Light-Driven Paramagnetic Tags for Efficient Pseudocontact Shifts Measurments in Protein NMR Spectroscopy

Pseudocontact shifts (PCS) values are essential for studies of protein structure and dynamics. However, structural calcu-lations typically require multiple tags or labeling at multiple sites, which can be both time-consuming and expensive. In this study, we demonstrate that two independent sets of PCS values can be obtained using an azobenzene-based paramag-netic probe. Upon photo-isomerization, the magnetic field around the protein is redistributed, resulting in a distinct NMR spectrum and enabling the acquisition of a new set of structural constraints. This light-driven spatial motion of the para-magnetic center eliminates the need for additional mutations or chemical activators to induce magnetic transitions, pav-ing the way for the development of tensor-switchable paramagnetic tags.