Abstract Nuclear magnetic relaxation formulae are given for dipolar nuclei interacting with quadrupolar nuclei. The following cases are distinguished: High-and low-field case with respect to the quadrupole energy levels and, on the other hand, quasi rigid lattices and tumbling lattices with respect to molecular motions.As examples of these cases, the proton T1-dispersion of Polyvinylchloride (quasi rigid lattice) and of protein solutions (tumbling lattice) are discussed and compared with theory. It is shown that the influence of the interaction with quadrupole nuclei is normally not negligible.PVC shows a quadrupolar dip below room temperature as an especially remarkable consequence of the interaction with chlorine. An oscillator model is discussed in order to explain the molecular motion at low temperatures.Proteins contain imino-groups acting as relaxation centers and mediating the contact to the aqueous solvent via hydrogen bonds. These relaxation centers can explain the low absolute values of the longitudinal relaxation times in protein solutions. Furthermore, several effects in such systems, reported previously, can easily be interpreted on the basis of the presented formalism.
Specificity of concanavalin A binding to asparagine-linked glycopeptides. A nuclear magnetic relaxation dispersion study.
