Laurent Nahon | Synchrotron SOLEIL (original) (raw)
Papers by Laurent Nahon
Origins of Life and Evolution of Biospheres, 2015
All life on Earth is characterized by its asymmetry - both the genetic material and proteins are ... more All life on Earth is characterized by its asymmetry - both the genetic material and proteins are composed of homochiral monomers. Understanding how this molecular asymmetry initially arose is a key question related to the origins of life. Cometary ice simulations, L-enantiomeric enriched amino acids in meteorites and the detection of circularly polarized electromagnetic radiation in star-forming regions point to a possible interstellar/protostellar generation of stereochemical asymmetry. Based upon our recently recorded anisotropy spectra g(λ) of amino acids in the vacuum-UV range, we subjected amorphous films of racemic (13)C-alanine to far-UV circularly polarized synchrotron radiation to probe the asymmetric photon-molecule interaction under interstellar conditions. Optical purities of up to 4 % were reached, which correlate with our theoretical predictions. Importantly, we show that chiral symmetry breaking using circularly polarized light is dependent on both the helicity and the wavelength of incident light. In order to predict such stereocontrol, time-dependent density functional theory was used to calculate anisotropy spectra. The calculated anisotropy spectra show good agreement with the experimental ones. The European Space Agency's Rosetta mission, which successfully landed Philae on comet 67P/Churyumov-Gerasimenko on 12 November 2014, will investigate the configuration of chiral compounds and thereby obtain data that are to be interpreted in the context of the results presented here.
Current research focuses on a better understanding of the origin of biomolecular asymmetry by the... more 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
Angewandte Chemie International Edition, 2010
Dedicated to Professor Henri B. Kagan on the occasion of his 80th birthday Biopolymers such as nu... more Dedicated to Professor Henri B. Kagan on the occasion of his 80th birthday Biopolymers such as nucleic acids and proteins are composed of chiral monomers that show identical stereochemical configuration. Naturally occurring proteins are made up of l-amino acids. Hypotheses for the origin of symmetry breaking in biomolecules include the absolute asymmetric photochemistry model by which circularly polarized (CP) light induces an enantiomeric excess (ee) in chiral organic molecules. This model is supported by both the observation of CP light in the star-forming region of Orion and the occurrence of l-enantiomer-enriched amino acids in carbonaceous meteorites. [8] However, the differential absorption of CP light by amino acid enantiomers, which determines the speed and intensity of enantioselective photolysis, is unknown over a large spectral range. Here we show that significant circular dichroic transitions in amino acids can be observed by extending circular dichroism (CD) spectroscopy to the vacuum-ultraviolet (UV) spectral range. a-H amino acids show the same CD magnitude and sign over a large wavelength range. In a given spectral window CP light is therefore capable of inducing enantiomeric excesses of the same handedness into the proteinogenic amino acids we have studied. Absolute asymmetric photochemistry might thus well have triggered the appearance of l-amino acid based life on Earth. Our results demonstrate that enantiomers of "meteoritic" a-methyl amino acids show dichroic absorption with equal magnitude, yet opposite sign to a-H amino acids. Therefore CP light cannot induce l enantiomeric excesses into a-methyl and a-H amino acids as found in meteorites.
