[gmx-users] query about making a pdb file

[Jagannath Mondal]

Hi all,
    I am a gromacs beginner. I am dealing with a 10-residue molecule  
each of which is un-natural amino acid called beta-peptide. I was  
wondering whether there is any option of making a PDB file so that I  
can use it to prepare the corresponding .gro file in gromacs. I  
somehow could generate the cartesian coordinates of the molecule.  At  
least, can you  suggest some software which are free and have mac- 
version so that I can generate the coresponding PDB file of the  
molecule from the cartesian coordinates.
  Thanks,
   Jagannath Mondal