Table S2.

Fitting parameters for unfolding rates of titin I27 domain as a function of guanidinium chloride concentration for a set of single-residue mutants and WT (8)

Name	$k_L^{{\text{H}}_2\text{O}}$	$k_H^{{\text{H}}_2\text{O}}$	$m_L$	$m_H$	$k^{H_{2}O}$	$m^{‡}$	$P_2/P_1$
A75G	6.3	4.7	0.28	1.35	2.2	0.54	$\sim {10}^{12}$
C47A	21.4	2.9	0.21	1.38	16.3	0.29	$\sim {10}^{19}$
F21L	14.8	0.005	0.41	2.40	6.6	0.58	$\sim {10}^{40}$
G32A	6.0	0.3	0.38	1.91	2.3	0.63	$\sim {10}^{42}$
I23A	3.2	4.3	0.26	1.36	0.8	0.64	$\sim {10}^{67}$
I49V	14.4	26.1	0.44	1.31	9.4	0.57	$\sim {10}^8$
L36A	44.4	6.0	0.33	1.60	25.0	0.49	$\sim {10}^{39}$
L58A	9.6	4.3	0.28	1.35	4.9	0.45	$\sim {10}^8$
L60A	43.8	4.1	0.29	1.58	26.0	0.43	$\sim {10}^{23}$
L8A	23.2	235.2	0.44	1.19	11.6	0.68	$\sim {10}^{14}$
V30A	9.0	4.3	0.30	1.35	4.4	0.47	$\sim {10}^6$
V71A	7.3	2.5	0.29	1.33	3.7	0.44	$\sim {10}^{0.7}$
WT	5.8	0.6	0.25	1.36	4.6	0.31	$\sim {10}^6$
Units	${10}^{-4}{\text{s}}^{-1}$	${10}^{-7}{\text{s}}^{-1}$	mol/L−1	mol/L−1	${10}^{-4}{\text{s}}^{-1}$	mol/L−1

Two types of fits were made: exponential fits $k_u=k^{{\text{H}}_2\text{O}}\exp \left(m^{‡}\left[C\right]\right)$ and double exponential fits $k_u=k_L^{{\text{H}}_2\text{O}}\exp \left(m_L\left[C\right]\right)+k_H^{{\text{H}}_2\text{O}}\exp \left(m_H\left[C\right]\right)$. $P_2/P_1$ shows relative likelihood of the double-exponential model with respect to the single-exponential model, as assessed by Akaike information criterion.