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How Autodock 4 converts binding energy (kcal/mol) into Ki

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This FAQ applies to: AutoDock 4

Shows formula Autodock is using to convert binding energy into Ki.
This is taken from printEnergies.cc that is distributed with AutoDock source code:

    // equilibrium:   E  +  I  <=>    EI
    // binding:       E  +  I   ->    EI         K(binding),      Kb
    // dissociation:     EI     ->  E  +  I      K(dissociation), Kd
    //
    //                            1
    //         K(binding) = ---------------
    //                      K(dissociation)
    // so:
    //      ln K(binding) = -ln K(dissociation)
    //              ln Kb = -ln Kd
    // Ki = dissociation constant of the enzyme-inhibitor complex = Kd
    //      [E][I]
    // Ki = ------
    //       [EI]
    // so:
    //              ln Kb = -ln Ki
    // deltaG(binding)    = -R*T*ln Kb
    // deltaG(inhibition) =  R*T*ln Ki
    //
    // Binding and Inhibition occur in opposite directions, so we
    // lose the minus-sign:  deltaG = R*T*lnKi,  _not_ -R*T*lnKi
    // => deltaG/(R*T) = lnKi
    // => Ki = exp(deltaG/(R*T))


See also: ADL: calculation of Ki in Autodock 4
by Sargis Dallakyan last modified 2010-08-25 11:42

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