Paramagnetic susceptibility tensor

Metal sites with anisotropic paramagnetic susceptibility tensors will induce pseudocontact shifts, 5pc,... 

The (temperature-independent) paramagnetic susceptibility tensor is given by the perturbation formula... 

Then the reduced paramagnetic susceptibility tensor becomes expressed as... 

In a seminal contribution, Bleaney demonstrated that when the crystal-field splitting of the ground multiplet is smaller or comparable to kT, a situation often met with lanthanide complexes, the anisotropic part of the axial paramagnetic susceptibility tensor originates from second-order effects and can be simply estimated by the product of magnetic constants Cj, characteristics of the electronic configuration of each lanthanide (i.e., Bleaney factor), multiplied by the second-rank crystal-field parameter Bq (Eq. (34), Bleaney, 1972). 

Lanthanide-labeled proteins present a similar situation, where pseudocontact shifts are large and contact shifts are often small. In addition, the paramagnetic susceptibility tensor of lanthanide ions is expected to be only mildly dependent on chemical environment. Prudencio et aP used a caged lanthanide complex, derivatived by two reactive thiol groups, as the paramagnetic probe. Attachment... 

Bertini et report a detailed study of the magnetic properties of myglobin, in which they determined the axial and orthorhombic terms of the paramagnetic susceptibility tensor using a combination of hyperfine chemical shift measurements and static suscetibility measurements (Evans Method). The determination of the magnetic anisotropy provided a measurement of the residual dipolar couplings and also permitted a separation of the contact and pseudocontact chemical shift contributions of resonances of the Fe(III) ligands. 

Du et have determined the magnitude and orientation of the paramagnetic susceptibility tensor of the cyanomet complex of an 02-avid hemoglobin from the trematode Paramphistomum epiclitum. They used proton hyperfine chemical shifts and paramagnetic relaxation enhancements to probe the chemical bonding at the metal center. 

As another example, the three-dimensional structure of Cytochrome c has been determined on the basis of structural information from pseudocontact paramagnetic chemical shifts, Curie-Dipolar cross-correlation, secondary structure constraints, dipolar couplings and 15N relaxation data [103]. This protein has a paramagnetic center, and therefore the above-mentioned conformational restraints can be derived from this feature. Dipolar couplings do not average to zero because of the susceptibility tensor anisotropy of the protein. The structure determination of this protein without NOE data gives an RMSD (root... 

The subscripts a and n are used by Ramsey [52] and others, but we use the more explicit subscripts parallel and perpendicular. The paramagnetic part of the susceptibility tensor, given in equation (8.116), has a zero component in the z direction because it depends upon the mixing brought about by the x and y components of the orbital angular momentum L Hence ... 

In addition to the temperature-independent diamagnetism, any substance possesses a temperature-independent paramagnetism. Both these components form the magnetic susceptibility tensor and their partitioning, like X = Xdia + Xtip. is somehow artificial better to speak about the underlying... 

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