The mechanism leading to the formation of aliphatic components in sedimentary rocks and petroleum products has been the subject of debate. Recent research has concluded that algaenan is not as widespread ecologically or phylogenetically, so may contribute less to the resistant aliphatic content of kerogens where such algae are source organisms. We conducted experiments with the non-algaenan producing alga, Chlamydomonas reinhardtii, at 260 and 350 degrees C and 700 bar to simulate fossilization of the microorganism under confined pyrolysis conditions. Pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) analysis revealed that the unheated alga consisted of biopolymers primarily related to proteins and lipids, including C-16 and C-18 fatty acids (FAs). However, heating at 260 and 350 degrees C resulted in macromolecules with a significant aliphatic component similar to high hydrogen content kerogen, derived from lipids in the alga, primarily from saturated and unsaturated C-16 and C-18 FAs, as determined from experiments with model compounds. The presence of amides, nitriles and oximes in the heated alga was likely due to the reaction of the lipids with the abundant N-containing proteinaceous compounds. Py-GC-MS of the residue of Scenedesmus quadricauda at 350 degrees C (a green alga containing algaenan as a control) demonstrated survival of algaenan at that temperature. The solvent insoluble residue of a cyanobacterium (Oscillatoria sp.) and a purple non S containing bacterium Rhodopseudomonas palustris subjected to similar high temperature and pressure, resulted in a residue with significant aliphatic content. The results reveal that algaenan survived the P/T conditions of the experiments, which additionally suggest an alternative mechanism that may lead to aliphatic geopolymers. Since this mechanism seems to be valid for organisms that are phylogenetically wide apart, it may be valid for organism cells in general. Thus, bacterial biomass may also contribute to the insoluble organic inventory of ancient sediments. (C) 2013 Elsevier Ltd. All rights reserved.

Organic nanoglobules are microscopic spherical carbon-rich objects present in chondritic meteorites and other astromaterials. We performed a survey of the morphology, organic functional chemistry, and isotopic composition of 184 nanoglobules in insoluble organic matter (IOM) residues from seven primitive carbonaceous chondrites. Hollow and solid nanoglobules occur in each IOM residue, as well as globules with unusual shapes and structures. Most nanoglobules have an organic functional chemistry similar to, but slightly more carboxyl-rich than, the surrounding IOM, while a subset of nanoglobules have a distinct, highly aromatic functionality. The range of nanoglobule N isotopic compositions was similar to that of nonglobular 15N-rich hotspots in each IOM residue, but nanoglobules account for only about one third of the total 15N-rich hotspots in each sample. Furthermore, many nanoglobules in each residue contained no 15N enrichment above that of bulk IOM. No morphological indicators were found to robustly distinguish the highly aromatic nanoglobules from those that have a more IOM-like functional chemistry, or to distinguish 15N-rich nanoglobules from those that are isotopically normal. The relative abundance of aromatic nanoglobules was lower, and nanoglobule diameters were greater, in more altered meteorites, suggesting the creation/modification of IOM-like nanoglobules during parent-body processing. However, 15N-rich nanoglobules, including many with highly aromatic functional chemistry, likely reflect preaccretionary isotopic fractionation in cold molecular cloud or protostellar environments. These data indicate that no single formation mechanism can explain all of the observed characteristics of nanoglobules, and their properties are likely a result of multiple processes occurring in a variety of environments.

The interaction of hydrogen and deuterium with dimethylamine borane (Me2NHBH3) was studied at pressures from 0 to 10 GPa. Me2NHBH3 is stable to isothermal compression in noble gas pressure media up to 16 GPa. During these compressions a strong positive pressure dependence of the frequencies of BN and BH stretching fundamentals was observed. The opposite trend was observed with NH modes. Me2NHBH3 + He mixtures remain phase separated over the entire 0-16 GPa range. During the isothermal compression of Me2NHBH3 + H-2 mixtures two separate phases are observed at low pressure which subsequently collapse into one phase above 3 GPa. Prior to the formation of the Me2NHBH3/H-2 phase loss of the H-2 vibron was observed concurrently with the growth of broad features in the 3600-4000 region. Further compression of the Me2NHBH3:H-2 results in the growth of new Raman-active BN, BH, and NH modes not present in noble gas compressions. These modes are assigned to the new high pressure solid: [(Me2NH)(2)BH2+][BH4-] similar called diammoniate of diborane often observed in experiments with ammonia and diborane at ambient pressure.

