[gmx-users] struggles with cyclic peptides

[Nikhil]

Thank you very much Justine,
now it making bond between first and last residue of amino acids but there 
as an extra oxygen atom is coming  when i select any option other than 
None.but when i select None for the second terminals it shows an error 
as
There is a dangling bond at at least one of the terminal ends. Fix 
yourcoordinate file, add a new terminal database entry (.tdb), or select 
the
 proper existing terminal entry.**For more information and tips for 
troubleshooting, please check the GROMACS*

should i edit the .tdb file ?
thanks in advance