Hi Hernando, The SMTRY and MTRIX records in PDB files are only used to describe crystal packing. SMTRY describes only crystallographic symmetries. MTRIX describes only symmetries within the crystallographic asymmetric unit when the deposited coordinates do not contain the full crystal asymmetric unit (typically used for virus capsids). Other cases, e.g. all electron microscopy structures use REMARK 350 biological unit BIOMT matrices. See PDB 2tmv for an example of REMARK 350 for a helical structure. Tom hsosa@aecom.yu.edu wrote:
I have another related question: If I were to deposit a PDB coordinates file of a helical structure, what would be the best place to put helical symmetry information (the file includes the full coordinates for only one asymmetric unit) so that chimera can generate a model with more than one asymmetric unit ?. The idea being to be able to see the contacts between asymmetric units and the symmetry of the complex. Should I use the the SMTRY, or the MTRIX entries ?. Does it make any difference in chimera ?.
Thanks
Hernando .