  The isocyanate radical (NCO) is the simplest molecule containing the backbone
of the peptide bond, C(=O)-N. This bond has a prebiotic interest since is the
one linking two amino acids to form large chains of proteins. It is also
present in some organic molecules observed in space such as HNCO, NH2CHO and
CH3NCO. In this letter we report the first detection in space of NCO towards
the dense core L483. We also report the identification of the ion H2NCO+,
definitively confirming its presence in space, and observations of HNCO, HOCN,
and HCNO in the same source. For NCO, we derive a column density of 2.2e12
cm-2, which means that it is only about 5 times less abundant than HNCO. We
find that H2NCO+, HOCN and HCNO have abundances relative to HNCO of 1/400,
1/80, and 1/160, respectively. Both NCO and H2NCO+ are involved in the
production of HNCO and several of its isomers. We have updated our previous
chemical models involving NCO and the production of the CHNO isomers. Taking
into account the uncertainties in the model, the observed abundances are
reproduced relatively well. Indeed, the detection of NCO and H2NCO+ in L483
supports the chemical pathways to the formation of the detected CHNO isomers.
Sensitive observations of NCO in sources where other molecules containing the
C(=O)-N subunit have been detected could help in elucidating its role in
prebiotic chemistry in space.