![Research paper thumbnail of Synchrotron vacuum ultraviolet radiation studies of the D [sup 1]Π[sub u] state of H[sub 2]](https://attachments.academia-assets.com/44578393/thumbnails/1.jpg)
](The Journal of Chemical Physics, 2010
The 3pD 1 ⌸ u state of the H 2 molecule was reinvestigated with different techniques at two synch... more The 3pD 1 ⌸ u state of the H 2 molecule was reinvestigated with different techniques at two synchrotron installations. The Fourier transform spectrometer in the vacuum ultraviolet wavelength range of the DESIRS beamline at the SOLEIL synchrotron was used for recording absorption spectra of the D 1 ⌸ u state at high resolution and high absolute accuracy, limited only by the Doppler contribution at 100 K. From these measurements, line positions were extracted, in particular, for the narrow resonances involving 1 ⌸ u − states, with an accuracy estimated at 0.06 cm −1 . The new data also closely match multichannel quantum defect calculations performed for the ⌸ − components observed via the narrow Q-lines. The ⌳-doubling in the D 1 ⌸ u state was determined up to v = 17. The 10 m normal incidence scanning monochromator at the beamline U125/2 of the BESSY II synchrotron, combined with a home-built target chamber and equipped with a variety of detectors, was used to unravel information on ionization, dissociation, and intramolecular fluorescence decay for the D 1 ⌸ u vibrational series. The combined results yield accurate information on the characteristic Beutler-Fano profiles associated with the strongly predissociated ⌸ u + parity components of the D 1 ⌸ u levels. Values for the parameters describing the predissociation width as well as the Fano-q line shape parameters for the J = 1 and J = 2 rotational states were determined for the sequence of vibrational quantum numbers up to v = 17.
The Journal of Chemical Physics, 2011
The first comprehensive high-resolution photoabsorption spectrum of 14 N 15 N has been recorded u... more The first comprehensive high-resolution photoabsorption spectrum of 14 N 15 N has been recorded using the Fourier-transform spectrometer attached to the Desirs beamline at the Soleil synchrotron. Observations are made in the extreme ultraviolet (XUV) and span 100 000-109 000 cm −1 (100-91.7 nm). The observed absorption lines have been assigned to 25 bands and reduced to a set of transition energies, f values, and linewidths. This analysis has verified the predictions of a theoretical model of N 2 that simulates its photoabsorption and photodissociation cross section by solution of an isotopomer independent formulation of the coupled-channel Schrödinger equation. The mass dependence of predissociation linewidths and oscillator strengths is clearly evident and many local perturbations of transition energies, strengths, and widths within individual rotational series have been observed.
Proceedings of the National Academy of Sciences of the United States of America, Jan 27, 2015
Evolved interstellar ices observed in dense protostellar molecular clouds may arguably be conside... more Evolved interstellar ices observed in dense protostellar molecular clouds may arguably be considered as part of precometary materials that will later fall on primitive telluric planets, bringing a wealth of complex organic compounds. In our laboratory, experiments reproducing the photo/thermochemical evolution of these ices are routinely performed. Following previous amino acid identifications in the resulting room temperature organic residues, we have searched for a different family of molecules of potential prebiotic interest. Using multidimensional gas chromatography coupled to time-of-flight mass spectrometry, we have detected 10 aldehydes, including the sugar-related glycolaldehyde and glyceraldehyde--two species considered as key prebiotic intermediates in the first steps toward the synthesis of ribonucleotides in a planetary environment. The presence of ammonia in water and methanol ice mixtures appears essential for the recovery of these aldehydes in the refractory organic r...
Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life, 2002
Different mechanisms for the generation of circular polarization by the surface of planets and sa... more Different mechanisms for the generation of circular polarization by the surface of planets and satellites are described. The observed values for Venus, the Moon, Mars, and Jupiter obtained by photo-polarimetric measurements with Earth based telescopes, showed accordance with theory. However, for planet Mercury asymmetric parameters in the circular polarization were measured that do not fit with calculations. For BepiColombo, the ESA cornerstone mission 5 to Mercury, we propose to investigate this phenomenon using a concept which includes two instruments. The first instrument is a high-resolution optical polarimeter, capable to determine and map the circular polarization by remote scanning of Mercury's surface from the Mercury Planetary Orbiter MPO. The second instrument is an in situ sensor for the detection of the enantiomorphism of surface crystals and minerals, proposed to be included in the Mercury Lander MSE.
Instruments, Methods, and Missions for Astrobiology X, 2007
Assuming an extra-terrestrial formation of life's molecular building blocks such as amino-aci... more Assuming an extra-terrestrial formation of life's molecular building blocks such as amino-acids, a possible abiotic explanation for the selection of the L enantiomers could be the exposure to an asymmetric bias such as far UV Circularly Polarized Light (CPL), during their journey towards Earth, inducing some enantiomeric excess (e.e) that could then be amplified on Earth via suitable autocatalytic mechanisms.
