Nuclear magnetic relaxation study of hindered rotational diffusion in gels

Abstract

Polymeric gels are widely used in biotechnology, primarily for purification purposes in separation processes, but also as matrices for the physical entrapment of cells and macromolecules, or for the covalent attachment of enzymes and ligands (Mosbach. 1976). The restricted diffusion of molecules through these gels is an important concern in the design and operation of chromatographic separations, bioreactors, electrophoretic media, etc. Yet the fundamental aspects of the interactions between the gel fibers and the diffusing substances are still poorly understood. In this research note, nuclear magnetic relaxation is shown to be a useful probe pf the tumbling motion of molecules embedded in a gel. The technique is applied to study the rotational diffusion of cyclic guanosine monophosphate (cGMP) in polyacrylamide and agarose matrices.