Nuclear Magnetic Resonance (NMR) spectroscopy is a valuable tool for studying the dynamic behavior of biomolecules. It employs properties such as nuclear relaxation and chemical exchange saturation transfer to determine interconversion rates and populations of conformations . NMR parameters reflect conformational averaging on parameter-specific timescales: for 1 H chemical shift, slow exchange (conformational lifetime >> ~ 1 ms) yields distinct resonances for individual states, fast exchange (conformational lifetime << ~ 1 ms) results in population-weighted average resonance frequencies, and intermediate exchange leads to characteristic resonance lineshapes. The distinction between slow and fast exchange depends on the difference in the resonance frequencies of the individual states and the relative populations; e.g., for a two-state system with 1 H chemical shift differences between 0.1 and 1 ppm at 800 MHz, intermediate exchange corresponds to rates from ca. 10 to 250,000 s -1 . Chemical shift refocusing experiments like Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion and T1rho relaxation experiments, and saturation transfer experiments (e.g., chemical exchange by saturation transfer, CEST), can provide quantitative information about conformational exchange on the intermediate or slow chemical shift timescale and can be used to characterize sparsely-populated states that cannot otherwise be observed in NMR spectra . NOESY and residual dipolar coupling (RDC) data can reveal multiple conformations in fast dynamic equilibrium, and may provide structural restraints for modeling each state . Paramagnetic effects in metal-containing biomolecules provide ensemble-averaged distance restraints and can also determine ensemble-averaged relative orientations of structural domains . In many cases, the structures of the conformations in dynamic exchange are modeled by fitting back-calculated NMR parameters (e.g., chemical shifts) to ensemble-averaged NMR data.