Preservation of homochirality of aspartic acid films irradiated with 8.5Â eV vacuum ultraviolet light

Enantiomeric excess was reported for amino acids detected from some meteorites. These results imply that these amino acids might escape from racemization processes in space. Here, in an attempt to examine whether non-polarized vacuum ultraviolet (VUV) light was one of racemization factors, we irradiated solid films of homochiral l- or d-aspartic acid (l- or d-Asp) with a 146 nm excimer lamp in vacuum at 290 K. After irradiation for l-Asp films, l-alanine (l-Ala) and β-Ala were observed, but d-Asp or d-Ala was not observed. On the contrast, for irradiation to d-Asp films, d-Ala and β-Ala were observed, but l-Asp or l-Ala was not observed. Therefore, we concluded that the chirality was preserved through the photolysis of Asp to Ala. It is of interest to carry out the similar experiments using high-energy particles and/or γ-ray irradiation.