Engineering of a bis-chelator motif into a protein alpha-helix for rigid lanthanide binding and paramagnetic NMR spectroscopy

Attachment of two nitrilotriacetic acid-based ligands to a protein alpha-helix in an i, i + 4 configuration produces an octadentate chelating motif that is able to bind paramagnetic lanthanide ions rigidly and with high affinity, leading to large pseudocontact shifts and residual dipolar couplings in the NMR spectrum.