Searching Torsion Space

Two general options are available for searching torsion space. These are the use of predefined groups ("tgroups") with recursive simultaneous searches and the searchin of any single torsion angle.

TGROUP,TSEARCH. With this option you define a torsion group which is a set of less than 200 atoms. Tsearch then searches up to 8 simultaneous groups. This is most applicable for searching side chain conformations. The non-bonded potential used in tsearch is a special purpose version of the point atom non-bonded potential. It is optimized to only use the atoms which change in position and is relatively fast. The draw window geometry menu option to search side chains uses this construct.

tgroup id i1 i2 i3 i4 start nstep; defines a tgroup, and tsearch id <id2-id8>; searches them.

TSET,TMIN,TMAP. These routines use the current potentials and set search or map a given torsion angle. This option can search any torsion, including virtual ones where the atoms are not bonded, but uses the current potentials. It can be very slow if there is a large molecule. This construct is used by the draw window geometry menu option to search any torsion.

tset i1 i2 i3 i4 target; sets the torsion angle to target.

tmin i1 i2 i3 i4 nstep; searches the angle.

tmap i1 i2 i3 i4 j1 j2 j3 j4 ni nj; loops through the two torsion angles and outputs a map of the energy.