Cy5 maleimide is widely used in biochemical and biophysical research for labeling proteins, peptides, and other biomolecules. Its maleimide group specifically reacts with thiol groups (-SH) in cysteine residues, enabling targeted conjugation to biomolecules. This property makes it valuable for fluorescence imaging, flow cytometry, and microscopy studies, where it helps visualize and track cellular processes in real time. Additionally, it is employed in FRET (Förster Resonance Energy Transfer) assays to study molecular interactions and conformational changes. Its near-infrared fluorescence emission is particularly useful for in vivo imaging due to reduced background autofluorescence and deeper tissue penetration. Cy5 maleimide is also utilized in diagnostic applications, such as developing fluorescent probes for detecting specific biomarkers in biological samples.