The Astrophysical Journal, 2014
ABSTRACT
Review of Scientific Instruments, 2005
A refocusing modified velocity map imaging electron/ion spectrometer adapted to synchrotron radia... more A refocusing modified velocity map imaging electron/ion spectrometer adapted to synchrotron radiation studies. [Review of Scientific Instruments 76, 053302 (2005)]. Gustavo A. Garcia, Laurent Nahon, Chris J. Harding, Elisabeth A. Mikajlo, Ivan Powis. Abstract. ...
Review of Scientific Instruments, 2004
... KLReid (private communication). A copy of the pBasex program source running under linux is av... more ... KLReid (private communication). A copy of the pBasex program source running under linux is available by contacting GA Garcia at gustavo.garcia@lure.u-psud.fr. ... 2453, Bât 522, CE de Saclay, 91191 Gif sur Yvette, France; electronic mail: gustavo.garcia@lure.u-psud.fr. ...
Physics of Life Reviews, 2011
Proteins of all living organisms including plants, animals, and humans are made up of amino acid ... more Proteins of all living organisms including plants, animals, and humans are made up of amino acid monomers that show identical stereochemical L-configuration. Hypotheses for the origin of this symmetry breaking in biomolecules include the absolute asymmetric photochemistry model by which interstellar ultraviolet (UV) circularly polarized light (CPL) induces an enantiomeric excess in chiral organic molecules in the interstellar/circumstellar media. This scenario is supported by a) the detection of amino acids in the organic residues of UV-photo-processed interstellar ice analogues, b) the occurrence of L-enantiomer-enriched amino acids in carbonaceous meteorites, and c) the observation of CPL of the same helicity over large distance scales in the massive star-forming region of Orion. These topics are of high importance in topical biophysical research and will be discussed in this review. Further evidence that amino acids and other molecules of prebiotic interest are asymmetrically formed in space comes from studies on the enantioselective photolysis of amino acids by UV-CPL. Also, experiments have been performed on the absolute asymmetric photochemical synthesis of enantiomer-enriched amino acids from mixtures of astrophysically relevant achiral precursor molecules using UV-circularly polarized photons. Both approaches are based on circular dichroic transitions of amino acids that will be highlighted here as well. These results have strong implications on our current understanding of how life's precursor molecules were possibly built and how life selected the left-handed form of proteinogenic amino acids.
The Astrophysical Journal, 2011
... Here we report the first abiotic cosmic ice simulation experiments that produce species with ... more ... Here we report the first abiotic cosmic ice simulation experiments that produce species with enantiomeric excesses (ee's). Circularly polarized ultraviolet light (UV-CPL) from a synchrotron source induces asymmetric photochemistry on initially achiral inter/circumstellar ice ...
Chemistry & Biodiversity, 2010
Amino acids that pass the RNA machinery in living organisms occur in l-configuration. The questio... more Amino acids that pass the RNA machinery in living organisms occur in l-configuration. The question on the evolutionary origin of this biomolecular asymmetry remains unanswered to this day. Amino acids were detected in artificially produced interstellar ices, and l-enantiomer-enriched amino acids were identified in CM-type meteorites. This hints at a possible interstellar/circumstellar origin of the amino acids themselves as well as their stereochemical asymmetry. Based upon the current knowledge about the occurrence of circularly-polarized electromagnetic radiation in interstellar environments, we subjected rac-leucine to far-UV circularly-polarized synchrotron radiation. Asymmetric photolysis was followed by an analysis in an enantioselective GC/MS system. Here, we report on an advanced photolysis rate of more than 99% for leucine. The results indicate that high photolysis rates can occur under the chosen conditions, favoring enantioselective photolysis. In 2014, the obtained results will be reexamined by cometary mission Rosetta.
