Hello,
thank you very much for the different answers.
In order to close the discussion, the solution is to expand first
the I213 asymmetric unit to a full I213 unit
cell contents (24 asu, 12 from the rotational symmetry and 12 from
the body-centering) using pdbset.
Then the coordinates have to be rotated using again pdbset and the
matrix :
| -0,577335655 |
0,5773878412 |
0,5773878412 |
| 0,4083025328 |
-0,4082287321 |
0,816531265 |
| 0,7071581216 |
0,7071581216 |
0 |
This matrix combines the passage from the cubic to the primitive
triclinic P1 (or actually rhombohedral R3) unit cell (a=b=c,
alpha=beta=gamma=109.47°) and the re-orthogonalization of the
structure in the triclinic unit cell.
Finally, the symmetry information in the pdb header has to be
changed from I213 to P1 and the 12 excess molecules
(asu's) have to be removed manually to stay with 12 molecules
(asu's) filling the primitive triclinic unit cell ( or 4 ones
filling the rhombohedral R3 asymmetric unit.
Greetings
Wim