My MMPBSA input file worked well with protein-ligand system but fail to work with protein-nucleic acid system. The input file is as follows:

/

&pb

istrng=0.100,

/

I have made a subtle changes and it worked well but the delta G values of PBSA are positive even though the delta G value of GBSA is negative. The input file is as follows:

/

&pb

istrng=0.100, radiopt=0

/

Any suggestions/comments to fix the issue are highly appreciated.