Cy3 Bis NTA-Ni Chelator can be applied either to an SDS-PAGE gel or Western blot membrane for fluorescence imaging or used in living cells in combination with the addition of a heavy metal ion such as Ni2+. Detection with Cy3 Bis NTA-Ni complex requires less incubation time than for protein-antibody binding. No secondary reaction is required since Ni-NTA complex is directly conjugated to the Cy3 fluorophores. Cy3 and Cy5 dyes demonstrate strong fluorescent signals at commonly available wavelengths and with little quenching. Polyhistidine is one of the most popular affinity tags incorporated into recombinant proteins. It can be inserted either at the N- or C-terminus and expressed in a variety of hosts. Due to its small size, the polyhistidine tag serves as an elegant tool for both protein purification and detection. AAT Bioquest also offers HIS Lite™ Cy3 Bis NTA-Ni and Cy5 Bis NTA-Ni Complexes that can be directly used for the specific and highly sensitive detection of His-tagged fusion proteins without the addition of a heavy metal ion.