I will discuss results on the photostability of some simple prebiotic molecules, as well as aminoacids and nucleic acid bases, which we have studied in the gas phase using synchrotron radiation as excitation source. Formic acid, HCOOH, is an  example of a simple prebiotic molecule. It is one of the possible building blocks of biomolecules and it has been observed by radioastronomy in several sites in the interstellar medium (ISM), in particular in regions of massive star formation. It is a general component of ices occurring in the vicinity of embedded high-mass young stellar objects. Its photochemical decomposition products, such as HCO, have been observed in interstellar clouds. Although the ion HCOOH+ has not been observed directly in the ISM, decomposition products such as HCO+, which plays an important role in molecule formation in interstellar clouds, and HOCO+,  have been observed by radioastronomy. The photophysical properties of HCOOH which we have studied  in the VUV are thus of direct interest for radioastronomy searches and for exobiology studies. Results on HCOOH, CH3COOH, CH3CN, etc., will be presented.
 Aminoacids  have been postulated to be formed, and have been searched for, in certain astrophysical sites, while abiotic aminoacids have been detected in carbonaceous chondrite meteorites. Determining the nature of the fragmentation products under UV radiation will help in choosing prospective observational sites, as well as providing information on possible mechanisms of formation and destruction of aminoacids in meteoritic materials. Some of the photofragmentation products of glycine, ?-alanine and ?-alanine  include species observed in the ISM, e.g. HCNH+.  We observed marked effects of alanine isomerisation on the photostability and nature of the dissociative ionization products. We have also investigated other aminoacids observed in meteorites, for example ?-amino-isobutyric acid, which is the most abundant aminoacid in the Murchison meteorite, as well as valine and leucine.
 Preliminary studies on three nucleic acid bases, uracil, thymine and adenine have shown the importance of the reactions in which neutral or ionized HCNO species are formed. HCNO has been observed in the ISM by radioastronomy. These initial laboratory experiments are being extended in order to study in more detail some of the minor products.
 A comparison will be made between the results of our studies and those of condensed phase species that have been exposed to solar UV radiation in a BIOPAN-1 and BIOPAN-2 experiments fixed to the Russian FOTON-9 satellite.  Space radiation exposure experiments planned to be carried out on the International Space Station will be discussed.