Boosting protein dynamics studies using quantitative nonuniform sampling NMR spectroscopy.

NMR spectroscopy is uniquely suited to study protein dynamics over a wide range of time scales at atomic resolution. However, existing NMR relaxation methods require highly serial, lengthy data collection, ultimately limiting their application to short-lived samples, such as proteins in living cells. In recent years, the utility of nonuniform sampling (NUS) NMR methodologies has been increasingly recognized, but their application has been rare in relaxation measurements where highly accurate spectral quantification is demanded. Recently, Matsuki et al. developed a new NUS-processing method, SIFT (Spectroscopy by Integration of Frequency and Time domain information), which is highly robust and faithful in reproducing signals. In this work, we demonstrate the gains that are possible with more aggressive use of frequency domain information than was employed previously. This improvement is crucial for SIFT to be used in accelerating relaxation measurements while preserving full analytical accuracy. By taking the KIX domain of mouse CREB-binding protein (CBP) as an example, we demonstrate that this quantitative NUS processing method enables total 10-fold expedition of the R(2) relaxation dispersion measurements. The advanced SIFT processing should be equally useful for other NMR relaxation measurements.