Cy5.5-SE (Cyanine5.5 NHS ester) DIPEA, a cyanine (CY) dye, comprises two nitrogen atoms linked by an odd number of methyl units. Characterized by long wavelength, tunable absorption and emission, high extinction coefficient, and good water solubility, alongside relatively straightforward synthesis [1], CY dyes are frequently utilized for labeling proteins, antibodies, and small molecular compounds. Their application in protein antibody labeling is achieved through a simple mixing reaction, providing a method of notable reference significance [2]. Storage instructions include protection from light.