It is intended to complete work on two projects dealing with new methodology in high-field NMR spectroscopic studies of biomolecules. In the first project, the magnetic susceptibility tensors of atomic groupings occurring in peptides and DNA duplexes are being determined by observation of the magnetic dipolar and electric quadrupolar splittings in the high-field NMR spectra of selected model compounds. Groups remaining to be examined are the amide, sulfide and disulfide linkages, and the phosphodiester group. When these values have been obtained, splittings will be measured for a small peptide and for a small DNA duplex, in order to establish the possible conformations in solution. In the second project, we are developing computational methods allowing the precise calculation of the evolution of a coupled spin system under the simultaneous influence of chemical shift, spin-spin coupling, dipolar and other forms of relaxation, and continuous application of an r.f. field of arbitrary strength and phase. We are using this predictive ability to explore new types of NMR experiments involving continuous application of the field (e.g. CAMELSPIN), in order to develop new approaches to structural investigation of biomolecules. Two new approaches which will be evaluated are 2-D spectroscopy connecting the rotating frame and laboratory frame, and r.f. phase modulation for selective inversion in the rotating frame.
