CONDITIONS FOR THE MEASUREMENT OF QUANTITATIVE OFF-RESONANCE ROESY INTENSITIES

Two phenomena hamper the quantification of ROESY intensities: the off- resonance effect and the coherent magnetization transfer between scala r-coupled spins. The off-resonance application of the r.f. irradiation has been proposed to reduce these artefacts. Here the reliability of this method for the quantification of ROESY intensities measured on a sample containing a macromolecule was investigated. The threshold of i rradiation offset fdr which the coherent magnetization transfer can be neglected was determined. It is shown that for offsets larger than th is threshold, the off-resonance effect does not hinder the quantificat ion, provided that the irradiation is alternatively applied at high an d low field. (C) 1998 John Wiley & Sons, Ltd.