The use of spin relaxation phenomena in the investigation of the structure of model and biological systems by the method of spin labels

Electron paramagnetic relaxation enhancement produced onT1by anisotropic g-tensors in rigid systems

“…This effect has been originally described by Bloembergen [6] and later by Abragam [7] in an NMR context, and later for the case of EPR by Kulikov and Lichtenshtein [1] and Hyde and Rao [8] for rigid systems where no spatial averaging occurs. There are many theoretical aspects of the literature on NMR that are immediately relevant, most of which have been discussed in Abragam's book [9].…”

“…and, in the same system, the components of G (1) are The form of F (1) in (5) implies that the fast-relaxing spin S f forms part of the 'lattice' undergoing time-dependent fluctuations. In paramagnetic systems in frozen solutions, which is typical for EPR samples, the time dependence of F (1) originates exclusively from the motion of the fast-relaxing electron spin S f .…”

“…The components of the first-rank tensor F (1) are constructed by contracting the tensors G (1) and C (2) [3,4,27]…”

“…al [13]. Most importantly this method has been applied for distance estimate in complicated biological systems, such as milk Xanthane Oxidase [14], Cytochrome c Oxidase [15] In all the cited cases the expression used for the estimation of the 1/T s 1 (dipolar) was that developed by Kulikov and Likhtenstein [1] and Hyde et al, [2,8], which is valid for isotropic gtensors for the slow as well as for the fast relaxing electron spins, based on the original works [1,2,8]. No expression for 1/T s 1 (dipolar) is available for the general case where the fast relaxer has an anisotropic g-tensor.…”

“…Fast relaxing electron spins can affect the relaxation properties T s 1 and T s 2 of nearby slow relaxing, electron [1,2] or nuclear [3][4][5] spins. This effect has been originally described by Bloembergen [6] and later by Abragam [7] in an NMR context, and later for the case of EPR by Kulikov and Lichtenshtein [1] and Hyde and Rao [8] for rigid systems where no spatial averaging occurs.…”