- ADSORPTION STUDIES OF THE AMINO ACIDS L-PHENYLALANINE AND L-DOPA TO THE RUTILE SURFACE
Salima Bahri (Barnard College), Caroline Jonsson, and Christopher Jonsson
The study of amino acid adsorption to mineral surfaces has implications for the origins of life as well as applications in medicine and research on possible sources of energy. It is possible that in the prebiotic ocean mineral surfaces could have acted as catalysts to peptide bonding by providing a surface onto which amino acids could adsorb, cluster close to one another, and eventually form proteins. In this study, adsorption levels of the amino acids L-phenylalanine and L-3,4-dihydroxyphenylalanine (or L-dopa) to rutile TiO2 were investigated with changes in pH and initial amino acid concentrations, with particular interest in the effect of the presence of a benzene ring in the structures, as well as the effect of two extra hydroxyl groups on L-dopa. This was done with batch adsorption experiments, and analyzed via ultra-violet spectroscopy. Initial concentrations of the amino acids ranging from 0.1 mM to 1mM were used, all with a background electrolyte concentration of 100mM NaCl. pH adjustments between 3 and 10 were made for Phe. Each suspension was bubbled with Argon gas to minimize CO2 contamination. After overnight rotation and accurate pH measurement the ninhydrin method was used in order to analyze the supernatant with a UV-Vis spectrophotometer. The same procedure was followed for L-dopa, in the dark, and with pH adjustments between 3 and 6 due to the molecule's instability at high pH. In addition, it was found that the ninhydrin method was not necessary for this amino acid.
A value of 17,139 M-1cm-1 was measured for Phe, and 2,670 M-1cm-1 for L-dopa. Experimental results showed that Phe does not adsorb significantly regardless of pH adjustments or initial concentration. On the other hand, L-dopa shows adsorption ranging from 20% to 94% depending on initial concentration and pH. Furthermore, it seems that adsorption increases with both pH and initial concentration. This indicates that the additional hydroxyl groups on the benzene ring play a crucial role in the dopa's adsorption to rutile.
- MINERALS, MOLECULES AND THE ORIGIN OF LIFE
Mickey Kopstein (College of William and Mary) and Jim Cleaves
Possible mechanisms for the polymerization of biologically useful molecules on the early prebiotic earth are examined in this study. Previous studies (Miller 1953, Johnson et al. 2008) have described feasible pathways to describe the emergence of simple organic building blocks such as formaldehyde (HCOH), hydrogen cyanide (HCN), and even nucleotide bases and amino acids such as glycine, thymine, and adenine. In addition, the process of forming a complex genome like DNA has been described simply as an emergence of a superior complexity via Darwinian evolution (Orgel 2004). However, the step between monomers and a useful genetic material remains largely unknown. Organic building blocks were present in very dilute aqueous solution in the primitive oceans, and were unlikely to polymerize. Mineral surfaces were suggested in the 1950s as a possible factor in concentrating necessary building blocks (Bernal 1951). This study focuses on five mineral surfaces and their interactions with single-stranded DNA oligomers of adenine and thymine. Oligomers studied included monomers and dimers, increasing in increments of two to ten bases. Nucleotides were in 1.7 mL of solution with .05 M NaCl and .1 M KHCO3, buffered at pH 8. Solutions were mixed for 24 hours and then analyzed by spectrophotometer. Using Beer's law, the equilibrium solution concentration was determined and used to find moles adsorbed per square meter. Langmuir isotherms were constructed using the experimental data. It was found that adenine bases tend to bond much more frequently than thymine bases. It was also found that saturation tends to fall with chain length, while K values tend to rise. However, it appears that chain length affects adsorption more than the specific mineral surface. Trends in free energy appear to be complex and will need further study to be well characterized. Implications for horizontal gene transfer in the environment are also discussed.
