Table 1.

Melting temperatures and thermodynamic parameters for urea-induced unfolding equilibrium of FXN wild type and variants measured by far-UV CD and fluorescence spectroscopy

Protein Variant	aTm (°C)	b ΔGH2O (kcal/mol)		b m (kcal/mol•M)		c [Urea]0.5 (M)
		CD ([Θ]222)	Fluorescence ( $\overline{\lambda }$)	CD ([Θ]222)	Fluorescence ( $\overline{\lambda }$)	CD ([Θ]222)	Fluorescence ( $\overline{\lambda }$)
Wild type	71.0	9.23 ± 0.47	9.77 ± 0.40	1.88 ± 0.10	2.00 ± 0.08	4.91	4.87
p.D104G	74.0	9.44 ± 0.46	10.39 ± 0.31	1.82 ± 0.09	1.99 ± 0.06	5.20	5.22
p.A107V	68.0	10.03 ± 0.91	9.06 ± 0.22	2.13 ± 0.19	1.95 ± 0.05	4.71	4.64
p.F109L	59.6	7.14 ± 0.34	6.18 ± 0.16	2.09 ± 0.10	1.85 ± 0.05	3.42	3.34
p.Y123S	56.6	4.31 ± 0.18	4.48 ± 0.18	1.60 ± 0.06	1.59 ± 0.06	2.69	2.84
p.S161I	60.0	5.88 ± 0.58	6.95 ± 0.24	1.88 ± 0.19	2.11 ± 0.07	3.12	3.30
p.S181F	59.9	6.12 ± 0.27	6.86 ± 0.33	1.84 ± 0.08	1.99 ± 0.09	3.32	3.45
p.S202F	70.7	9.07 ±0.32	9.60 ±0.33	1.89 ± 0.07	2.18 ± 0.07	4.78	4.40

^aT_m values were calculated by taking the first derivative of the ellipticity at 222 nm with respect to temperature, as described in the text. Urea-induced unfolding equilibrium data were obtained by monitoring the ellipticity at 222 nm ([Θ₂₂₂]) and fluorescence intensity averaged emission wavelength ($\overline{\text{λ}}$), as described in Materials and Methods.

^bΔG^H₂^O and m values were obtained from Eq (2);

^c[Urea]_0.5 was calculated from Eq (4). Data are reported as the mean ± SE of the fit.