Fig. 3.

Kinetics of R1617 wild-type and mutants. The data shown in red represent the folding and unfolding of the R16 domain in R1617, and the data shown in cyan represent the folding and unfolding data for the R17 domain in R1617. The data shown in filled symbols were determined by using single-jump stopped flow measurements. The data shown in open circles could only be observed in double-jump, interrupted unfolding experiments. (a) The kinetics of R1617 wild-type (data taken from ref. 6 where details of the full assignment of the kinetic phases can also be found). (b) The kinetics of R1617 S20A. As for wild-type at [urea] below ≈6 M, only a single unfolding phase can be detected. (c) The kinetics of R1617 L203A. Two unfolding phases are observed at all [urea]. Note that the rollover in the folding kinetics of R1617 reflects dead-time formation of a collapsed intermediate, which is marginally stable, has little secondary structure, and is not populated at equilibrium (6).