- INTERACTIONS BETWEEN GLYCINE DERIVATIVES AND MINERAL SURFACES IMPLICATED IN THE ORIGINS OF LIFE ON PLANETARY SURFACES
Karina Marshall-Bowman (University of Vermont) and Jim Cleaves
Derivatives of glycine (G, GG, DKP, GGG) were reacted with six different mineral surfaces in the presence of a buffer at pH 8 to determine the whether the minerals had catalytic effects. The minerals included calcium carbonate (CaCO3), iron (III) oxide (Fe2O3), montmorillonite, rutile (TiO2), silica (SiO2), and pyrite (FeS2). The experiments were performed at 25 °C, 50 °C, and 70 °C and samples were taken out after 30h, 60h, 90h, and 140h. Samples were then analyzed using high performance liquid chromatography to separate, identify and quantify the glycine derivatives in the solution. It was determined that degradation of GGG proceeds via GGG→DKP→GG mechanism, and does not go straight to GG. It was also determined that at 70 °C, Pyrite was the only mineral with detectible catalytic effects on the degradation of GGG. Also, the amount of glycine present in the solution was proportional to the rate constant of the degradation reaction. Polymerization reactions of amino acid monomers like glycine have many implications in the origin of life, as the peptides formed go on to form proteins and many necessary components for self-replicable life forms. By studying the reverse reaction of polymer degradation, the rate constant could be determined, as polymerization reactions are thermodynamically unfavorable and very slow. As the prebiotic oceans were too dilute with regards to amino acid concentration, mineral surfaces were proposed as the mechanism present for the selection and concentration of these essential biomolecules. Quantifying the catalytic properties of pyrite helps support the theory of mineral surfaces as a catalyst for the important polymerization reactions implicated in the origins of life.
- SEA FLOOR VOLCANIC GLASSES AS A SOURCE OF AVAILABLE PHOSPHATE FOR PREBIOTIC REACTIONS
Justine Hart (University of Iowa) and George Cody
The goal of this project was to explore the possibility of volcanic glasses as a source of available phosphate for phosphoryl group transfer reactions. A series of reactions was run using five different solutions. The solutions used were: 200mM pyrophosphate, pH 7.2; 200mM pyrophosphate, pH 6.7; 200mM pyrophosphate and 100mM glycine, pH 7.2; 200mM tripolyphosphate and 100mM glycine, pH 7.2; and 100mM glycine at pH 7.2 as a control. Each solution was placed in an oven at two different temperatures - one set was run at 85°C, and one at 100°C. From the solutions that included glycine, we found that tripolyphosphate created tri-gly, which was not found in the pyrophosphate solution. The tripolyphosphate solution also produced higher concentrations of di-gly than pyrophosphate, and did not produce any DKP. From this, we saw that tripolyphosphate hydrolyzes more effectively than pyrophosphate. These results show that it is possible for seafloor volcanic glass to hydrolyze in the presence of glycine, allowing for a phosphoryl group transfer reaction to take place.
- MEASUREMENT OF THE THERMAL CONDUCTIVITY OF MG0.9FE0.1SIO3 PEROVSKITE AT HIGH PRESSURE AND TEMPERATURE
Alex Savello (Emory University) and Alexander Goncharov
High-pressure laser spectroscopy was performed on Mg0.9Fe0.1SiO3 perovskite to determine the thermal conductivity constant k (W/[m⋅K]) at the pressure and temperature conditions of the lower mantle. Two samples of perovskite were cut 10 microns thick and coated with a 0.1- micron layer of platinum to act as an absorber of the laser light. The two samples were placed on top of one another and positioned in a diamond anvil cell pressurized to 29 GPa. An 8 ns IR laser pulse (1064 nm, YAG) with 10-20 kHz repetition rate was used to temporarily heat the sample and a spectrometer recorded the heat dissipation. Delay time between laser firings was lengthened with each spectrum recorded and each was normalized with a fitting routine to identify specific temperatures. The temperature data was plotted against theoretical thermal conductivity curves of varying k values. Using this new sampling method, our initial measurements yielded a value of ~10-30 W/(m⋅K) for the thermal conductivity of Mg0.9Fe0.1SiO3 perovskite, which compares favorably with previous measurements using other sample preparation techniques.
- HIGH-PRESSURE RAMAN STUDIES OF FERROELECTRIC PEROVSKITES
Angela Schad (University of Notre Dame), Panchapakesan Ganesh and John Janik
Recently, pure compounds, specifically PbTiO3, have been shown to display a morphotropic phase boundary (MPB) under pressure at which electromechanical properties are maximal, although previously only complex solid-solutions were thought to exhibit such a boundary. In this project, high-pressure and low-temperature Raman spectra are computed for PbTiO3. Raman susceptibility tensors are calculated using Density Functional Perturbation Theory (DFPT) as implemented in the ABINIT first-principles computational package. These tensors are then used to calculate Raman intensities. The computed intensities agree qualitatively with the experimental data measured on powder samples. The accurate computational prediction of Raman intensity dependence with pressure raises the possibility of using calculations to calibrate experimental measurements of Raman spectra at any pressure in the future. The results additionally substantiate previous claims of the presence of a low-temperature monoclinic phase at the MPB at approximately 10 GPa in PbTiO3 as well as refute the possibility of the phase being an R-3c or I4cm phase as suggested by other groups. Furthermore, this project provides new insight into the structure of PbTiO3 at very high pressures (> 60GPa) where new experimental results challenge existing theory.
