Papers by Wolfram Thiemann
Science (New York, N.Y.), Jan 31, 2015
Comets harbor the most pristine material in our solar system in the form of ice, dust, silicates,... more Comets harbor the most pristine material in our solar system in the form of ice, dust, silicates, and refractory organic material with some interstellar heritage. The evolved gas analyzer Cometary Sampling and Composition (COSAC) experiment aboard Rosetta's Philae lander was designed for in situ analysis of organic molecules on comet 67P/Churyumov-Gerasimenko. Twenty-five minutes after Philae's initial comet touchdown, the COSAC mass spectrometer took a spectrum in sniffing mode, which displayed a suite of 16 organic compounds, including many nitrogen-bearing species but no sulfur-bearing species, and four compounds-methyl isocyanate, acetone, propionaldehyde, and acetamide-that had not previously been reported in comets.
Interstellar dust particles in dense clouds accrete ice mantles. As seen in infrared (IR) observa... more Interstellar dust particles in dense clouds accrete ice mantles. As seen in infrared (IR) observations, this ice layer consists mainly of water ice, but also carbon and nitro- gen containing molecules. In order to study the physico-chemical processes in in- terstellar ices, we simulated such conditions in the laboratory. We deposited a gas mixture consisting of H_2O, CO_2, CO, CH_3OH,
Chirality, 1999
Recent theoretical and experimental investigations referring to the origin of homochirality are r... more Recent theoretical and experimental investigations referring to the origin of homochirality are reviewed and integrated into the hitherto known state of the art. Attention is directed to an extraterrestrial scenario, which describes the interaction of circularly polarized synchrotron radiation with interstellar organic matter. Following this Bonner-Rubenstein hypothesis, optically active molecules could be transferred to Earth via comets. We plan to identify any enantiomeric enhancement in organic molecules of the cometary matter in situ. The present preliminary experimental study intends to optimize gas-chromatographic conditions for the separation of racemates into their enantiomer constituents on the surface of the comet 46P/Wirtanen. Underivatized racemic pairs of alcohols, diols, and phenyl-substituted amines have been separated with the help of a stationary trifluoroacetyl-cyclodextrin phase. We are still developing a technique that will enable us to detect any enantiomeric enhancement of specific simple organic molecules both in cometary or Martian matter in situ and in meteorites found on Earth.
Circular polarized electromagnetic radiation can be measured with earth based telescopes in galax... more Circular polarized electromagnetic radiation can be measured with earth based telescopes in galaxies, stars, the interstellar medium, and planets. The observed values for Venus, Moon, Mars, and Jupiter obtained by photo-polarimetric measurements were "symmetric" and showed accordance with theory. However, for planet Mercury asymmetric parameters in the circular polarization were measured that do not fit with calculation. For BepiColombo, the
In the dense interstellar medium dust particles accrete ice layers of known molecular composition... more In the dense interstellar medium dust particles accrete ice layers of known molecular composition. In the diffuse interstellar medium these ice layers are subjected to energetic UV-irradiation. Here, photoreactions form complex organic molecules. The interstellar processes were recently successfully simulated in two laboratories. At NASA Ames Research Center three amino acids were detected in interstellar ice analogues [1], contemporaneously, our
ABSTRACT In the context of the evolution of biologically relevant compounds from abiotic precurso... more ABSTRACT In the context of the evolution of biologically relevant compounds from abiotic precursors and conditions, the so called 'chemical evolution', a novel method for the analysis of N-heterocyclic compounds was developed. N-heterocycles are of importance in this context due to the fact that nucleic acid bases, which encode genetic information in the form of DNA (or RNA) in biological life as we understand it, are cyclic compounds with cycles made of carbon and nitrogen. The groups of organics called pyrimidines and purines are of most interest here, since each group contributes two compounds to the total of four of the nucleic acid bases used in DNA. These are adenine and guanine for the purine-bases and cytosine and thymine for the pyrimidine-bases. So the aim of this publication is to add another method to the pool of already established methods for analysing a number of biologically relevant compounds in extraterrestric environments (eg. amino acids, sugars).
