IRDye® 650 Maleimide

IRDye® 650 Maleimide is a near-infrared (NIR) fluorescent labeling reagent built on an IRDye® 650 fluorophore and a maleimide functional group for efficient conjugation to thiols. In bioconjugation workflows, the maleimide enables attachment to cysteine-containing biomolecules and thiol-derivatized surfaces, supporting sensitive fluorescence readouts in imaging and quantitative assays. Its NIR emission is widely leveraged to reduce background from autofluorescence in fluorescence microscopy and in vivo-style optical imaging setups used in research.

1. Protein Thiol Labeling

IRDye® 650 Maleimide is frequently used by protein engineering and chemical biology groups to generate fluorescently labeled antibodies, affinity reagents, enzymes, and protein domains for downstream characterization. The maleimide-thiol coupling supports site-specific labeling strategies when proteins are engineered to present accessible cysteine residues or are reduced to expose thiols under controlled conditions. Labeled proteins are then used for fluorescence imaging, binding studies, and quantitative fluorescence measurements where NIR signal reporting helps improve contrast against complex backgrounds.

2. Antibody Conjugates For Imaging

IRDye® 650 Maleimide supports construction of IRDye® 650-labeled antibody conjugates used in immunofluorescence and optical imaging reagent development. Researchers commonly use it to prepare antibody-fluorophore conjugates for workflow optimization, target-binding visualization, and comparative studies across labeling densities. Because the reagent reacts with thiols, it is also used to label antibody fragments or to incorporate fluorophores into antibody-based probes where controlled conjugation to cysteine residues is preferred.

3. Surface And Biomaterial Functionalization

IRDye® 650 Maleimide is used in biomaterials science to fluorescently tag thiol-functionalized polymers, hydrogels, and engineered surfaces for imaging-based material characterization. Teams in materials development apply the reagent to label surfaces that have been modified with thiol groups, enabling visualization of coating uniformity, surface retention, and material-associated distribution in microscopy workflows. NIR fluorescence helps maintain signal detectability when imaging polymeric or biological matrices with significant autofluorescence.

4. Thiol-Modified Oligonucleotide Labeling

IRDye® 650 Maleimide is also applied for fluorescent labeling of thiol-modified nucleic acids used in nucleic acid analysis and fluorescence-based binding assays. Researchers label cysteine- or thiol-functionalized oligonucleotides to create fluorescent reporters for hybridization experiments, probe tracking, and assay development where NIR emission provides reduced background relative to visible dyes. The resulting labeled oligos are commonly incorporated into optical readouts for monitoring nucleic acid interactions in research settings.