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Modeling of the prebiotic synthesis of oligopeptides: silicate catalysts help to overcome the critical stage. Origins of Life and Evolution of the Biosphere, 27:325–337. E-mail: nkitadai@ess.​sci.​osaka-u.​ac.​jp Formation and Photo-Stability of Pyrimidine Derivatives from the UV Irradiation of Pyrimidine in Ices Michel Nuevo1, Stefanie Milam1,2, Scott Sandford1, Jamie Elsila3 1NASA Ames Research Center, Moffett Field, CA 94035, USA; 2, 3NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA The detection of amino acids in organic residues formed by the UV photolysis of ices mimicking interstellar and cometary environments (H2O, CO, CO2, CH3OH, NH3, etc.) showed that molecules of prebiotic interest can form easily in space (Bernstein et al. 2002; Muñoz Caro et al. 2002). This result agrees with the detection 4SC-202 solubility dmso of amino acids in meteorites (Engel and Macko 1997; Cronin and Pizzarello 1997) although their distribution appears

to be different (Nuevo et al. 2008), and the (still debated) detection of glycine in molecular clouds (Kuan et al. 2003; Snyder et al. 2005), supporting a scenario where the organic molecules required for life are of extraterrestrial (interstellar or proto-planetary) origin, before being delivered by asteroids, Cyclic nucleotide phosphodiesterase comets, micrometeorites and interstellar dust particles on Earth. Nucleobases, the building blocks of DNA, constitute another family of prebiotic compounds likely to be formed in space. Larger than amino acids, they are expected to be formed with smaller abundances,

and their detection in organic residues requires a specific chemical analytical protocol. Small functionalized polycyclic aromatic hydrocarbons (PAHs), whose structures are close to some of the nucleobases, as well as Proteasome cleavage nucleobases themselves have been detected in meteorites (Stoks and Schwartz 1979; Martins et al. 2004). The formation of nucleobase-like compounds from the UV irradiation of PAHs mixed in ices has been studied in the laboratory (Bernstein et al. 1999, 2001). In this work, we present a study of the formation of organic compounds from the UV irradiation of pyrimidine at low temperature in ices (H2O, NH3). Pyrimidine (C4H4N2) is the base molecule for three of the five biological nucleobases (cytosine, thymine and uracil), as well as many other derivative compounds. This work aims at studying how pyrimidine is affected by UV photons when it is mixed with precometary ice analogs. In particular, we show how pyrimidine leads to the production of oxidized and amino compounds including nucleobases using high-performance liquid chromatography (HPLC), and study the photo-stability of pyrimidine and its photo-products when subjected to UV photons. Bernstein, M. P., Sandford, S. A., Allamandola, L. J., Gillette, J. S., Clemett, S. J.