This research project involves the development of experimental methods for detecting less receptive nuclei (13C, 15N and 2H) with special emphasis placed on 13C. The application of such methods to biologically important system and their theoretical consequences are stressed. The value of chemical shifts in structure correlations of liquid samples has been very well documented and these concepts are now being developed in the full shielding tensor. The three dimensional aspects of shielding tensors becomes one of the significant aspects of the proposal. Solid state work on either powders or single crystals is required to obtain shielding tensors and their principal orientations in the molecular frame. Use of tensor data along with theory is advancing our understanding of the origins of chemical shielding and its use in shift structure correlations. The expansion from one isotropic shift to six tensor parameters in solids provides details unavailable in isotropic liquid shifts. Thus, work will be directed towards the development of single crystal methods for biomolecules of a size not here-to-fore possible. The dipolar interactions, which averages to zero in isotropic liquids, also is readily studied in the solid state and its inverse cubic distance dependence contributes valuable structural information. The relaxation of 13C spin multiplets in CH, CH2 and CH3 groups provides information on molecular diffusional reorientation and these methods are proving to be beneficial in the study of segmental motion in flexible molecular chains. the increased use of multidimensional NMR methods is increasing the need for coupled relaxation methods and analysis tools which properly account for complex relaxation effects arising in coupled spin systems. the detailed treatment of model systems has now advanced to the point where these concepts and methods may be applied to small peptides of biological importance to determine the importance of molecular motion on functionality. The use of 2D pattern recognition methods in NMR are significantly advancing the use of NMR methods in biomedical fields, and the use of these methods for characterizing important natural products is being investigated. Use of such methods in the 2D INADEQUATE experiment have reduced the required sample size requirements by better than ten fold.