Enantiomeric two-armed lanthanide-binding tags for complementary effects in paramagnetic NMR spectroscopy

Two-armed lanthanide-binding tags induce significant, long-range paramagnetic effects in the NMR spectra of attached proteins. An enantiomeric pair of rigid, two-armed, cyclen-based tags are reported that produce markedly different effects from the same tagging site, allowing for the measurement of complementary paramagnetic restraints for structural studies. A new pair of two-armed lanthanide-binding tags provide distinct sets of structural restraints when attached to the same site of a protein.