Structural analysis of non-native states of proteins by NMR methods.

Established NMR methods are increasingly being applied to the non-native states of proteins. For small denatured proteins, full assignment of proton, 15N and 13C resonances is often straightforward. Sensitive methods exist for detecting fractionally populated alpha helices and beta strands, but defining transient interactions among side chains is proving more problematic. The non-native states of several small proteins are being intensively investigated to address a number of questions about protein folding.