QM/MM biding free energy

From: Mi Yang (drmiyang2019_at_gmail.com)
Date: Sun Oct 03 2021 - 09:58:44 CDT

Dear Colleagues,
 we want to calculate binding free energy of Ligand-Protein complex. After
completing QM/MM run we got following energies for complex:
----------here Ligand_at_B3LYP/6-31G* and protein_at_UFF=qeq -------------
UFF calculation of energy.
 Energy= 0.453152500 NIter= 0.
 Dipole moment= -1.265215 2.913698 -3.244704
 ONIOM: saving gridpoint 1
 ONIOM: restoring gridpoint 3
 ONIOM: calculating energy.
 ONIOM: gridpoint 1 method: low system: model energy:
 ONIOM: gridpoint 2 method: high system: model energy:
 ONIOM: gridpoint 3 method: low system: real energy:
 ONIOM: extrapolated energy = -1550.652022506156
 ONIOM: calculating electric field derivatives.
 ONIOM: Integrating ONIOM file 4 number 619
 ONIOM: Dipole = 3.51466451D+00 7.85225957D+00 6.59929946D+00
 ONIOM: Dipole moment (Debye):
    X= 8.9334 Y= 19.9585 Z= 16.7737 Tot= 27.5591
My question is how to get binding free energy from these values? or is
there need to run ligand and protein separately on QM and MM levels also as
in complex?
Any information on working equations for QM?MM binding free energy
calculation will be greatly appreciated!!


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