IRDye® 650 NHS Ester

IRDye® 650 NHS Ester is a reactive near-infrared fluorophore labeling reagent built on an NHS ester functional group for efficient amide coupling to primary amines on proteins, peptides, and other biomolecular targets. Its long-wavelength emission supports low-background fluorescence workflows in imaging and fluorescence-based assays, where conjugate brightness and reduced tissue autofluorescence are often advantageous. Researchers use this dye to generate stable fluorescent conjugates for optical detection, microscopy, and quantitative bioanalytical applications.

1. Antibody And Protein Labeling

IRDye® 650 NHS Ester is widely used to prepare fluorescent antibody conjugates and other protein labeling reagents for optical detection workflows. Common users include immunoassay developers and molecular imaging researchers who need a near-infrared imaging handle on antibodies, antibody fragments, enzymes, or affinity proteins. After conjugation to lysine-rich biomolecules, the resulting IRDye® 650-labeled constructs are used to track binding in fluorescence imaging experiments, validate reagent performance in binding studies, and support fluorescence readouts in assay development. The NHS ester chemistry enables straightforward labeling of amine-containing proteins under standard bioconjugation conditions, making it a practical choice for generating research-grade fluorescent conjugates for optical assays.

2. Fluorescence Imaging Tracers

IRDye® 650 NHS Ester supports the preparation of near-infrared fluorescence tracers used in cellular and biomolecular localization studies where long-wavelength detection improves contrast against background. Researchers incorporate the dye into protein-based tracers such as labeled serum proteins, receptor-binding ligands, or engineered binding proteins to visualize distribution patterns in fluorescence imaging experiments. This reagent is also used in workflow development for imaging reagent qualification, including verifying labeling consistency across batches and ensuring that conjugates can be detected with compatible near-infrared imaging systems. The reactive NHS ester format is particularly convenient when the target biomolecule contains accessible primary amines for labeling without requiring site-specific engineering.

3. Enzyme And Affinity Reagent Conjugates

IRDye® 650 NHS Ester is frequently employed to generate fluorescent enzyme conjugates and labeled affinity reagents for fluorescence-based bioassays and binding assays. In research settings, users label enzymes, binding domains, or capture reagents to enable fluorescent quantification of assay components, monitor reagent immobilization performance, or track assay workflow steps. The resulting IRDye® 650 conjugates are used as detection reagents in formats such as fluorescence readout assays and imaging-compatible binding studies, where the near-infrared spectral region helps reduce interference from common autofluorescent species. This application is especially relevant for teams building multiplexable fluorescence workflows that rely on robust dye conjugation to amine-bearing biomolecules.

4. Surface And Biomaterial Functionalization

IRDye® 650 NHS Ester is also used to fluorescently functionalize amine-containing surfaces and biomaterials for materials characterization and imaging-guided studies. Researchers working on coatings, polymeric scaffolds, and bioconjugated matrices employ the NHS ester to attach the dye to surface-accessible primary amines, enabling visualization of coating coverage, localization of immobilized biomolecules, or tracking of material-associated components. This approach is commonly adopted in biomaterials research and assay development where fluorescent readouts are needed to confirm successful surface modification and to monitor spatial distribution during experimental workflows. The dye's near-infrared emission supports imaging in setups where background suppression is important for clear visualization of labeled materials.