Asymmetric photolysis of (RS)-leucine with circularly polarized ultraviolet light

Flores, José Juan Alvarado; Bonner, William A.; Massey, G. A.

doi:10.1021/ja00453a018

Cited by 256 publications

(193 citation statements)

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“…In the laboratory, two methods using these forces have been confirmed to produce EE in compounds. One is photolysis of enantiomers by circularly polarized UV light (UV CPL) (39). UV CPL is also suggested as a possible interstellar mechanism for the production of EE (40,41).…”

Section: Discussionmentioning

confidence: 99%

“…UV CPL is also suggested as a possible interstellar mechanism for the production of EE (40,41). Laboratory experiments with UV CPL have demonstrated a slight preferential destruction of one enantiomer, which resulted in relatively small but reversible EE (depending on the direction of the CPL) from an initially racemic mixture of amino acids (39). When performed at low (i.e., interstellar) temperatures, UV CPL is reported to induce EE during the actual synthesis of compounds (42).…”

Section: Discussionmentioning

confidence: 99%

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Enantiomer excesses of rare and common sugar derivatives in carbonaceous meteorites

Cooper

Rios

2016

Proc. Natl. Acad. Sci. U.S.A.

123

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Biological polymers such as nucleic acids and proteins are constructed of only one-the D or L-of the two possible nonsuperimposable mirror images (enantiomers) of selected organic compounds. However, before the advent of life, it is generally assumed that chemical reactions produced 50:50 (racemic) mixtures of enantiomers, as evidenced by common abiotic laboratory syntheses. Carbonaceous meteorites contain clues to prebiotic chemistry because they preserve a record of some of the Solar System's earliest (∼4.5 Gy) chemical and physical processes. In multiple carbonaceous meteorites, we show that both rare and common sugar monoacids (aldonic acids) contain significant excesses of the D enantiomer, whereas other (comparable) sugar acids and sugar alcohols are racemic. Although the proposed origins of such excesses are still tentative, the findings imply that meteoritic compounds and/or the processes that operated on meteoritic precursors may have played an ancient role in the enantiomer composition of life's carbohydrate-related biopolymers.carbonaceous meteorites | sugar acids | enantiomer excesses | aldonic acids | polyols T he organic phase of carbonaceous meteorites comprises an insoluble "macromolecular" material (1-3), a complex mixture of largely uncharacterized solvent-extractable compounds (4), as well as discrete (identified) soluble organic compounds such as amino acids (3, 5) nucleobases (6, 7), and sugar derivatives (8). Analyses of this prebiotic organic carbon have been important in understanding its early Solar System synthesis and history: Characteristics of the organic phase suggest that it consists of both products and survivors of interstellar/presolar grain irradiation (9) and subsequent encapsulation and aqueous reactions (10, 11) in asteroids "parent bodies."Several identified meteoritic organic compounds are chiral: They can exist as two nonsuperimposable mirror image compounds called enantiomers, commonly designated D and L. To date, most chiral meteoritic compounds are reported to be racemic mixtures, i.e., their D and L enantiomers are equal in abundance (3). Racemic compounds are expected in nature because typical abiotic synthetic processes are (historically) thought to occur in the absence of asymmetric influences. Racemic mixtures are equated with pristine/uncontaminated abiotic samples when discussing meteoritic compounds. However, some meteoritic amino acids that are rare on Earth, i.e., they are not constituents of proteins and therefore less likely to be contaminants, have been confirmed to contain L enantiomer excesses (EE) (3, 12, 13). The origins of such excesses are unknown.Sugars, aldehydes, or ketones that contain multiple carbon hydroxyl (carbon alcohol) groups, are also chiral and were likely necessary for the origin of life. In the majority of extant biological sugars and derivatives ("polyols"), the D enantiomers are significantly more abundant than the L enantiomers (we will note exceptions in Results and Natural Occurrence of Relevant Sugar Derivatives and Enantiomers)...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Enantiomer excesses of rare and common sugar derivatives in carbonaceous meteorites

Cooper

Rios

2016

Proc. Natl. Acad. Sci. U.S.A.

123

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“…Such selective destruction of D amino acids by right circularly polarized light has been demonstrated experimentally (8). The excess of light with right, rather than left, circular polarization is often ascribed to a synchrotron or cyclotron process from a nearby neutron star.…”

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confidence: 91%

L-amino acids catalyze the formation of an excess of D-glyceraldehyde, and thus of other D sugars, under credible prebiotic conditions

Breslow

Cheng

2010

Proc. Natl. Acad. Sci. U.S.A.

