Discovery in space of ethanolamine, the simplest phospholipid head group

Abstract

Cell membranes are a key element of life because they keep the genetic material and metabolic machinery together. All present cell membranes are made of phospholipids, yet the nature of the first membranes and the origin of phospholipids are still under debate. We report here the presence of ethanolamine in space, NH2CH2CH2OH, which forms the hydrophilic head of the simplest and second-most-abundant phospholipid in membranes. The molecular column density of ethanolamine in interstellar space is N = (1.51± 0.07)× 1013 cm−2, implying a molecular abundance with respect to H2 of (0.9−1.4) × 10−10. Previous studies reported its presence in meteoritic material, but they suggested that it is synthesized in the meteorite itself by decomposition of amino acids. However, we find that the proportion of the molecule with respect to water in the interstellar medium is similar to the one found in the meteorite (10−6). These results indicate that ethanolamine forms efficiently in space and, if delivered onto early Earth, could have contributed to the assembling and early evolution of primitive membranes.

Synthesis of methanediol [CH 2 (OH) 2 ]: The simplest geminal diol

“…Once formed, the transition from the molecular cloud phase to star-forming regions ( 33 , 34 ), such as Sagittarius B2, leads to sublimation of the ice components so that reactive intermediates can be searched for in the gas phase by radio telescopes. The recent detection of ethanolamine (NH 2 CH 2 CH 2 OH) ( 35 ) in the Sagittarius B2 complex demonstrates the capability of the next generation of radio telescopes to identify exotic molecules in deep space. This offers a versatile strategy to first synthesize transient molecules, such as geminal diols, prior to their search in star-forming regions, eventually bringing us closer to an understanding of the molecular structure and chemical bonding of exotic organic molecules, which conventional wisdom suggests do not exist.…”

Gas-phase identification of (Z)-1,2-ethenediol, a key prebiotic intermediate in the formose reaction

“…This hypothesis is also supported by the detection of interstellar glycolaldehyde 10 and many other complex, bio-relevant species in molecular clouds, star-forming regions, and Solar-type protostars. 11–15 Such observations demonstrate the existence of formation mechanisms of organic molecules compatible with the harsh conditions of the ISM ( T = 10–100 K, number densities ≈ 10 4 cm −3 ), whose detailed comprehension still requires a huge effort and, in particular, the identification of key intermediate species linking small organic species to bio-relevant molecules. Hydroxymethylene (HCOH, 3 ) is a prototypical short-lived species involved in sugar formation in non-aqueous conditions that escaped detection for a long time.…”

Probing the chemical complexity of amines in the ISM: detection of vinylamine (C$_2$H$_3$NH$_2$) and tentative detection of ethylamine (C$_2$H$_5$NH$_2$)

“…To properly evaluate the line contamination by other molecules, over 300 species have been searched for in our dataset. This included not only all the molecules detected towards G+0.693 in previous studies (Requena-Torres et al 2008;Zeng et al 2018;Rivilla et al 2018Rivilla et al , 2019Rivilla et al , 2020Rivilla et al , 2021Jiménez-Serra et al 2020;Rodríguez-Almeida et al 2021), but also those reported in the ISM 5 . The molecule blended 5 See https://cdms.astro.uni-koeln.de/classic/molecules with the transition of C 2 H 3 NH 2 and C 2 H 5 NH 2 is listed in the last column of Table 1.…”

“…Following the search, two key precursors in the synthesis of prebiotic nucleotides, hydroxylamine (NH 2 OH) and urea (NH 2 CONH 2 ) have also been identi-fied towards G+0.693 (Rivilla et al 2020;Jiménez-Serra et al 2020). The very recent discovery of by far the most complex amine, ethanolamine (NH 2 CH 2 CH 2 OH), the simplest head group of phospholipids in cell membrances, towards G+0.693 attests the potential of this source for finding more complex molecules of prebiotic relevance (Rivilla et al 2021). This has thus prompted us to keep hunting for more amines in order to understand the chemical processes yielding related ingredients for life in space.…”