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 (1)H-(15)N coherences as a function of applied (1)H and (15)N 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 (15)N and (1)H 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 (1)H 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 degrees C.