Paramagnetic ions rigidly attached to biomolecules cause pronounced changes in NMR signals that directly translate to the biomolecule’s structure if the magnetic anisotropy of the ion is known. Conversely when protein structure is (approximately) known, the location and magnetic anisotropy of the ion can be computed from the NMR observables. We have developed software tools to efficiently perform both these tasks and applied them to determine the anisotropic magnetic susceptibility tensors of several new lanthanide tags attached to proteins.
We have further developed a new algorithm to determine simultaneously the structure and the magnetic anisotropy of a paramagnetic protein. The program PCR-ROSETTA can determine the structures of proteins up to 150 residues in size from only backbone NMR chemical shift measurements. (With G. Otting, H. Yagi, X. Jia, T.H.D. Nguyen, M.J. Stanton-Cook at ANU, C. Schmitz at U. Uetrecht; R. Vernon, D. Baker at U. Washington)