[gmx-users] charges in dppc.itp

[Yulia Smolinsky]

Dear all gmx-users,

It's a shame to me, but I did not understand why are such atomic charges in topology file for dppc from Tieleman website (dppc.itp)?
For example, why is a charge of nitrogen negatively?

[ atoms ]

;   nr    type   resnr  residu    atom    cgnr        charge          mass

     1     LC3       1    DPPC      C1       0         0.4000   15.0350 ; qtot:0.36    

     2     LC3       1    DPPC      C2       0         0.4000   15.0350 ; qtot:0.72 

     3     LC3       1    DPPC      C3       0         0.4000   15.0350 ; qtot:1.08 

     4     LNL       1    DPPC      N4       0        -0.5000   14.0067 ; qtot:0.76 

     5     LH2       1    DPPC      C5       0         0.3000   14.0270 ; qtot:1.0 

     6     LC2       1    DPPC      C6       1         0.4000   14.0270 ; qtot:1.0 

     7     LOS       1    DPPC      O7       1        -0.800   15.9994 ; qtot:0.54 

     8     LP        1    DPPC      P8       1         1.700   30.9738 ; qtot:2.3 

     9     LOM       1    DPPC      O9       1        -0.800   15.9994 ; qtot:1.5 

    10     LOM       1    DPPC     O10       1        -0.800   15.9994 ; qtot:0.7 

    11     LOS       1    DPPC     O11       1        -0.700   15.9994 ; qtot:0 

    12     LC2       1    DPPC     C12       2         0.400   14.0270 ; qtot:0.08 

    13     LH1       1    DPPC     C13       2         0.300   13.0190 ; qtot:0.52 

    14     LOS       1    DPPC     O14       2        -0.700   15.9994 ; qtot:-0.14 

    15      LC       1    DPPC     C15       2         0.7000   12.0110 ; qtot:0.56 

    16      LO       1    DPPC     O16       2        -0.700   15.9994 ; qtot:0.0 

    17     LP2       1    DPPC     C17       3         0.0      14.0270 ; qtot: 


Would you please give me some advice about this?

Thanks!!

 

Best wishes,

Yulia