Photochemical processing of amino acids in Earth orbit

Space technology in Earth orbit has been used to investigate whether amino acids and peptides required for the emergence of life can be safely transported to Earth vicinity when they are associated with minerals. In the BIOPAN-1 flight experiment, l-amino acids and one dipeptide were exposed to space conditions, free and associated with clays. Six amino acids found in the Murchison meteorite (Gly, Ala, Leu, Val, Asp, Glu) were tested with respect to chemical degradation and racemization. In addition, photosensitive l-tyrosine was used to check possible oligotyrosine formation. The dipeptide l-alanyl-l-alanine was chosen to test the stability of the peptide bond. No detectable traces of d-amino acids could be found after the flight in any of the samples. Aspartic acid and glutamic acid exposed as free samples have been partially decomposed during exposure to solar UV. Decomposition was prevented when the amino acids were embedded in montmorillonite or kaolinite. The other amino acids were unaffected by the flight. Tyrosine did not condense and the dipeptide remained stable.