The novel hydrogen-rich BN materials Me2NHBH3 and c-N2B2H4Me4 have been studied by a combination of vibrational spectroscopy and single crystal X-ray diffraction over the pressure range 0-40 GPa. Assignments of Raman-active vibrational modes were made for c-N2B2H4Me4 on the basis of a combination of gas-phase predictions and previous assignments for similar compounds. The Raman spectrum of single crystals were found to have excellent signal-to-noise for pressures over the 0-40 GPa range, making it an ideal method for in situ analysis of high pressure reactions involving c-N2B2H4Me4. The enthalpy of the reaction c-N2B2H4Me4 + 2 H-2 -> 2 Me2NHBH3 was estimated to be 2.9 kcal/mol endothermic at ambient pressure. The corresponding pressure dependence of Delta G(rxn), was estimated from the P-V equations of state (EOS) measured for Me2NHBH3, c-N2B2H4Me4, and H-2 over the 0-12 GPa range. Using the EOS for fluid hydrogen, the reaction is estimated to have a favorable Delta Delta G(rxn) of 10 kcal/mol over the 0-2 GPa pressure range. Above 2 GPa, a positive pressure dependence of Delta G(rxn) is observed. On the basis of these experimental observations, we estimate the reaction thermochemistry to approach a thermoneutral equilibrium over the 0-2 GPa range. Above 2 GPa, the reaction volume becomes positive, causing this hydrogenation pathway to remain unfavorable over a pressure range extending to greater than 100 GPa at 298 K.

Here, we present the results of a multitechnique study of the bulk properties of insoluble organic material (IOM) from the Tagish Lake meteorite, including four lithologies that have undergone different degrees of aqueous alteration. The IOM C contents of all four lithologies are very uniform and comprise about half the bulk C and N contents of the lithologies. However, the bulk IOM elemental and isotopic compositions vary significantly. In particular, there is a correlated decrease in bulk IOM H/C ratios and delta D values with increasing degree of alteration-the IOM in the least altered lithology is intermediate between CM and CR IOM, while that in the more altered lithologies resembles the very aromatic IOM in mildly metamorphosed CV and CO chondrites, and heated CMs. Nuclear magnetic resonance (NMR) spectroscopy, C X-ray absorption near-edge (XANES), and Fourier transform infrared (FTIR) spectroscopy confirm and quantitate this transformation from CR-like, relatively aliphatic IOM functional group chemistry to a highly aromatic one. The transformation is almost certainly thermally driven, and probably occurred under hydrothermal conditions. The lack of a paramagnetic shift in C-13 NMR spectra and 1s-sigma* exciton in the C-XANES spectra, both typically seen in metamorphosed chondrites, shows that the temperatures were lower and/or the timescales were shorter than experienced by even the least metamorphosed type 3 chondrites. Two endmember models were considered to quantitatively account for the changes in IOM functional group chemistry, but the one in which the transformations involved quantitative conversion of aliphatic material to aromatic material was the more successful. It seems likely that similar processes were involved in producing the diversity of IOM compositions and functional group chemistries among CR, CM, and CI chondrites. If correct, CRs experienced the lowest temperatures, while CM and CI chondrites experienced similar more elevated temperatures. This ordering is inconsistent with alteration temperatures based on mineralogy and O isotopes.

The Sutter's Mill (SM) meteorite fell in El Dorado County, California, on April 22, 2012. This meteorite is a regolith breccia composed of CM chondrite material and at least one xenolithic phase: oldhamite. The meteorite studied here, SM2 (subsample 5), was one of three meteorites collected before it rained extensively on the debris site, thus preserving the original asteroid regolith mineralogy. Two relatively large (10 mu m sized) possible diamond grains were observed in SM2-5 surrounded by fine-grained matrix. In the present work, we analyzed a focused ion beam (FIB) milled thin section that transected a region containing these two potential diamond grains as well as the surrounding fine-grained matrix employing carbon and nitrogen X-ray absorption near-edge structure (C-XANES and N-XANES) spectroscopy using a scanning transmission X-ray microscope (STXM) (Beamline 5.3.2 at the Advanced Light Source, Lawrence Berkeley National Laboratory). The STXM analysis revealed that the matrix of SM2-5 contains C-rich grains, possibly organic nanoglobules. A single carbonate grain was also detected. The C-XANES spectrum of the matrix is similar to that of insoluble organic matter (IOM) found in other CM chondrites. However, no significant nitrogen-bearing functional groups were observed with N-XANES. One of the possible diamond grains contains a Ca-bearing inclusion that is not carbonate. C-XANES features of the diamond-edges suggest that the diamond might have formed by the CVD process, or in a high-temperature and -pressure environment in the interior of a much larger parent body.

