Model for Transient Interactions

For unfolded and partly folded states, the spin label reports on parts of the polypeptide chain that are in transient contact with the segment bearing the spin label. The extent of relaxation enhancement (line broadening) depends on both the distance to the paramagnetic spin label and the lifetime of the interaction. When the chain conformers rapidly interconvert, as is the case 

The most highly populated macrostates in the pH 2.3 ensemble in the absence of urea include, as expected, the species with no association (A-B-C-G-H). What is perhaps more surprising is that this completely unfolded substate is a minority (30%) most ensemble members have one or more long-range interaction. The most populated (17-40% population) interactions involve 

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