Table 1.

Three-state equilibrium parameters from global fit of the GuHCl-induced unfolding transition of Fe²⁺ cyt c in the presence of 1 atm CO (pH 7, 20 °C).¹

	Cm (M)	m (kcal mol−1 M−1)	ΔG (kcal mol−1)	ΔGNU (kcal mol−1)
N ⬄ M-CO	2.487 ± 0.004	1.604 ± 0.015	3.99 ± 0.04	15.3 ± 0.3
M-CO ⬄ U-CO	3.559 ± 0.003	3.179 ± 0.047	11.3 ± 0.2

¹Equilibrium parameters were obtained by global fitting of heme absorbance data in the Soret region (380–430 nm), the visible bands at 520 and 550 nm, and the far-UV CD signal at 225 nm. Fitting also yielded the following spectroscopic properties for the M-CO intermediate: a Soret band at 413.5 nm with ε(413.5 nm) = 239 mM⁻¹ cm⁻¹; a visible band at ε(550 nm) = 24.4 mM⁻¹ cm⁻¹ (87% of the native 550 nm band); relative ellipticity at 225 nm of 0.2 (80% of native far-UV CD signal).