Table 1.

Thermodynamic parameters for unfolding of free Ub, free Bn, and the Bn domain of BU. Bn and BU parameters are determined from multi-wavelength fits of fluorescence data. Ub parameters are obtained from fitting CD ellipticity at 230 nm. Sample conditions are 1–2 μM protein, 10 mM sodium acetate (pH 5.0), 0.1 M NaCl, 10 °C. Reported values are the averages of three measurements. Standard deviations are typically ± 0.2–0.4 kcal·mol⁻¹ (ΔG_app^H2O), ± 0.1–0.3 kcal·mol⁻¹·M⁻¹ (m_app), ± 0.01–0.02 M (C_m).

Protein	Variant	ΔGappH2O (kcal·mol−1)	mapp (kcal·mol−1·M−1)	Cm (M)
Ub	WT	6.9	1.9	3.63
Ub	R42E	7.2	1.8	4.00
Ub	K29Q	6.7	1.8	3.72
Ub	K29N	5.7	1.9	3.00
Ub	V26A	4.4	2.1	2.10
Ub	V26G	1.8	2.5	0.72
Bn	WT	11.8	4.6	2.58
Bn	I96V	8.9	3.8	2.38
Bn	I96A	8.7	4.5	1.96
BU	WT	3.8	4.3	0.87
BU	R42E	3.7	4.2	0.87
BU	K29Q	3.6	4.0	0.90
BU	K29N	4.0	3.8	1.04
BU	V26A	7.3	4.6	1.57
BU	V26G	7.5	4.8	1.56
BU	I96V	n.d.a	n.d.	0.72b
BU	I96A	n.d.	n.d.	0.35b

^aNot determined due to insufficient native baseline.

^bObtained from constrained fits of F_max values (see text).