Context.Peptide-like bond molecules, which can take part in the formation of proteins in a primitive Earth environment, have been detected only towards a few hot cores and hot corinos up to now.Aims.We present a study of HNCO, HC(O)NH₂, CH₃NCO, CH₃C(O)NH₂, CH₃NHCHO, CH₃CH₂NCO, NH₂C(O)NH₂, NH₂C(O)CN, and HOCH₂C(O)NH₂towards the hot core G31.41+0.31. The aim of this work is to study these species together to allow a consistent study among them.Methods.We have used the spectrum obtained from the ALMA 3 mm spectral survey GUAPOS, with a spectral resolution of ~0.488 MHz (~1.3–1.7 km s⁻¹) and an angular resolution of 1.′′2 × 1.′′2 (~4500 au), to derive column densities of all the molecular species presented in this work, together with 0.′′2 × 0.′′2 (~750 au) ALMA observations from another project to study the morphology of HNCO, HC(O)NH₂, and CH₃C(O)NH₂.Results.We have detected HNCO, HC(O)NH₂, CH₃NCO, CH₃C(O)NH₂, and CH₃NHCHO, but no CH₃CH₂NCO, NH₂C(O)NH₂, NH₂C(O)CN, or HOCH₂C(O)NH₂. This is the first time that these molecules have been detected all together outside the Galactic centre. We have obtained molecular fractional abundances with respect to H₂from 10⁻⁷down to a few 10⁻⁹and abundances with respect to CH₃OH from 10⁻³to ~4 × 10⁻², and their emission is found to be compact (~2′′, i.e. ~7500 au). From the comparison with other sources, we find that regions in an earlier stage of evolution, such as pre-stellar cores, show abundances at least two orders of magnitude lower than those in hot cores, hot corinos, or shocked regions. Moreover, molecular abundance ratios towards different sources are found to be consistent between them within ~1 order of magnitude, regardless of the physical properties (e.g. different masses and luminosities), or the source position throughout the Galaxy. Correlations have also been found between HNCO and HC(O)NH₂as well as CH₃NCO and HNCO abundances, and for the first time between CH₃NCO and HC(O)NH₂, CH₃C(O)NH₂and HNCO, and CH₃C(O)NH₂and HC(O)NH₂abundances. These results suggest that all these species are formed on grain surfaces in early evolutionary stages of molecular clouds, and that they are subsequently released back to the gas phase through thermal desorption or shock-triggered desorption.

Numerous studies have suggested that the n→π* interactions between carbonyls could contribute significantly to the stability of proteins. Nevertheless, their evaluation is challenging because of the solvent environment or crystal packing forces in solids. Here we study the rotational spectrum of HGlyProOH dipeptide, a very common sequence found in collagen, the most abundant protein in vertebrates, in isolated conditions. Three different structures are unequivocally characterized in the gas phase. Interestingly, the most abundant structure is stabilized by an n→π* interaction and adopts the same conformation as is found in crystalline collagen. This observation serves to support the importance of the n→π* interactions between carbonyl groups.

The unbiased, naked structures of tartaric acid, one of the most important organic compounds existing in nature and a candidate to be present in the interstellar medium, has been revealed in this work for the first time. Solid samples of its naturally occurring (R,R) enantiomer have been vaporized by laser ablation, expanded in a supersonic jet, and characterized by Fourier transform microwave spectroscopy. In the isolation conditions of the jet, we have discovered up to five different structures stabilized by intramolecular hydrogen‐bond networks dominated by O−H⋅⋅⋅O=C and O−H⋅⋅⋅O motifs extended along the entire molecule. These five forms, two with an extended (trans) disposition of the carbon chain and three with a bent (gauche) disposition, can serve as a basis to represent the shape of tartaric acid. This work also reports the first set of spectroscopy data that can be used to detect tartaric acid in the interstellar medium.

The steric effects imposed by the isopropyl group of valine in the conformational stabilization of the capped dipeptide N-acetyl-l-valinamide (Ac-Val-NH₂) have been studied by laser ablation molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopy.

We have successfully characterized the structure of testosterone, one of the essential steroids, through high-resolution rotational spectroscopy. A single conformer has been detected, and a total of 404 transitions have been fitted, allowing a precise determination of the rotational constants. It allowed us to unravel that the isolated structure of testosterone adopts an extended disposition. The results obtained in this work highlight how using laser ablation techniques in combination with Fourier transform microwave techniques allow the study of large biomolecules or common pharmaceuticals. It is an important step toward studying relevant biomolecules and developing new analytical techniques with unprecedented sensitivity and resolution.