Nuclear relaxation due to dipolar coupling with unpaired electrons

Nuclear relaxation due to dipolar coupling with unpaired electrons [Pg.89]

4 NUCLEAR RELAXATION DUE TO DIPOLAR COUPLING WITH UNPAIRED ELECTRONS [Pg.89]

While keeping in mind the general picture of nuclear relaxation in paramagnetic systems as described in Section 3.1, it is appropriate to consider first the simple case of dipolar coupling between two point-dipoles as if the unpaired electrons were localized on the metal ion. The enhancement of the nuclear longitudinal relaxation rate Rim due to dipolar coupling with unpaired electrons can be calculated starting from the Hamiltonian for the system [Pg.89]

This Hamiltonian is constituted by two time-independent terms, which refer to the Zeeman interactions for the electron (first term) and the nucleus (hyi = gifiN, [Pg.89]

2 Nuclear relaxation thus originates from the modulation of the hyperfine interaction [Pg.90]

The dipolar coupling with the unpaired electron is the main source of relaxation for protons and for nuclei of the metal ligands other than those coordinated to the metal ion. This dipolar coupling can be modulated by Tr (due to motion of part or whole of the molecule) or by Tj (from the change of state of the electron spin). Due to the relatively large molecular weight of protein molecules, electron relaxation is dominant and Tc = Tj. The nuclear relaxation rates are given by (Solomon, 1955)... [Pg.403]

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