Table 1.

Folding kinetics and fitting statistics at moderate stability

Conditions		Single-exponential model				Stretched-exponential model
Temperature, °C	ΔGu, kcal/mol	kobs, s−1	Correlation coefficient, r2	Residuals		Heterogeneity, h	Correlation coefficient, r2	Residuals
				Mean amplitude, %	Serial correlation, r2			Mean amplitude, %	Serial correlation, r2
37	3.8	63.0  ± 2.0	0.996	1.6	0.003	0.98  ± 0.08	0.996	1.6	0.07
25	4.5	36.4  ± 2.2	0.996	1.0	0.001	1.07  ± 0.08	0.992	1.0	0.02
5.0	5.5	6.6  ± 0.4	0.941	3.6	0.0003	1.07  ± 0.17	0.942	3.6	0.0001
−3.5	6.7	1.3  ± 0.2	0.992	1.2	0.001	1.06  ± 0.08	0.992	1.1	0.001
−15	>9.1*	62.0  ± 3.4†	0.996	1.4	0.597	0.84  ± 0.06‡	0.997	1.2	0.481

^*Technical difficulties preclude the determination of stability under these conditions. Shown stability estimated from extrapolations of stability at higher temperatures. 

^† Rapid folding (despite low temperatures and high viscosity) because of significantly enhanced stability in the presence of ethylene glycol (data not shown). 

^‡ Heterogeneity factors <1 are unrelated to glassy kinetics and apparently arise because of a small linear instrument drift. Fitting these data to a stretched-exponential model with a linear baseline predicts a heterogeneity factor of 1.04 ± 0.07 (see Results).