Survival of gas phase amino acids and nucleobases in space radiation conditions

Abstract

Abstract.We present experimental studies on the photoionization and photodissociation processes (photodestruction) of gaseous amino acids and nucleobases in interstellar and interplanetary radiation analogs conditions. The measurements have been undertaken at the Brazilian Synchrotron Light Laboratory (LNLS), employing vacuum ultraviolet (VUV) and soft X-ray photons. The experimental set up basically consists of a time-of-flight mass spectrometer kept under high vacuum conditions. Mass spectra were obtained using a photoelectron photoion coincidence technique. We have shown that the amino acids are effectively more destroyed (up to 70-80%) by the stellar radiation than the nucleobases, mainly in the VUV. Since polycyclic aromatic hydrocarbons have the same survival capability and seem to be ubiquitous in the ISM, it is not unreasonable to predict that nucleobases could survive in the interstellar medium and/or in comets, even as a stable cation.

Electron asymmetries in the photoionization of chiral molecules: possible astrophysical implications

“…Besides, an important point for this astrophysical scenario is the fact that the b 1 parameter keeps a constant sign over the whole studied VUV range, except for the very limited range between the ionization energy and 9.6 eV, for which b 1 has an opposite sign compared to the rest of the spectrum, and for which the photoionization cross section and m/z 89 absolute yields are quite small, one order of magnitude below the corresponding one at 10.2 eV (Lyman-α radiation energy) [148]. Overall, by integrating over the whole UV/VUV spectrum encountered either in the ISM/CSM or close to the solar system [135], largely dominated by the Lyman-α radiation, and taking into account the ionization cross sections reaching a plateau around 18 eV and then decreasing [148], and the fact that the PECD effect vanishes in general in the 10's eV above the ionization energy, there is no way, at least in the case of alanine, that the asymmetry would cancel out because of the alternating sign of b 1 , nor because of a possible blurring out due to the various conformer contributions.…”

“…We focus first on Ala, the simplest chiral amino acid which is the second one, after the non-chiral amino acid glycine, to have been recruited by life [132]. Ala has been the subject of a thorough VUV PECD study [72] with a specific focus onto the PECD recorded at the Lyman-α radiation wavelength (121.6 nm = 10.2 eV) [133], of major astrophysical relevance, since it dominates by far the UV/ VUV ISM/CSM spectrum [129,134,135].…”

VUV state-selected photoionization of thermally-desorbed biomolecules by coupling an aerosol source to an imaging photoelectron/photoion coincidence spectrometer: case of the amino acids tryptophan and phenylalanine

“…3 In this particular context, UV irradiation experiments of small biomolecules have been performed using condensed phase samples and lamps with broad spectral emission, 4 as well as tunable synchrotron radiation (SR) based experiments with gaseous samples. 5,6 These experiments have shown for instance that amino acids are more destroyed by VUV radiation-induced dissociative ionization than nucleobases. 6 Considering the biological importance of amino acids, a better understanding of their interactions and chemical reactivity needs precise knowledge of their valence-shell ionic electronic structure which can be probed, for example, by photoelectron spectroscopy (PES).…”

“…5,6 These experiments have shown for instance that amino acids are more destroyed by VUV radiation-induced dissociative ionization than nucleobases. 6 Considering the biological importance of amino acids, a better understanding of their interactions and chemical reactivity needs precise knowledge of their valence-shell ionic electronic structure which can be probed, for example, by photoelectron spectroscopy (PES). 7,8 There is therefore a growing scientific need for experimental methods to transport fragile biomolecules into the gas phase.…”

Fragmentation patterns of core-ionized thymine and 5-bromouracil

“…5,6 The response of the DNA bases to x-rays or UV-radiation has received recent attention also by those interested in the origins and development of the molecular ingredients of life in early earth environments. 14 This paper investigates the soft x-ray induced fragmentation processes of thymine ͑T͒, one of the four nucleobases in DNA, and its radiosensitizing analog 5-bromouracil ͑5-BrU͒, using photoelectron-photoion-photoion coincidence ͑PEPIPICO͒ spectroscopy. [9][10][11][12][13] One important aspect when discussing, for example, the possible delivery of DNA bases to our planet from outer space is the exposure and reactions of these molecules to ionizing radiation.…”