The radioracemization of isovaline. Cosmochemical implications

Bonner, William A.; Blair, Neal E.; Lemmon, Richard M.; Flores, José Juan Alvarado; Pollock, Glenn E.

doi:10.1016/0016-7037(79)90032-2

Cited by 19 publications

(8 citation statements)

References 27 publications

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“…A large number of experiments have been performed to test this hypothesis, on a broad suite of amino acids, using several different radioactivity sources. The literature is extensive (see [ 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 ] for a representative sampling), yielding either positive reports of small enantiomeric excesses (typically <1%) or products were determined to be racemic within measurement error. Definitive conclusions for the viability of this mechanism have proven elusive because of difficulties associated with measuring small enantiomeric excesses, but the preponderance of evidence suggests that β-decay can in fact lead to amino acid asymmetry, at least to a small extent (<1%), which would need to undergo subsequent amplification to match enantiomeric excess levels observed in meteorites.…”

Section: Origins Of Meteoritic Amino Acid Enantiomeric Excessesmentioning

confidence: 99%

“…Radioactivity sources relevant to meteorite parent bodies include 60 Fe [ 109 , 110 ], which decays to 60 Ni via 60 Co, giving off two β-particles, an antineutrino, and Bremsstrahlung in the decay process. Nearly all of the reports in the literature have focused on proteinogenic amino acids, with only two related studies having been reported on isovaline, the only α-methyl amino acid studied [ 102 , 111 ]. Although it was shown that isovaline could be interconverted between enantiomers by irradiation, no net enantiomeric excesses were observed.…”

Section: Origins Of Meteoritic Amino Acid Enantiomeric Excessesmentioning

confidence: 99%

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Insights into Abiotically-Generated Amino Acid Enantiomeric Excesses Found in Meteorites

Burton

Berger

2018

Life

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Biology exhibits homochirality, in that only one of two possible molecular configurations (called enantiomers) is used in both proteins and nucleic acids. The origin of this phenomenon is currently unknown, as nearly all known abiotic mechanisms for generating these compounds result in equal (racemic) mixtures of both enantiomers. However, analyses of primitive meteorites have revealed that a number of amino acids of extraterrestrial origin are present in enantiomeric excess, suggesting that there was an abiotic route to synthesize amino acids in a non-racemic manner. Here we review the amino acid contents of a range of meteorites, describe mechanisms for amino acid formation and their potential to produce amino acid enantiomeric excesses, and identify processes that could have amplified enantiomeric excesses.

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Section: Origins Of Meteoritic Amino Acid Enantiomeric Excessesmentioning

confidence: 99%

Section: Origins Of Meteoritic Amino Acid Enantiomeric Excessesmentioning

confidence: 99%

Insights into Abiotically-Generated Amino Acid Enantiomeric Excesses Found in Meteorites

Burton

Berger

2018

Life

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“…For the mechanism of racemization of amino acids lacking an -H atom, see: Pizzarello & Groy (2011). For the role that crystallization can play in the enrichment of l-isovaline, see: Glavin & Dworkin (2009); Bada (2009); Bonner et al (1979). For normal bond lengths and angles, see: Orpen (1993).…”

Section: Related Literaturementioning

confidence: 99%

“…However, little is known about the mechanism of racemization of amino acids lacking an alpha hydrogen atom (Pizzarello & Groy, 2011). The structure of isovaline given here can be used to examine the role that crystallization can play in the enrichment of L isovaline (Glavin & Dworkin 2009;Bada, 2009), and as a starting point in mechanistic studies of racemization mechanisms of isovaline (Bonner et al, 1979).…”

Section: S1 Commentmentioning

confidence: 99%

Isovaline monohydrate

et al. 2013

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Key indicators: single-crystal X-ray study; T = 123 K; mean (C-C) = 0.005 Å; R factor = 0.056; wR factor = 0.162; data-to-parameter ratio = 13.2.The title compound, C 5 H 11 NO 2 ÁH 2 O, is an isomer of theamino acid valine that crystallizes from water in its zwitterion form as a monohydrate. It is not one of the 20 proteinogenic amino acids that are used in living systems and differs from the natural amino acids in that it has no -H atom. The compound exhibits hydrogen bonding between the water molecule and the carboxylate O atoms and an amine H atom. In addition, there are intermolecular hydrogen-bonding interactions between the carboxylate O atoms and amine H atoms. In the crystal, these extensive N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds lead to the formation of a three-dimensional network.

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“…The cosmological, geochemical and paleontological implications of isovaline radioracemization were subsequently discussed in detail. 48,49 Radioracemization experiments were later extended 50,51 to include amino acids in the presence of both silica and clay surfaces, with the findings that such mineral surfaces rendered the amino acids even more vulnerable to radioracemization.It was pointed out 46 early in the above studies that radioracemization must exert a detrimental influence on the efficacy of the Vester-Ulbricht mechanism. Depending on the relative rates of formation of an excess of one enantiomer by enantioselective ␤-radiolysis compared to the rate of its radioracemization, it is clear that the latter effect could in principle nullify the former, particularly considering the enhancing role of mineral surfaces.…”

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confidence: 99%