A Combined Experimental and Theoretical Study on the Formation of the Amino Acid Glycine (NH2CH2COOH) and Its Isomer (CH3NHCOOH) in Extraterrestrial Ices

Holtom, P. D.; Bennett, Chris J.; Osamura, Yoshihiro; Mason, Nigel J.; Kaiser, Ralf I.

doi:10.1086/430106

Cited by 220 publications

(270 citation statements)

References 47 publications

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“…Conformer I was later characterized (Suenram & Lovas 1980) and the energy difference estimated to be ∼2 kcal/mol together with dipole moments of 0.9 and 5.4 debye for comformers I and II, respectively (Lovas et al 1995). Seven conformers of glycine can be found within ∼7 kcal/mol of conformer I; the relative energies and structures of five, with whom the present calculations agree, were reported by Holtom et al (2005). The relative energies and dipole components of conformers I to VIII are presented in Table 2 (structural details being given in Appendix A).…”

Section: Neutral Glycine and Isomerssupporting

confidence: 56%

“…For example, thermal reactions or reactions triggered by energetic particle bombardment end up forming N-methyl carbamic acid rather than glycine (e.g. Holtom et al 2005;Bossa et al 2008). Only successive UV irradiation would then form glycine (Bossa et al 2009).…”

Section: Discussionmentioning

confidence: 99%

“…It has been shown in the laboratory that glycine is present under a zwitterionic form NH + 3 CH 2 COO − in the ice (e.g. Holtom et al 2005), this intramolecular ion pair being unstable in the gas phase. Only N-methyl carbamic acid can produce another viable ion pair, CH 3 NH + 2 COO − but it is less stable by ∼3.3 kcal/mol than that of glycine which should be the major product in these conditions (structural details are given in Appendix D).…”

Section: Positive and Negative Ion Isomers Of Glycinementioning

confidence: 99%

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About the detectability of glycine in the interstellar medium

Lattelais

Pauzat

Pilmé

et al. 2011

A&A

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Context. Glycine, the simplest of aminoacids, has been found in several carbonaceous meteorites. It remains unclear, however, wether glycine is formed in the interstellar medium (ISM) and therefore available everywhere in the Universe. For this reason, radioastronomers have searched for many years unsuccessfully to detect glycine in the ISM. Aims. We provide possible guidelines to optimize the return of these searches. Since, for most of the species observed so far in the ISM, the most abundant isomer of a given generic chemical formula is the most stable one (minimum energy principle (MEP)), we assess whether neutral glycine is the best molecule to search for or whether one of its isomers/conformers or ionic, protonated, or zwitterionic derivatives would have a higher probability of being detected. Methods. The question of the relative stability of these different species is addressed by means of quantum density functional theory (DFT) simulations within the hybrid B3LYP formalism. Each fully optimized structure is verified as a stationary point by means of a vibrational analysis. A comprehensive screening of 32 isomers/conformers of the C 2 H 5 O 2 N chemical formula (neutral, negative, and positive ions together with the corresponding protonated species and the possible zwitterionic structures) is carried out. In the sensitive case of the neutral compounds, more accurate relative energies were obtained by means of high level post Hartree-Fock coupled cluster calculations with large basis sets (CCSD(T)/cc-pVQZ). Results. We find that neutral glycine is not the most stable isomer and, therefore, probably not the most abundant one, which might explain why it has escaped detection so far. We find instead that N-methyl carbamic acid and methyl carbamate are the two most stable isomers and, therefore, probably the two most abundant ones. Among the non-neutral forms, we found that glycine is the most stable isomer only if protonated or zwitterionic if present in interstellar ices. Conclusions. Assuming that MEP can be applied to optimize our search for glycine, our conclusion is that this search will remain extremely difficult with the present instruments and we propose searching instead for other examples among the most stable isomers.

