Cross-relaxation systematic errors

Considering all potential experimental and systematic errors of NOE/ROE crosspeak intensities, it is remarkable how robust the derived distance restraints still are. The reason Ues in the dependence of the cross-relaxation rate even if a cross-peak intensity is determined wrongly by a factor 2, the resulting distance restraint is only affected by the factor 1.12, which usually lies within the error range of distance restraints used in structure calculations. It should be further noted that the quaUty of a resulting structure is not so much determined by the... 

Differential relaxation of in-phase and anti-phase operators involving a spin C [10], which are due to additional Tj relaxation effects active only for the anti-phase components and which depend on the geometry of the spin system, can lead to systematic errors of the coupling constant derived from cross-peak multiplets observed in an E. COSY-type experiment [11]. Since these errors depend for a given differential relaxation rate Ap on the frequency difference of the coherences with C in the a or yS state, according to Eq. (1) a remedy to the problem is to maximize the relevant J such that the condition J 3> Ap/2n is fulfilled ... 

Optimisation of CT cross-relaxation rate measurement experiments to reduce systematic errors Measurement of (dipole) /... 

The deconvolution method proposed earlier by our group, translated the 3D cross peak intensities into 2D NOE intensities, which can be used to derive accurate distance constraints that can be used in structure refinement by an iterative relaxation matrix approach (11). This approach avoids systematic errors while retaining computational efficiency. 

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