The hexahistidine-tag (His6) provides binding sites for three Ni-NTA moieties. Tris-NTA is thus perfectly suited for non-covalent, stable, highly selective Protein Labeling of hexahistidine tags in a stoichiometric ratio of 1:1 at sub-nanomolar affinity. In RED-tris-NTA labeling kits the tris-NTA scaffold is conjugated with TRIC and Spectral Shift optimized NanoTemper Technologies Fluorophores.

Tip: Sometimes the addition of 25 µM EDTA to the assay buffer can improve tris-NTA labeling. Through this, contaminating metal ions that can be present in a buffer at several 100 nM to low µM concentration can be neutralized.