Sāo Paulo, S.P., Brazil - June 1974, 1975
Since Pasteur's times it has been accepted that optical activity and life are intimately ... more Since Pasteur's times it has been accepted that optical activity and life are intimately correlated with each other, i.e. the one could not exist without the other. This argument logically allows the following speculation related to interplanetary exploration: detection of optical activity in an extraterrestrial sample would be the most straightforward proof of the existence of living matter outside the earth. On the other hand it has been shown that spontaneous production of optical activity can be achieved without the help of living matter, so that the close association of optical activity with life is not necessarily true. The paper discusses the possibilities which allow a proof of some sort of life on other planets by polarimetric methods.
Gas Und Wasserfach Wasser Abwasser, 1987
Symmetries in Science IV, 1990
Nature offers us spectacular demonstration of symmetry breaking in the architecture of the molecu... more Nature offers us spectacular demonstration of symmetry breaking in the architecture of the molecular building blocks of biological organisms. It has been pointed out by numerous authors for over a century that the monomer aminoacids (making up the proteins) as well as the sugars (making up the back bone of DNA and RNA) are almost exclusively of the strictly dissymmetric left-resp. right-handedness which has disturbed the minds of symmetry-obsessed chemists and physicists. This observation violates not only the “esthetics” of science but equally experimental evidence where organic chemists always synthetize in laboratory only the racemic compounds, i.e. a stoichiometric mixture of both the right and the left handed molecular in equal amounts.
Origins of Life and Evolution of the Biosphere, 2004
Biopolymers like DNA and proteins are strongly selective towards the chirality of their monomer u... more Biopolymers like DNA and proteins are strongly selective towards the chirality of their monomer units. The use of homochiral monomers is regarded as essential for the construction and function of biopolymers; the emergence of the molecular asymmetry is therefore considered as a fundamental step in Chemical Evolution. This work focuses on physicochemical mechanisms for the origin of biomolecular asymmetry. Very recently two groups, one from Allamandola at NASA Ames and the other from our Inter-European team, demonstrated simultaneously the spontaneous photoformation of a variety of chiral amino acid structures under simulated interstellar conditions. Since both groups used unpolarized light for the photoreaction the obtained amino acids turned out racemic as expected. The obtained experimental data support the assumption that tiny ice grains can furthermore play host to important asymmetric reactions when irradiated by interstellar circularly polarized ultraviolet light. It is possible that such ice grains could have become incorporated into the early cloud that formed our Solar System and ended up on Earth, assisting life to start. Several lines of evidence suggest that some of the building blocks of life were delivered to the primitive Earth via (micro-) meteoroids and/or comets. These results suggest that asymmetric interstellar photochemistry may have played a significant part in supplying Earth with some of the enantioenriched organic materials needed to trigger life. The search for the origin of biomolecular homochirality leads to a strong interest in the fields of asymmetric photochemistry with special emphasis on absolute asymmetric synthesis. We outline here the theoretical background on asymmetric interstellar ice photochemistry, summarize recent concepts and advances in the field, and discuss briefly its implications. The obtained data are crucial for the design of the enantioselective COSAC GC-MS experiment onboard the ROSETTA spacecraft to a comet to be launched in the very near future.
Zeitschrift für medizinische Laboratoriumsdiagnostik, 1981
New crucial theoretical investigations on the origin of biomolecular chirality are reviewed brief... more New crucial theoretical investigations on the origin of biomolecular chirality are reviewed briefly. With the goal to investigate these theories our team is going to perform the 'chirality-experiment' in the near future with cometary matter. In 2012 the robotical lander RoLand will detach from the orbiter of the ROSETTA spacecraft and set down on the surface of comet 46P/Wirtanen in order to separate and identify cometary organic compounds via GC-MS in situ. Chiral organics will be separated into their enantiomers by application of 3 capillary columns coated with different kinds of stationary phases. Non-volatile compounds like amino acids will be derivatized in especially developed gas phase alkylation steps avoiding reactions in the liquid phase. The results of these preliminary gas phase reactions are presented in this article.
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Papers by Wolfram Thiemann