Lanthanides: Shift Reagents

Abstract The presence of paramagnetic metal centers causes enhanced shift and relaxation effects on the resonances of NMR‐active nuclei of ligand molecules. In this chapter, we describe the basic theory and main applications of paramagnetic NMR shift effects of Ln 3+ ions as structural reporters of small flexible ligands and paramagnetic complexes and their supramolecular constructs. Their applications on the structure and dynamics of proteins are also discussed, with particular emphasis on the aspects relevant to the development of Gd 3+ ‐based MRI contrast agents and powerful NMR shift reagents for in vivo MRS of alkali ions (e.g., 23 Na + , 7 Li + ).