An optional identifier of the second of the four atom sites that
define the torsion angle specified by _geom_torsion.value.
This data item is a pointer to _atom_site.auth_atom_id in the
ATOM_SITE category.
This HTML dictionary was created using the CIFLIB C Language Application Program Interface
at the
Resource Collaboratory for Structural Bioinformatics
Rutgers University, Department of Chemistry
New Brunswick, New Jersey help@rcsb.rutgers.edu