I have a simulated trajectory in GROMACS of lipid, protein, and explicit water. I only have the .xtc output and the .tpr input for the production run. I want to calculate the energy of the lipid bilayer over time. I've used gmx -select to specify the lipid groups from the .tpr file and the .xtc file (using convert-tpr and trjconv). I then performed a -rerun to obtain an .edr file. From there, I calculated the energies as usual. The energy profile is what I expected from the this system.

Is mine a reasonable approach, since it uses all the available information about lipid molecule positions and velocities? Or will it somehow leave out interaction terms between the lipid and protein/water molecules since those weren't included in the -rerun?

Thank you in advance!