Lanthanide induced residual dipolar couplings for the conformational investigation of peripheral (NH2)-N-15 moieties

The Ca-2 calbindin protein in which one calcium has been substituted with C e(III), Yb(III) and Dy(III) displays substantial alignment in high magnetic fields due to the high anisotropy of the metal magnetic susceptibility. Th is property has allowed the measurement of residual dipolar coupling contri butions to (1)J(H)Nand (2)J(HH) couplings of asparagine and glutamine NH2 m oieties. Such data have been used to aid structural characterization of the se groups. The exploitation of auto-orientation of magnetic anisotropic met alloproteins represents a step ahead in the investigation of the conformati onal space of peripheral residues that are not fixed by the protein folding .