Solid-State NMR Spectroscopy of a Paramagnetic Protein: Assignment and Study of Human Dimeric Oxidized CuII-ZnII Superoxide Dismutase (SOD)

摘要

Solution NMR studies of paramagnetic systems are well-developed.[1] Paramagnetic centers originate from unpaired electrons that are intrinsic features of many transition-metal ions. A paramagnetic center changes the appearance of the NMR spectrum in several ways, most obviously by altering chemical shifts and increasing relaxation rates. On one side, these changes constitute a unique, direct probe of the electronic structure of the metals in these systems.[2] On the other hand, as the paramagnetic effects depend in a well-defined manner on the structure of the molecule, they provide a variety of structural restraints in the determination of the molecular geometry.[3] Paramagnetic phenomena thus provide information on electronic structure, protein-protein or protein-nucleic acid docking, ligand binding, solvent mapping, and the flexibility of multidomain proteins. However, NMR studies of paramagnetic molecules are often hindered by the very same large hyperfine effects, and mostly by the paramagnetically enhanced nuclear relaxation,[1] which undermines the acquisition of the NMR experiments.