Relation Between Binding Affinity And Free Energy

Binding affinity and free energy are related by the following equation,

ΔG = - RTLnKa

ΔG = RTLnKd

R = 8.3145 J/mol x K (Ideal gas constant)

at 298 K,

Kd Ka ΔG (kJ/mol) ΔG (kcal/mol)
100 mM 10 -5.7 -1.36
10 mM 100 -11.4 -2.73
1 mM 1,000 -17.1 -4.09
100 μM 10,000 -22.8 -5.45
10 μM 100,000 -28.5 -6.82
1 μM 1,000,000 -34.2 -8.18
100 nM 10,000,000 -39.9 -9.54
10 nM 100,000,000 -45.6 -10.91
1 nM 1,000,000,000 -51.3 -12.27
100 pM 10,000,000,000 -57.1 -13.64
10 pM 100,000,000,000 -62.8 -15.00
1 pM 1,000,000,000,000 -68.5 -16.36
100 fM 10,000,000,000,000 -74.2 -17.73
10 fM 100,000,000,000,000 -79.9 -19.09
1 fM 1,000,000,000,000,000 -85.6 -20.45
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