113

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Previous work by us, and others, has shown that the formation of amino acids on prebiotic earth with the geometric arrangement called the L configuration can be understood. Some meteorites of the carbonaceous chondritic type deliver unusual amino acids, with alpha-methyl groups, which have an excess of the L isomers. We previously showed that in decarboxylative transamination reactions under credible prebiotic conditions they produce normal amino acids that also have a preference for the L isomer, as is found in our proteins. We, and others, showed that as little as a 1% excess of the L isomers could be amplified up to a 95/5 ratio of L over D on simple evaporation of a solution, so life could start with such a solution in which the dominant L isomers would be selectively chosen. We now find that the geometry of sugars referred to D, as in D-ribose or D-glucose, is not an independent mystery. D-glyceraldehyde, the simplest sugar with a D center, is the basic unit on which other sugars are built. We find that the synthesis of glyceraldehyde by reaction of formaldehyde with glycolaldehyde is catalyzed under prebiotic conditions to D/L ratios greater than 1, to as much as 60/40, by a representative group of L-amino acids (with the exception of L-proline). The D/L glyceraldehyde ratio in water solution is amplified to 92/8 using simple selective solubilities of the D and the DL forms. This D center would then be carried into the prebiotic syntheses of larger sugars.aldol reaction | formaldehyde | formose reaction | meteorites F or life to start, it was necessary that the amino acids that are building blocks for proteins, and the sugars that play many biological roles and are part of both RNA and DNA, have a single handedness, called chirality. The amino acids could have been all in the handedness referred to as L, analogous to the left hand, or they could have been all D, analogous to the right hand, but on our planet the L geometry was preferred. After many years of speculation about why this is so, evidence has now accumulated that the L handedness of amino acids was derived from a special group of amino acids, with an extra methyl group that prevented loss of their small excess of the L form by a process that can scramble the handedness of ordinary amino acids on prolonged heating. These special L-amino acids with the extra methyl group were isolated from a meteorite that fell in Murchison Australia in 1969 (1, 2). We showed that they could generate normal amino acids (without the methyl group) under credible prebiotic conditions, and those also had an excess of the L isomer, along with a smaller amount of the D amino acids (3).Once there was a small excess of the L-amino acid, we showed that it could be amplified in solution, because the DL 1∶1 mixture was less soluble in water (4). By evaporating a water solution with only a 1% excess of L-phenylalanine, for instance, we obtained a solution with a 95/5 L/D ratio; equal amounts of the D and L components precipitated from the solution as a less soluble crystal in...

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“…The highest magnitude of the g factors (0.025-0.035) among the proteinogenic amino acids were found for the aliphatic (alanine, leucine, valine, isoleucine, and proline) and two hydroxyl amino acids (serine and threonine), respectively, at pH 1. However, Flores et al [103] reported an enantiomeric excess for originally racemic leucine in acidic solution of 2.50% (l-CPL, left-handed) and 1.98% (r-CPL, right-handed) using UVCPL at 212 nm, with photolysis rates of 75% and 59%, respectively.…”

Section: Asymmetric Photolysis Of Racemic Organic Moleculesmentioning

confidence: 99%

Photochirogenesis: Photochemical Models on the Origin of Biomolecular Homochirality

et al. 2010

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Current research focuses on a better understanding of the origin of biomolecular asymmetry by the identification and detection of the possibly first chiral molecules that were involved in the appearance and evolution of life on Earth. We have reasons to assume that these molecules were specific chiral amino acids. Chiral amino acids have been identified in both chondritic meteorites and simulated interstellar ices. Present research reasons that circularly polarized electromagnetic radiation was identified in interstellar environments and an asymmetric interstellar photon-molecule interaction might have triggered biomolecular symmetry breaking. We review on the possible prebiotic interaction of 'chiral photons' in the form of circularly polarized light, with early chiral organic molecules. We will highlight recent studies on enantioselective photolysis of racemic amino acids by circularly polarized light and experiments on the asymmetric OPEN ACCESS Symmetry 2010, 2 1056 photochemical synthesis of amino acids from only one C and one N containing molecules by simulating interstellar environments. Both approaches are based on circular dichroic transitions of amino acids that will be presented as well.

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Asymmetric photolysis of (RS)-leucine with circularly polarized ultraviolet light

Cited by 256 publications

References 3 publications

Enantiomer excesses of rare and common sugar derivatives in carbonaceous meteorites

Enantiomer excesses of rare and common sugar derivatives in carbonaceous meteorites

L-amino acids catalyze the formation of an excess of D-glyceraldehyde, and thus of other D sugars, under credible prebiotic conditions

Photochirogenesis: Photochemical Models on the Origin of Biomolecular Homochirality

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