Angewandte Chemie, 2010
zum 80. Geburtstag gewidmet Biopolymere wie Nucleinsäuren und Proteine sind aus chiralen Monomere... more zum 80. Geburtstag gewidmet Biopolymere wie Nucleinsäuren und Proteine sind aus chiralen Monomeren einheitlicher stereochemischer Konfiguration aufgebaut. Natürlich vorkommende Proteine enthalten ausschließlich l-Aminosäuren. Eine der Hypothesen zur Erklärung dieses biomolekularen Symmetriebruchs beruht auf dem Modell der absoluten asymmetrischen Photochemie, dem zufolge circular polarisiertes (CP-)Licht einen Enantiomerenüberschuss in chiralen organischen Verbindungen zu induzieren vermag. Dieses Modell wird sowohl durch den Nachweis von CP-Licht in der sternenbildenden Region des Orions als auch durch die Bestimmung von l-Enantiomerangereicherten Aminosäuren in kohlenstoffhaltigen Meteoriten [8] genährt. Allerdings ist die differenzielle Absorption des CP-Lichtes durch Aminosäure-Enantiomere, die die Geschwindigkeit und Intensität einer enantioselektiven Photolyse bestimmt, über einen weiten Spektralbereich unbekannt. Wir zeigen, dass massive Übergänge im Circulardichroismus (CD) von Aminosäuren beobachtet werden können, indem die CD-Spektroskopie auf den Vakuumultravioletten (Vakuum-UV-)Spektralbereich ausgeweitet wird. a-H-Aminosäuren zeigen über einen großen Spektralbereich dieselbe Größe und dasselbe Vorzeichen im CD. In einem gegebenen spektralen Fenster kann CP-Licht einen Enantiomerenüberschuss derselben Händigkeit in den untersuchten proteinogenen Aminosäuren induzieren. Absolute asymmetrische Photochemie vermag daher die Entwicklung von Leben auf der Erde, das auf l-Aminosäuren beruht, ausgelöst zu haben. Unsere Befunde zeigen, dass Enantiomere von "meteoritischen" a-Methylaminosäuren eine dichroitische Absorption derselben Größe, jedoch unterschiedlichen Vorzeichens aufweisen. Daher ist es nicht möglich, dass CP-Licht einen l-Enantiomerenüberschuss in sowohl a-Methylaminosäuren als auch a-H-Aminosäuren induziert, wie sie in Meteoriten gefunden werden.
Angewandte Chemie International Edition, 2010
Dedicated to Professor Henri B. Kagan on the occasion of his 80th birthday Biopolymers such as nu... more Dedicated to Professor Henri B. Kagan on the occasion of his 80th birthday Biopolymers such as nucleic acids and proteins are composed of chiral monomers that show identical stereochemical configuration. Naturally occurring proteins are made up of l-amino acids. Hypotheses for the origin of symmetry breaking in biomolecules include the absolute asymmetric photochemistry model by which circularly polarized (CP) light induces an enantiomeric excess (ee) in chiral organic molecules. This model is supported by both the observation of CP light in the star-forming region of Orion and the occurrence of l-enantiomer-enriched amino acids in carbonaceous meteorites. [8] However, the differential absorption of CP light by amino acid enantiomers, which determines the speed and intensity of enantioselective photolysis, is unknown over a large spectral range. Here we show that significant circular dichroic transitions in amino acids can be observed by extending circular dichroism (CD) spectroscopy to the vacuum-ultraviolet (UV) spectral range. a-H amino acids show the same CD magnitude and sign over a large wavelength range. In a given spectral window CP light is therefore capable of inducing enantiomeric excesses of the same handedness into the proteinogenic amino acids we have studied. Absolute asymmetric photochemistry might thus well have triggered the appearance of l-amino acid based life on Earth. Our results demonstrate that enantiomers of "meteoritic" a-methyl amino acids show dichroic absorption with equal magnitude, yet opposite sign to a-H amino acids. Therefore CP light cannot induce l enantiomeric excesses into a-methyl and a-H amino acids as found in meteorites.
