Determination of amino acid enantiomers in soils

The Mars Organic Analyzer (MOA), a microfabricated capillary electrophoresis (CE) instrument for sensitive amino acid biomarker analysis, has been developed and evaluated. The microdevice consists of a four-wafer sandwich combining glass CE separation channels, microfabricated pneumatic membrane valves and pumps, and a nanoliter fluidic network. The portable MOA instrument integrates high voltage CE power supplies, pneumatic controls, and fluorescence detection optics necessary for field operation. The amino acid concentration sensitivities range from micromolar to 0.1 nM, corresponding to part-per-trillion sensitivity. The MOA was first used in the lab to analyze soil extracts from the Atacama Desert, Chile, detecting amino acids ranging from 10 -600 parts per billion. Field tests of the MOA in the Panoche Valley, CA, successfully detected amino acids at 70 parts per trillion to 100 parts per billion in jarosite, a sulfate-rich mineral associated with liquid water that was recently detected on Mars. These results demonstrate the feasibility of using the MOA to perform sensitive in situ amino acid biomarker analysis on soil samples representative of a Mars-like environment.amino acid analysis ͉ astrobiology ͉ capillary electrophoresis ͉ microfabrication E xtraterrestrial life on Mars or elsewhere most likely requires three fundamental elements: liquid water, organic molecules capable of forming combinatorial polymers, and a redox energy source (1). The Mars Global Surveyor imaged features attributed to aqueous seeps (2), and the Mars Exploration Rovers recently detected mineralogical signs of liquid water (3). Opportunity observed rocks with layering patterns that could have been formed by water, the Mössbauer spectrometer detected significant concentrations of jarosite, an iron-sulfate mineral that is only formed in the presence of liquid water, and the alphaparticle x-ray spectrometer detected abundant sulfates (3). These observations point to the existence of a liquid habitat on Mars that could have supported life.Attempts have already been made to detect organic molecules on Mars. The Viking landers carried pyrolysis gas chromatograph͞mass spectrometers (GCMS) that did not detect significant organic molecules (4). This result does not preclude the presence of organic molecules on Mars because of the difficulty of detecting low levels of organics in situ in a highly oxidizing environment (1, 5). It has been suggested that the Viking pyrolysis GCMS would not have detected even high concentrations of the remnants of organisms in soil because of the low volatility of organic oxidation products (5); similar difficulties were encountered when duplicating the Viking experiments in an arid terrestrial environment (6). In addition, water and CO 2 interfere with the detection of likely organic pyrolysis products, resulting in an elevated detection limit of Ϸ10 ppm (7). Improved instrumentation must be developed that is capable of sensitive detection and analysis of key biomarkers from Mars-like soils.Microfabricated m...

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“…Metals were first eluted with 6 ml of 0.1 M oxalic acid, pH 7 (17). Amino acids were eluted with 2.5 M ammonium hydroxide and dried.…”

Section: Methodsmentioning

confidence: 99%

Development and evaluation of a microdevice for amino acid biomarker detection and analysis on Mars

Skelley

Scherer

Aubrey

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

250

252

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“…Particulate and dissolved amino acid hydrolysis was conducted with 6 N HCl at 105°C for 12 h (Amelung & Zhang 2001). Amino acids were purified by passage over a cation exchange resin (AG 50W-X8 Resin, Bio-Rad) and then derivatized to N-pentafluoropropionyl (N-PFP) isopropyl esters.…”

Section: Methodsmentioning

confidence: 99%

Bioreactivity of peptidoglycan in seawater

Kitayama

Hama²,

Yanagi³

2007

Aquat. Microb. Ecol.