- CRYSTALLZATION OF PERIODIC MESOPOROUS ORGAONOSILICAS UNDER HIGH PRESSURE AND HIGH TEMPERATURE
Zhili Liang (Lehigh University), Kai Landstron (Lehigh University), and Yingwei Fei
Experiments were performed to crystallize organosilicas under high-pressure and -temperature conditions with the multi-anvil apparatus. Periodic mesoporous oragnisilicas (PMOs) with ethyl group (Et-PMO) and methyl group (Me-PMO) were chosen as the starting materials. Four samples from each type of the PMOs were heated to 150 °C, 300 °C, 450°C, and 600°C individually under 12 GPa within the multi-anvil apparatus. Each sample was then quenched after remaining at its final temperature for 15 minutes. Wide-angle x-ray diffraction (WAXD) patterns showed the crystallization began to occur at 300 °C for both Et-PMO and Me-PMO. Silica in the coesite phase was obtained as the final product for all eight experiments. Scanning electron microscopy (SEM) showed nanocrystals as the morphology for both the Et-PMO and Me-PMO that were treated at 300 °C. Crystal growth was observed as the quenching temperature increased for either type of PMO. Coesite nanocrystals with rod-like morphology was also found in the sample of Et-PMO after 600 °C treatment. The results indicate that the kinetic pathway of crystallization of silica might have been altered due to the mesoporous nature of the PMOs.
- CALCULATING DISTANCES AND MOTIONS OF STARS IN THE TW HYDRAE ASSOCIATION
Rebecca Rattray (Vanderbilt University) and Alycia Weinberger
Distances and proper motions were calculated for seven stars of the TW Hydrae association (TWA) using images from the Carnegie Astrometric Planet Search Camera (CAPSCam) on the 100-inch telescope at Las Campanas Observatory. Zero-point adjustments were made to the parallax calculations to correct for motion of background stars. Spatial velocities were calculated from the distances and proper motions measured. Based on the distance and spatial velocities of TWA 14 being inconsistent with distances and spatial velocities of other known TWA members, it is proposed that TWA 14 may not be a member of TWA. The age of TWA was estimated by plotting the positions and velocities of the stars and calculating the instant of closest approach, but the age calculated (1.82 ± .43 Myr) was inconsistent with previous estimates of the age of TWA (5-10 Myr), which may suggest that the association is not expanding as expected, or that it is larger than expected.
- IN SITU CHARACTERIZATION OF PRIMITIVE ORGANIC MATTER IN QUE 99177 THROUGH CORRELATED MICROANALYTICAL TECHNIQUES
Allison Wende (SUNY-Oswego) and Larry Nittler
A correlated, in situ, microanalytical approach was utilized to characterize local heterogeneities of organic matter in a polished thin section of the CR3 meteorite QUE 99177. This study is based on the previous NanoSIMS studies of Nguyen et al. (2008) and Floss et al. (2009). NanoSIMS imaging provided information on molecular chemistry as well as isotopic compositions of C, N, O, and H. SEM analysis provided topographical information, while Raman Spectroscopy informed the degree of amorphization of the carbonaceous organic material. Finally, UV fluorescence was employed as an exploratory technique in the in situ identification of nanoglobules. Combined NanoSIMS and SEM analysis proved effective in identifying and characterizing the heterogeneities but, due to C coating the sample for the SEM analysis, subsequent Raman analyses proved inconclusive. Given QUE 99177s degree of surface C contamination, matrix fragments from the primitive Tagish Lake meteorite were used for UV Fluorescence. Five fragments were mounted and pressed into gold foil. Only one fragment showed fluorescence, indicating that nanoglobules likely do not fluoresce preferentially.
- FRACTIONATION OF SULFUR ISOTOPES IN THE FORMATION OF MARS
Neil Foley (Carleton College) and Anat Shahar
High pressure and temperature piston cylinder experiments were performed to determine the fractionation factor of sulfur isotopes caused by the differentiation of the core of Mars from its mantle during planetary accretion. Homogeneous samples of a mixture representing the bulk composition of Mars were pressed at constant pressure (1 GPa) and various temperatures (1600°, 1700°, 1850° C) in a graphite furnace. The "three isotope exchange method", involving the addition of a pure 32S spike, was used to determine isotopic equilibrium. Samples' compositions were characterized on SEM and electron microprobe and the fractionation of the sulfur isotopes was determined on the Carnegie Institution of Washington's Cameca ims 6f SIMS. Measurements of isotopes are ongoing; preliminary data suggest that such fractionation did occur. When sufficient data are collected, the fractionation factor will be extrapolated to 2200° C, the temperature at which equilibration is believed to have happened on Mars. Knowledge of "background fractionation" caused by planetary formation will give better context to observed fractionations in Martian meteorites and be particularly useful in the search for biogenic fractionation of sulfur.
