Table 2.
Thermodynamic parameters of Aβ42 binding to different conformations of Na,K-ATPase at 25 °C.
| Na,K-ATPase State a | Ka,b M−1 |
Kd c µM |
∆H d kcal/mol | T∆S e kcal/mol |
∆G f kcal/mol |
|---|---|---|---|---|---|
| E1/E2 | 7.7 × 105 | 1.3 | −2.54 | 5.48 | −8.02 |
| E1 | 3.7 × 105 | 2.7 | −1.54 | 6.02 | −7.56 |
| E2 | 4.9 × 105 | 2.0 | −2.21 | 5.55 | −7.76 |
| E2P | 5.1 × 105 | 2.0 | −1.59 | 6.19 | −7.78 |
| OBN | 8.3 × 105 | 1.2 | −1.21 | 6.87 | −8.08 |
a The measurements of Aβ42 binding to Na,K-ATPase in different states were performed in the four different solutions: E1/E2 state: 10 mM imidazole, 0.1 mM DTT, 130 mM NaCl, 20 mM KCl, 3 mM MgCl2, pH 7.5; E1 state: 10 mM imidazole, 1 mM EDTA, 3 mM NaCl, 0.1 mM DTT, pH 7.5; E2 state: 10 mM imidazole, 1 mM EDTA, 3 mM KCl, 0,1 mM DTT, pH 7,5; E2P state: 10 mM imidazole, 1 mM EDTA, 3 mM MgCl2, 3 mMTris/Pi, 0.1 mM DTT, pH 7.5; OBN state: 26 µM ouabain, 10 mM imidazole, 1 mM EDTA, 3 mM MgCl2, 3 mMTris/Pi, 0.1 mM DTT, pH 7.5. All measurements were performed three to four times at 25 °C. b Ka—affinity constant; standard deviation did not exceed ±20%. c Kd—dissociation constant; calculated as 1/Ka. d ∆H—enthalpy variation; standard deviation did not exceed ±10%. e T∆S—entropy variation; calculated from the equation ∆G = ∆H − T∆S. f ∆G—Gibbs energy; calculated from the equation ∆G = −RTlnKa.