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 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 substructural relationships.
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.