- AN INVESTIGATION OF THE MINERALOGY, PETROLOGY AND GEOCHEMISTRY OF BANDED IRON FORMATIONS FROM THE NUVVUAGITTUQ SUPRACRUSTAL BELT, CANADA
Adrianna Rajkumar (Appalachian State University) and Dominic Papineau
The Nuvvuagittuq supracrustal belt (NSB) in northwestern Québec is one of the few Eoarchean volcano-sedimentary rocks worldwide. Chemical sedimentary rocks from the NSB comprise banded iron formations (BIFs) dated to be >3.75 Ga. We present a systematic study of the petrography, mineral associations and geochemistry of BIFs from the NSB which was metamorphosed to the amphibolite facies. Petrographic observations of the BIFs revealed four to five different types: amphibole + magnetite, amphibole + magnetite + quartz, quartz + magnetite, quartz + magnetite + hematite and possibly quartz + magnetite + calcite. Petrographic analyses showed that amphiboles in these BIFs were formed by a reaction between quartz and carbonate and also between quartz and magnetite under metasomatic conditions. Apatite grains both associated and not associated with opaque minerals were mapped and found to occur mainly in quartz bands and in the BIFs with little to no quartz, they occurred in the amphiboles. In the latter BIFs, apatite grains occur with veins of magnetite and amphibole leading to the apatite, suggesting a metasomatic origin. In a few amphibole + quartz + magnetite BIFs, several grains of apatite associated with graphite were found. Petrographic and geochemical analyses suggest that apatites in most BIFs are unlikely to be detrital in origin and the lack of correlation between P and Fe-oxides abundances suggests that little P was adsorbed onto Fe-oxide particles in the water column during deposition. Finally, data indicate very small amounts of organic carbon in these rocks and δ13C values range from -13% to -30% presumably due to microscopic heterogeneity in the samples. Overall results suggest a strong influence of metamorphism and metasomatism on the mineralogy of these BIFs, but there may be mineral associations that survived since diagenesis.
- METHANE OXIDATION UNDER HYDROTHERMAL CONDITIONS: IMPLICATIONS FOR THE STABILITY OF ORGANICS ON MARS
Niya Grozeva (SUNY-Stony Brook)and Dionysis Foustoukos Evaluating the stability of organic compounds in the presence of oxidizing agents is necessary to assess the likelihood of finding life on Mars under present-day conditions. For instance, the evolution of methane in Martian environments may be greatly constrained by oxidants proposed to exist in the soil and atmosphere. Since methane is likely to form through hydrothermal processes driven by possible subsurface liquid water, the oxidation of organic compounds should be investigated under hydrothermal conditions.
To determine how oxidizing agents form under hydrothermal conditions, this study used iron oxides to decompose hydrogen peroxide to hydroxyl radicals through the Fenton reaction: Fe2+ + H2O22 ⇌ Fe3+ + OH + OH¯. H2O22(aq) was decomposed in the presence of a heterogeneous catalyst (FeO, FeH2O22OH2O23) at a constant pressure of 3500 psi and temperatures of 60 to 150ºC using a Ti flow-through reactor. The kinetic rate, activation energy (Ea) and preexponential factor (A) were calculated for each experiment utilizing different amounts and types of catalyst. The addition of a catalyst did not appreciably change Ea, but significantly increased A, resulting in enhanced rates of H2O22 decomposition relative to the uncatalyzed H2O-H2O22 system. Since A is related to activation entropy, a higher value suggests Fe-oxides enhance kinetic rates by increasing the entropy of the transition state, which likely involves the metastable formation of radicals. Forthcoming experiments will measure the production of OH to assess the extent to which the Fenton reaction may be contributing to oxidizing conditions on Mars.
In addition, the kinetics of methane oxidation were investigated in a closed-system flexible Au/Ti reaction cell to evaluate the stability of organic compounds under similar oxidizing conditions. CH4 was decomposed by O2(aq) in solution at 300 bars and 250ºC. The pseudo first order reaction rate for the oxidation of methane was determined to be 2.4e-6 s-1, while the estimated half-life was ~3.3 days. Future experiments will oxidize CH4 in the presence of H2O22 and OH to further evaluate the residence time of organic compounds on Mars and, thus, the potential habitability of the planet.