I need parameters for (Dimethylsulfoniopropionate) DMSP which is not available within CGenFF (when submitted to Cgenff parmchk, I received atom type error). However, I found that in another discussion, S-Adenosyl-L-methionine / SAM co-factor to have parameters for positively charged sulfur (https://www.charmm.org/ubbthreads/ubbthreads.php?ubb=showflat&Number=35309). If I define atom types of sulfur as of this paper and use it to model DMSP and its derivatives, is there any way I can validate my parameters?. Since these parameters are not in CGenFF, I don't know how to get penalties for analog parameters as well. And enthalpy of vap is not available for DMSP for a quick validation as well.
Any help/guidance with this is greatly appreciated.
Thank you,