Didesulfo Cyanine 3 Monofunctional Hexanoic Acid Dye is a light sensitive compound related to Cyanine 3 Monofunctional Hexanoic Acid Dye, Potassium Salt and its free acid (CAS# 146368-13-0), which is useful in the preparation of dUTPs conjugated with zwitterionic Cy3 or Cy5 fluorophore analogs for use as substrates for DNA amplification and labelling by Taq polymerase.