Current research focuses on a better understanding of the origin of biomolecular asymmetry by the... more 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
Origins of Life and Evolution of Biospheres, 2015
All life on Earth is characterized by its asymmetry - both the genetic material and proteins are ... more All life on Earth is characterized by its asymmetry - both the genetic material and proteins are composed of homochiral monomers. Understanding how this molecular asymmetry initially arose is a key question related to the origins of life. Cometary ice simulations, L-enantiomeric enriched amino acids in meteorites and the detection of circularly polarized electromagnetic radiation in star-forming regions point to a possible interstellar/protostellar generation of stereochemical asymmetry. Based upon our recently recorded anisotropy spectra g(λ) of amino acids in the vacuum-UV range, we subjected amorphous films of racemic (13)C-alanine to far-UV circularly polarized synchrotron radiation to probe the asymmetric photon-molecule interaction under interstellar conditions. Optical purities of up to 4 % were reached, which correlate with our theoretical predictions. Importantly, we show that chiral symmetry breaking using circularly polarized light is dependent on both the helicity and the wavelength of incident light. In order to predict such stereocontrol, time-dependent density functional theory was used to calculate anisotropy spectra. The calculated anisotropy spectra show good agreement with the experimental ones. The European Space Agency's Rosetta mission, which successfully landed Philae on comet 67P/Churyumov-Gerasimenko on 12 November 2014, will investigate the configuration of chiral compounds and thereby obtain data that are to be interpreted in the context of the results presented here.
Current research focuses on a better understanding of the origin of biomolecular asymmetry by the... more 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
Angewandte Chemie International Edition, 2010
Dedicated to Professor Henri B. Kagan on the occasion of his 80th birthday Biopolymers such as nu... more Dedicated to Professor Henri B. Kagan on the occasion of his 80th birthday Biopolymers such as nucleic acids and proteins are composed of chiral monomers that show identical stereochemical configuration. Naturally occurring proteins are made up of l-amino acids. Hypotheses for the origin of symmetry breaking in biomolecules include the absolute asymmetric photochemistry model by which circularly polarized (CP) light induces an enantiomeric excess (ee) in chiral organic molecules. This model is supported by both the observation of CP light in the star-forming region of Orion and the occurrence of l-enantiomer-enriched amino acids in carbonaceous meteorites. [8] However, the differential absorption of CP light by amino acid enantiomers, which determines the speed and intensity of enantioselective photolysis, is unknown over a large spectral range. Here we show that significant circular dichroic transitions in amino acids can be observed by extending circular dichroism (CD) spectroscopy to the vacuum-ultraviolet (UV) spectral range. a-H amino acids show the same CD magnitude and sign over a large wavelength range. In a given spectral window CP light is therefore capable of inducing enantiomeric excesses of the same handedness into the proteinogenic amino acids we have studied. Absolute asymmetric photochemistry might thus well have triggered the appearance of l-amino acid based life on Earth. Our results demonstrate that enantiomers of "meteoritic" a-methyl amino acids show dichroic absorption with equal magnitude, yet opposite sign to a-H amino acids. Therefore CP light cannot induce l enantiomeric excesses into a-methyl and a-H amino acids as found in meteorites.
