Double- and Zero-Quantum NMR Relaxation Dispersion Experiments Sampling Millisecond Time Scale Dynamics in Proteins

Abstract
TROSY-based NMR relaxation dispersion experiments that measure the decay of double- and zero-quantum 1H−15N coherences as a function of applied 1H and 15N radio frequency (rf) fields are presented for studying millisecond dynamic processes in proteins. These experiments are complementary to existing approaches that measure dispersions of single-quantum 15N and 1H magnetization. When combined, data from all four coherences provide a more quantitative picture of dynamics, making it possible to distinguish, for example, between two-site and more complex exchange processes. In addition, a TROSY-based pulse scheme is described for measuring the relaxation of amide 1H single-quantum magnetization, obtained by a simple modification of the multiple-quantum experiments. The new methodology is applied to a point mutant of the Fyn SH3 domain that exchanges between folded and unfolded states at 25 °C.