[gmx-users] Distance restraints

[zhong qiang]

Hi:
   I want to constuct my .top file, In my molecular system four calcium 
ions binding at four site, I use pdb2gmx  make a top file, But there is not 
topology information about calcium ions, I insert a distance restraints in 
.top file, just like below:
[ distance restraints ]
;  ai    aj  type index type’ low up1 up2 fac
 1460   207     1     2   1   0.0 0.3 0.4 1.0
 1460   208     1     2   1   0.0 0.3 0.4 1.0
 1460   210     1     2   1   0.0 0.3 0.4 1.0
 1460   229     1     2   1   0.0 0.3 0.4 1.0
.........................

then I run
grompp -f fullmd_sol.mdp -c minimized_water.gro -p 1ckk.top -o fullmd.tpr
But error message present:
ERROR 1 [file "1ckk.top", line 9029]:
  Invalid directive distance restraints

Then I delete line [ distance restraints ]
the error report:
Fatal error:
Incorrect number of parameters - found 4, expected 3 or 6.

Could somebody tell me how to add a distance restraints correctly?
Thank you very much!

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