Table 3.

Thermodynamic parameters measured using isothermal titration calorimetry.

A. Binding enthalpy of FPs to POPC:POPG:Chol = 60:20:20 SUVs at 37 °C at 1 mM Ca2+ and at pH 5, obtained by titrating the FP into SUVs. The average and standard deviations were calculated from three repeats.
Peptide	ΔH (kCal/mol) In 1 mM Ca2+	ΔH (kCal/mol) In 1 mM EGTA	Difference ΔΔH (kCal/mol)
SARS-2 FP	− 37.9 ± 0.4	–32.3 ± 0.5	5.6
SARS-1 FP	− 34.8 ± 0.4	−31.8 ± 0.3	3.0
MERS FP	− 26.4 ± 0.6	−24.4 ± 0.4	2.0

B. Interaction between Ca2+ cations and the FPs measured at 37 °C, obtained by titration the Ca2+ into FP in solution. ΔH (reaction enthalpy), Kb (binding constant), and n (stoichiometry) were calculated from the fitting using the one-site model. The average and standard deviations were calculated from three repeats.
Peptides	ΔH (kCal/mol)	Kb (×104 M−1)	N	ΔG (kCal/mol)	-TΔS (kCal/mol)
SARS-2	7.2 ± 0.4	2.7 ± 0.2	1.86 ± 0.06	6.3	−0.9
SARS-2 _E4A_D5A_D15A	5.5 ± 0.5	1.0 ± 0.2	1.03 ± 0.06	5.6	0.1
SARS-1	6.8 ± 0.5	2.5 ± 0.3	1.70 ± 0.04	6.2	−0.5
MERS	3.1 ± 0.4	1.1 ± 0.2	1.12 ± 0.08	5.6	2.5