Fig. 1.
A molecular toolbox for determining the role of osmolyte molecules in the unfolding transition state of a protein. Using an array of osmolytes of varying size and hydrogen bonding abilities, we test the importance of solvent bridging in the I27 protein. Force-clamp protein unfolding traces for the (I27)8 polyprotein at a constant force of 180 pN in (A) water and a range of osmolyte solutions at a concentration of 1M (B) ethylene glycol, (C) propylene glycol, (D) glycerol, (E) sorbitol, and (F) sucrose. Each unfolding trace shows the characteristic staircase of unfolding events, with each step of 24 nm corresponding to the unfolding of one I27 module of the polyprotein.