Fig. 2.
(a) Three parallel routes leading to the dimer R2 starting from an ensemble of denatured states. The symbols ŨA and ŨB denote collapsed denatured states of chains A and B, respectively. In pathway I both chains fold to the native conformation and subsequently dimerize, whereas in pathway II only one of the chains folds. In both these pathways dimerization is preceded by substantial unfolding of the folded chains. Kinetically, the most assembly occurs when R2 is formed directly from ŨA and ŨB. The time for forming ŨA from U, namely τD, is much less than τF, that is, τT/τF ≫ 1. The flux of molecules φi (i = 1, 2, and 3) through the pathways depends on temperature. At T = TF the values are φ1 = 36% (58%), φ2 = 40% (23%), φ3 = 24% (19%), where the numbers in parenthesis are for T = TH. Also, at T = TF the average conversion times are τCI ∼ 30 τF, while τCIII ⋍ 2 τF and at T = TH τCI ∼ 10 τF and τCIII ⋍F, where τF is the monomeric folding time. (b) The two pathways in the templated assembly (TA) of Rn−1 + U → Rn (n ≥ 3). Because N has to unfold prior to assembly, the conversion time along pathway I is greater than along pathway II. Just as in (a), the amplitudes of the fast and slow pathways depend on T . At T = TH, they are 75% (for I) and 25% (for II). The average conversion time for pathway I is ∼100 τF, while for II it is τCII ∼ τF.