biostudies-literatureBellomo GMinistero della SaluteMinistero dell’Istruzione, dell’Università e della RicercaHorizon 2020Fondazione Cassa di Risparmio di Firenze25-31https://www.ebi.ac.uk/biostudies/studies/S-EPMC10539754biostudies-literatureUnknown2(1)Cross-relaxation terms in paramagnetic systems that reorient rigidly with slow tumbling times can increase the effective longitudinal relaxation rates of protons of more than 1 order of magnitude. This is evaluated by simulating the time evolution of the nuclear magnetization using a complete relaxation rate-matrix approach. The calculations show that the Solomon dependence of the paramagnetic relaxation rates on the metal-proton distance (as r-6) can be incorrect for protons farther than 15 Å from the metal and thus can cause sizable errors in R1-derived distance restraints used, for instance, for protein structure determination. Furthermore, the chemical exchange of these protons with bulk water protons can enhance the relaxation rate of the solvent protons by far more than expected fromMagnetic resonance (Gottingen, Germany)Revisiting paramagnetic relaxation enhancements in slowly rotating systems: how long is the long range?PMC10539754n/aPRIN 2017A2KEPL, “Rationally designed nanogels embedding paramagnetic ions as MRI probes”GR-2016-02361586Fragai MLuchinat CBellomo GCalderone VParigi GRavera EBotta MfalseRevisiting paramagnetic relaxation enhancements in slowly rotating systems: how long is the long range?Cross-relaxation terms in paramagnetic systems that reorient rigidly with slow tumbling times can increase the effective longitudinal relaxation rates of protons of more than 1 order of magnitude. This is evaluated by simulating the time evolution of the nuclear magnetization using a complete relaxation rate-matrix approach. The calculations show that the Solomon dependence of the paramagnetic relaxation rates on the metal-proton distance (as r-6) can be incorrect for protons farther than 15 Å from the metal and thus can cause sizable errors in R1-derived distance restraints used, for instance, for protein structure determination. Furthermore, the chemical exchange of these protons with bulk water protons can enhance the relaxation rate of the solvent protons by far more than expected from2021-01-01T00:00:00Z20212026-05-29T00:45:33.962Z2025-04-20T01:33:11.67ZS-EPMC105397543790476610.5194/mr-2-25-2021