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

**URL:** <https://gromacs.bioexcel.eu/t/calculating-relative-free-energy-of-binding-gbind-from-100ns-simulation-of-2-proteins/10547>\
**Category:** User discussions\
**Created:** [November 14, 2024, 2:06am UTC](https://gromacs.bioexcel.eu/t/calculating-relative-free-energy-of-binding-gbind-from-100ns-simulation-of-2-proteins/10547 "2024-11-14T02:06:18Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![isilver](https://avatars.discourse-cdn.com/v4/letter/i/13edae/32.png) [@isilver](https://gromacs.bioexcel.eu/u/isilver)\
**Post date:** [November 14, 2024, 2:06am UTC](https://gromacs.bioexcel.eu/t/calculating-relative-free-energy-of-binding-gbind-from-100ns-simulation-of-2-proteins/10547/1 "2024-11-14T02:06:18Z")

</div>

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