The major goal of this project is the development of new, high resolution nuclear magnetic resonance (NMR) methodologies for use in studies of the structure and dynamics of biomolecules such as proteins and nucleic acids. NMR spectroscopy has become an extremely powerful tool for the study of biomolecules in solution, due to its ability to provide detailed information at an atomic level The extent to which NMR spectroscopy can be exploited for three-dimensional structure determinations of biomolecules, the investigation of intermolecular interactions in systems such as drug/receptor, enzyme/substrate and antibody/antigen complexes, and the characterization of the dynamics of molecular fragments, will depend on the ability to manipulate the system to yield EM desired information. The enormous contribution that biological NMR has made during the last decade in the investigation of biomolecules and biophysical processes is due largely to the continuing development of new or improved techniques for extracting useful data from the systems of interest. A prerequisite step in any NMR study is the assignment of resonances to individual nuclei in the molecule of interest. One of the most efficient experiments currently in use for resonance assignment is based on the principle of isotropic mixing. Despite the popularity of such experiments, they have not been well characterized theoretically.
One aim of the proposed research is a detailed analysis and development of various aspects of isotropic mixing experiments, in particular, the development of novel schemes employing multiple frequency irradiation to improve the efficiency. Also, new experiments employing isotropic mixing for heteronuclear coherence transfer will be explored. In the development of new NMR techniques and the analysis of their characteristics, it is common to make simplifying assumptions. However, in some of the most recent experiments, especially those employing long periods of radio-frequency irradiation, it is necessary to conduct a more rigorous analysis which includes the effects of NMR relaxation phenomena. It is vital to consider relaxation processes in the development of new experiments designed to separate the effects of relaxation and coherence transfer. One of the major goals in this proposal is to derive a convenient formalism for including relaxation effects into NMR simulations, and to use this for the development of improved isotropic mixing and related techniques. While NMR is the method of choice for obtaining detailed information in physical studies of biomolecules in solution, it unfortunately is a comparatively insensitive technique. It is proposed to investigate promising schemes for improving the sensitivity of various, important techniques such as isotropic mixing, heteronuclear correlation methods and relaxation time measurements. Theoretically, the new experiments to be developed can reduce the required measuring time in half. Dynamical processes in biomolecular systems often play a key role in biological function, and thus it is very important to have suitable methods for characterizing such phenomena. NMR spectroscopy is a very powerful tool for obtaining detailed information on the dynamics of molecular fragments. One important aim of this proposal is to characterize theoretically and demonstrate the usefulness of multiple quantum techniques for studying chemical reorganization processes. Another major goal is to develop techniques which will facilitate the measurement of heteronuclear relaxation rates. Such data would be invaluable for use in functional and structural studies of biomolecules such as proteins and nucleic acids.
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