The multidimensional filter diagonalization method - II. Application to 2Dprojections of 2D, 3D, and 4D NMR experiments

The theory of the multidimensional filter diagonalization method (FDM) desc ribed in the previous paper (V. A. Mandelshtam, 2000, J. Magn. Reson. 144, 343-356 (2000)) is applied to NMR time signals with up to four independent time variables. Direct projections of the multidimensional time signals pro duce new kinds of 2D spectra. The resolution obtained by FDM can be far sup erior to that obtained by conventional phase-sensitive FT processing, and c orrelation peaks in heteronuclear and homonuclear experiments can be conden sed to sharp singlets, removing all spin-spin couplings. Examples of single t-HSQC and single-TOCSY spectra show big gains in resolution. It is not nec essary to have a finely digitized spectrum, in which the individual multipl et components are resolved, for the methods to work. Examples of FDM spectr a, ranging from simple organic molecules and steroids to metalloproteins, a re shown. (C) 2000 Academic Press.