Propionamide (C2H5CONH2): The largest peptide-like molecule in space

TL;DR

This paper reports the first tentative detection of propionamide, a large peptide-like molecule, in space, indicating such complex molecules can form and survive in star-forming regions, with implications for prebiotic chemistry.

Contribution

It presents the first detection and laboratory spectral measurements of propionamide in space, expanding knowledge of complex organic molecules in star-forming regions.

Findings

Propionamide detected in Sagittarius B2(N1)

Column density of propionamide is 1.5×10^{16} cm^-2

Detection suggests formation of complex prebiotic molecules in space

Abstract

Peptide bonds, as the molecular bridges that connect amino acids, are crucial to the formation of proteins. Searches and studies of molecules with embedded peptide-like bonds are thus important for the understanding of protein formation in space. Here we report the first tentative detection of propionamide (C2H5CONH2), the largest peptide-like molecule detected in space toward Sagittarius B2(N1) at a position called N1E that is slightly offset from the continuum peak. A new laboratory measurements of the propionamide spectrum were carried out in the 9-461 GHz, which provide good opportunity to check directly for the transition frequencies of detected interstellar lines of propionamide. Our observing result indicates that propionamide emission comes from the warm, compact cores in Sagittarius B2, in which massive protostellars are forming. The column density of propionamide toward Sgr B2(N1E) was derived to be 1.5\times 10^{16} cm^-2, which is three fifths of that of acetamide, and one nineteenth of that of formamide. This detection suggests that large peptide-like molecules can form and survive during star-forming process and may form more complex molecules in the interstellar medium. The detection of propionamide bodes well for the presence of polypeptides, as well as other complex prebiotic molecules in the interstellar medium.