Convection compensated electrophoretic NMR.

A novel method of convection compensated ENMR (CC-ENMR) has been developed to detect electrophoretic motion of ionic species in the presence of bulk solution convection. This was accomplished using a gradient moment nulling technique to remove spectral artifacts from heat-induced convection and using the polarity switch of the applied electric field to retain spin phase modulations due to electrophoretic flow. Experiments were carried out with a mixture of 100 mM L-aspartic acid and 100 mM 4,9-dioxa-1,12-dodecanediamine to demonstrate this new method of ENMR. CC-ENMR enhances our previously developed capillary array ENMR (CA-ENMR) in solving the convection problem. The combined CA- and CC-ENMR approach strengthens the potential of multidimensional ENMR in simultaneous structural determination of coexisting proteins and protein conformations in biological buffer solutions of high ionic strength. Structural mapping of interacting proteins during biochemical reactions becomes possible in the future using ENMR techniques, which may have a profound impact on the understanding of biological events, including protein folding, genetic control, and signal transduction in general.