Fluorescein-Maleimide | CAS 2228857-33-6

Fluorescein-Maleimide is a fluorescein-based labeling reagent designed for thiol-reactive conjugation via a maleimide functional group. It is commonly used to fluorescently tag cysteine-containing biomolecules, peptides, and proteins for fluorescence imaging and quantitative fluorescence readouts, with excitation and emission centered in the visible green range. Because the maleimide reacts selectively with accessible sulfhydryl groups, it is frequently employed in probe and conjugate construction where controlled attachment of a fluorescein reporter is required.

1. Protein Thiol Labeling

Fluorescein-Maleimide is widely used by protein chemistry and chemical biology labs to generate fluorescently labeled proteins for fluorescence microscopy, gel-based tracking, and binding or interaction studies. Researchers typically label purified proteins, antibodies, or protein domains engineered to present accessible cysteine residues, enabling visualization of distribution and dynamics in solution or on surfaces. The fluorescein reporter provides a convenient green fluorescence readout for downstream characterization of conjugates, including monitoring labeling efficiency and tracking labeled species in assay workflows.

2. Peptide And Biomolecule Conjugates

Fluorescein-Maleimide supports fluorescent tagging of peptides, small biomolecules, and other thiol-bearing reagents used in molecular imaging and assay development. In practice, teams in biomaterials and molecular imaging often prepare fluorescein-labeled ligands or peptide constructs by reacting the maleimide group with available sulfhydryl functionalities, producing conjugates that can be followed by fluorescence microscopy or plate-based fluorescence measurements. This approach is especially useful when the labeling needs to be performed under conditions compatible with maintaining biomolecular function for subsequent binding, uptake, or localization experiments.

3. Surface And Hydrogel Functionalization

Fluorescein-Maleimide is also used in biomaterials research to incorporate fluorescent reporters onto thiol-functionalized surfaces, coatings, and hydrogels. By reacting maleimide with surface-exposed thiols, researchers can create fluorescently trackable materials for studying material assembly, diffusion, and retention of biomolecules within polymer networks. Fluorescein labeling enables straightforward visualization of functionalized regions and supports fluorescence-based quantification of labeling density and spatial distribution during materials characterization and method development.

4. Flow Cytometry Labeling

Fluorescein-Maleimide is frequently employed to generate thiol-labeled fluorescent reagents for flow cytometry workflows where green fluorescence detection is appropriate. Investigators use it to label cysteine-containing targeting ligands, affinity reagents, or other thiol-bearing components that are subsequently applied to cells or cell-derived samples for fluorescence readout. The maleimide-thiol conjugation strategy helps researchers attach fluorescein to defined biomolecular constructs, enabling consistent staining and comparative analysis across experimental conditions.