Cyanine5 maleimide | CAS 1437796-65-0

Cyanine5 maleimide is a reactive cyanine dye designed for thiol-selective bioconjugation via its maleimide functional group, enabling fluorescent labeling of cysteine-containing biomolecules and thiol-bearing surfaces. The bright far-red cyanine signal supports fluorescence imaging workflows where reduced background and longer-wavelength detection are advantageous, including conjugate tracking and multicolor assay development.

1. Protein Thiol Labeling

Cyanine5 maleimide is widely used for fluorescent labeling of proteins and peptides that contain accessible cysteine residues, supporting downstream fluorescence imaging, binding studies, and conjugate characterization. Researchers commonly incorporate it into labeling workflows for antibodies, affinity proteins, enzyme reagents, and engineered protein constructs to generate fluorescent conjugates for assay development and microscopy readouts. The maleimide handle enables straightforward incorporation into thiol-containing biomolecules, which is particularly useful when maintaining the native activity of the labeled partner is important for biochemical experiments.

2. Cell Surface Conjugation

Cyanine5 maleimide is frequently applied to label cell surfaces and membrane-associated targets through thiol groups presented on extracellular proteins or engineered with cysteine residues. In cellular imaging and flow cytometry development, the far-red cyanine signal helps visualize labeled populations while supporting multicolor panels that use spectrally separated channels. This reagent is also used in materials and biomaterials research to fluorescently tag thiol-functionalized coatings or capture layers that interface with cells, enabling visualization of surface modification and cell-material interactions.

3. Biomolecule Tracking Assays

Cyanine5 maleimide supports fluorescence-based tracking of labeled biomolecules in binding kinetics experiments, wash-based retention studies, and conjugate stability assessments. In chemical biology and molecular imaging workflows, fluorescent tagging with a far-red cyanine dye helps monitor reagent distribution and conjugate integrity during assay incubation and separation steps. The maleimide-thiol labeling approach is commonly used to prepare fluorescent standards and tracer conjugates for method development in fluorescence microscopy, plate-based fluorescence assays, and imaging-guided workflows where consistent labeling is needed.

4. Fluorescent Probe Conjugate Building

Cyanine5 maleimide is used as a fluorescent component in probe construction and labeling of recognition elements that carry thiols, including affinity ligands and engineered nucleic acid-associated or peptide-associated reporters. Teams developing fluorescence imaging probes often attach the cyanine dye to targeting scaffolds to create modular conjugates for localization studies and signal readout optimization. The far-red emission of the cyanine dye supports multiplexing strategies where probe emission must be separated from common background fluorophores used in biological assays.