Tor_residue [id an atom] or [mol res atom]
This allows one to make dihedral rotations around bonds between pairs of atoms. All of the torsional angles associated with the identified residue can be changed via the dials. The number of dials activated depends on how many angles are defined for the particular residue. Therefore, Dial_previous or Dial_next may have to be used. Use Yes/No to accept or reject the result.
The program needs to know what angles are associated with the residue and how they are defined. This torsional information is kept in the data base as an entry .torsion_information. The distributed version of this information can be loaded from $ODAT/torsion.o and is also in $ODAT/startup.o. It is very easy to add new residues to this entry. For example, a serine residue is encoded as
RESIDUE SER TORSION PHI -57. C- N CA C C O N+ CB OG TORSION PSI -47. N CA C N+ N+ O CB OG TORSION CHI1 -60. N CA CB OG OG
In this residue there are 3 torsion angles (PHI, PSI and CHI1) with preferred values 57., 47., 60 respectively. The first four atom names describe how each angle is defined, the remaining names specify which atoms are affected by the angle. The CHI1 angle is, therefore, defined by looking along the CA-CB bond and measuring the angle subtended by the lines N-CA and CB-OG. Only the OG atom moves when this angle is changed.
Note that atoms from last and next residues have `-' and `+' signs in their names. In the distributed database, we have chosen to move the N of the next residue as PHI and PSI change. If the list of atoms is too long, you can go into the next line by typing a back-slash character. Begin the next line with at least 6 spaces for tidiness's sake.
If you do not follow the standard atomic naming convention, or if you have extra atoms (e.g. hydrogens) in your residues, you must make a new version of .torsion_information.
The program reports atoms that are defined in the torsion database but not present in the residue. If an atom is in the residue but not defined as a moving atom, it will never move.
We would love to receive entries for new types of residues, and will place them on the ftp server for the benefit of other O users.