Hi dear all: I'm trying to obtain the deltaH (enthalpy = potential energy + pV) in a given molecular process, so for that I'm drawing the enthalpy values of my systems (a small protein conveniently solvated and neutralized) from using gmx_energy on the .edr files.
Then, my questions and reflexions are: Are the enthalpy or energy values I'm here obtaining actually reliable in terms of experimental real values taking into account I'm using the pretty rigorous CHARMM27 force field?? My doubts here come up given that I'm obtaining values for my systems in a 10 to the 6 kJ/mol order (e.g -1 155 621 kJ/mol), which seems to me excessively high. I know, of course, these enthalpy or energy values strongly depend on the amount of solvent you have in your system, and I have done some tests in order to verify how is the variation of these energies in relation with the number of water molecules solvating my protein. But, what I wouldn't expect here is that such energy and enthalpy values were varied in about a 10 to 4 or 10 to the 5 order in simulation replicas carried out on my solvated protein. See the following data: replica Ave Enthalpy (kJ/mol) 1 -1161980 2 -1142910 3 -1217530 Believe you that these significant changes are a normal variation of these energies in my simulations taking into account the system is exactly the same (just gen_seed in the velocity options was different)?? Any suggestion to obtain reliable enthalpy values in the event the results I'm getting are really senseless??? Thanks a lot. Juan José Galano Frutos Department of Biochemistry and Molecular and Cellular Biology, Faculty of Sciences, University of Zaragoza Pedro Cerbuna # 12, 50009 Zaragoza (Spain) +34 976 76 28 06 Institute for Biocomputation and Physics of Complex Systems (BIFI) Mariano Esquillor, Edificio I + D - 50018 Zaragoza (Spain) -- Gromacs Users mailing list * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/GMX-Users_List before posting! * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists * For (un)subscribe requests visit https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-users or send a mail to gmx-users-requ...@gromacs.org.