Observations of interstellar glycine

Abstract

We report observational results on interstellar glycine which have been performed using the 45-m radio telescope of the Nobeyama Radio Observatory toward the Sgr B2 molecular cloud. Glycine is the smallest biologically important amino acid. The detection would lead to the understanding of evolution of biological molecules in space, and may answer our basic question Where are we born ?. Many saerches for this molecule in interstellar molecular clouds have been done, but without success. Recently, Snyder et al. (1994) claimed a possible detection of glycine in Sgr B2. But the spectrum contains many lines and the contamination is so severe, and it is neccesary to confirm. We have been making a spectral line survey toward the Sgr B2 cloud in the last five years, covering from 30 GHz to 116 GHz expept for the telluric 02 band near 60 GHz. We noticed that several glycine transitions fall in our survey data. The glycine frequencies were taken from the table by F. Lovas (private communication) No clear signals from glycine were detected above the detection limit (the rms of the noise fluctuation is ~ 0.02 K). We conclude that the possible glycine line that Snyder et al. (1994)claimed at 107517 MHz should be identified to the J=12-11, K_I=10 line of C2HsCN. Our result is consistent with the recent paper by Combes et al. (1996).