Table 1. The description of the models and the corresponding parameters implemented in CalFitter.

Model	Description	Model parametersa	Data sets
1 step
N −> D	A fully irreversible transition	T f, Ea, ΔH‡, ΔCp	All
N = D	A fully reversible transition with equilibrium	T m, ΔH, ΔCp	Calorimetry & spectroscopy
N = D (Van’t Hoff's)	A fully reversible transition with equilibrium and van’t Hoff's enthalpy	T m, ΔH, ΔHvh, ΔCp	Calorimetry & spectroscopy
N < = > D	A general transition with forward and reverse components	T fwd, Efwd, Trev, Erev, ΔCp	All
2 steps
N −> I −> D	A fully irreversible transition	Step 1: Tf, Ea, ΔH‡, ΔCp
		Step 2: Tf, Ea, ΔH‡, ΔCp	All
N = I −> D	A transition with a reversible step in equilibrium and an irreversible step	Step 1: Tm, ΔH, ΔCp Step 2: Tf, Ea, ΔH‡, ΔCp	Calorimetry & spectroscopy
N < = > I −> D	A general Lumry-Eyring model	Step 1: Tfwd, Efwd, Trev, Erev, ΔCp Step 2: Tf, Ea, ΔH‡, ΔCp	All
N = I = D	A fully reversible transition	Step 1: Tm, ΔH, ΔCp Step 2: Tm, ΔH, ΔCp	Calorimetry & spectroscopy
3 steps
N −> I1 −> I2 −> D	A fully irreversible transition	Step 1: Tf, Ea, ΔH‡, ΔCp	All
		Step 2: Tf, Ea, ΔH‡, ΔCp
		Step 3: Tf, Ea, ΔH‡, ΔCp
N = I1 −> I2 −> D	A transition with the reversible first step in equilibrium	Step 1: Tm, ΔH, ΔCp	Calorimetry & spectroscopy
	and the irreversible second and third steps	Step 2: Tf, Ea, ΔH‡, ΔCp
		Step 3: Tf, Ea, ΔH‡, ΔCp
N < = > I1 −> I2 −> D	A general Lumry-Eyring model with two intermediates	Step 1: Tfwd, Efwd, Trev, Erev, ΔCp	All
		Step 2: Tf, Ea, ΔH‡, ΔCp
		Step 3: Tf, Ea, ΔH‡, ΔCp
N = I1 = I2 −> D	A transition with two reversible steps in equilibrium	Step 1: Tm, ΔH, ΔCp	Calorimetry & spectroscopy
	and an irreversible step	Step 2: Tm, ΔH, ΔCp
		Step 3: Tf, Ea, ΔH‡, ΔCp
4 steps
N −> I1 −> D	A two-branch irreversible unfolding pathway	Step 1: Tf, Ea, ΔH‡, ΔCp	All
N −> I2 −> D		Step 2: Tf, Ea, ΔH‡, ΔCp
		Step 3: Tf, Ea, ΔH‡, ΔCp
		Step 4: Tf, Ea, ΔH‡, ΔCp

^a T _m – the melting temperature, T_f – the reference temperature of an irreversible step at which the corresponding rate is 1 (fwd. – forward rates; rev. – reverse rates), ΔH – the enthalpy change (at T_m if ΔC_p is nonzero; vh – van’t Hoff's); ΔH^‡– the activation enthalpy change (at T_f or T_m for irreversible and general steps, respectively, if ΔC_p is nonzero); E_a – the activation energy; ΔC_p – the heat capacity change. Since T-jumps are based on the relaxation kinetics, they cannot be simulated by the models with reversible steps assumed in equilibrium.