Book of Abstracts: Albany 2011
June 14-18 2011
©Adenine Press (2010)
Formation and Chiroptical Properties of Amino Acids in Interstellar Ice Analogues
Comets are accretions of frozen volatiles and rocky debris left over from the formation of the outer Solar System (1). In order to better understand the chemical and molecular composition of comets their formation was artificially and stepwie reproduced in the laboratory. To this end, representative interstellar molecules containing C1 and N1 units such as 13CO and NH3 were condensed on a solid surface at 12 K while being irradiated at Lyman α. The obtained interstellar ice analogues were subjected to enantioselective gas chromatographic and mass spectrometric analysis allowing us the identification of 16 different amino acids and diamino acids (2) The molecular composition of these ices was found to be similar, but not identical, to the amino acids and diamino acids identified in meteorites (3) and will be discussed in the context of the molecular origin of life on Earth. Terrestrial life uses homochiral L amino acids for the expression of proteins (4). In a follow-up study we investigated whether a chiral symmetry breaking in amino acids is feasible under simulated interstellar conditions based upon an asymmetric photochemical mechanism. In a UHV-chamber we deposited amorphous amino acid films of defined thickness on MgF2 windows (see Figure) and subjected them to circularly polarized light. The differential absorption of circularly polarized light by individual amino acid enantiomers, which determines speed and intensity of enantioselective photolysis, was recorded in the vacuum-ultraviolet spectral range, where massive circular dichroic transitions were observed (5). We report on the formation of amino acids and diamino acids under interstellar conditions and on chiroptical properties of amino acids in the solid state. These data are of importance for the molecular understanding for both origin and evolution of life on Earth and its molecular asymmetry.
This research has been supported by grants from the ANR and the European Community’s Seventh Framework Program
Uwe J. Meierhenrich
University of Nice-Sophia Antipolis