2.3. MMPBSA Binding Free Energy

The molecular mechanics Poisson–Boltzmann surface area (MMPBSA) method was utilized to determine the binding affinity of FmtA–drug(s) complexes.⁴⁵⁻⁴⁷ Here, a total of 2000 snapshots from the last 20 ns of molecular dynamics were utilized to calculate the binding energy of FmtA–gemifloxacin, FmtA–paromomycin, FmtA–streptomycin, and FmtA–tobramycin complexes.⁴⁸ The per residue decomposition analysis was performed to calculate the binding energy contribution of active site residues with the ligand in FmtA–drug(s) complexes.^49,50