Improved spectral resolution in COSY proton NMR spectra of proteins via double quantum filtering

A double quantum filter is inserted into a 2-dimensional correlated (COSY) 1H NMR expt. to obtain phase-sensitive spectra in which both cross-peak and diagonal-peak multiplets have antiphase fine structure, and in which the cross peaks and the major contribution to the diagonal peaks have absorption lineshapes in both dimensions. The elimination of the dispersive character of the diagonal peaks in phase-sensitive, double quantum-filtered COSY spectra allows identification of cross peaks lying immediately adjacent to the diagonal, which represents a significant improvement over the conventional COSY expt. [on SciFinder (R)]