Perturbation of isotherms below topography: constraints from tunnel transects through the Alps, Gotthard road tunnel

For many years it has been known that near surface isotherms are influenced by the topography (Lees 1910). Recently, a number of studies were pursued to quantify the effect of topography on low temperature isotherms (e.g. Stüwe et al. 1994, Mancktelow & Grasemann 1997). The magnitude of perturbation depends on several parameters: exhumation rate, geothermal gradient, wavelength and amplitude of topography, and finally by the age of surface relief change (Braun 2002).conferenc

The Origin of Primitive Cells, Nutrient Intake, and Non-Enzymatic Elongation of Encapsulated Nucleotides

Fatty acids and fatty alcohols are commonly found in experiments simulating the prebiotic 'soup'. These amphiphiles can be synthesized under prebiotic conditions, at least as long as the molecules are chemically relatively simple and do not need to be enantiomerically pure. In the context of topical origin-of-life theories, two distinct formation pathways for amphiphiles have been described; one related to geophysical sites, such as marine hydrothermal systems, and another to extraterrestrial sources, such as the proto-solar nebula, which was fed by interplanetary and interstellar nebulae. The chemical analysis of each provides individual characteristic challenges

Life-Detection Technologies for the Next Two Decades

Since its inception six decades ago, astrobiology has diversified immensely to encompass several scientific questions including the origin and evolution of Terran life, the organic chemical composition of extraterrestrial objects, and the concept of habitability, among others. The detection of life beyond Earth forms the main goal of astrobiology, and a significant one for space exploration in general. This goal has galvanized and connected with other critical areas of investigation such as the analysis of meteorites and early Earth geological and biological systems, materials gathered by sample-return space missions, laboratory and computer simulations of extraterrestrial and early Earth environmental chemistry, astronomical remote sensing, and in-situ space exploration missions. Lately, scattered efforts are being undertaken towards the R&D of the novel and as-yet-space-unproven life-detection technologies capable of obtaining unambiguous evidence of extraterrestrial life, even if it is significantly different from Terran life. As the suite of space-proven payloads improves in breadth and sensitivity, this is an apt time to examine the progress and future of life-detection technologies.Comment: 6 pages, the white paper was submitted to and cited by the National Academy of Sciences in support of the Astrobiology Science Strategy for the Search for Life in the Univers

The use of MS classifiers and structure generation to assist in the identification of unknowns in effect-directed analysis

Structure generation and mass spectral classifiers have been incorporated into a new method to gain further information from low-resolution GC-MS spectra and subsequently assist in the identification of toxic compounds isolated using effect-directed fractionation. The method has been developed for the case where little analytical information other than the mass spectrum is available, common, for example, in effect-directed analysis (EDA), where further interpretation of the mass spectra is necessary to gain additional information about unknown peaks in the chromatogram. Structure generation from a molecular formula alone rapidly leads to enormous numbers of structures; hence reduction of these numbers is necessary to focus identification or confirmation efforts. The mass spectral classifiers and structure generation procedure in the program MOLGEN-MS was enhanced by including additional classifier information available from the NIST05 database and incorporation of post-generation 'filtering criteria'. The presented method can reduce the number of possible structures matching a spectrum by several orders of magnitude, creating much more manageable data sets and increasing the chance of identification. Examples are presented to show how the method can be used to provide 'lines of evidence' for the identity of an unknown compound. This method is an alternative to library search of mass spectra and is especially valuable for unknowns where no clear library match is available

Tracking ligand-binding effect on protein stability by CD spectroscopy

International audienceThe influence of protein-ligand interactions on protein stability is usually assessed by measurements in the liquid phase. CD spectroscopy appears to be a tool of choice to i) measure the conformation of the protein in different phases and to ii) follow the conformational changes of the protein upon binding.We therefore studied the stability of the rat odorant binding protein 3 (OBP3), its ability to remain functional and a preliminary test of its ligand binding specificity in the dry state. Solid-state spectra were performed on dry thin films prepared by drop casting of initial buffered aqueous solutions of the rat OBP3 onto optically transparent CaF2 windows and subsequently dried under low vacuum.We successfully recorded CD spectra of solid-state apo OBP3 from 280 to 130 nm. A previously unknown positive dichroic band became measurable in the solvent-free state at 175 nm. The reproducibility of the solid-state CD spectrum of apo OBP3 was confirmed by measuring several individually prepared films. We then assessed the time-dependent alteration of the protein in this dry environment. No change in the spectra was observed (storage at constant humidity with binary saturated salt solution), highlighting the stability of the OBP films on a monthly basis.Our results revealed that protein folding is not affected during film formation and remains stable over long-time scales

