Cy3 NHS ester | CAS 1393363-07-9

Cy3 NHS ester is a reactive cyanine dye designed for covalent fluorescent labeling of primary amines via NHS ester chemistry. As a bright, orange-red emitting fluorophore, Cy3 is widely used to generate fluorescent conjugates for microscopy and fluorescence-based assays, including antibody and protein labeling workflows. Its NHS-ester reactivity supports straightforward preparation of labeled bioconjugates for research applications where stable dye attachment to amine-containing biomolecules is required.

1. Antibody And Protein Labeling

Cy3 NHS ester is routinely used by antibody and protein engineers to prepare Cy3-labeled immunoreagents for fluorescence microscopy, flow cytometry, and binding assays. The NHS ester targets lysine residues and N-termini on proteins, enabling fluorescent conjugate preparation for experiments that require robust labeling of affinity reagents, recombinant proteins, and enzyme conjugates. Researchers typically use Cy3-labeled antibodies to visualize target binding patterns on cells, to track protein localization in fixed samples, and to build fluorescent detection reagents for plate-based assays.

2. Fluorescence Microscopy Staining

Cy3 NHS ester supports fluorescence microscopy workflows where amine-containing biomolecules are used as staining reagents or structural probes. In immunofluorescence and related staining formats, Cy3-labeled secondary antibodies and protein probes provide orange-red fluorescence for multicolor imaging when paired with compatible excitation/emission channels. The covalent attachment offered by NHS ester labeling helps maintain dye association during washing steps, which is particularly valuable for repeated imaging, co-localization studies, and quantitative fluorescence imaging of labeled targets.

3. Flow Cytometry Conjugate Preparation

Cy3 NHS ester is used to generate Cy3-labeled proteins for flow cytometry experiments that rely on fluorescent readouts from amine-bearing biomolecules. Researchers prepare Cy3-conjugated antibodies or protein probes to quantify binding to cell-surface targets or to monitor labeling intensity across populations. Covalent dye attachment helps reduce dye loss during sample processing, supporting reproducible staining and consistent fluorescence measurements in instrument-based workflows that use orange-red detection channels.

4. Fluorescent Bioassay Reagent Building

Cy3 NHS ester is commonly incorporated into fluorescence assay development by labeling assay components that contain primary amines, such as enzymes, binding proteins, and affinity reagents. Fluorescently tagged proteins can be used as detection reagents in homogeneous or wash-based fluorescence assays, including binding and interaction studies where signal reporting depends on the Cy3 fluorophore. In assay optimization, researchers often leverage Cy3-labeled reagents to construct calibration standards, to map assay performance across labeling densities, and to enable fluorescence readouts compatible with standard plate readers and imaging systems.