Eta-prime quark-antiquark and eta-prime NN vertex suppression in   effective theories
  In an effective theory containing only quark degrees of freedom, such as the extended Nambu-Jona-Lasinio model, the influence of the axial anomaly can be incorporated by a self-interaction of the 't Hooft determinant type.   I will show that despite the theshold problem related to the eta-prime meson this leads to a significant suppression of the eta-prime coupling g_{\eta' q \bar{q}} to dynamical quarks which suggests a suppression of the eta-prime-NN vertex as compared to the eta-NN vertex. 
Dirk Lehmann (Erlangen U., Theorie III)