Design of a binuclear Ni(II)–iminodiacetic acid (IDA) complex for selective recognition and covalent labeling of His-tag fused proteins

Abstract Selective protein labeling with a small molecular probe is a versatile method for elucidating protein functions under live-cell conditions. In this Letter, we report the design of the binuclear Ni(II)–iminodiacetic acid (IDA) complex for selective recognition and covalent labeling of His-tag-fused proteins. We found that the Ni(II)–IDA complex 1 -2Ni(II) binds to the His6-tag (HHHHHH) with a strong binding affinity ( K d  = 24 nM), the value of which is 16-fold higher than the conventional Ni(II)–NTA complex ( K d  = 390 nM). The strong binding affinity of the Ni(II)–IDA complex was successfully used in the covalent labeling and fluorescence bioimaging of a His-tag fused GPCR (G-protein coupled receptor) located on the surface of living cells.