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Section: Neutral Glycine and Isomerssupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Section: Positive and Negative Ion Isomers Of Glycinementioning

confidence: 99%

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About the detectability of glycine in the interstellar medium

Lattelais

Pauzat

Pilmé

et al. 2011

A&A

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“…From a chemical point of view, the case of ices (Watanabe & Kouchi 2008) is particularly interesting for the synthesis of oxygen-containing molecules such as for example H 2 O, CO 2 , H 2 CO, CH 3 OH, or glycine isomers (Watanabe et al 2003(Watanabe et al , 2004Holtom et al 2005;Bossa et al 2008Bossa et al , 2009Dulieu et al 2010). …”

Section: Introductionmentioning

confidence: 99%

Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

Lattelais

Bertin

Mokrane

et al. 2011

A&A

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Context. Over 20 of the ∼150 different species detected in the interstellar and circumstellar media have also been identified in icy environments. For most of the species observed so far in the interstellar medium (ISM), the most abundant isomer of a given generic chemical formula is the most stable one (minimum energy principle -MEP) with few exceptions such as, for example, CH 3 COOH/HCOOCH 3 and CH 3 CH 2 OH/CH 3 OCH 3 , whose formation is thought to occur on the icy mantles of interstellar grains. Aims. We investigate whether differences found in the compositions of molecular ices and the surrounding gas phase could originate from differences between the adsorption of one isomer from that of another at the ice surface. Methods. We performed a coherent and concerted theoretical/experimental study of the adsorption energies of the four molecules mentioned above, i.e. acetic acid (AA)/methyl formate (MF) and ethanol (EtOH)/dimethyl ether (DME) on the surface of water ice at low temperature. The question was first addressed theoretically at LCT using solid state periodic density functional theory (DFT) to represent the organized solid support. The experimental determination of the ice/molecule interaction energies was then carried out independently by two teams at LPMAA and LERMA/LAMAp using temperature programmed desorption (TPD) under an ultra-high vacuum (UHV) between 70 and 160 K. Results. For each pair of isomers, theory and experiments both agree that the most stable isomer (AA or EtOH) interacts more efficiently with the water ice than the higher energy isomer (MF or DME). This differential adsorption can be clearly seen in the different desorption temperatures of the isomers. It is not related to their intrinsic stability but instead to both AA and EtOH producing more and stronger hydrogen bonds with the ice surface. Conclusions. We show that hydrogen bonding may play an important role in the release of organic species from grains and propose that, depending on the environment, differential adsorption should not be rejected as a possible way of interpreting MEP exceptions.

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“…In the laboratory, it has been demonstrated that glycine can be formed from ultraviolet irradiation of icy interstellar analogs, [9][10][11][12][13][14] in the midst of a complex assortment of chemical species generated in the reactions induced by the irradiation. Although recent works have extended the spectroscopic range of study of amino acids even up to the vacuum ultraviolet, 15 infrared spectroscopy is a frequently used tool to study laboratory generated amino acids, 16 as well as to derive much of the available information on astrophysical ices, either from space or terrestrial observatories.…”

Section: Introductionmentioning

confidence: 99%

An infrared study of solid glycine in environments of astrophysical relevance

Maté

Rodrı́guez-Lazcano

Gálvez

et al. 2011

Phys. Chem. Chem. Phys.

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The conversion from neutral to zwitterionic glycine is studied using infrared spectroscopy from the point of view of the interactions of this molecule with polar (water) and non-polar (CO 2 , CH 4 ) surroundings. Such environments could be found on astronomical or astrophysical matter. The samples are prepared by vapour-deposition on a cold substrate (25 K), and then heated up to sublimation temperatures of the co-deposited species. At 25 K, the neutral species is favoured over the zwitterionic form in non-polar environments, whereas for pure glycine, or in glycine/water mixtures, the dominant species is the latter. The conversion is easily followed by the weakening of two infrared bands in the mid-IR region, associated to the neutral structure. Theoretical calculations are performed on crystalline glycine and on molecular glycine, both isolated and surrounded by water. Spectra predicted from these calculations are in reasonable agreement with the experimental spectra, and provide a basis to the assignments. Different spectral features are suggested as probes for the presence of glycine in astrophysical media, depending on its form (neutral or zwitterionic), their temperature and composition.

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A Combined Experimental and Theoretical Study on the Formation of the Amino Acid Glycine (NH₂CH₂COOH) and Its Isomer (CH₃NHCOOH) in Extraterrestrial Ices

Cited by 220 publications

References 47 publications

About the detectability of glycine in the interstellar medium

About the detectability of glycine in the interstellar medium

Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

An infrared study of solid glycine in environments of astrophysical relevance

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