Possible HIS inconsistency in Gromacs CpHMD example

User discussions
1

GROMACS version: Gromacs 2021.b constantph
GROMACS modification: No

Hi there,

For the constantph implementation of titratable His (HSPT), Fig.2 in the JCTC paper (DOI: /10.1021/acs.jctc.2c00516) suggests that state 1 is HSP, state 2 is HSD and state 3 is HSE. But if we look at the example given in with the code:

https://gitlab.com/gromacs-constantph/tutorials/-/blob/main/2_1CVO_titration/tutorial_files/input_files/md_cph.mdp ,

the partial charges (lambda-dynamics-group-type3-state-2-charges and …state-3-charges) seem to be exchanged, with charges for state 2 corresponding to HSE, and vice-versa. The same is also seen in other examples deposited in Zenodo.

Can you please clear this out for me? And what about the dvdl-coefficients shown there for states 2 and 3, are they correct (state-2 is HSD and state 3 is HSE)?

Cheers,

Guilherme