NMR Ensembles of Models

When a macromolecular structure is determined by nuclear magnetic resonance (NMR) in solution, the result is an ensemble of models, each of which is consistent with the experimental data. This is in contrast to the result of an X-ray crystallographic experiment, which is a single model which best fits the empirical electron density. (In some cases where the resolution is very high, the model may include alternative positions for some atoms.)