Biology – Quantitative Biology – Biomolecules
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufm.p43a0916s&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #P43A-0916
Biology
Quantitative Biology
Biomolecules
6200 Planetology: Solar System Objects (New Field), 6225 Mars, 6297 Instruments And Techniques
Scientific paper
Detection of life on Mars requires definition of a suitable biomarker and development of sensitive yet compact instrumentation capable of performing in situ analyses. Our studies are focused on amino acid analysis because amino acids are more resistant to decomposition than other biomolecules, and because amino acid chirality is a well-defined biomarker. Amino acid composition and chirality analysis has been previously demonstrated in the lab on microfabricated capillary electrophoresis (CE) chips (1, 2). To analyze amino acids in situ, we have developed the Mars Organic Analyzer (MOA), a portable analysis system that consists of a compact instrument and a novel multi-layer CE microchip. The heart of the MOA is the microchip that contains the CE separation channels as well as microfabricated valves and pumps (3) for sample handling. The pneumatic microfabricated valves are created by combining an etched displacement chamber, an actuated PDMS membrane layer, and a discontinuous fluidic channel structure. A microfabricated pump is created by combining three individually-addressable valves in series. These membrane valves and pumps are integrated with the glass separation channel using a novel multilayer design in which sample enters the top fluidic layer for routing and is directed to the bottom glass layers for CE separation and analysis. The microfabricated device is operated by the portable instrument which contains solenoids for controlling fluidic valves, electronics, a 15 mW 400 nm diode laser, confocal detection optics, and a fiber-optic coupled photomultiplier for fluorescence detection. Limits of detection of fluorescamine-labeled amino acids are in the nM to pM range corresponding to part-per-trillion sensitivities in soil samples (4). The portable CE instrument, in combination with the Mars Organic Detector (MOD) (5), was recently successfully field tested on soil samples rich in jarosite from Panoche Valley, CA. Jarosite has recently been detected on Mars and is a key mineral indicating that liquid water was once present on the planet's surface. Amino acids from jarosite samples were sublimed by MOD and deposited onto a fluorescamine-coated cold finger. The microfabricated pumps were used to direct buffer through the MOA sipper to dissolve the sample, and then to return the sample for analysis. The jarosite sample was found to contain low levels of methyl and ethylamine (5 ppb), alanine/serine (0.4 ppb), glycine (0.2 ppb), glutamic (0.07 ppb) and aspartic (0.1 ppb) acid as well as a higher concentration of valine ( ˜100 ppb). These results clearly demonstrate that amines and amino acids can be extracted from sulfate-rich acidic soils such as jarosite and analyzed using the MOA (http://astrobiology.berkeley.edu). References 1. Hutt, L. D., Glavin, D. P., Bada, J. L. & Mathies, R. A. (1999) Anal. Chem. 71, 4000-4006. 2. Skelley, A. M. & Mathies, R. A. (2003) J. Chromatogr. A 1021, 191-199. 3. Grover, W. H., Skelley, A. M., Liu, C. N., Lagally, E. T. & Mathies, R. A. (2003) Sens. Actuators B 89, 325-323. 4. Skelley, A. M., Scherer, J. R., Aubrey, A. D., Grover, W. H., Ivester, R. H. C., Ehrenfreund, P., Grunthaner, F. J., Bada, J. F. & Mathies, R. A. (2004) Proc. Natl. Acad. Sci. USA, manuscript in preparation. 5. Kminek, G., Bada, J. L., Botta, O., Glavin, D. P. & Grunthaner, F. (2000) Planetary & Space Science 48, 1087-1091.
Aubrey Andrew D.
Bada Jeffrey L.
Ehrenfreund Pascale
Grunthaner Frank J.
Ivester R. H.
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