Cyanine5 NHS ester iodide（Cat No.:I044517）is a reactive fluorescent dye commonly used for labeling biomolecules such as proteins, peptides, and nucleic acids. The NHS (N-hydroxysuccinimide) ester functional group specifically reacts with primary amines on lysine residues or N-termini to form stable amide bonds, enabling covalent attachment. Cyanine5 emits in the far-red spectrum (~670 nm), offering high photostability, low background fluorescence, and compatibility with various imaging platforms. The iodide counterion enhances solubility. This dye is ideal for fluorescence microscopy, flow cytometry, in vivo imaging, and multiplexed assays requiring minimal spectral overlap.