Anisotropy-Guided Enantiomeric Enhancement in AlanineUsing Far-UV Circularly Polarized Light
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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 13C-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.
KeywordsAmino acids Anisotropy Homochirality Asymmetric photolysis Origins of life Chiral photons
We are grateful to the general technical staff of the ASTRID synchrotron and for technical and beam line assistance at the SOLEIL facilities. This work was supported by the Agence Nationale de la Recherche (ANR-07-BLAN-0293 and ANR-12-IS07-0006). This work was furthermore supported by the I3 Integrated Activity on Synchrotron and Free Electron Laser Science (IA-SFS), contract no. RII3-CT-2004-506008, under the Research Infrastructure Action of the FP6 EC program Structuring the European Research Area as well as the European Community’s Seventh Framework Program (FP7/2007–2013; grant no. 226716).
Conflicts of Interest
All authors are requested to disclose any actual or potential conflict of interest including any financial, personal or other relationships with other people or organizations
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