engleski

Cross Correlated Curie Spin Relaxation and Molecular Structure

Curie-spin relaxation (CSR) is caused by the dipolar interaction between the nuclear and the thermally averaged electron magnetic moments, but it acts like a single-spin interaction for the nuclear spins involved. Therefore, cross-correlation effects between dipole-dipole (DD) and CSR relaxation are formally indistinguishable from cross-correlation effects between DD and chemical shift anisotropy (CSA). Cross-correlation effects between DD interactions and the Curie spin of paramagnetic ions contain information about the angle theta between the H-N bond and the vector connecting the proton with the paramagnetic centre. Due to the long-range effect of paramagnetic relaxation, these angle restraints provide a powerful tool for obtaining long-range structural information. We show experiments and simulations of the influence of the anisotropy of the magnetic susceptibility on DDxCSR relaxation effects for high- and low-spin met-myoglobin complexes and consequences on the angular constraints derived from these data. Strategies for dealing with the DDxCSA intereference are also given. Acknowledgement: This work was supported by the EU by a postdoctoral fellowship for G.P. within the Research Training Network on Cross-Correlation (HPRN-CT-2000-00092) and by the Swedish and Australian Research Councils as well as the Austrian Science Funds (FWF, project P15380) and the ÖAD (Austro-Croatian pilot project).

NMR; Curie-spin relaxation; chemical shift anisotropy; cross-correlation effects

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