Table 1. Thermodynamic Parameters of the First and Second Binding Processes Obtained by Fitting the TSIS Model to the Binding Isotherm of the NaPSS-to-BSA and BSA-to-NaPSS Titration^a.

	I. binding process		II. binding process
order of mixing	Kb,1 × 10–7	ΔGb,1⊖ [kJ/mol]	Kb,2 × 10–7	ΔGb,2⊖ [kJ/mol]	n2	ΔHb,2⊖ [kJ/mol]	TΔSb,2⊖ [kJ/mol]
NaPSS-to-BSA	4 ± 1	–43.4 ± 0.6	2 ± 1	–42 ± 2	0.12 ± 0.02	(−4 ± 2) × 102	(−4 ± 2) × 102
BSA-to-NaPSS	9 ± 4	–45 ± 1	0.13 ± 0.01	–34.9 ± 0.2	3.68 ± 0.06	–43.7 ± 0.6	–8.8 ± 0.7

^aAll solutions were prepared in the phosphate buffer (I_total = 20 mM, pH = 8.0). Data were collected at T = 25 °C. Apparent binding constants of the first and second binding processes (K_b,1, K_b,2), binding stoichiometry (n₂), and change in the standard binding enthalpy (ΔH_b,2^⊖) of the second binding process are fitting parameters, while the corresponding binding free energy changes (ΔG_b,1, ΔG_b,2^⊖) and change in standard entropy (TΔS_b,2) were calculated via eqs 4 and 5, respectively.