Paramagnetic relaxation enhancements

The magnitude of the paramagnetic relaxation enhancement (PRE) caused by dipolar interactions depends on the square of the gyromagnetic ratios of both involved spins, the inverse sixth power of the inter-spin distance, and the correlation time rc of the vector connecting the two spins. For the transverse relaxation rate enhancement, R2para of a spin I,... 

In the case of second-site screening with a spin-labeled first ligand, the dependence of the paramagnetic relaxation enhancement on the inverse sixth power of the distance (Eq. (1)) leads to differential quenching effects on the second ligand, depending on its... 

A more general theory for outer-sphere paramagnetic relaxation enhancement, valid for an arbitrary relation between the Zeeman coupling and the axial static ZFS, has been developed by Kruk and co-workers (96 in the same paper which dealt with the inner-sphere case. The static ZFS was included, along with the Zeeman interaction in the unperturbed Hamiltonian. The general expression for the nuclear spin-lattice relaxation rate of the outer-sphere nuclei was written in terms of electron spin spectral densities, as ... 

C. Equations describing the paramagnetic relaxivity enhancement caused by Gd(III)-loaded, porous systems... 

C. Equations Describing the Paramagnetic Relaxivity Enhancement Caused by Gd(IH)-LoADED, Porous Systems... 

Maliakal AJ, Turro NJ, Bosman AW, Cornel J, Meijer EW. Relaxivity studies on dinitroxide and polynitroxyl functionalized dendrimers effect of electron exchange and structure on paramagnetic relaxation enhancement. J Phys Chem A 2003 107 8467-8475. 

For monomer Gd(III) complexes the inner and outer sphere mechanisms contribute more or less to the same extent to the overall paramagnetic relaxation enhancement. The development of high relaxivity contrast agents mainly involves increasing the inner sphere term, since the outer sphere contribution can hardly be modified. For the new generation macromolecular agents, therefore, the inner sphere relaxivity becomes much more significant (over 90% of total relaxivity). 

Paramagnetic relaxation enhancement (PRE) approach was introduced for identifying the asymmetric insertion depths of membrane proteins in lipid bilayers. By applying Mn2+ ions on the outer but not the inner leaflet of lipid bilayers, the sidedness of protein residues in the lipid bilayer was determined. Protein-free lipid membranes with one-side Mn2+ bound surfaces exhibit... 

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