Tracking ligand-binding effect on protein stability by CD spectroscopy

International audienceThe influence of protein-ligand interactions on protein stability is usually assessed by measurements in the liquid phase. CD spectroscopy appears to be a tool of choice to i) measure the conformation of the protein in different phases and to ii) follow the conformational changes of the protein upon binding.We therefore studied the stability of the rat odorant binding protein 3 (OBP3), its ability to remain functional and a preliminary test of its ligand binding specificity in the dry state. Solid-state spectra were performed on dry thin films prepared by drop casting of initial buffered aqueous solutions of the rat OBP3 onto optically transparent CaF2 windows and subsequently dried under low vacuum.We successfully recorded CD spectra of solid-state apo OBP3 from 280 to 130 nm. A previously unknown positive dichroic band became measurable in the solvent-free state at 175 nm. The reproducibility of the solid-state CD spectrum of apo OBP3 was confirmed by measuring several individually prepared films. We then assessed the time-dependent alteration of the protein in this dry environment. No change in the spectra was observed (storage at constant humidity with binary saturated salt solution), highlighting the stability of the OBP films on a monthly basis.Our results revealed that protein folding is not affected during film formation and remains stable over long-time scales

Interstellar ices: a possible scenario for symmetry breaking of extraterrestrial chiral organic molecules of prebiotic interest

International audienceIn the laboratory, the photo-and thermochemical evolution of ices, made of simple molecules of astrophysical relevance, always leads to the formation of semi-refractory water-soluble organic residues. Targeted searches for specific molecules do reveal the notable presence of two families of important molecular " bricks of life " , amino acids, key molecules in metabolism, and sugars, including ribose, the backbone of RNA molecules which support the genetic information in all living entities. Most of these molecules are indeed found in primitive carbonaceous meteorites and their implication in prebiotic chemistry at the surface of the early Earth must be seriously considered. These molecules are, almost all, chiral. In meteorites, some amino acids do show significant enantiomeric excesses practically exclusively of the L-form. In our experiments, we investigate the role of circularly polarized light obtained from the DESIRS beamline of the synchrotron SOLEIL, a light commonly observed in regions of star formation, in order to generate an initial symmetry breaking in chiral amino acids produced, and then indeed detected in our samples. We present first a brief global description of the chemical evolution of the Galaxy. Then, using our laboratory simulations, we suggest the importance of cosmic ices in the build-up of complex organic matter, including enantioenrichment at the surface of telluric planets like the Earth, thus establishing a link between astrochemistry and astrobiology

The Astrophysical Formation of Asymmetric Molecules and the Emergence of a Chiral Bias

International audienc

Uncovering the chiral bias of meteoritic isovaline through asymmetric photochemistry

Abstract Systematic enrichments of l-amino acids in meteorites is a strong indication that biological homochirality originated beyond Earth. Although still unresolved, stellar UV circularly polarized light (CPL) is the leading hypothesis to have caused the symmetry breaking in space. This involves the differential absorption of left- and right-CPL, a phenomenon called circular dichroism, which enables chiral discrimination. Here we unveil coherent chiroptical spectra of thin films of isovaline enantiomers, the first step towards asymmetric photolysis experiments using a tunable laser set-up. As analogues to amino acids adsorbed on interstellar dust grains, CPL-helicity dependent enantiomeric excesses of up to 2% were generated in isotropic racemic films of isovaline. The low efficiency of chirality transfer from broadband CPL to isovaline could explain why its enantiomeric excess is not detected in the most pristine chondrites. Notwithstanding, small, yet consistent l-biases induced by stellar CPL would have been crucial for its amplification during aqueous alteration of meteorite parent bodies