Analysis of cross peak fine structure in multiple-quantum filtered COSY spectra

Abstract

Phase-sensitive COSY and multiple-quantum filtered COSY experiments have been carried out using the spin systems of the amino acids aspartic acid and tryptophan as model systems. The factors which contribute to the cross peak fine structure and the procedures which are used to calculate the form that a cross peak takes in the weak coupling limit are described. The distribution of antiphase components in the cross peak multiplets from multiple-quantum filtered COSY experiments is shown to depend upon the order of the coherence transfer pathway selected and on the number of active and passive spinspin couplings involved in the cross peak. The variation of cross peak intensity as a function of both linewidth and coupling constants is investigated using spectral simulations. The application of phase-sensitive triple-quantum filtration to the protein hen lysozyme is also presented.