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The components of bacterial peptidoglycan (PG), D-amino acids and muramic acid, have been identified as constituents of marine dissolved organic matter (DOM), suggesting that PG is a possible component of the recalcitrant DOM. However, little is known about the bioreactivity of PG directly released from bacterial cells. We conducted an incubation experiment on marine bacteria and examined the degradation processes of PG and protein released from bacterial cells using 13 C as a tracer. We used D-Ala for an indicator of PG, and L-Ala and L-Val for protein. Most PG released from bacterial cells degraded immediately, but a small portion remained at the end of the incubation experiment (240 d), accounting for 1.1% of maximum particulate PG in bacterial cells. Protein was more bioreactive than PG by one order of magnitude. The D:L ratio of Ala released from bacterial cells increased as the diagenetic stage progressed, indicating that this ratio is a useful indicator of bioavailability for dissolved organic compounds. The recalcitrant bulk organic carbon released from bacterial cells accounted for 1.8-4.8% of the bacterial organic cellular carbon. Our results suggest that PG is more stable than protein, but more bioreactive than bulk dissolved organic carbon (DOC).KEY WORDS: Dissolved organic matter · Peptidoglycan · Bacteria · Biological availability · Carbon 13 · Amino acid Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 46: [85][86][87][88][89][90][91][92][93] 2007 samine and N-acetyl-muramic acid units, cross-linked by short peptides (Schleifer & Kandler 1972). Amino acids in these peptides include D-enantiomers of Ala, Asp, Ser, and Glu, in contrast to cellular protein consisting of only L-amino acids. The occurrences of muramic acid and D-amino acids are known as typical features of PG and are used as molecular markers.In marine DOM, 4 D-amino acids (Ala, Asp, Ser, and Glu) have been found ubiquitously, and the pattern of their D:L ratios of marine DOM is similar to that of PG (Lee & Bada 1977, McCarthy et al. 1998, Dittmar et al. 2001, Pérez et al. 2003. Furthermore, muramic acid has been widely observed in marine DOM (Benner & Kaiser 2003). Therefore, PG is likely to be resistant to microbial degradation and is a possible component of R-DOM.In decomposition experiments on PG extracted from bacteria, however, PG is readily utilized by bacteria (Jørgensen et al. 2003, Nagata et al. 2003. One component of PG, muramic acid, was not detected in DOM after a lengthy incubation experiment (Ogawa et al. 2001). Thus, little direct evidence exists that PG released from bacterial cells survives as recalcitrant DOM, and the bioreactivity of PG is still a matter of controversy.We quantitatively analysed the degradation processes of PG released from bacterial cells by an incubation experiment of marine bacterial populations. We labelled bacterially produced organic matter with 13 C and traced 13 C-labelled D-Ala as an indicator of PG using gas chromatography-mass s...

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“…Consequently, GC, in particular on Chirasil-l-Val or cyclodextrin fused silica capillary columns (Schurig et al, 1999), together with flame ionization or mass spectrometric detection, has found broad applications ranging from life sciences including nutritional sciences to geo sciences or the search for extraterrestrial amino acids (Casal et al, 2005;Amelung and Zhang, 2001;Cronin and Pizzarello, 1997).…”

Section: Introductionmentioning

confidence: 99%

Gas chromatographic quantification of free D‐amino acids in higher vertebrates

Pätzold¹,

Schieber²,

Brückner³

2005

Biomedical Chromatography

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D-amino acids were determined in brain, body fluids (urine, blood coagulate, serum, plasma) and faeces of animals belonging to nine out of 11 taxonomic orders of vertebrates (Artiodactyla, Aves, Carnivora, Lagomorpha, Marsupalia, Osteichthyes, Primates, Rodentia, Tubilidentata). Free amino acids were isolated by means of cation exchangers and converted into volatile N(O)-perfluoroacylamino acid propyl esters. Derivatives of amino acids were separated into d-and l-enantiomers using Chirasil-l-Val capillary columns and detected by selected ion monitoring mass spectrometry. Quantification of amino acids was achieved by comparison of analytes with amino acid standards using l-norleucine as internal standard. Large relative amounts of d-serine were determined in brains of mammals but not of birds. In body fluids the d-enantiomers of most proteinogenic l-amino acids were detected, largest absolute and relative amounts were found in urine. Therein quantities of d-Ala and d-Ser exceeded 50% relative to the l-enantiomers in many instances.

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Determination of amino acid enantiomers in soils

Cited by 130 publications

References 33 publications

Development and evaluation of a microdevice for amino acid biomarker detection and analysis on Mars

Development and evaluation of a microdevice for amino acid biomarker detection and analysis on Mars

Bioreactivity of peptidoglycan in seawater

Gas chromatographic quantification of free D‐amino acids in higher vertebrates

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