Addressing the overlap problem in the quantitative analysis of two dimensional NMR spectra: application to (15)N relaxation measurements.

A quantitative analysis of 2D (1)H-(15)N spectra is often complicated by resonance overlap. Here a simple method is presented for resolving overlapped correlations by recording 2D projection planes from HNCO data sets. Applications are presented involving the measurement of (15)N T(1rho) relaxation rates in a high molecular weight protein, malate synthase G, and in a system that exchanges between folded and unfolded states, the drkN SH3 domain. By supplementing relaxation data recorded in the conventional way as a series of 2D (1)H-(15)N data sets with a series of a pair of projection planes the number of dynamics probes is increased significantly for both systems studied.