats prepared by attaching the dye to biomolecules or materials through available reactive handles.

1. Fluorescence Labeling Conjugates

Cy5 is commonly used by chemical biology and biomolecular labeling teams to generate fluorescent conjugates for tracking proteins, peptides, and other research reagents in solution and on surfaces. In these workflows, Cy5 serves as a far-red reporter compatible with standard fluorescence microscopes and plate readers when appropriate excitation/emission filters are selected. Researchers use Cy5-labeled conjugates for binding studies, reagent localization experiments, and fluorescence readouts in assay development, including workflows where reduced spectral overlap with green channels is advantageous.

2. Fluorescence Microscopy Imaging

Cy5 is frequently incorporated into fluorescence microscopy experiments to visualize labeled biomolecules and to map their distribution in fixed-cell or fixed-tissue samples, as well as in labeled biomaterial systems. Far-red emission supports imaging of targets with reduced interference from cellular autofluorescence, which is helpful when imaging low-abundance signals or when multiple fluorophores are present. Microscopy users often prepare Cy5-tagged probes or conjugates to follow localization patterns, wash-dependent retention on surfaces, and spatial colocalization with other fluorescent markers.

3. Flow Cytometry Dye Labeling

Cy5 is used in flow cytometry workflows as a far-red fluorescence label for analyzing stained or conjugated biomolecules associated with cells and cell-derived materials. Flow cytometry users typically incorporate Cy5 into labeling panels where far-red channels help separate signals from common green/orange fluorophores, supporting clearer gating and multicolor analysis. In these applications, Cy5 conjugates are used to quantify fluorescence intensity distributions corresponding to labeled targets, enabling comparative studies across experimental conditions in cell biology and reagent characterization.

4. Fluorescence-Based Bioassays

Cy5 is also applied in fluorescence assay development where far-red signal readout is required for monitoring binding events, labeling efficiency, or reporter release in homogeneous or wash-based formats. Assay developers use Cy5-labeled reagents to generate measurable fluorescence changes in plate reader experiments, including endpoint assays and kinetic readouts when the reporter remains stable under assay conditions. This dye is frequently selected for assay panels that benefit from red-channel separation and for experiments where the fluorescent reporter must be robustly detected in microplate instrumentation.