[gmx-users] pdb2gmx cannot generate the right residue and atom numbers

[WH]

Dear Gromacs users,

I want to use Gromacs to process a system with more than 80000 water moelcules. However, when use pdb2gmx to deal the the pdb file, the out put .gro file has the form like this:
 3409HOH    HW234995  -5.617  -6.883  -8.771
 3409HOH     OW34996  -6.108  -6.959  -7.760
 3409HOH    HW134997  -6.107  -6.973  -7.855
 3409HOH    HW234998  -6.199  -6.971  -7.735
 3409HOH     OW34999  -4.964  -8.455  -9.110
 3409HOH    HW135000  -5.054  -8.441  -9.081
 3409HOH    HW235001  -4.939  -8.372  -9.150
 3409HOH     OW35002  -6.157  -7.576  -8.913
 3409HOH    HW135003  -6.187  -7.499  -8.962

Only 4 digits will be used for the residue number and 5 for the atom number. Thus, the actual residue number and atom number cannot be written correctly and lead to failure for the MD simulation.
Does anyone know how to fix this problem? I really appreciate it.