Cy5 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 Cy5 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 Cy5 fluorophores. Cy5 demonstrates strong fluorescent signals at ~670 nm with a common red laser excitation (e.g., He-Ne laser or 647 nm red laser). 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™ Cy5 Bis NTA-Ni Complex 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.