fluoresceinlabeled

Fluorescein-labeled refers to molecules that have been covalently tagged with fluorescein or a fluorescein derivative to enable fluorescence-based detection. In biology and biochemistry, common fluorescein labels include fluorescein isothiocyanate (FITC) and 5-carboxyfluorescein derivatives. The label is typically attached to reactive sites on the target molecule, such as amines on lysine residues, thiols on cysteines, or other functional groups, using chemistries like NHS ester coupling, maleimide conjugation, or click reactions.

Labeling workflows generally involve reacting the fluorescein reagent with the substrate under controlled conditions, followed by purification to remove unreacted dye and characterization to confirm labeling and integrity. The choice of dye, linker length, and labeling density can influence the performance, including fluorescence intensity, solubility, and biological activity of the labeled molecule. FITC and related dyes are often chosen for their bright green fluorescence and wide compatibility with standard fluorescence microscopes and flow cytometers.

Applications of fluorescein-labeled probes span a range of techniques. They are widely used in immunofluorescence and immunohistochemistry to visualize antibodies, in flow cytometry for cell analysis, in fluorescence in situ hybridization for detecting nucleic acids, and in various assay formats such as ELISA or Western blot detection. Fluorescein-labeled nucleotides and probes enable hybridization-based assays, while labeled antibodies enable targeted visualization.

Key properties to consider include the excitation and emission peaks around 495 nm and 519–530 nm, pH sensitivity, photobleaching tendency, and spectral overlap with other fluorophores. Careful selection of experimental conditions and proper controls are important to minimize artifacts and ensure reliable interpretation.