ABSTRACT
The most common goal of a nuclear magnetic resonance (NMR) investigation of an organic substance or of a biological macromolecule is to obtain information about its structure. In a protein, on the other hand, typically the interesting questions concern the secondary structure and the overall fold. Dipole-dipole relaxation has found widespread use in all fields of chemistry and biochemistry, since it provides a way of estimating internuclear distances in molecules. Nuclear Overhauser enhancement, or the cross-relaxation phenomenon, has, together with J-coupling measurements, until recently been the most important NMR tool for investigating structure and conformation. Chemical structure investigations as well as conformational analyses of organic compounds are readily made by NMR methods. In organic chemistry, the structure determination of small molecules is mainly concerned with investigating positional substitutions, conformation around double bonds and chirality. In addition to the investigation of chemical structure, it is also feasible to obtain information about the molecular conformation of organic molecules.
