Lanthanide induced residual dipolar couplings for the conformational investigation of peripheral 15NH2 moieties

The Ca₂ calbindin protein in which one calcium has been substituted with Ce(III), Yb(III) and Dy(III) displays substantial alignment in high magnetic fields due to the high anisotropy of the metal magnetic susceptibility. This property has allowed the measurement of residual dipolar coupling contributions to ¹J_HNand ²J_HH couplings of asparagine and glutamine NH₂ moieties. Such data have been used to aid structural characterization of these groups. The exploitation of auto-orientation of magnetic anisotropic metalloproteins represents a step ahead in the investigation of the conformational space of peripheral residues that are not fixed by the protein folding.