Enumerations for _Chem_comp_atom.Stereo_config (A closed enumeration) 
E '(E)- alkene (German, entgegen = opposite)' 
N 'atom is not a chiral center' 
R 'rectus - right handed configuration' 
S 'sinister - left handed configuration' 
Z '(Z)- alkene (German, zusammen = together)'