| New methods to obtain multidimensional NMR spectra with ultra-high frequency resolution are described. Analysis of experimental signals is carried out by novel, non-Fourier, data processing algorithms based on the Filter Diagonalization Method (FDM). Experiments using the “Constant-Time” (CT) evolution are designed to obtain 2D and 3D time signals that fit a deterministic (Lorentzian) model and are ideally suited for FDM analysis. New partly selective 180° pulses with compensation for resonance offset and magnetic field inhomogeneity are presented for these applications. Modified 2D CT HSQC and 3D CT HCACO experiments are described and demonstrated on a labeled protein. The procedure developed can potentially be extended to improve resolution in several other types of NMR spectra for protein backbone assignment. The J-TOCSY-J experiment is designed. The resulting signal is analyzed by FDM to obtain a singlet-TOCSY spectrum. This is a new type of homonuclear correlation spectrum, in which 1H-1H homonuclear spin-spin couplings are removed, and correlation peaks are condensed into sharp singlets. Results are compared to the leading methods of spectral analysis. |
