Identification and characterization of protein folding intermediates

In order to understand the mechanism by which a polypeptide chain folds into its functionally active native state it is necessary to characterize in detail all the species accumulated along the pathway. The elusive nature of protein folding intermediates poses their identification and characterization as an extremely difficult task in the protein folding field. In the case of small single domain proteins, the direct measurement of the thermodynamics and structural parameters of protein folding intermediates has provided new insights on the nature of the forces involved in the stabilization of nascent protein structures. Here we summarize some of the experimental approaches aimed at the detection and characterization of folding intermediates along with a discussion of some general structural features emerging from these studies.