Notes on editing PDB format

The essential fields of pdb format are CRYST1, HETATM (or ATOM), and CONECT (minimum that is needed). Also TITLE and COMPND fields can be included. Here is an example of these fields:

TITLE     The title
COMPND    compound name
REMARK    A remark
CRYST1    5.000    5.000    9.111  90.00  90.00 120.00 P63/mmc
ATOM    293 1HG  GLU A   18    -14.861  -4.847   0.361  1.00  0.00           H
HETATM    3  As                  0.000  -0.719   0.000
CONECT   10    1    2    3    4

The fields TITLE and COMPND begin at column 11.

Description of the field CRYST1:

Minimal description of the coordinate section:

Description of the field CONECT:

Note that for generating crystals in Mercury program you should specify in pdb-file only one atom for each symmetry position.

Complete description of PDB format can be found here, see also Wikipedia.