The Journal of Chemical Physics, 2010
The 3pD 1 ⌸ u state of the H 2 molecule was reinvestigated with different techniques at two synch... more The 3pD 1 ⌸ u state of the H 2 molecule was reinvestigated with different techniques at two synchrotron installations. The Fourier transform spectrometer in the vacuum ultraviolet wavelength range of the DESIRS beamline at the SOLEIL synchrotron was used for recording absorption spectra of the D 1 ⌸ u state at high resolution and high absolute accuracy, limited only by the Doppler contribution at 100 K. From these measurements, line positions were extracted, in particular, for the narrow resonances involving 1 ⌸ u − states, with an accuracy estimated at 0.06 cm −1 . The new data also closely match multichannel quantum defect calculations performed for the ⌸ − components observed via the narrow Q-lines. The ⌳-doubling in the D 1 ⌸ u state was determined up to v = 17. The 10 m normal incidence scanning monochromator at the beamline U125/2 of the BESSY II synchrotron, combined with a home-built target chamber and equipped with a variety of detectors, was used to unravel information on ionization, dissociation, and intramolecular fluorescence decay for the D 1 ⌸ u vibrational series. The combined results yield accurate information on the characteristic Beutler-Fano profiles associated with the strongly predissociated ⌸ u + parity components of the D 1 ⌸ u levels. Values for the parameters describing the predissociation width as well as the Fano-q line shape parameters for the J = 1 and J = 2 rotational states were determined for the sequence of vibrational quantum numbers up to v = 17.
The Journal of Chemical Physics, 2011
The first comprehensive high-resolution photoabsorption spectrum of 14 N 15 N has been recorded u... more The first comprehensive high-resolution photoabsorption spectrum of 14 N 15 N has been recorded using the Fourier-transform spectrometer attached to the Desirs beamline at the Soleil synchrotron. Observations are made in the extreme ultraviolet (XUV) and span 100 000-109 000 cm −1 (100-91.7 nm). The observed absorption lines have been assigned to 25 bands and reduced to a set of transition energies, f values, and linewidths. This analysis has verified the predictions of a theoretical model of N 2 that simulates its photoabsorption and photodissociation cross section by solution of an isotopomer independent formulation of the coupled-channel Schrödinger equation. The mass dependence of predissociation linewidths and oscillator strengths is clearly evident and many local perturbations of transition energies, strengths, and widths within individual rotational series have been observed.
Proceedings of the National Academy of Sciences of the United States of America, Jan 27, 2015
Evolved interstellar ices observed in dense protostellar molecular clouds may arguably be conside... more Evolved interstellar ices observed in dense protostellar molecular clouds may arguably be considered as part of precometary materials that will later fall on primitive telluric planets, bringing a wealth of complex organic compounds. In our laboratory, experiments reproducing the photo/thermochemical evolution of these ices are routinely performed. Following previous amino acid identifications in the resulting room temperature organic residues, we have searched for a different family of molecules of potential prebiotic interest. Using multidimensional gas chromatography coupled to time-of-flight mass spectrometry, we have detected 10 aldehydes, including the sugar-related glycolaldehyde and glyceraldehyde--two species considered as key prebiotic intermediates in the first steps toward the synthesis of ribonucleotides in a planetary environment. The presence of ammonia in water and methanol ice mixtures appears essential for the recovery of these aldehydes in the refractory organic r...
Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life, 2002
Different mechanisms for the generation of circular polarization by the surface of planets and sa... more Different mechanisms for the generation of circular polarization by the surface of planets and satellites are described. The observed values for Venus, the Moon, Mars, and Jupiter obtained by photo-polarimetric measurements with Earth based telescopes, showed accordance with theory. However, for planet Mercury asymmetric parameters in the circular polarization were measured that do not fit with calculations. For BepiColombo, the ESA cornerstone mission 5 to Mercury, we propose to investigate this phenomenon using a concept which includes two instruments. The first instrument is a high-resolution optical polarimeter, capable to determine and map the circular polarization by remote scanning of Mercury's surface from the Mercury Planetary Orbiter MPO. The second instrument is an in situ sensor for the detection of the enantiomorphism of surface crystals and minerals, proposed to be included in the Mercury Lander MSE.
Instruments, Methods, and Missions for Astrobiology X, 2007
Assuming an extra-terrestrial formation of life's molecular building blocks such as amino-aci... more Assuming an extra-terrestrial formation of life's molecular building blocks such as amino-acids, a possible abiotic explanation for the selection of the L enantiomers could be the exposure to an asymmetric bias such as far UV Circularly Polarized Light (CPL), during their journey towards Earth, inducing some enantiomeric excess (e.e) that could then be amplified on Earth via suitable autocatalytic mechanisms.
