How Do Nuclei Couple to the Magnetic Moment of a Paramagnetic Center? A New Theory at the Gauntlet of the Experiments

Linda Cerofolini; José Malanho Silva; Enrico Ravera; Maurizio Romanelli; Carlos F G C Geraldes; Anjos L Macedo; Marco Fragai; Giacomo Parigi; Claudio Luchinat

doi:10.1021/acs.jpclett.9b01128

How Do Nuclei Couple to the Magnetic Moment of a Paramagnetic Center? A New Theory at the Gauntlet of the Experiments

J Phys Chem Lett. 2019 Jul 5;10(13):3610-3614. doi: 10.1021/acs.jpclett.9b01128. Epub 2019 Jun 15.

Authors

Linda Cerofolini¹, José Malanho Silva^{1

2

3}, Enrico Ravera^{1

4}, Maurizio Romanelli⁵, Carlos F G C Geraldes², Anjos L Macedo³, Marco Fragai^{1

4}, Giacomo Parigi^{1

4}, Claudio Luchinat^{1

4}

Affiliations

¹ Magnetic Resonance Center (CERM) , University of Florence, and Consorzio Interuniversitario Risonanze Magnetiche di Metalloproteine (CIRMMP) , via Sacconi 6 , Sesto Fiorentino 50019 , Italy.
² Department of Life Sciences and Coimbra Chemistry Center , University of Coimbra , Coimbra 3004-531 , Portugal.
³ UCIBIO-Requimte, Faculty of Sciences and Technology , Universidade NOVA de Lisboa , Caparica 2829-516 , Portugal.
⁴ Department of Chemistry , University of Florence , Sesto Fiorentino 50019 , Italy.
⁵ Department of Earth Sciences , University of Florence , Sesto Fiorentino 50019 , Italy.

PMID: 31181162
DOI: 10.1021/acs.jpclett.9b01128

Abstract

The recent derivation, based on pure quantum chemistry (QC) first-principles, of the pseudocontact shifts (PCSs) caused by a paramagnetic metal center on far away nuclei has cast doubts on the validity of the semiempirical (SE) theory, predicting PCSs to arise from the metal magnetic susceptibility anisotropy. The SE theory has been used and applied countless times, especially in the last 2 decades, to obtain structural information on proteins containing paramagnetic metal ions. We show here that the QC and SE predictions can be directly tested against experiments, provided a suitable macromolecular system is used. The SE approach yields a good prediction of the experimental PCSs while the QC one does not. It appears that the classic theory is able to grasp satisfactorily the underlying physics.