Data items in the CHEMICAL_CONN_BOND category would not, in
general, be used in a macromolecular CIF. See instead the
ENTITY data items.
Data items in the CHEMICAL_CONN_ATOM and CHEMICAL_CONN_BOND
categories record details about the two-dimensional (2D)
chemical structure of the molecular species. They allow a
2D chemical diagram to be reconstructed for use in a
publication or in a database search for structural and
The CHEMICAL_CONN_BOND data items specify the connections
between the atoms in the CHEMICAL_CONN_ATOM list and the nature
of the chemical bond between these atoms.