Macromolecular dictionary (mmCIF) version 2.0.09
The total number of hydrogen atoms attached to this atom, regardless of whether they are included in the refinement or the ATOM_SITE list. This number is the same as _atom_site.attached_hydrogens only if none of the hydrogen atoms appear in the ATOM_SITE list.
Mandatory item: noAlias:
_chemical_conn_atom_NH (cif_core.dic version 2.0.1)
The permitted range is [0, infinity)