Stability, structural and vibrational properties of compounds where an Rg atom (Xe, Kr, or At) is inserted into different bonds of glycine molecule are investigated using accurate ab initio methods. The most stable configuration is found to correspond to insertion of Rg atoms into the O-H bond of glycine. These NH(2)CH(2)COORgH compounds are metastable, but separated from the Rg + glycine dissociation products by significant potential barriers. Preliminary calculations show that NH2CH2COOXeH compound may be energetically stable with respect to the three-body dissociation (H + Rg + NH2CH2CO2), while the corresponding Ar compound is energetically unstable in this respect. The compound with the inserted Kr is a borderline case, with the three-body dissociation products close in energy to the NH2CH2COOKrH minimum. (C) 2004 Elsevier B.V. All rights reserved.