– Cy7.5 maleimide, a CY dye (short for Cyanine), consists of two nitrogen atoms connected by an odd number of methyl units. Cyanine compounds are characterized by long wavelength, adjustable absorption and emission, high extinction coefficient, good water solubility, and relatively simple synthesis [1]. CY dyes are often used for labeling proteins, antibodies, and small molecular compounds. For labeling protein antibodies, the combination can be completed through a simple mixing reaction. Below, we introduce the labeling method of protein antibody labeling, which has certain reference significance [2].