The id of the first of the four atoms that define the torsion
angle.
This data item is a pointer to _chem_comp_atom.atom_id in the
CHEM_COMP_ATOM 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