Cy3.5 diacid, SE is widely used in fluorescence labeling and imaging applications, particularly in biological and biomedical research. Its reactive succinimidyl ester (SE) group allows for efficient conjugation to primary amines, making it suitable for labeling proteins, antibodies, peptides, and other biomolecules. The Cy3.5 dye emits in the far-red region, which is advantageous for reducing background autofluorescence and improving signal clarity in complex biological samples. It is commonly employed in fluorescence microscopy, flow cytometry, and in vivo imaging studies. Additionally, its stability and brightness make it a preferred choice for multiplexing experiments, where multiple fluorescent dyes are used simultaneously to track different targets.