The Astrophysical Journal, 2014
ABSTRACT
Review of Scientific Instruments, 2005
A refocusing modified velocity map imaging electron/ion spectrometer adapted to synchrotron radia... more A refocusing modified velocity map imaging electron/ion spectrometer adapted to synchrotron radiation studies. [Review of Scientific Instruments 76, 053302 (2005)]. Gustavo A. Garcia, Laurent Nahon, Chris J. Harding, Elisabeth A. Mikajlo, Ivan Powis. Abstract. ...
Review of Scientific Instruments, 2004
... KLReid (private communication). A copy of the pBasex program source running under linux is av... more ... KLReid (private communication). A copy of the pBasex program source running under linux is available by contacting GA Garcia at gustavo.garcia@lure.u-psud.fr. ... 2453, Bât 522, CE de Saclay, 91191 Gif sur Yvette, France; electronic mail: gustavo.garcia@lure.u-psud.fr. ...
Physics of Life Reviews, 2011
Proteins of all living organisms including plants, animals, and humans are made up of amino acid ... more Proteins of all living organisms including plants, animals, and humans are made up of amino acid monomers that show identical stereochemical L-configuration. Hypotheses for the origin of this symmetry breaking in biomolecules include the absolute asymmetric photochemistry model by which interstellar ultraviolet (UV) circularly polarized light (CPL) induces an enantiomeric excess in chiral organic molecules in the interstellar/circumstellar media. This scenario is supported by a) the detection of amino acids in the organic residues of UV-photo-processed interstellar ice analogues, b) the occurrence of L-enantiomer-enriched amino acids in carbonaceous meteorites, and c) the observation of CPL of the same helicity over large distance scales in the massive star-forming region of Orion. These topics are of high importance in topical biophysical research and will be discussed in this review. Further evidence that amino acids and other molecules of prebiotic interest are asymmetrically formed in space comes from studies on the enantioselective photolysis of amino acids by UV-CPL. Also, experiments have been performed on the absolute asymmetric photochemical synthesis of enantiomer-enriched amino acids from mixtures of astrophysically relevant achiral precursor molecules using UV-circularly polarized photons. Both approaches are based on circular dichroic transitions of amino acids that will be highlighted here as well. These results have strong implications on our current understanding of how life's precursor molecules were possibly built and how life selected the left-handed form of proteinogenic amino acids.
The Astrophysical Journal, 2011
... Here we report the first abiotic cosmic ice simulation experiments that produce species with ... more ... Here we report the first abiotic cosmic ice simulation experiments that produce species with enantiomeric excesses (ee's). Circularly polarized ultraviolet light (UV-CPL) from a synchrotron source induces asymmetric photochemistry on initially achiral inter/circumstellar ice ...
Chemistry & Biodiversity, 2010
Amino acids that pass the RNA machinery in living organisms occur in l-configuration. The questio... more Amino acids that pass the RNA machinery in living organisms occur in l-configuration. The question on the evolutionary origin of this biomolecular asymmetry remains unanswered to this day. Amino acids were detected in artificially produced interstellar ices, and l-enantiomer-enriched amino acids were identified in CM-type meteorites. This hints at a possible interstellar/circumstellar origin of the amino acids themselves as well as their stereochemical asymmetry. Based upon the current knowledge about the occurrence of circularly-polarized electromagnetic radiation in interstellar environments, we subjected rac-leucine to far-UV circularly-polarized synchrotron radiation. Asymmetric photolysis was followed by an analysis in an enantioselective GC/MS system. Here, we report on an advanced photolysis rate of more than 99% for leucine. The results indicate that high photolysis rates can occur under the chosen conditions, favoring enantioselective photolysis. In 2014, the obtained results will be reexamined by cometary mission Rosetta.
