Crystallographic Information Framework

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Index

Macromolecular dictionary (mmCIF) version 2.0.09

Category GEOM_TORSION

Name:
'geom_torsion'

Description:

   Data items in the GEOM_TORSION category record details about
   torsion angles as calculated from the
   contents of the ATOM, CELL and SYMMETRY data.

   The vector direction _geom_torsion.atom_site_id_2 to
   _geom_torsion.atom_site_id_3 is the viewing direction, and the
   torsion angle is the angle of twist required to superimpose the
   projection of the vector between site 2 and site 1 onto the
   projection of the vector between site 3 and site 4. Clockwise
   torsions are positive, anticlockwise torsions are negative.

   Ref: Klyne, W. & Prelog, V. (1960). Experientia, 16, 521-523.

Example:

Example 1 - based on data set CLPHO6 of Ferguson, Ruhl, McKervey & Browne [Acta Cryst. (1992), C48, 2262-2264]. 
 
    loop_
    _geom_torsion.atom_site_id_1
    _geom_torsion.atom_site_id_2
    _geom_torsion.atom_site_id_3
    _geom_torsion.atom_site_id_4
    _geom_torsion.value
    _geom_torsion.site_symmetry_1
    _geom_torsion.site_symmetry_2
    _geom_torsion.site_symmetry_3
    _geom_torsion.site_symmetry_4
    _geom_torsion.publ_flag
     C(9)   O(2)    C(7)    C(2)     71.8  .  .  .  .      yes
     C(7)   O(2)    C(9)    C(10)  -168.0  .  .  .  2_666  yes
     C(10)  O(3)    C(8)    C(6)   -167.7  .  .  .  .      yes
     C(8)   O(3)    C(10)   C(9)    -69.7  .  .  .  2_666  yes
     O(1)   C(1)    C(2)    C(3)   -179.5  .  .  .  .      no
     O(1)   C(1)    C(2)    C(7)     -0.6  .  .  .  .      no


Category groups:
    inclusive_group
    geom_group
Category keys:
    _geom_torsion.atom_site_id_1
    _geom_torsion.atom_site_id_2
    _geom_torsion.atom_site_id_3
    _geom_torsion.atom_site_id_4
    _geom_torsion.site_symmetry_1
    _geom_torsion.site_symmetry_2
    _geom_torsion.site_symmetry_3
    _geom_torsion.site_symmetry_4

Mandatory category: no


International Tables for Crystallography

Volume G: Definition and exchange of crystallographic data

First online edition (2006)

Edited by S. R. Hall and B. McMahon

An essential guide and reference to CIF for programmers, data managers handling crystal-structure information and practising crystallographers.