Stable Europium(III) Complexes with Short Linkers for Site-Specific Labeling of Biomolecules

摘要

Abstract In this study, two new terpyridine-based Eu III complexes were synthesized, the structures of which were optimized for luminescence resonance energy-transfer (LRET) experiments. The complexes showed high quantum yields (32 %); a single long lifetime (1.25 ms), which was not influenced by coupling to protein; very high stability in the presence of chelators such as ethylenediamine- N , N , N ?￠???2, N ?￠???2-tetraacetate and ethylene glycol-bis(2-aminoethylether)- N , N , N ?￠???2, N ?￠???2-tetraacetic acid; and no interaction with cofactors such as adenosine triphosphate and guanosine triphosphate. A special feature is the short length of the linker between the Eu III ion and the maleimide or hydrazide function, which allows for site-specific coupling of cysteine mutants or unnatural keto amino acids. As a consequence, the new complexes appear particularly suited for accurate distance measurements in biomolecules by LRET.