Chemical, Thermal, and Radiation Resistance of an Iron Porphyrin: A Model Study of Biosignature Stability.

Metal complexes of porphyrins and porphyrin-type compounds are ubiquitous in all three domains of life, with hemes and chlorophylls being the best-known examples. Their diagenetic transformation products are found as geoporphyrins, in which the characteristic porphyrin core structure is retained and which can be up to 1.1 billion years old.

A Possible Prebiotic Ancestry of Porphyrin-Type Protein Cofactors.

In previous experiments that simulated conditions on primordial volcanic islands, we demonstrated the abiotic formation of hydrophobic porphyrins. The present study focused on the question whether such porphyrins can be metalated by prebiotically plausible metal ion sources. We used water-insoluble octaethylporphyrin (Hoep) as a model compound.

Influence of the metal ion on the enzyme activity and kinetics of PepA from Lactobacillus delbrueckii.

The aminopeptidase A (PepA; EC 3.4.11.

Inhabited or Uninhabited? Pitfalls in the Interpretation of Possible Chemical Signatures of Extraterrestrial Life.

The "Rare Earth" hypothesis-put forward by Ward and Brownlee in their 2000 book of the same title-states that prokaryote-type organisms may be common in the universe but animals and higher plants are exceedingly rare. If this idea is correct, the search for extraterrestrial life is essentially the search for microorganisms. Various indicators may be used to detect extant or extinct microbial life beyond Earth.

The Influence of Mineral Matrices on the Thermal Behavior of Glycine.

On the Hadean-Early Archean Earth, the first islands must have provided hot and dry environments for abiotically formed organic molecules. The heat sources, mainly volcanism and meteorite impacts, were also available on Mars during the Noachian period. In recent work simulating this scenario, we have shown that neat glycine forms a black, sparingly water-soluble polymer ("thermomelanoid") when dry-heated at 200 °C under pure nitrogen.

Gas chromatographic separation of stereoisomers of non-protein amino acids on modified γ-cyclodextrin stationary phase.

Stereoisomers (enantiomers and diastereoisomers) of synthetic, non-protein amino acids comprising α-, β-, and γ-amino acids, including α,α-dialkyl amino acids, were converted into the respective N-trifluoroacetyl-O-methyl esters and analyzed and resolved by gas chromatography (GC) on a commercial fused silica capillary column coated with the chiral stationary phase octakis(3-O-butyryl-2,6-di-O-pentyl)-γ-cyclodextrin. This column is marketed under the trade name Lipodex(®) E. Chromatograms, retention times, and a chart displaying the retention times of approximately 40 stereoisomers of amino acids are presented.

Hypercondensation of an amino acid: synthesis and characterization of a black glycine polymer.

A granular material was obtained by thermal polymerization of glycine at 200 °C. It has been named "thermomelanoid" because of its strikingly deep-black color. The polymerization process is mainly a dehydration condensation leading to conventional amide bonds, and also CC double bonds that are formed from CO and CH2 groups ("hypercondensation").

A possible prebiotic origin on volcanic islands of oligopyrrole-type photopigments and electron transfer cofactors.

Tetrapyrroles are essential to basic biochemical processes such as electron transfer and photosynthesis. However, it is not known whether these evolutionary old molecules have a prebiotic origin. We have serendipitously obtained pyrroles, which are the corresponding monomers, in laboratory experiments that simulated the interaction of amino acid-containing seawater with molten lava.

Coordination of biologically important alpha-amino acids to calcium(II) at high pH: insights from crystal structures of calcium alpha-aminocarboxylates.

A series of calcium alpha-aminocarboxylates was prepared by refluxing aqueous solutions/suspensions of calcium hydroxide and the respective alpha-amino acid. The colorless, crystalline hydrates Ca(gly)2.H2O (1), Ca(ala)2.

A Coordination-Chemical Basis for the Biological Function of the Phytochelatins.

To fix toxic heavy-metal ions, plants synthesize the ligands (γ-Glu-Cys) -Gly (PC ), whose simplest representative is the pentapeptide PC . The knowledge of the composition and stabilities of the cadmium complexes of PC allow a better understanding of biological processes like the one outlined.