Calculating relative free energy of binding, ΔΔGbind from 100ns Simulation of 2 proteins

Hi,

I have ran several simulations between large proteins and would like to calculate the relative free energy of binding (ΔΔGbind). I usually use MMPBSA for shorter simulations, but now when I try that for these larger ones, there is a RAM issue on my computer. Is there a way using GROMACS to calculate that as well as the contributions of specific amino acids?

I see on the GROMACS tutorial the LJ and Coul energies are mentioned. Are those of use for me?

I would greatly appreciate any help.

Thank you in advance,
Isaac