Quantitative description of how proteins fold under experimental conditions remains a challenging problem. Experiments often use urea and guanidinium chloride to study folding whereas the natural variable in simulations is temperature. To bridge the gap, we use the molecular transfer model that combines measured denaturant-dependent transfer free energies for the peptide group and amino acid residues, and a coarse-grained C α -side chain model for polypeptide chains to simulate the folding of src SH 3 domain. Stability of the native state decreases linearly as ½C (the concentration of guanidinium chloride) increases with the slope, m, that is in excellent agreement with experiments. Remarkably, the calculated folding rate at ½C ¼0 is only 16-fold larger than the measured value. Most importantly ln k obs (k obs is the sum of folding and unfolding rates) as a function of ½C has the characteristic V (chevron) shape. In every folding trajectory, the times for reaching the native state, interactions stabilizing all the substructures, and global collapse coincide. The value of m f m (m f is the slope of the folding arm of the chevron plot) is identical to the fraction of buried solvent accessible surface area in the structures of the transition state ensemble. In the dominant transition state, which does not vary significantly at low ½C , the core of the protein and certain loops are structured. Besides solving the long-standing problem of computing the chevron plot, our work lays the foundation for incorporating denaturant effects in a physically transparent manner either in all-atom or coarse-grained simulations.kinetic cooperativity | self-organized polymer model | pathway diversity | protein denaturation U nderstanding how proteins fold in quantitative molecular detail can provide insights into protein aggregation and dynamics of formation of multisubunit complexes. As a result there have been intense efforts in deciphering the folding mechanisms of proteins using a variety of experiments (1-6), theories (7-13), and simulations (14-16). Despite these advances, a number of issues such as the denaturant-dependent characteristics of the unfolded states and the link between protein collapse and folding remain unclear (17-21). Single molecule experiments have provided clear evidence for folding pathway diversity, and have shown that polypeptide chains undergo almost continuous collapse as the denaturant concentration (½C ) is decreased (1,(19)(20)(21). These and other experiments (5, 22) raise the need for computational models whose predictions can be directly compared to experiments, which often use denaturants [guanidinium chloride (GdmCl) and urea] to initiate folding and unfolding.Global thermodynamic and kinetic behavior of small proteins often exhibit two-state behavior (23), which implies that at all values of ½C only the population of native (N) and the unfolded (U) states are detectable. Experimentally two-state behavior is characterized by (i) the free energy of stability, ΔG NU ð½C Þ ð¼ G N ð½C Þ − G U ð½C ...