I carried out MMPBSA calculation using gmx MMPBSA module and allowed for entropy calculation through mmbsa.in the parameter file. it yielded two values

1- interaction entropy approximation

2-c2 entropy approximation

my assumption that the first vale is the entropy of the interaction whole the second value is the binding free energy of the system and interaction entropy is subtracted from it.

its worth noting that one my ligands showed negative interaction entropy does, should this implicate high flexibility of ligand?