Rcpl

1.11*

* Designated e.e.-values give excesses for a-l-alanine and l-DAP enantiomers

* Designated e.e.-values give excesses for a-l-alanine and l-DAP enantiomers

22,0 22,5 23,0 23,5 24,0 24,5 25,0 25,5 26,0 26,5 27,0 27,5 28,0

f/min

Fig. 7.6 Gas chromatograms of the chiral amino acids a-alanine (top) and 2,3-diaminopropanoic acid (bottom) identified in residues made from UV-photoprocessing of interstellar ice analogues after irradiation with unpolarized light (red line) and right-circularly polarized synchrotron irradiation (blue line). Chromatograms were taken on a 25 m Chirasil-d-Val stationary phase and recorded in single ion monitoring (SIM) mode at 118 amu for alanine and 177 amu for 2,3-diaminopropanoic acid. In the blank sample (green line) no amino acids and/or diamino acids were detected

22,0 22,5 23,0 23,5 24,0 24,5 25,0 25,5 26,0 26,5 27,0 27,5 28,0

f/min

Fig. 7.6 Gas chromatograms of the chiral amino acids a-alanine (top) and 2,3-diaminopropanoic acid (bottom) identified in residues made from UV-photoprocessing of interstellar ice analogues after irradiation with unpolarized light (red line) and right-circularly polarized synchrotron irradiation (blue line). Chromatograms were taken on a 25 m Chirasil-d-Val stationary phase and recorded in single ion monitoring (SIM) mode at 118 amu for alanine and 177 amu for 2,3-diaminopropanoic acid. In the blank sample (green line) no amino acids and/or diamino acids were detected

In the field of absolute asymmetric photochemistry, it is hard to obtain evidence by laboratory simulation experiments only. Because of this, all of the experimental results based on the use of circularly polarized light, and in particular those obtained for amino acids (Flores et al. 1977; Meierhenrich et al. 2005b), should be compared with extraterrestrial material data, i.e., analyses of meteorites such as Murchison and Murray, where amino acids were detected and found to display L-enantiomeric excesses after chemical analysis. The next chapter is therefore dedicated to systematically describing the enantioselective analysis of extraterrestrial samples.

The determination of values for enantiomeric excesses in various extraterrestrial samples has become part of ambitious space scientific programs. Today, the measurement of enantioenrichments is included for the first time in one of the cornerstone missions of the European Space Agency (ESA) whose 'chirality-part' was constructed at the Max Planck Institute for Solar System Research in KatlenburgLindau, Germany. For this program, the cometary mission ROSETTA is designed -among else - to separate chiral organic molecules on the surface of a comet and to determine values of enantiomeric excesses for a wide range of chiral organic molecules. The enantioselective GC-MS analyses taken on the Agilent 6890/5973 GC-MSD system in our laboratory are indeed envisaged to be reproduced by the GC-MS system developed for the ROSETTA-Lander Cometary Sampling and Composition experiment COSAC. The COSAC gas chromatograph-module is consequently equipped with the same set of capillaries/stationary phases (Goesmann et al. 2007b) that will be explained in Chap. 9.

The US space agency NASA has independently demonstrated its interest in measurements of the enantiomeric composition of chiral molecules in extraterrestrial samples. Scientists are willing to separate and quantify enantiomers of hydrocarbons originating from Saturn's moon Titan. A future mission, described in a special 2001 issue of the journal 'Enantiomer' called 'Chirons on Titan: A Search for Extraterrestrial Enantioenrichment', will focus on this task.

Moreover, in 2014, the joint ESA-NASA mission ExoMars envisages to set down two instruments on the surface of the planet Mars that are capable of distinguishing between enantiomers. One instrument, the Mars Organic Molecule Analyser (MOMA) is equipped with an enantioselective gas chromatograph on chiral stationary phases; the other is the UREY-instrument, which relies on enantioselective capillary electrophoresis with a liquid mobile phase. The objectives, scientific concepts, advantages (and eventual limitations) of these instruments, which are of crucial importance to the study of the origin of biomolecular asymmetry, will be introduced in Chap. 9.

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