4.1.1.48	urea	the structure of partially folded states of the enzyme is assessed by hydrogen exchange mass spectrometry and Gö model simulations. HX-MS analysis of the peptic peptides derived from the pulse-labeled product of the submillisecond folding reaction from the urea-denatured state reveal strong protection in the (betaalpha)4 region, modest protection in the neighboring (betaalpha)1–3 and (betaalpha)5beta6 segments and no significant protection in the remaining N and C-terminal segments. The results demonstrate that this species is not a collapsed form of the unfolded state under native-favoring conditions nor is it the native state formed via fast-track folding	681463