Consider a mechanism for the helix-coil transition in which nucleation occurs in the middle of the chain:

We saw in Impact 122.1 that this type of nucleation is relatively slow, so neither step may be rate-determining.
(a) Set up the rate equations for this mechanism.
(b) Apply the steady-state approximation and show that, under these circumstances, the mechanism is equivalent to hhhh ... cece ....
(c) Use your knowledge of experimental techniques and your results from parts (a) and (b) to support or refute the following statement: It is very difficult to obtain experimental evidence for intermediates in protein folding by performing simple rate measurements and one must resort to special flow, relaxation, or trapping techniques to detect intermediates directly.

hhhh... hchh... hchh... cccc...