Angewandte Chemie, 2010
zum 80. Geburtstag gewidmet Biopolymere wie Nucleinsäuren und Proteine sind aus chiralen Monomere... more zum 80. Geburtstag gewidmet Biopolymere wie Nucleinsäuren und Proteine sind aus chiralen Monomeren einheitlicher stereochemischer Konfiguration aufgebaut. Natürlich vorkommende Proteine enthalten ausschließlich l-Aminosäuren. Eine der Hypothesen zur Erklärung dieses biomolekularen Symmetriebruchs beruht auf dem Modell der absoluten asymmetrischen Photochemie, dem zufolge circular polarisiertes (CP-)Licht einen Enantiomerenüberschuss in chiralen organischen Verbindungen zu induzieren vermag. Dieses Modell wird sowohl durch den Nachweis von CP-Licht in der sternenbildenden Region des Orions als auch durch die Bestimmung von l-Enantiomerangereicherten Aminosäuren in kohlenstoffhaltigen Meteoriten [8] genährt. Allerdings ist die differenzielle Absorption des CP-Lichtes durch Aminosäure-Enantiomere, die die Geschwindigkeit und Intensität einer enantioselektiven Photolyse bestimmt, über einen weiten Spektralbereich unbekannt. Wir zeigen, dass massive Übergänge im Circulardichroismus (CD) von Aminosäuren beobachtet werden können, indem die CD-Spektroskopie auf den Vakuumultravioletten (Vakuum-UV-)Spektralbereich ausgeweitet wird. a-H-Aminosäuren zeigen über einen großen Spektralbereich dieselbe Größe und dasselbe Vorzeichen im CD. In einem gegebenen spektralen Fenster kann CP-Licht einen Enantiomerenüberschuss derselben Händigkeit in den untersuchten proteinogenen Aminosäuren induzieren. Absolute asymmetrische Photochemie vermag daher die Entwicklung von Leben auf der Erde, das auf l-Aminosäuren beruht, ausgelöst zu haben. Unsere Befunde zeigen, dass Enantiomere von "meteoritischen" a-Methylaminosäuren eine dichroitische Absorption derselben Größe, jedoch unterschiedlichen Vorzeichens aufweisen. Daher ist es nicht möglich, dass CP-Licht einen l-Enantiomerenüberschuss in sowohl a-Methylaminosäuren als auch a-H-Aminosäuren induziert, wie sie in Meteoriten gefunden werden.
Angewandte Chemie International Edition, 2010
Dedicated to Professor Henri B. Kagan on the occasion of his 80th birthday Biopolymers such as nu... more Dedicated to Professor Henri B. Kagan on the occasion of his 80th birthday Biopolymers such as nucleic acids and proteins are composed of chiral monomers that show identical stereochemical configuration. Naturally occurring proteins are made up of l-amino acids. Hypotheses for the origin of symmetry breaking in biomolecules include the absolute asymmetric photochemistry model by which circularly polarized (CP) light induces an enantiomeric excess (ee) in chiral organic molecules. This model is supported by both the observation of CP light in the star-forming region of Orion and the occurrence of l-enantiomer-enriched amino acids in carbonaceous meteorites. [8] However, the differential absorption of CP light by amino acid enantiomers, which determines the speed and intensity of enantioselective photolysis, is unknown over a large spectral range. Here we show that significant circular dichroic transitions in amino acids can be observed by extending circular dichroism (CD) spectroscopy to the vacuum-ultraviolet (UV) spectral range. a-H amino acids show the same CD magnitude and sign over a large wavelength range. In a given spectral window CP light is therefore capable of inducing enantiomeric excesses of the same handedness into the proteinogenic amino acids we have studied. Absolute asymmetric photochemistry might thus well have triggered the appearance of l-amino acid based life on Earth. Our results demonstrate that enantiomers of "meteoritic" a-methyl amino acids show dichroic absorption with equal magnitude, yet opposite sign to a-H amino acids. Therefore CP light cannot induce l enantiomeric excesses into a-methyl and a-H amino acids as found in meteorites.
Current research focuses on a better understanding of the origin of biomolecular asymmetry by the... more 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