The genus Ecphora of Muricid gastropods from the mid-Miocene Calvert Cliffs, Maryland is characterised by distinct reddish-brown colouration that results from shell-binding proteins associated with pigments within the outer calcite (CaCO3) portion of the shell. The mineral composition and robustness of the shell structure make Ecphora unique among the Neogene gastropods. Acid-dissolved shells produce a polymeric sheet-like organic residue of the same colour as the initial shell. NMR analysis indicates the presence of peptide bonds, while hydrolysis of the polymeric material yields 11 different amino acid residues, including aspartate and glutamate, which are typical of shell-binding proteins. Carbon and nitrogen elemental and isotopic analyses of the organic residue reveals that total organic carbon ranges from 4 to 40 weight %, with 11 < C/Nat < 18. Isotope values for carbon (-17 < delta C < - 15%) are consistent with a shallow marine environment, while values for nitrogen (4 < delta N < 12.2%) point to Ecphora's position in the trophic structure with higher values indicating predator status. The preservation of the pigmentation and shell-binding proteinaceous material presents a unique opportunity to study the ecology of this important and iconic Chesapeake Bay organism from 8 to 18 million years ago.

Aqueous abiotic methane concentrations in a range of geologic settings are below levels expected for equilibrium with coexisting CO2 and H-2, indicating that kinetics can control the speciation of reduced carbon-bearing fluids. Previous studies have suggested that mineral catalysts or gas-phase reactions may increase the rate of methanogenesis. Here, we report on experiments that indicate pressure can also accelerate aqueous reduction of CO2 to CH4. Four series of cold-seal hydrothermal experiments were performed from 1 to 3.5 kbar at 300 degrees C for two weeks and analyzed using gas chromatography/mass spectrometry. The starting fluids were 10-20-mu L solutions of 70-mmolal C-13-labeled formic acid ((HCOOH)-C-13) contained in welded gold capsules. Increasing pressure (P) resulted in a systematic, reproducible log-linear increase in (CH4)-C-13 yields. The pressure effect could be quantified the log-linear slope, Delta log[(CH4)-C-13]/Delta P (log mmolal per kbar). The mean slope was 0.66 +/- 0.05 (+/- 1s.e.), indicating that (CH4)-C-13 yields increased by an average factor of 40-50 over a P range of 2.5 kbar. Pressure-independent variations in [(CH4)-C-13] were observed as scatter about the log-linear regressions and as variations in the y-intercepts of the regressions. These variations were attributed to trace amounts of catalytic Fe along the inner capsule wall that remained despite cleaning the Au capsules in nitric acid prior to each experimental series. The mechanism for the pressure-dependent effect was interpreted to result from one or more of the following three processes: reduction of a metastable reaction intermediate such as methanol, formation of Fe-carbonyl complexes in the fluid, and/or heterogeneous catalysis by Fe. The results suggest that pressure may influence aqueous abiotic CH4 yields in certain geological environments, particularly when the relative effects of other kinetic factors such as temperature are diminished, e. g., in cool forearcs or other settings with a steep geothermal gradient. Because the experiments were performed over a limited pressure range, even modest isothermal increases in pressure may substantially enhance CH4 yields. A kinetic pressure effect may be especially important on the deep ocean floors of planetary bodies where pressure may compensate for the otherwise sluggish reaction kinetics expected at low T. (C) 2014 Elsevier Ltd. All rights reserved.

Proteins are responsible multiple biological functions, such as ligand binding, catalysis, and ion channeling. This functionality is enabled by proteins' three-dimensional structures that require long polypeptides. Since plausibly prebiotic synthesis of functional polypeptides has proven challenging in the laboratory, we propose that these functions may have been initially performed by alternative macromolecular constructs, namely hyperbranched polymers (HBPs), during early stages of chemical evolution. HBPs can be straightforwardly synthesized in one-pot processes, possess globular structures determined by their architecture as opposed to folding in proteins, and have documented ligand binding and catalytic properties. Our initial study focuses on glycerol-citric acid HBPs synthesized via moderate heating in the dry state. The polymerization products consisted of a mixture of isomeric structures of varying molar mass as evidenced by NMR, mass spectrometry and size-exclusion chromatography. Addition of divalent cations during polymerization resulted in increased incorporation of citric acid into the HBPs and the possible formation of cation-oligomer complexes. The chelating properties of citric acid govern the makeup of the resulting polymer, turning the polymerization system into a rudimentary smart material.