1996A&A...308..618C

Because of its central biological significance, glycine, has extensively been searched for in the 1980s, after the laboratory determination of its millimeter-wave spectrum in 1978. Using the 30m IRAM telescope, we have recently carried out high sensitivity observations to search for both conformers I and II of glycine in several spectral regions at 3mm (around 101GHz, 107GHz, 111GHz), at 2mm (around 136GHz and 144GHz), and at 1.4mm (around 217GHz and 223GHz) with a bandwidth of 512MHz. The targets were Orion and Sagittarius-B2. We covered spectral regions which included 98 expected lines of glycine: some did show some signal at various levels (10mK-1K), but many were not detected, while comparable signals are expected. Since the level of confusion is reached in Orion, we believe that glycine is below the confusion limit, and will be impossible to detect in this source, as well as other complex molecules of similar or lower abundance (≲10^–11). During these observations, we detect 334 lines in Orion, of which 157 are unidentified.