The long range goal of work proposed here is to increase our quantitative understanding of local motions in natural and synthetic polynucleotides. There is a growing awareness that such motions persist even in solid fibers and crystals of DNA and RNA and are strongly influenced by waters of hydration and other small molecules that are associated with the polynucleotide. A detailed picture at the molecular level of how water and bound cations influence the amplitudes and rates of local motion is important to our understanding of the mechanisms of DNA replication and transcription. The primary experimental tool to be exploited for motional studies in deuterium nuclear magnetic resonance and relaxation, supplemented as necessary with relaxation and lineshape studies of other nuclei. Quadrupole echo spectra of specifically deuterated polynucleotides will provide dynamic information about processes on a timescale of roughly one microsecond, while faster processes may be studied via numerous techniques for measurement of spin-lattice relaxation behavior. The maximal amount of dynamic information available from such experiments will be obtained by analysis of the data in terms of different motional models incorporated in the common framework of the stochastic Liousville equation. Oriented fibers of DNA and RNA will be used to the maximal extent to define the types of motion present in the polynucleotides. Specific projects are proposed to elucidate the role of hydration and temperature in increasing the local mobility in solid samples, to investigate possible differences in internal motions of polyribo- and polydeoxyribonucleic acids, and to characterize the effects of helix stabilizing agents (e.g. polyamines) on local motions. The dynamic information to be obtained in these studies will complement x-ray diffraction studies which commonly provide static measures of disorder. Deuterium NMR has been little used in DNA studies and the proposed experiments should expand the scope of measurements and explore the limitations of these NMR techniques. 1p measurements of the phosphate and H1 and H2 measurements on bound water (H2O, D2O) will be combined to provide a more complete picture of the early stages of hydration of DNA and the extent to which backbone motions are correlated with motions of the bases.
